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CLOSE THIS BOOKSmall-Scale Manufacture of Footwear (ILO - WEP, 1982, 228 p.)
CHAPTER II. MANUFACTURING TECHNOLOGY FOR TYPE 1 FOOTWEAR
VIEW THE DOCUMENT(introduction...)
VIEW THE DOCUMENTI. Operation sequence
II. Detailed description of processing stages
VIEW THE DOCUMENTII.1 Cutting uppers (Operation reference No. 1)
VIEW THE DOCUMENTII.2 Upper preparation
VIEW THE DOCUMENTII.3 Upper stitching (Operation reference No. 9)
VIEW THE DOCUMENTII.4 Stitched upper finishing
VIEW THE DOCUMENTII.5 Bottom component preparation
VIEW THE DOCUMENTII.6 Making
VIEW THE DOCUMENTII.7 Shoe finishing and packing (Operation reference No. 31)
III. Table of technical data
VIEW THE DOCUMENTIII.1 Material handling resources, work force and production floor area
VIEW THE DOCUMENTIII.2 Workforce allocation: Table II.4
VIEW THE DOCUMENTIII.3 Equipment specification: Table II.5
VIEW THE DOCUMENTIV. Floor plans for production areas

Small-Scale Manufacture of Footwear (ILO - WEP, 1982, 228 p.)

CHAPTER II. MANUFACTURING TECHNOLOGY FOR TYPE 1 FOOTWEAR

The objectives of this chapter are to describe methods of constructing walking shoes of conventional design and to examine the range of manufacturing techniques available at each processing stage. Such shoes have cement-lasted leather uppers and cemented on sole units that do not require finishing once assembled. This manufacturing technique is now widely used by shoe manufacturers.

These shoes are referred to throughout the text as Type 1. A reason for their popularity is that lasting tacks and the accompanying heavy insoles are unnecessary, which results in light and flexible footwear. Also, unit soles avoid the need for skilled and lengthy finishing operations often required when soles and heels are 'built' on the lasted shoe.

I. Operation sequence

Stages in the manufacture of a Type 1 man's shoe are shown in Figure II.1. In summary, manufacture first involves cutting out the upper components from skins and the linings and insoles from leather or fabric and man-made sheets. Next, the edges of the upper components are tapered, or skived, to reduce the bulk of seams. The eyelets are then inserted in lacing styles and the various upper components are stitched and cemented together, stitched upper counter puff insole lasted shoe V shank sole unit completed shoe


Figure II.1 Stages in the manufacture of Type 1 footwear

The stitched upper of a plain lacing style is shown at 1. The insoles are then attached temporarily to the bottom of the last by tacks, and the heel stiffeners and the toe puffs (which respectively help shape the backs and toes) are located. At II, a toe puff, a heel stiffener, and an insole ready for assembly with the upper on a wooden last, are illustrated. Cement lasting involves stretching the edge of the upper round the last bottom and attaching it to the insole bottom with cement. After removing the tacks holding the insole to the last, the shoes are conditioned, the shanks which stiffen up the waist of the shoe are attached to the insoles, and the sole units are stuck on to the bottom. IV shows a shank and sole unit, and V a finished shoe after the removal of the last. The final manufacturing stages involve cleaning, inspecting and packaging.

A full list of the manufacturing stages is given in Table II.1. The departmental divisions indicated in the table are often ignored in small enterprises. The points at which major inputs occur are listed, but for the sake of clarity minor consumables such as tacks, cements and finishing solutions (mentioned in the text) are not shown. In terms of human resources, cutting, stitching and lasting require more inputs than the other operations and, consequently, they receive the greatest attention.

II. Detailed description of processing stages

II.1 Cutting uppers (Operation reference No. 1)

The way in which upper components are cut, or 'clicked', out of skins can have a considerable influence on the cost, appearance, comfort and wear resistance of finished shoes and on how well they retain their shape in use. Because leather is expensive, it is important that it is cut in the most economical manner, thus providing cut components of the required quality while minimising the amount of waste leather.

II.1.1 Hand cutting

Hand cutting is exclusively used in scales 1 and 2 (8 and 40 pairs per day) and used in some of the operations in scales 3 and 4 (200 and 1000 pairs per day). Choosing the best cutting pattern on a particular skin is the most important and difficult part of a leather cutter's task. Cutting by hand rather than machine should not affect the quality of the components. In hand cutting, a knife held in one hand cuts round the contour of the required shape with the material laid on a board, and the second hand preventing the pattern from slipping. Long continuous clean cuts are desirable since short cutting strokes will leave the profile with irregular edges and cause problems during the subsequent edge tapering, or skiving, operation.

Table II.1 Stages in the production of leather-upper cement shoes with cemented-on unit soles

Production stages

Op. Ref

Operations

Major materials

Upper-cutting

1.

Cutting upper components

Skins and lining materials

Upper preparation

2.

Leather splitting



3.

Lining marking



4.

Stitch marking



5.

Hole punching



6.

Sock embossing



7.

Skiving



8.

Edge folding and cementing


Upper stitching

9.

Stiching of uppers

Threads, tapes

Stitched Upper finishing

10.

Seam reducing



11.

Taping

Tapes


12.

Eyelet reinforcing



13.

Punching and eyelet insertion

Eyelets


14.

Temporary lacing

String


15.

General fitting and puff attaching

Trim, puffs


16.

Upper trimming


Bottom component preparation

17.

Insole preparation

Insole sheeting


18.

Sole cementing and

Sole units



drying


Making

19.

Insole tacking



20.

Stiffener insertion

Heel stiffeners


21.

Upper conditioning



22.

Cement lasting



23.

Tack removal and inspection



24.

Heat setting



25.

Bottom roughing



26.

Shank attaching

Shanks


27.

Bottom cementing



28.

Bottom filler insertion

Felt


29.

Sole laying



30.

Last removal


Upper finishing

31

Upper finishing operations and packing

Packing materials

The edges of hand-cut components should be cut square to their surfaces to faithfully reproduce the required shape. Cutting at acute angle to the leather surface with a straight blade produces vertical as well as horizontal forces which help hold thin leather and fabric against the board, thus preventing buckling and tearing.

When upper components are cut from skins, only one thickness can be cut at a time so that blemishes may be seen and avoided by operatives. This puts hand cutting at less of a disadvantage compared to machine cutting than if it were technically feasible to cut skins in a stack.

The equipment used in hand cutting includes the following:

(i) Clicking knives

Ranges of interchangeable, differently shaped, blades are available to fit specially designed hand clicking knives. Blades used for heavy leathers have longitudinal concave cutting edges about 30 mm. long so that the cutting edge is nearly at right angles to the surface of the leather. This type of blades avoids over-running at corners.

To keep hand cutting knives very sharp, a strip of waxed calf skin can be fixed along the edge of the cutting bench. Stropping the blade on this strip between cuts reduces the frequency with which it is necessary to sharpen the blade on emery. Apart from accelerating the blade wear, rubbing the blade on emery heats it up and tends to remove the temper.

Clicking knives may be made out of a broken hacksaw by grinding one edge of the hacksaw to shape, and by wrapping insulating tape around part of the blade. These knives may be used in place of the special purpose knives marketed by various tools manufacturers.

Figure II.2 shows three differently shaped clicking knives.

(ii) Patterns and cutting boards

Patterns are sometimes made of galvanised sheet steel, but more often they are of rigid fibre-board with their edges bound all round with a brass channel strip to prevent knives from cutting into the card.

Cutting boards are normally 70-100 mm. thick with a roughly square surface of about one half square metre (e.g. 70 cm x 70 cm). Boards can be of artificial fibre or of wood with blocks of pine or lime bonded together so that their end grains form the cutting surface. This reduces the rate at which the surface is cut away. The benches are usually high enough to permit cutting in the standing position.

(iii) Awls

Awls about the size of old fashioned gramophone needles can be fitted to the end of a knife handle, and are used to prick stitching and lapping guide holes on upper components.

II.1.2 Mechanised Cutting

Mechanised cutting should be used in some of the operations in scales 3 and 4. It commonly uses cutting presses and strip steel knives cold bent to the shape of the pattern. Some high speed automatic processes using lasers or water jets are available for cutting stacked man-made materials but such equipment is only economical if output volumes are very large.

