Small-Scale Manufacture of Footwear (ILO - WEP, 1982, 228 p.) CHAPTER III. MANUFACTURING TECHNOLOGIES FOR FOOTWEAR TYPES 2 TO 6 (introduction...) I. Type 2 footwear: Leather-upper, cement-lasted shoes with directly moulded-on soles (introduction...) I.1 Scrim attaching (Operation reference No. 32) I.2 Heel Core attaching (Operation reference No. 33) I.3 Bottom solutioning (Operation reference No. 34) I.4 Direct sole mouldinq-on (Operation reference No. 35) I.5 Subsequent operations I.6 Tables of technical data for type 2 footwear II. Type 3 footwear: Leather-upper, tack-lasted shoes with machine-sewn leather soles (introduction...) II.1 Insole preparation (Operation reference No. 36) II.2 Sole preparation (Operation reference No. 37) II.3 Insole tacking (Operation reference No. 38) II.4 Tack lasting (Operation reference No. 39) II.5 Bottom pounding (Operation reference No. 40) II.6 Bottom cementing (Operation reference No. 41) II.7 Sole laying (Operation reference No. 42) II.8 Last removal (Operation reference No. 43) II.9 Sole stitching (Operation reference No. 44) II.10 Sole levelling (Operation reference No. 45) II.11 Seat nailing (Operation reference No. 46) II.12 Heel attaching (Operation reference No. 47) II.13 Re-lasting (Operation reference No. 48) II.14 Heel trimming (Operation reference No. 49) II.15 Edge trimming (Operation reference No. 50) II.16 Bottom finishing (Operation reference No. 51) II.17 Tables of technical data III. Type 4 footwear: Welded synthetic upper, string lasted shoes with moulded-on soles (introduction...) III.1 Cutting and welding upper components (Operation reference No. 52) III.2 Welding upper components together (Operation reference No. 53) III.3 Lasting string attaching (Operation reference No. 54) III.4 String lasting and moulding-on of soles (Operation reference No. 55) III.5 Sock insertion (Operation reference No. 56) III.6 Tables of technical data IV. Type 5 footwear: Stitched synthetic upper cement-lasted sandals and casual shoes with built or unit soles (introduction...) IV.1 Sole and insole preparation (Operation reference No. 57) IV.2 Heel preparation (Operation reference No. 58) IV.3 Lasting uppers (Operation reference No. 59) IV.4 Heel attaching (Operation reference No. 60) IV.5 Sole, finishing (Operation reference No. 61) IV.6 Tables of technical data V. Type 6 footwear: Single injection, moulded plastic sandals (introduction...) V.1 Single injection moulding technique and equipment (Operation reference No. 62) V.2 Tables of technical data

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

CHAPTER III. MANUFACTURING TECHNOLOGIES FOR FOOTWEAR TYPES 2 TO 6

This chapter considers techniques of manufacturing footwear types 2 to 6. Methods and equipment discussed in Chapter II are referred to in this chapter but not dealt with again. Production stages are first described for each footwear type and are then followed by technical tables covering the four selected scales of production.

I. Type 2 footwear: Leather-upper, cement-lasted shoes with directly moulded-on soles

The moulding-on process occurs in a single operation. It is a development of the vulcanising method of forming a rubber blank by heat and pressure while bonding its top surface to the shoe bottom.

The principal materials used for this type are Ethylene-Vinyl-Acetate (EVA), Thermoplastic Rubber, Polyvinyl Chloride (PVC) and Polyurethan (PU). This section refers to (PVC) and (PU), The popularity of these methods rose rapidly between the mid 60s and the energy crisis of the mid-70s, and has since continued to grow but at a reduced rate.

Table III.1 lists the manufacturing stages for this type of footwear. Operations unique to this type are listed without asterisks and are discussed below.

I.1 Scrim attaching (Operation reference No. 32)

To prevent soling material from stocking to the insole and filler, it is necessary sometimes to cement a paper scrim to the forepart of the lasted shoe so that its edge overlaps the lasted margin. This paper scrim, which is pre-cut to be a little smaller than the sole bottom, also prevents the plastic from forcing its way between the upper and insole.

Equipment - the equipment required for this operation is a cement pot, brushes and a lasting jack to hold the shoe while attaching the scrim.

I.2 Heel Core attaching (Operation reference No. 33)

Heel core attaching is an unskilled cementing operation. Heel cores, also called filler blocks, are often cardboard blanks. These cores are attached to the underside of the seat before moulding and are buried in PVC during moulding.

Advantages - these cores speed up cooling, make the soles cheaper, lighter and reduce their elasticity. Heel cores replace the seat fillers used on cemented-on sole shoes.

I.3 Bottom solutioning (Operation reference No. 34)

A polyurethane (PU) solution is applied to the lasting margin to ensure that the PVC adheres to it.

The following operation is last removal. It has already been dealt with in Chapter II.

I.4 Direct sole mouldinq-on (Operation reference No. 35)

Direct sole moulding-on constitutes one of a number of alternative bottoming processes. Figure III.1 shows the sequence of operations used in bottoming processes for footwear types 1 to 5. Soles may be moulded-on (footwear types 2 and 4), cemented-on (footwear types 1 and 5) or sewn-on (footwear type 3) . The figure highlights the relative complexity levels of the five alternative bottoming processes.

Table III.1 Stages in the production of leather-upper, cement-lasted shoes with directly moulded-on 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*	Stitching of uppers	Threads and tapes
Stitched upper finishing	10*	Seam reducing
	11*	Taping	Tapes
	12*	Eyelet reinforcing
	13*	Punching and eye-let insertion	Eyelets
	14*	Temporary lacing	String
	15*	General fitting and puff attaching	Trim, puffs
	16*	Upper trimming
Bottom component preparation	17*	Insole preparation	Insole board
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
	32	Scrim attaching	Scrim paper
	33	Heel core attaching	Heel cores
	34	Bottom solutioning
	30*	Last removal
	35	Direct sole moulding on	Sole raw materials
Finishing	31*	Upper finishing operations and packing	Packing materials

Note: The operations marked (*) are discussed in the section dealing with leather-upper, cement-lasted shoes with cemented-on soles.

Figure III.1 Comparison of alternative bottoming processes

I.4.1 Work-in-progress storage

A buffer stock of work-in-progress waiting for sole moulding is required for the following reasons:

(i) extended runs of one size and style are desirable as mould changing is time consuming,

(ii) moulding machines are expensive and, therefore, small enterprises run the machines for more than one shift a day.

Mobile storage racks are suitable for this operation.

I.4.2 Moulding machines

The use of a moulding machine is required regardless of the scale of production.

(i) Description of the moulding process

The soling material, usually PVC, is supplied in bags of granules. The bags are loaded into a hopper feeding a heating chamber. A revolving screw or plunger forces the softened plastic through a nozzle into a cavity. This cavity's upper surface is formed by the shoe bottom. During moulding, the shoes are mounted on last-shaped footforms of steel or aluminium. Average moulding stations can complete a full mould-on cycle in less than 3 minutes.

(ii) Equipment

Moulding machines are available with single, twin or multiple stations. Machines with twelve stations or more are uneconomical whenever frequent mould size and style changes occur since every station must be stopped for each change. A battery of small machines (e.g. with a single or twin stations) may therefore be preferable to a single multiple stations machine even when large outputs are contemplated. In particular small enterprises should employ single or twin stations moulding machines.

A recent innovation is the introduction of multi-mould machines that run three or four different styles simultaneously. This innovation overcomes, to some extent, the problem related to frequent size and style changes.

Prices of moulding machines vary with the precision of injection equipment and the quality of the heating arrangement. Moulds and footforms are made by specialist firms or machinery suppliers and are justifiable only for long sole style lives.

(iii) Machine operating tasks

An operator on a twin station machine can, normally, perform additional tasks within the moulding cycle time. Little skill is required to mount shoes onto the metal footforms, unload them after moulding and to remove any moulding flash by hand. Any waste PVC is ground and re-melted for further use.

(iv) Moulded-on polyurethane(PU)

An increasing number of footwear manufacturers in developed countries produce directly injected moulded-on soles of PU which has better wear resistance than PVC but has only one third of its density.

Process: The PU moulding process is similar to that of PVC except that a hardener and a resin in liquid states are injected into the mould. They react in the mould and expand into a cellular structure which fills the mould cavity and solidifies. Small enterprises in developing countries will probably find PU moulding unattractive because the process is relatively complex. Furthermore, the technical back-up from chemicals and equipment suppliers may be inadequate and could be responsible for frequent disruptions of production.

I.5 Subsequent operations

Processing stages after sole moulding are the same as those used for type 1 footwear, namely finishing and packing. These operations are described in Chapter II and need not be further elaborated in this chapter.

I.6 Tables of technical data for type 2 footwear

Table III.2 provides estimates of labour requirements for scales of production 1 to 4, while Table III.3 lists the additional equipment needed for Type 2 footwear.