Figure II. 2 Simply made cutting tools


STRAIGHT

The knife may be made from hacksaw blades wrapped with insulating tape.


CONCAVE


FLAT SKIVING KNIFE


GROOVING TOOL

The grooving tool can be made from an old screwdriver softened before drilling, with its cutting edge formed with a very small round file, then sharpened with a narrow strip of fine emery cloth.

Note: The steel may be softened by heating and slow cooling then hardened by heating and quenching in oil.

The equipment used in mechanised cutting include the following:

(i) Press knives

Press knives for cutting single thickness of material are usually reversible with cutting blades on both their top and bottom edges so that only one knife needs to be used for pairs of right and left foot components. In cases where it is unnecessary to see the top surface of the material before cutting, cuts can be made from both sides of the material with a single edged cutter to produce left and right foot components. These knives are made from thin strips of steel. Frequent checks are required in order to ensure that they have not been distorted. To produce clean cuts, the knives must be sharp. Special purpose edge dressing machines are available to help regrind knives. Rotating grinding wheels can also be used for knife sharpening but care is necessary to avoid "burning" the edge by exerting too much pressure.

Notches to indicate the component size can be incorporated into the knives. Alternatively, cut edges on components can be hand dabbed with paint of different colours and in different positions so that machinists may bring together the correct components. Machines carrying several rotating wheels which each dip into a different coloured paint, can be used for this purpose. Alternatively, the cutter may merely write the necessary details on the back of the cut components with a piece of chalk. Sometimes, colour marking is undertaken in the preparation and stitching department.

(ii) Cutting presses

Some cutting presses have a "beam" supported between two columns and a cutting head that can be traversed along the beam. Other presses have a cantilevered beam that can swing over the table. The surface of the tables of swing arm presses are usually 1 m long by 0.5 m wide, while travelling head press tables are usually 1.5 or 2m long by 0.5 m wide. The maximum press cutting forces vary from below 10 tonnes on small beam presses to 30 tonnes on large travelling head machines. The simpler presses have hardwood, synthetic rubber or fibreboard cutting blocks, and are mechanically or hydraulically activated. Electronically controlled hydraulic machines are also available, with the attached beam reversing as soon as the knife completes an electric circuit by touching the lower cutting block. This cutting block is made of a soft aluminium alloy to avoid damaging the hardened steel cutting edge. Most manually controlled presses have two hand operated tripping buttons located on top of the beam. These buttons must be pressed simultaneously to activate the cutting cycle, thus reducing the chance of accidents. Some travelling head presses can be controlled by a joystick located on one of the columns, while other presses have a completely automatic pre-programmed cycle to traverse the head and initiate the cutting cycle. Both swing arm and travelling head presses can be equipped with devices for unrolling and feeding fabrics and synthetic material in single or multiple layers. Swinging beam presses can be used to cut wide fabric fed from rolls by arranging one cutting table under two swinging beams facing each other at right angles to the direction in which the material is fed.

The economic break-even scale of production between hand and press cutting is about two thousand pairs of cuts. The point at which the costs switch in favour of one of the two cutting techniques is not a function of the wage level since the cost of knives is the determining factor. Thus, differences in wage levels between developed and developing countries should not determine the use of hand or press cutting. It is the scale of production which determines the choice of cutting technique. For example, even the most highly mechanised factories in developed countries use hand cutting for small scales of production.

II.2 Upper preparation

Manufacturing leather uppers involves preparation, stitching and finishing operations. They consist of a relatively large number of short operations ranging from visual inspection at a bench to assembling the various components on a stitching machine. In terms of work content, stitching is usually the most important of the three types of operations involved, in upper manufacture. Usually, a greater proportion of the workforce is engaged in stitching than in any other activity. Even in its most capital-intensive form, stitching is still a labour-intensive process.

Figure II.3 shows an example of the sequence of operations necessary to produce uppers for an elaborate style of men's leather upper. The sequence of operations required to prepare components prior to stitching and finishing may vary widely from style to style. In large factories, each type of work may be carried out in a separate department and, sometimes, stitching of different types of upper is divided between a number of departments. If the lot, or batch, sizes of components were very large, each operation shown in Figure II.3 may need to be performed on a separate machine. On the other hand, small enterprises may carry out many of the stitching operations on a single machine. Since this memorandum is principally concerned with small-scale production, descriptions of the equipment available for the different types of work are grouped together.

II.2.1 Leather splitting (Operation reference No. 2)

The leather splitting may be economically performed by shoe manufacturing plants producing at least 2000 pairs per day (i.e. scale 4).

Cut leather components that are thicker than required or have uneven thickness due to loose flesh adhering to their underside can be split on a band knife machine. The thickness of the split may vary from about 5 mm. down to zero. The machine has a continuos strip knife blade running horizontally between two large rotating wheels using the principle employed in a band saw. The components to be reduced are fed between a pair of feed rolls which move the work past the knife blade. The whole area of the component is reduced to the pre-set thickness and the waste is collected in a box.


Figure II.3 Typical work flow during preparation and stitching

Footwear manufacturing enterprises in developing countries that do not find it necessary to invest in band knife splitters (i.e. enterprises operating at scales 1 to 3) may depend on local tanners to supply leather of the required thicknesses. Otherwise, they may remove uneven flesh areas by hand, with a sharp steel scraper blade held at right angles to the surface of the leather.

II.2.2 Lining marking (Operation reference No. 3)

It is common for details of each pair of shoes to be marked on the uppers. Marking helps identify pairs of shoes at subsequent stages of manufacture, and facilitates the ordering of repeats by trade customers. Details usually include style number, size, width fitting and last number. On unlined shoes, the information is sometimes printed on top of the tongue, but in the majority of cases it is marked on the quarter linings.

Three techniques may be used for lining marking:

(i) Details may be written by hand with ball point pens if one wishes to convey an expensive individual appearance,

(ii) Use of an inkpad and rubber stamp,

(iii) Specially designed stamping machines, that can be mounted on a bench, are available for large-scale production. These machines have stamping heads, and use automatically dispensed foil embossing strips. The type is mounted on the circumference of adjustable wheels.

II.2.3 Stitch marking (Operation reference No. 4)

Guide marks help stitching machinists to accurately overlap upper sections, and to correctly position fancy stitches, buckles, eyelets and trims. Two techniques may be used for stitch marking, depending on the adopted scale of production:

(i) Use of press cutting knives

This method may be adopted for scales 1 to 3 (i.e. 8 pairs to 200 pairs per day).

Press cutting knives may incorporate notches to indicate the positions at which seams are to start and stop, as well as pricker pins which produce stitch guidance holes. Guide lines can be drawn on upper components with a ball point pen through slots in a flat pattern or template made of fireboard. The template will, in this case, have the same shape as the component on which it is laid.

(ii) Treadle and hand-operated marking machines

For scales of production of 1000 pairs per day and higher, enterprises may use treadle and hand-operated marking machines. These machines use a printing die consisting of a sheet of pattern board to which raised metal or plastic ribs of the desired seam configuration are attached. Ink from a wide ribbon is transferred on the die to a component which is located by pegs on a guide board. Each end of the die block is located by two radial arms to provide a parallel motion. The die block is thus held in a horizontal plane as it swivels over between the inking ribbon and the component laid on the guide board. Springs centre the swivelling die block clear of both the guide board and the ribbon when the machine is not in use.

A similar manual inking method uses fibreboard patterns cut to the component shape. The patterns have plastic ribs attached to both sides in the desired stitch pattern. The pattern with the ribs on its underface loaded with ink is placed on top of a component to be marked. By inking the ribs on the top face of the pattern while pressing the pattern down onto a component, left and right components can be marked alternatively. The replenishment of ink to the ribs on the top face is by means of an inking ribbon running across the bottom face of a hinged plate. The latter is spring loaded upwards so that the operator can load and unload work, and turn the pattern over between strokes of the machine. Each pattern board may be used to cover a range of one and a half British sizes of adult shoes.

These machines can be of wood but are most often of cast iron.

II.2.4 Hole punching (Operation reference No. 5)

Some leather upper design styles require decorative perforations round the edge of toe caps. Hole patterns are also often cut on the foreparts of children's sandals. The following devices may be used for hole punching:

(i) Manual punching tools

Manual punching tools may be used for scales 1 to 3. These tools have blades of the required shape which cut one hole at a time with each hammer blow.

(ii) Hole punching machines

For larger scales of production (scales 4 and higher) hole punching machines become cost-efficient. These machines may consist of top male punches and lower female recesses which are capable of producing a whole pattern (e.g. on a sandal vamp) in one cycle of a hand fly press or light powered bench press. Edge perforations may also be produced by powered punches in which the punch action is synchronised to the edge feed.

II. 2. 5 Sock embossing (Operation reference No. 6)

Brand names and trade marks are usually embossed onto the plastic coated fabric or thin leather socks that are cemented over the seat or the whole of the insole once the sole has been lasted. Normally, gold coloured plastic foil is used for this transfer process although, in the past ,the discolouring action of a heated die was sometimes used to produce a contrast on leather socks.

(i) Local production of embossing equipment

At production scales 1 and 2, a very inexpensive machine can be constructed by mounting an electric iron (which has a variable temperature control) on a hinged arm with the brass embossing die attached to the bottom of the iron. The pressure and duration of contact is controlled by the operator. Consequently, the work quality relies on the operator rather than on predetermined machine settings. Such machines are used by small-scale footwear manufacturing enterprises in developing countries. When used on a continuous basis, these machines may process fifty pairs of socks per hour (see Figure II.4).

(ii) Semi-automatic embossing machines

For higher scales of production (3 and above) high throughput semi-automatic embossing machines are available. Control of die temperature, embossing pressure and dwell time are preset and the operator merely feeds the socks in one after the other. The production rates of these sophisticated machines can reach seven hundred pairs per hour on long runs. Slower, manually operated machines are less expensive but less convenient to operate.

II.2.6 Skiving (Operation reference No. 7)

Skiving is the term used to describe the tapering required on the flesh side of some edges of upper components. On fabric backed materials, it may be necessary to skive the top rather than the flesh surface. The objectives of this important operation are to permit easy assembly, good appearance and wearer comfort.

(i) Manual skiving

Manual skiving may be efficiently adopted for scales of production 1 and 2. The traditional way of carrying out this operation is by hand, using a very sharp flexible steel knife blade and a flat surface such as a solid steel plate, a slab of marble or a sheet of plate glass. The component is laid flesh side up on the surface and held down with the free hand while the excess thickness is sliced off. The knife is held across the flat of the hand and drawn back towards the operator. This method is relatively slow, with a typical output rate of ten pairs of components per operator hour. A good deal of practice is required to produce uniform tapers.


Figure II.4 A simply made insole embosser for small volume production

PARTS LIST

A. Domestic electric iron with adjustable thermostat with handle removed.

B. Steel tube, 30 mm. diameter by 650 mm. long drilled for hinge bolt and screws to hold iron.

C. Proprietary brass embossing die.

D. Hinge blocks of steel angle section or wood drilled to hinge and screwing to work bench.

E. 10 mm. diameter bolt, nut and washers to act as hinge pin.

F. Screws to attach the body of the iron to tube and the die to the sole of the iron.

G. Insulating tape.

H. Workpiece to be embossed with precut strip of embossing foil laid on it.

I. Flex for mains.

J. Sole of iron drilled and tapped for attachment of embossing die.

K. Work bench.

L. Two hinge bracket screwed to work bench.

Note: The best combination of pressure, temperature and application time should be found by means of trials.

(ii) Skiving machines

For higher scales of production (3 and above) the use of skiving machines may become more efficient. The most widely used type of skiving machine employs a rapidly rotating steel disc with the cutting edge on its circumference, past which the component is carried. The edge support plate, which guides the component, is adjustable for scarf width and angle.

Machines are available that can be preset to produce two or three different knive angles at the flick of a pedal so that a component requiring different treatments along different edges may be completed in one pick up. The skill required to set these rotating cutter machines varies considerably from model to model. In operation, these machines require substantially less skill to produce good results than skiving by hand and their output can be about fifty pairs per operator hour on a typical men's style with five leather upper components per shoe.

(iii) Matrix skiving

A more recently introduced method, called matrix skiving, requires fixtures or matrices made from sheets of hard rubber or composite material which have recesses sculptured into one side. These recesses are shaped to the size and contour of the finished component. This method is, in general, economically viable when more than two edges of a component require skiving, and when there is a sufficient volume of work to justify the cost of producing the recessed work holding fixtures for each size of each component. In matrix skiving, components are laid flat in the recesses, with only the material to be removed protruding. The loaded fixtures are then guided through a band knife splitting machine similar to that described earlier in connection with leather splitting. The knife removes the surplus thickness from the areas of the component protruding above the top surface of the fixture.

II.2.7 Edge folding and cementing (Operation reference No. 8)

This operation may be carried out on unassembled components or on partly stitched uppers. Several methods of folding over and cementing down the top lines of uppers are available.

(i) Manual folding and cementing

Manual folding and cementing may be efficiently used for scales of production 1 and 2. The output rate of manual methods is estimated at approximately 12 to 15 pairs per operator hour. The usual sequence used in manual folding and cementing includes the following: adhesive application, notching of curves, folding over the straights, pleating the bends, and flattening the folds. The last operation involves tapping down the folds with a short, flat-ended metal bar or similar tool. A metal template can be useful in maintaining an even fold line.

Figure II.5 shows a hand tool for cementing down folded skived edges.


Figure II.5 Hand tool for cementing down folded skived edges

(ii) Folding and cementing machines

For higher outputs (e.g. production scales 3 and above) various expensive electronically controlled machines are available. These machines require relatively little operator skill, but need a good deal of maintenance back-up.

Electronically controlled machines incorporate photo-electric cells that automatically sense bends requiring snipping and pleating, and also dispense thermoplastic adhesive to bond the material in position. The operator feeds the components and controls the speed with a foot pedal. A narrow tape can be incorporated into the fold to limit stretch.

The output of these machines is estimated at approximately 80 pairs per operator hour. Simpler machines, similar in overall design concept to the above machines, are also available at lower prices. These simpler machines do not include electronic components, and their output rate is estimated at approximately 40 pairs per operator hour.

Equipment for producing other types of edge finishes is discussed in the section dealing with stitching.

II.3 Upper stitching (Operation reference No. 9)

II.3.1 Stitching methods

Stitching may be carried out by hand or by stitching machines. However, manual stitching is rarely used in the construction of uppers except in the stitching of mocassins for the production of decorative effects. Even in countries where capital is very scarce and wages very low, stitching machines are usually employed in very small production units. The reason for this is that stitching machines are extremely productive. An operator using such machines can construct as much as two metres of double rowed lapped seam per minute. He can also form regularly spaced and tensioned lock stitches at a rate of forty per second. Even the most skillful hand stitcher would find it difficult to achieve one per cent of this output. Consequently, the use of stitching machines may be shown to be much more cost-effective than manual stitching for all but the lowest scales of production.

II.3.2 Stitching machines

Most stitching machines produce lock stitches which have a top thread fed by the needle and a bottom thread fed from a bobbin. The lock between the top and the bottom threads should be concealed within the material. Chain stitches only require a top thread, but it unravels if the thread breaks.

Stitched seams can be produced on components with edges cut to matching or different contours when flat. When the contours do not match, stitching them together produces assemblies with seams curved in three dimensions at once. This reduces the amount of curvature that it is necessary to impart during lasting.

On some machines, the stitch length is adjustable. On variable stitch length machines, the work is stationary while the point of the needle is below the needle plate and the work is advanced between stitches. This type of machine is more often used on light work where variability of the feed rate is unimportant. It is necessary to change the gearing ratios to alter the stitch length on fixed feed rate machines. Their needles and needle plates oscillate at the same rates so that the work is advanced while the needle is below the needle plate. On all types of stitcher, the thread tension can be varied to suit particular types of work.

Machines having flat beds are used for a wide range of work, such as stitching in eyelet reinforcing strips and other work that can easily be stitched on a flat surface.

In post bed machines, the bobbin is located at the top of a vertical post below the needle. The small working platform at the top of the post enables sprung seams to be constructed more easily than on flat bed machines, since the material can hang down clear of the area being stitched. Machines are available with a choice of the post located to the left or right of the needle.

Figure II.6 Types of stitching machines


POST BED MACHINE


TWIN NEEDLE FLAT BED MACHINE


CYLINDER ARM MACHINE

Once uppers have been closed down the back seams, they can be stitched on cylinder arm machines in which the bobbin is located at the end of a horizontal arm cantilevered out from the main vertical column. Long boots are also closed on cylinder arm machines.

Special purpose treadle driven machines which are designed so that the work can be fed in any direction during stitching are still popular for repair work in developed countries.

(i) Semi-automatic machines

Semi-automatic machines can include under-bed thread trimming devices to cut off surplus yarn at the end of a seam as well as edge trimming devices. On some of these machines, the operator can pre-select to finish a seam with a needle up or down, which reduces the time required to remove work at the end of a run, or to turn sharp corners by rotating the work round the table.

(ii) Automatic machines

This type of machines, which costs approximately US$ 2,000, does not require the operator to guide the work past the needle. Manufacturers normally sell automatic machine set up with cams and guides to produce a pre-determined shape of stitch pattern. These machines may be easily adjusted for stitching patterns of different sizes. However, most footwear manufacturers would find it extremely difficult, if not impossible, to adjust these machines for stitching basically different patterns.

Most enterprises in developed countries which handle a sufficiently large volume of repetitive work such as bar tacking, buckle attaching and tongue attaching use a few automatic machines. It is sometimes possible for an operator to manage two of these machines by loading and unloading one machine while the other is stitching. Some machine manufacturers offer pairs of automatic machines ganged together to carry out a back seaming and frenching sequence.

Microprocessor controlled automatic machines, each requiring an initial investment of approximately US$ 20,000, are now available. These machines, which are programmed by means of tape cassettes, were first used for fancy stitch designs on the sides of boot uppers but are now also used for flat multi-part seaming.

(iii) Choice of stitching machines

Brief specifications of some types of stitching machines suitable for the footwear industry are given in Table II.2 The type of work for which each machine is likely to be appropriate is indicated in the table and further discussed below.

Stitchers are normally described according to their physical characteristics or the type of work that they are intended to carry out. Some of the more commonly specified options are listed below:

Number of needles:

single, twin or three Type of stitch: chain or lock

Type of top presser:

foot, idler roller or driven top roller

Stitch length:

variable or fixed

Stitch pattern:

straight or zig zag

One of the most popular combinations of these options found on machines used by small-scale enterprises in developing countries is: straight lock stitching, single needle, roller presser and flat bed. Without motor, stand clutch or lighting, such machines can cost less than US$400. It is feasible to make good quality footwear on such general purpose machines. However, some operations will take longer on these machines than on more specialised types costing approximately US$2,000.

Table II. 2 Brief description of some machines suitable for stitching uppers

Operations

Description

Under edge trimming of top lines

Single (needle) , post (bed), roller (presser)

Zig zag

Single, flat, roller

Barring machine

Single, cyl. (arm), barring tack set up

Flat binding

Single, cyl., tape feed with binder

Back strapping

Single, post, for non-parallel back straps

Cording (raised seam)

Twin, flat, roller with air cording attachments

Repairs machine (treadle Powered)

Often purchased second hand

French binding

Single, post, roller with guide, top tape drum and pad needle plate

Close row (1.5mm.) stitching

Twin, flat, roller

Silking or rowing back seams of leather linings

Twin, flat, with silking row modification

Intermediate operations,

Single, post, roller

For heavy (up to 8 cord) decorative stitching

Single, cyl., roller

Intermediate operations (lighter)

Single, flat, roller, auto-underbed trimming and needle control

Intermediate operations (lighter)

Single, flat, roller (simple machine)

(iv) Stitching aids

Stitching machine attachments and work guides can be inexpensive substitutes for operator training and experience in the achievement of high standards of accuracy and levels of output. Unfortunately, greater use of aids tends to be made in areas of the world with long experience in footwear manufacture than in areas where the industry has been recently established. Some types of aids are listed below for those readers who may not be familiar with their use:

Work guides

- Adjustable guide and presser foot for running on French bindings.




- Adjustable roller edge guide consisting of a short round vertical steel peg attached to the table for control of the overlap width on lapped seams. These guide stout leather better than soft leather.




- Presser foot and guide to aid the insertion of zips using twin needle machines.



Thread cutters

- Treadle operated thread-end cutting and thread pulling through devices. These are often offered as original equipment.



Needle threaders

- Can be fitted to a wide variety of stitching machines



Special control mechanisms

- Electronic controls to position - the needle up or down which enables work to be swivelled on the needle at corners.



Holding aids

- Clamps to hold work during such operations as decorative stitching and tongue attaching.



General aids

- Under edge trimming knives for cutting off excess lining material during top line stitching.



General aids

- Thread break detector which stops the stitcher after a break and when the bobbin runs out.




- Device for lowering clamp, starting machine and lifting clamp during semi-automatic tongue attaching work.

II.3.3 Mocassin seams

Mocassin seams are variants of open seams and are most often used to attach mocassin aprons to their vamp wings. They may be formed on an arm-type coarse stitching machine or by hand. Covered mocassin seams, in which the edge of the apron is doubled over the vamp, are more weather-proof than open seams, but hand stitching of the latter takes less than half as much time as on the former. Often, outworkers carry out hand stitching. Where it is carried out in-house, the operation can be simply mechanised without losing the hand-finished appearance. A needle, with an open barb to carry the thread, is fastened to the piston rod of a small air cylinder. To form each stitch, the upper components are first pushed manually onto the unthreaded needle, the thread is then laid into the bar, and finally, the cylinder is activated so that the needle pulls the thread back through the hole.

II.4 Stitched upper finishing

Between stitching operations, and after stitching is completed, it is usually necessary to perform several additional operations in order to prepare uppers for the lasting stage. These operations are briefly described below:

II.4.1 Seam reducing (Operation reference No, 10)

The first operation is seam reducing. It involves cutting down the bulk of stitched back seams by removing the excess material on the seam and then flattening what is left under pressure. These two operations are separated when performed manually. They are on the other hand combined when performed by special purpose seam reducing machines.

Figure II.7 shows the drawing of a simply made tool for reducing closed back seams. This tool can be easily manufactured locally.


Figure II.7 A simply made tool for reducing closed back seams

PART LIST

A. Bright steel support bar, 30mm diameter x 400 mm long drilled for fixing bolts.

B. Bright steel rubbing bar 30mm diameter x 600 mm long drilled with a clearance hole at one end for the swivel bolt.

C. 25 mm thick spacer block of hard wood drilled for swivel bolt.

D. 12 mm diameter bolts, nuts and washers for swivel and support bar clamping.

E. Back seam of upper F. Work bench.

Operation: The upper is gripped in the left hand so that the seam is stretched over the support bar. The right hand applies pressure to the rubbing bar while moving it back and forward across the seam.

11.4.2 Taping (operation reference No. 11)

As an alternative to a stitched silked seam, woven tape or paper tape can be cemented to the inside of the closed back seam either with the aid of a special purpose machine or by hand.

11.4.3 Eyelet Reinforcing (Operation reference No. 12)

Eyelet reinforcements can be stitched into uppers. Alternatively various labour saving machines are available which cement strips of fabric under the wings of uppers. In small enterprises, this simple operation is usually carried out manually.

11.4.4 Punching and Eyelet Insertion (Operation reference No. 13)

There are wide varieties of techniques available for the punching of eyelet holes and the insertion and clinching of metal eyelets. Some of these are briefly described below.

(i) Manual punching and eyelet insertion

A simple technique, suitable for scales 1 and 2, involves hole punching and eyelet clinching with hand held pliers. Although the cost of the needed equipment is very low, this technique yields an output of up to 30 pairs of shoes per hour. The technique may be further improved through the use of simple tools which may be manufactured locally. These tools are described on Figure II.8. They include an eyelet hole punching tube, and a punch and die for eyelets clinching.

(ii) Mechanised punching and eyelet insertion

For large outputs (e.g. scales 3 and above) various machines may be used for punching and eyelet insertion. The most elaborate machines punch a hole, insert and clinch an eyelet, then advance the work to the position of the next eyelet where the cycle is repeated. Depending on the type of shoe and the number of eyelets, these machines can process up to about 1,500 pairs per shift.

Figure II.8 Eyelet hole punch and eyelet clinching tools

The most sophisticated manually powered machines have automatic eyelet feeds but do not advance the work automatically. In a less expensive version of this machine, the operator has to locate the position of the eyelets manually.


EYELET HOLE PUNCH

The punch may be produced from a short length of solid steel tube, filed and buffed to shape in a revolving chuck. The hole is cleared with a steel rod after use.


EYELET CLINCHING TOOLS

The punch and die should be turned from a steel bar to fit eyelets.

II.4.5 Temporary lacing

This operation can be carried out by machine or by hand. Temporary laces are tied through the eyelets on lacing shoes so that the uppers maintain their shape during lasting. When casual styles of shoe have elastic gussets rather than laces, fabric tabs are sewn in at the same time as the gussets. The tabs are cut out after lasting.

II.4.6 General fitting and puff attaching (Operation reference No. 15)

When toe puffs are assembled to the upper at this stage rather than during lasting, they may be attached with the help of a mechanical cement applicator or by hand. Decorative trims may be stapled or stuck on after lasting to reduce the risk of their being damaged. In large enterprises in developed countries there is a trend towards the use of puffs consisting of cotton impregnated with thermoplastic resins which are heat printed onto the upper and reheated before lasting to soften them. Thermoplastics are being increasingly used in the same way on stiffeners of leather-board and fabric.

II.4.7 Upper trimming (Operation reference No. 16)

The final trimming of loose threads from the uppers is carried out by hand with scissors. Although a flame is sometimes used to burn off threads, no powered machine is available for this operation. Where the lasting allowance on uppers requires cementing prior to lasting, the cement can be applied by brush or with the aid of an automatic supply unit. If hot melt adhesives are used for cement lasting this operation is unnecessary.

Linings and toe puff edges usually require trimming back to expose the lasting margin or allowance of the upper. Machines are available which can carry out this simple operation and to also roughen up the margin of the upper in preparation for cementing. However, these two operations may also be carried out efficiently by hand.

II.5 Bottom component preparation

II.5.1 Insole Preparation (Operation reference No. 17) The operation includes the following sub-processes:

(i) Cutting

Insoles are cut to shape from sheets of leatherboard, cellulose board, blended strip or, exceptionally, leather. Cutting can be done manually with knives and templates of the required shape. Large enterprises often use heavy cast steel knives to cut several thicknesses of board with one stroke of a mechanical beam press. A heavy duty press/ used to cut stacks of up to four boards at once, can produce 2,400 pairs of insole blanks per shift. Swing arm mechanical presses, identical to those used for cutting upper leather, can usually cut two thicknesses of insole material.

(ii) Size stamping

To enable the various sizes and widths of insoles to be identified, numbers and letters are normally stamped onto them. This operation may be carried out with a stamping machine or manually with stamps and a hammer.

(iii) Seat bevelling

The edges of the back part of the insoles are bevelled to help the fit of the upper round the edge of the insole. This operation may be carried out either manually or with the help of a machine.

(iv) Slotting

Insoles for high heeled shoes may need a series of shallow slots cut across the undersides of their foreparts to assist flexing. These slots may be cut by hand or with the help of a rotary cutter.

(v) Insole moulding

The omission of an insole moulding operation at this stage can adversely affect the quality of the finished footwear. The operation involves shaping the insole into an exaggerated copy of the last bottom contour. During lasting, the moulded insole springs back to the last contour. The objectives are to achieve a close fit between the last and the insole (and thus prevent the insole from curving up round its edge during lasting) and to obtain a good shape retention and appearance. Many small-scale enterprises do not have presses equipped with male and female moulds capable of permanently forming the insole. They, therefore, rely on the insole being bent roughly to the required shape by hand. Another solution for small enterprises is to fit metal insole forming moulds or lasts that have been rounded off at the feather line with the help of the press used for cement sole attaching. Sole presses are discussed in a later section.

(vi) Shank grooving

In the past, the shank - which is the narrow reinforcing strip used to strengthen the waist of the shoe - was invariably attached to the bottom of the insole after lasting. Wooden shanks are still often tacked or cemented on at that stage but the use of metal shanks contoured to the shape of the moulded insole is increasing. Metal shanks can be laid in a groove specially cut into the insole and then riveted into position. The groove is cut out before moulding by hand or with a rotary cutter.

(vii) Cementing

Insoles that will be attached to the lasting margin of uppers by means of contact adhesive require to be cemented round their edges. Neoprene cement or pressure sensitive latex adhesive is usually used. Cement dispensing machines are available or the operation can be performed manually with a brush. Drying may be in air on a rack or in a heated cabinet.

II.5.2 Sole cementing and drying (operation reference No. 18)

To prepare their surfaces for sole attaching adhesives, sole units made of PVC or polyurethane are washed with solvents. Those made of resin rubber are scoured with wire brushes, while units of leather to be cemented on can be roughened with needle sharp saw toothed rotary cutters. Application of a synthetic rubber or polyurethane adhesive to the upper surface of the sole unit can be done by brush or under pressure from a nozzle. The cemented units are normally stored on wire racks while drying.

II.6 Making

II.6.1 Insole tacking (operation reference No. 19)

Insole tacking is one of several operations carried out before lasting, whereby insoles are temporarily fastened onto the bottom of the last. This operation may be carried out manually or with the help of special purpose tacking machines.

(i) Manual insole tacking

At small levels of output, insole tacking may be carried out with the help of a worn magnetised file for tapping the tacks through the insole into the last bottom. In this operation, the socket on top of the last is located on a vertical steel column -called a jack - fixed to a bench. Figure II.9 shows drawings of the file and of the lasting jack. These tools can be manufactured locally.


Figure II.9 Insole taking tools

(ii) Insole tacking machines

At high levels of output, the use of special purpose tacking machines may be justified. In some systems, steel studs are permanently fixed in the bottom of the last, and insoles are pushed onto them by a machine. Although expensive, this approach has the advantage that tacks cannot be inadvertently left in the shoe.

Normally, three tacks are inserted for each insole. However, small enterprises which do not possess an insole moulding machine, often insert five or six tacks on the forepart, and two or three tacks over the waist and seat. These tacks hold the insole tight to the last during lasting.

II.6.2 Stiffener Insertion (Operation reference No. 20)

Where stiffeners do not have to be inserted immediately before lasting, and there is a sufficient volume to justify the operation being separated from lasting, heel stiffeners may be manually placed into the pocket between the quarter lining and the quarter. At this point, French chalk may be applied to the seat of the upper, and last slip paste may also be applied to the toe of the last. Both substances assist in the removal of the last from the lasted shoe.

II.6.3 Upper Conditioning (Operation reference No. 21)

The absorption of moisture by leather uppers before lasting, and their subsequent drying after lasting greatly enhance the shape retention properties of leather uppers. Although synthetic upper materials do not absorb water, their fabric backers may do so. They may therefore be heated either with or without moisture prior to lasting and then dried in the normal manner after lasting.

A variety of moisture conditioning techniques are available. For scales 1, 2 and 3, water mixed with a soapy wetting solution may be sponged on the uppers. For the same scales, a more satisfactory result may be obtained if the upper are suspended over a tray of boiling water so that steam permeates the leather. The introduction of this relatively simple and inexpensive system can markedly improve appearance and shape retention.

A method which is unlikely to be appropriate at the lower levels of production, but which could be suitable for scale 4, involves suspending the uppers (until required for lasting) in a closed room where atomised water droplets are sprayed at ambient temperature. This approach is unsuitable when thermoplastic heel stiffeners and toe puffs requiring activation by heat before lasting are used. In a more sophisticated version of this approach, the uppers may be placed in a cabinet in which the temperature and moisture content of the air are controlled at predetermined levels. In this case, uppers require to spend a short period in the conditioning cabinet.

II.6.4 Cement-lasting (Operation reference No. 22)

Although many systems of lasting are available, they all involve pulling the upper over the last and fastening it over the bottom edge of the insole. Cement is now used in the majority of lasted shoes but the whole shoe is not always cement-lasted since tacks may be used to last the sides. A major benefit of cement-lasting a whole shoe is the elimination of the risk of having a loose tack injuring the wearer. Since other methods of lasting are described in later sections, only cement-lasting is considered here. Figure II.10 shows several alternative lasting systems.

(i) Manual cement-lasting

Manual cement-lasting techniques are usually appropriate at low production levels (e.g. scales 1 and 2). In general, one operator carries out cement lasting for a whole shoe. Some operators prefer to mount the last on a jack and to stand at a bench, while others find it most convenient to sit on a low stool beside a low bench on which are laid the materials and tools. A pair of special purpose lasting pincers, with curved and deeply serated jaws and incorporating a light hammer head, is used to stretch the upper over the last and to fix the lasting allowance to the insole.

If preassembled stiffeners are not used, the operator may have to dip a stiffener (usually pre-moulded leather-board) into a pot of latex and then position it. Similarly a puff (usually woven cotton) may have to be dipped into an acetone solvent before inserting it.

Hand lasting usually requires greater skill than any other footwear manufacturing task. The aspects of the job that are most difficult to master are the attainment of the correct directions and degrees of strain, and the achievement of uniformity between a pair of shoes in terms of squareness, back height and the fit and shape of the top line.

In manual cement lasting, tacks may be used to temporarily hold uppers in position on the last. Usually the toe is drafted over and fixed first. The back and sides are usually fixed after the toe area has been attached. The order in which each stage is completed depends on the preference of the operator. The final stage includes careful pleating of the lasting allowance and the removal of any puckers from the upper round the heel and toe.


Figure II.10 Alternative cement-lasting sequences

Note: Similar alternatives are available for tack lasting type 3 footwear

ii) Mechanised cement lasting

Manual cement lasting is generally inappropriate at high levels of production. This operation is therefore carried out with the help of special purpose machines at scales 3 and above. Simple lasting machines may be used at scale 3 while scale 4 usually requires rather more elaborate machinery.

A wide range of machines are available for cement lasting foreparts, sides and seats. Machines are also available that combine pairs of these operations. Consequently, there is a wide spectrum of complete systems that can either toe or seat-last first. As a result of recent technological developments, the quality of work now attainable with expensive modern machinery is often as good as if not better than, that produced by highly skilled operators.

(a) Simple lasting machine

Lasting systems consisting of a pair of manually powered machines are available. One operator using the two machines can generally cement last a shoe in under two minutes. In one such system, the upper is drafted onto the last and the forepart is secured by impact adhesive to the insole on the first machine. In the second machine, wiper plates sweep the lasting margin in over the insole. The wiper plates can be changed over so that toes and seats can be lasted on the same machine. A typical two machine system of this type costs approximately US$ 7,500.

(b) High output lasting machine

One type of high output lasting machine uses thermo-activated stiffeners. Before lasting proper, the backparts containing the stiffeners are pre-heated and then moulded to shape in special purpose machines off the last. During this operation the seat can be hot melt cemented to the insole between the internal mould (which is chilled to accelerate setting) and inflatable external seat supports. The last is then inserted into the upper and a tack placed at the toe to hold it in position.

A simpler and less expensive version of this technique involves as a first step back moulding and seat lasting on the last. The next step is to last the forepart. In sophisticated machines, adjustable pincers grip the lasted margin of the upper and wipe it over the bottom of the insole following the automatic application of hot melt adhesive.

In one widely used type of side lasting machine, the operator holds the shoe so that the lasting margins on the side and in the waist are in turn fed through a pair of rollers. As with other cement lasting techniques, the upper and insole can be pre-cemented or immediately cemented manually (prior to lasting) with the help of a hand gun. Alternatively, the adhesive can be applied automatically during lasting.

A lasting unit consisting of a backpart moulding and seat lasting machine, a forepart laster and a side laster with an operator on each machine, might be able to produce a lasted shoe in approximately ten seconds. A high quality system of this type, consisting of three machines, costs approximately US$100.000. Few footwear manufacturing enterprises in developing countries have sufficiently large markets for high quality footwear to justify such expensive systems.

II.6.5 Tack Removal and Inspection (Operation reference No. 23)

Tacks inserted to temporarily hold the insole to the last are removed after lasting. Usually hand held saw toothed tack lifters are used. For large scales of production, high speed tack extracting machines are also available. The operator removing tacks may also check on the quality of the lasting.

II.6.6 Heat Setting (Operation reference No. 24)

Allowing uppers that were conditioned with moisture before lasting to dry naturally has an important disadvantage: it increases the invesment in work-in progress and the number of lasts in circulation. It may also lead to the development of mildew and rust stains may be caused by steel plates fitted to last bottoms. Artificial drying may therefore be used in order to avoid the above problems. Infra-red and other forms of radiant heat constitute one artificial drying source. However, they may result in uneven drying. Blown air should, on the other hand, produce more satisfactory results. One expensive method now available involves passing the shoes through a heating chamber on a conveyor belt. In the first half of the chamber moist air is circulated at high speed to stress-relieve the surface. The air circulating in the second half is hot and dry to remove all moisture and set the upper firmly. Hot air blown from a hair dryer can carry out the same operation.

II.6.7 Bottom Roughing (Operation reference No. 25)

The object of this operation is to provide a good keying surface for the adhesive used to attach the lasted margin of the upper to the sole unit. The operation removes the finished outward facing surface of the upper material and flattens the pleats round the forepart and seat.

(i) Manual bottom roughing

For production scale 1, this operation can be performed manually with a knife for levelling the folds and a wire brush for roughening the grain.

(ii) Bottom roughing machines

For scales 2 and 3, small electric portable drilling machines, costing less than US$250 may be used for this operation. They are fitted with a wire brush or emery covered wheel and may be clamped to a bench top. Some skill is necessary to ensure that a clean "feather" edge is produced where the sole and upper meet.

A variety of similar machines working on the same principle as the electric drill arrangement are available. Some of these are fitted with wide scouring bands and powerful dust extractors. Figure II.11 shows a simply made scourer for small volume production.

For production scales 4 and above, fully automatic roughing machines are also available. They require the operator to simply fix the lasts carrying the shoes on fixtures, and remove them once the bottoms have been scoured. The cost of these machines is however high (US$25,000 each) and they should not be adopted unless it may be shown that they are more profitable than simpler machines.

II.6.8 Shank Attaching (Operation reference No. 26)

Shanks not riveted to the bottom of the insole before lasting are attached at this stage. They can be stapled in position with a manually powered or pneumatic powered staple gun, or can be attached with adhesive applied by brush.


Figure II.11 A simply made scourer for small volume production.

PARTS LIST

A. Small electric motor.

B. Wooden disc turned true to bore.

C. Bolts, nuts and washers to hold motor.

D. Work bench.

E. Replacable emery cloth cemented to outer diameter of disc.

F. Steel clamping plates bored for shaft and drilled for clamping screws. Clamps are screwed to disc with countersunk head screws,

G. Gib headed tapered machine key for securing and driving clamp plates. Guard cap shown dotted on figure.

H. Electric wire from mains.

Notes:

- Check before use that wheel is sufficiently strong so that it does not break up or loosen at high speed.


- The operator should wear goggles and a face mask since no wheel guards or dust extractors are fitted to cement a cap over the head of the key to avoid injury.


- As an alternative to the system shown, a power drill could be used with the disc clamped in its chuck.


- A pully belt drive from the motor to a separate shaft to carry one or more wheels would be more satisfactory than the design shown, but would be considerably more complicated.


- Polising discs, grind stones and rotary cutters can be power driven in a method similar to the one shown here.

II.6.9 Bottom Cementing (Operation reference No. 27)

A brush or cement applying machine can be used to spread adhesive onto the roughened lasted margin on the bottom of the shoe. Cement applying nozzles fed from drums pressurised by a hand pump via a flexible tube are available. The adhesive may be dried naturally or by heat.

II.6.10 Bottom Filler Insertion (Operation reference No. 28)

Pieces of felt or scraps of thick leather are attached to the eliptical area in the middle of the forepart of the insole, and to the exposed part of the seat inside the lasting margin. Usually, the operation is performed manually. The cement can be applied to one side of the component with a manually fed, electrically powered machine.

II.6.11 Sole Laying (Operation reference No. 29)

Before placing the sole unit on the shoe bottom, the adhesive on both surfaces must be activated. This is often done by infra-red or quartz-halogen radiant heating.

The next step is to attach the sole unit to the shoe bottom. A number of techniques are available for this operation.

(i) Manual sole laying

Manual sole laying is often used by certain small enterprises. It consists of hammering the units to effect adhesion after careful positioning of the components. Unless care is taken, hammering may cut the upper at the feather edge.

Another technique consists in applying a steady pressure for an extended period of time, so that the cement is allowed to permeate into the lasting margin. This technique is likely to be superior to hammering. It may be adopted for scales 1 to 3, using manually operated machines that may exert pressures of over a tonne. In this type of machines, the load is applied through a large hand wheel which, by means of a reduction gear, raises and lowers a pair of hold-down posts under which the lasted shoe sits. The sole unit is pressed into a hard rubber pad set in a metal box.

(ii) Hydraulically powered machines

For scales 4 and above, elaborate hydraulically powered machines, which can apply loads of about three tonnes, are widely used. Less expensive machines using compressed air to apply the load through a flexible rubber diaphragm are also available.

II.6.12 Last Removal (Operation reference No. 30)

Once the sole is attached, the last is removed or slipped from the shoe. This can be done manually using a lasting jack to support the last, or with the help of a pneumatically powered last-slipping machine. Whether lasts are slipped by hand or machine, top lines and seams can be damaged if care is not taken.

At this stage, the shoes are ready for finishing operations.

II.7 Shoe finishing and packing (Operation reference No. 31)

II.7.1 Crease Removal

Crease removal is the first operation of the finishing stage. It involves the removal of any creases on fine grained upper leathers. Various types of machines may be used for this purpose.

(i) Hot air treeing machine

These machines produce a blast of steam as well as one of hot air. They are appropriate only at higher levels of output such as 3 and 4. These machines are available at various levels of sophistication. Figure II.12 shows a simply made hot treeing machine for small volume production.


Figure II.12 A simply made hot treeing unit for small volume production

PARTS LIST

A. Domestic electric hair dryer stapled to bench on both sides.

B. Domestic electric kettle with handle removed

C. Lengths of copper or steel tube flattened into slits at one end to form fish tails for dryer outlet and kettle spout,

D. Short metal strip bent to remove drips.

E. Two lengths of bent wires for supporting dryer.

F. Work bench.

G. Leads from mains.

Notes:

The best size for the fish tail slots should be found by means of trials.


It is very dangerous to let hair dryers get wet.

(ii) Hair dryers

For lower levels of output, such as scales 1 and 2, a powerful domestic or professional hair dryer is capable of producing the same required finish as do treeing machines. However, the output rate is in this case much lower. The cost of a hair dryer is approximately US$30.

II.7.2 Upper Repair

The next step is to repair damages to the surface of the upper material. This may be done with the help of wax crayon to cover blemishes and with cement to fix down cuts.

II.7.3 Sock Insertion

A sock (which may have a backing pad of foam cemented to it) can be cemented either manually, with a brush, or by passing it through an electrically powered cement applying machine. The sock is then inserted into the shoe.

II.7.4 Upper Dressing

The sequence of this operation includes the following:

- Cleaning of upper with a detergent, e.g. a proprietary cleaning fluid or a spirit based solvent,

- Application of a cream dressing by hand,

- Application of a liquid dressing with a sponge or a sprayer. Some manufacturers in developing countries use a dressing mixture made of car enamel of the required pigmentation and solvent,

- An alternative to liquid dressing is the brushing of uppers. This may be done wth hand held brushes, bench mounted power drills fitted with mops, and specially designed brushing machines.

II.7.5 Lacing

In lacing styles, laces are inserted into the uppers by hand.

II.7.6 Packaging

Information on shoe styles and sizes are written or printed on labels which are attached to packaging.

Shoe boxes can be assembled either on machines or cemented or stapled by hand.

II.7.7 Inspection

Shoes rejected at the final inspection are returned to the repair section.

III. Table of technical data

III.1 Material handling resources, work force and production floor area

Table II.3 refers to type 1 footwear and to the four scales of production covered by this memorandum. However, it also constitutes a useful guide for other types of footwear. The provided floor area should, for example, be approximately the same for footwear types 1 to 4 at each particular scale (e.g. for scale 3, the area should be approximately 250 m2 for plants producing footwear types 1 to 4).

III.2 Workforce allocation: Table II.4

The table on workforce allocation gives a detailed account of the allocation of production workers with respect to each operation and scale of production. It also provides information on the level of skills required for each operation.

III.3 Equipment specification: Table II.5

Table II.5 provides information on the type and number of equipment required for each operation and scale of production. The four scales of production are shown on the same table in order to facilitate comparisons of equipment requirements between different volumes of output.

IV. Floor plans for production areas

A floor plan for each of the four scales considered in the memorandum are provided in this section. These floor plans are for type 1 footwear, but they may also partially apply to other types of footwear. The floor plan for scale 4 relates to the whole plant area (i.e. production areas as well as non-production areas - e.g. storage areas and offices).

Table II.3 Materials handling resources, work force and production floor area for type 1 footwear

Group of Operations

Scale 1 8prs/8hrs

Scale 2 40prs/8hrs

Scale 3 200prs/8hrs

Scale 4 1000prs/8hrs.

Raw materials storage

Racks

Racks

Separate store with storekeeper

Stores with storekeeper

Handling in cutting dept.

Boxes of work, carried

Boxes of work, carried

Boxes of work, carried

Boxes on gravity conveyor

Handling in preparation, stitching and upper finishing

Boxes

Mobile racks

Boxes on gravity conveyor

Boxes on gravity conveyor

Handling and storage before lasting

Rack

Mobile rack, last bins, bottom racks

As for scale 2

Buffer store to sort batches

Handling through making dept.

Carried by hand

Mobile trolleys

Mobile trolleys

Unpowered monorail tracks

Handling through finishing dept.

Carried by hand

Carried by hand

Mobile trolleys

Unpowered monorail tracks

Finished goods storage

Rack

Racks

Sharing raw material store

Separate store with storekeeper

Estimated cost of equipment

$100

$250

$750

$2,000

Number of indirect employees required 2

1

3

5

15

Production floor area(m2)

30

70

250

700

Table II.4 Workforce allocation at each output scale level for type 1 footwear

Up. Ref. No.

OPERATIONS

Scale 1 8prs/8hrs

Scale 2 40prs/8hrs

Scale 3 200prs/8hrs

Scale 4 1000prs/8hrs.

1

Cutting uppers

0.8 s

1.5 s

6 s

16 s

2

Leather split




1 ss

3

Lining marking


1.0 ss

1 us

1 us

4

Stitch marking




3 us

5

Hole punching



2 ss

1 ss

6

Sock embossing




2 ss

7

Skiving



2 ss

4 ss

8

Edge folding and cementing




3 us

9

Stitching uppers

1.0 s

2.0 s

9 s

40 s

10

Seam reducing


1.0 s

1 us

1 us

11

Taping




1 us

12

Eyelet reinforcing



1 us

1 us

13

Punch and eyelet insertion




1 us

14

Temporary lacing



3 s

2 us

15

General felting and puff attaching




2 ss

16

Upper trimming




8 s

17

Insole preparation

0.2

0.5 ss

1 ss

4 ss

18

Sole cementing, and drying




1 ss

19

Insole tacking

1.0 s

1.5 s

1 us

1 us

20

Stiffener insertion




1 us

21

Upper conditioning





22

Cement lasting



3 s

9 s

23

Tack removing and inspection


1.5 ss

1 ss

2 ss

24

Heat setting




1 us

25

Bottom roughening



1 ss

2 ss

26

Shank attaching




1 us

27

Bottom cementing



1 us

2 us

28

Bottom filling




1 us

29

Sole laying



1 ss

2 ss

30

Last removal


1.0 s

4 s

2 us

31

Upper finishing




14 s

TOTAL DIRECT WORKERS

3

10

38

130

Where an operative is only required part-time on an operation, the work is split.

*s = skilled (4 months training)
ss= semi-skilled (3 weeks training)
us= unskilled (1 week training)

Table II.5 Methods and Equipment Specifications for Type 1 footwear

Output per 8 hours: 8, 40, 200 and 1,000 pairs.

Type: leather-upper cement lasted shoes with cemented-on unit soles

Op. Ref No.

Operations and Major Equipment Items

Equipment source

No. required by scale

Estimated unit cost ($)




1

2

3

4


1

CUTTING UPPERS








- clicking bench

local

1

2

6

11

30


- clicking board

local

1

2

6

11

15


- cutting knives

sup. list 1

3

10

20

35

6


- mech. swing arm

sup. list 1

-

-

1

5

2,200


clicking press







2

LEATHER SPLITTING








- Band knife splitting machine

sup. list 2

-

-

-

1

10,000

3

LINING MARKING








- clicking bench


OP1

OP1

-

-


- marking bench

local

-

-

1

-

25

- lining stamping machine

sup. list 3

-

-

-

1

1,700

4

STITCH MARKING


OP1

-

-

-



- clicking bench








- preparation bench

local

-

1

-

-

25


- marking bench

local

-

-

OP3

2

25


- manually operated stitch marking machine

sup. list 4




1

600

5

HOLE PUNCHING








- bench

local

OP1

OP4

1

-

25


- handheld punches

Loc/foreign

1

1

1

-

-


- perforating mach.

sup. list 5

-

-

-

1

3,500

6

SOCK EMBOSSING








- press using electric iron element

local

1

1

-

-

35


- hand controlled press

sup. list 5

-

-

1

-

550


-semi-auto sock embosser

sup. list 6

-

-

-

1

3,000

7

SKIVING








- plate glass sheet

local

1

1

2

2



- paring knives

sup. list 1

3

6

12

12

6


- manually controlled skiving machines

sup. list 7

-

-

-

2

2,000


- skiving benches

local

OP1

OP4

2

-

50


- hand work benches

local

-

-

-

2

50

8

EDGE FOLDING AND CEMENTING








- bench


OP1

OP4

OP7

-



- mechanical edge

sup. list 8

-

-

-

1

3,500

9

STITCHING UPPERS








All machines listed in-








clude motors, clutches








and stands. The mix of








types is as follows:







Needle Presser Bed Features







Single roller flat basic

sup. list 9

1

1

4

16

740

Single roller post basic

sup. list 9

-

2

3

10

950

Single roller flat light speed light duty

sup. list 9

-

-

1

4

650

Single roller cy.arm basic

sup. list 9

-

-

1

3

1,700

Single roller post under edge trimming

sup. list 9

-

-

-

3

2,000

Single roller flat zig zag

sup. list 9

-

-

-

2

740

Single clamp flat barring auto

sup. list 9

-

-

-

1

2,200

Twin roller flat cording

sup. list 9

-

-

-

1

2,400

Single foot cyl, arm manual repair

sup. list 9

-

-

-

1

1,000

Twin roller flat silking machine

sup. list 9

-

-

-

1

2,100

10

SEAM REDUCING







- fitting bench, two steel tubes with 1 fixed to bench

local

1

1

1

-

30


- seam reducing machine

Sup. list 10

-

-

-

1

2,200

11

TAPING


OP10

OP10

OP10

-



- bench








- tape dispensing mach.

Sup. list 11

-

-

-

1

400

12

EYELET REINFORCING








- eyeletting bench

local

OP10

OP10

1


25


- tape dispensing mach.

Sup. list 11

-

-

-

1

400

13

PUNCHING AND EYELET INSERTION








- hand operated punch and clincher

Sup. list 13

2

2

-

-

10


- treadle operated punching and clinching machine

Sup. list 13

-

-

1

-

180


- hole punching mach.

Sup. list 13

-

-

-

1

500


- auto feed eyeletter

Sup. list 13

-

-

-

1

400


- bench


OP10

OP10

OP12

-


14

TEMPORARY LACING

local

OP10

OP10

1

2

25


- lacing bench







15

GENERAL FITTING AND PUFF ATTACHING








- fitting bench

local

OP10

OP10

2

1

25


- loose upper roughing machine

Sup. list 15

-

-

-

1

1,600

16

UPPER TRIMMING








- powered trimming mach.

Sup. list 16

-

-

-

2

850


- bench


OP10

OP10

OP15

-


17

INSOLE PREPARATION








- bench


OP1

OP1

OP1

-



- press knives


-

-

30

50

40


- sole bench


-

-

1

1

25


- insole moulding mach.

Sup. list 17

-

-

-

1

8,000


- insole bevelling mach.

Sup. list 17

-

-

-

1

2,500

18

SOLE CEMENTING AND DRYING








- wooden rack

local

1

1

6

10

10


- bench

local

OP10

OP1

OP17

1

25

19.

INSOLE TACKING








- lasting bench

local

1

1

1

1

30


- tubular steel jacks

local

1

2

1

1

5

20

STIFFENER INSERTION








- conditioning bench

local

OP19

OP19

OP19

1

25

21

UPPER CONDITIONING








- steamer using electric kettle element and feed tank

local

1

1

2

-

60


- lasting heater

Sup. list 21

-

-

-

1

250

22

CEMENT LASTING








- lasting pincers and knives

Sup. list 22

3

6

20

50

4


- lasting benches

local

OP19

OP19

3

4

25


- jacks


-

-

3

7

5


- manually operated drafting machine

Sup. list 22

-

-

1

-

3,000


- pull toe lasting mach.

Sup. list 22

-

-

-

1

18,000


- back part moulding machine

Sup. list 22

-

-

-

1

10,500

23

TACK REMOVAL AND INSPECTION








- tack lifters

Sup. list 23

2

2

3

6

4


- bench

local

OP19

1

1

2

25

24

HEAT SETTING








- hand held hot air dryer

local

1

1

1

-

30


- wrinkle chasing mach.

Sup. list 24

-

-

-

1

1,200


- bench


OP19

OP23

OP23

-


25

BOTTOM ROUGHING








- hand held wire brush

local

1

-

-


20


- scouring buff without dust extractor

Sup. list 25

-

1

1

-

400


- bottom roughing mach.

Sup. list 25

-

-

-

2

2,400


- bench


OP19

-

-

-


26

SHANK ATTACHING








- bench

local

1

OP23

1

1

25

27

BOTTOM CEMENTING








- cementing bench

local

OP26

OP23

1

2

25

28

BOTTOM FILLER INSERTION








- bench

local

OP26

OP23

OP27

1

25

29

SOLE LAYING








- manually powered sole press

Sup. list 29

1

1

1

-

1,900


- twin station hydraulic sole presses

Sup. list 29

-

-

-

2

8,000


- electric fire for heat activation local


1

1

2

-

40


- heat activator.

Sup. list 29

-

-

-

2

450

30

LAST REMOVAL








- lasting jack

local

OP19

1

1

2

5


- benches

local

-

-

-

2

25

31

UPPER FINISHING








- finishing bench

local

OP26

1

3

12

25


- hot blast treeing mach.

Sup. list 31

-

-

-

1

1,200


- spray booth and guns

Sup. list 31

-

-

-

1

500


- mopping and polishing machine

Sup. list 31

-

-

-

1

400


- manually operated cementing machine

Sup. list 31

-

-

-

1

200

1 See equipment suppliers list in Appendix II.

2 The same pieces of equipment may be used in a number of operations. This is indicated by reference to the number of operation where the equipment is used for the first time (e.g. OP1, OP3).


Figure II.13 Layout of production area for type 1 footwear - 8 pairs/day

Designation of work stations

1. Clicking
2. Embossing
3. Stitching
4. Upper finishing and packing
5. Lasting
6. Bottom preparation
7. Sole laying


Figure II.14 Layout of production areas for type 1 footwear - 40 and 200 pairs per day

Keys to layouts*

* The identification numbers in the diagrams are not Operation Reference Numbers.

40 pairs/8 hours

200 pairs/8 hours

1. Clicking

1. Clicking machine

2. Upper preparation

2. Hand clicking

3. Embossing

3. Marking

4. Stitching

4. Embossing

5. Upper finishing

5. Skiving

6. Lasting

6. Stitching

7. Bottom preparation

7. Seam reducing and taping

8. Sole laying

8. Eyeletting

9. Finishing and packing

9. Lacing


10. Upper fitting


11. Sole bench


12. Insole tacking


13. Lasting


14. Tack removal


15. Bottom roughing


16. Shank attaching


17. Bottom cementing


18. Sole laying


19. Finishing and packing


Figure II.15 Plant layout for type 1 foot-year - 1000 pairs per day

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