Table III.2 Workforce allocation at each output scale for type 2 footwear

Op. Ref	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 splitting				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/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/eyelet insertion				1 us
14	*Temporary lacing			3 s	2 us
15	*General fitting and puff insertion				2 ss
16	*Upper trimming				8 s
17	*Insole preparation	0.2 ss	0.5 ss	1 ss	4 ss
19	*Insole tacking				1 ss
20	*Stiffener insertion	0.5 s	1.5 s	1 us	1 us
21	*Upper conditioning				1 us
22	*Cement lasting
23	*Tack removing/inspection			3 s	9 s
24	*Heat setting		1.0 s	1 ss	2 ss
25	*Bottom roughing
26	*Shank attaching				1 us
32	Scrim attaching			1 us	1 us
33	Heel core attaching				1 us
34	Bottom solutioning			1 us	2 us
30	*Last removal				2 us
35	Mould-on sole			1 s	2 s
31	*Upper finishing	0.5 s	1.0 s	4 s	14 s
	TOTAL DIRECT WORKERS	3.0	10	38	128

Keys to table: s = skilled (4 months training). ss = semi-skilled (3 weeks training). us = unskilled (1 week training)

Notes: *See type 1 equipment specifications for these operations. Moulding on is unlikely to be undertaken at daily output levels of 8 and 40 pairs. Jobs are shared by operatives in some cases.

Table III.3 Methods and equipment specifications for type 2 footwear

Output per 8 hours: 8, 40, 200 and 1000 pairs.

Type: Leather-upper, cement-lasted shoes with moulded-on soles.

Op. Ref. No.	Operations and Major Equipment required	Equipment source	No required by scale				Estimated unit cost ($)
			1	2	3	4
1-26	See Type 1 at same scale
32	SCRIM ATTACHING
	See Type 1 for scales 1 and 2		OP 20	OP23	-	-
	- scrim bench	local	-	-	1	1	25
33	HEEL CORE ATTACHING	local
	See type 1 for scales 1 to 3 - core bench		OP 20	OP23	OP 32	1	25
34	BOTTOM SOLUTIONING
	See type 1 for scales		OP 20	OP23	-	-
	- solutioning bench	local	-	-	1	2	25
30	LAST REMOVAL
	See type 1 at same scale
35	MOULD-ON SOLE
	- single station PVC sole injection moulding-on machine	Sup. list 35	-	-	1	-	23,000
	- twin station PVC sole injection moulding-on machines (1 machine if work on a two-shift basis)	Sup. list 35	-	-	-	1/2	35,000
35	MOULD-ON SOLE
	- sets of moulds and foot forms	Sup. list 35	-	-	8	16	2,125
	- preheater	Sup. list 35	-	-	1	2	800
	- granulator	Sup. list 35	-	-	-	1	1,400
31	UPPER FINISHING AND PACKING
	See type 1 at same scale

II. Type 3 footwear: Leather-upper, tack-lasted shoes with machine-sewn leather soles

The type of shoes considered in this section are leather upper, tack-lasted shoes with stitched on leather soles.

As a result of the development of effective adhesives during the last thirty years, large scale footwear manufacturing enterprises in developed countries have steadily reduced their use of tack-lasting in favour of cement-lasting. Similarly, cemented-on unit soles have replaced stitched-on soles and heels finished on the shoe. However, the traditional techniques employed in constructing tack-lasted, stitched-on sole shoes may still constitute an appropriate alternative. They are often used by small-scale enterprises in developing countries, where the available insole materials are liable to delaminate and where locally tanned sole leather is more readily available than unit soles for each size and shape of last.

Some of the operations and equipment described in this section are used in two other methods of construction whereby the sole is attached by stitching. The first is known as the veldtschoen construction while the second is known as the welted construction. Neither of these methods of construction involves tack lasting of the complete shoe. The veldtschoen method rarely uses leather soles. The welted method is now almost exclusively used on expensive walking shoes for men which are unlikely to be made by small enterprises in developing countries. For these reasons, it was decided to describe the methods available for manufacturing tack-lasted stitched-on sole shoes only. Such shoes are often referred to as machine-sewn shoes.

Table III. 4 shows the operation sequence that can be used to construct these shoes. The operations marked by an asterisk have been dealt with in Chapter II and are thus not discussed below.

II.1 Insole preparation (Operation reference No. 36)

Insoles used on tack-lasted shoes require to be stouter than cemented insoles. The best insole material for this type of shoes is leather. Leather insoles are cut in the same way as leather soles, as described below. An often used substitute material is fibreboard. Insoles made with this material are cut according to the same techniques as those described for cemented-on soles. Insoles are further processed in the same way as fibreboard and composition soles used in cemented-on sole shoes.

Table III.4 Stages in the production of leather-upper, tack-lasted shoes with stitched-on leather soles

Production stages	Op. Ref.	Operations	Major materials
Upper cutting	1*	Cutting upper components	Skins and lining
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*	Stitching of uppers	Threads and 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	36	Insole preparation	Insole board
	37	Sole preparation	Sole leather
Making	38	Insole tacking
	20*	Stiffener insertion	Heel stiffeners
	21*	Upper conditioning
	39	Tack lasting
	23*	Tack removal, inspection
	40	Bottom pounding
	24*	Heat setting
	26*	Shank attaching	Shanks
	41	Bottom cementing
	28*	Bottom filler insertion
	42	Sole laying
	43	Last removal
	44	Sole stitching
	45	Sole levelling
	46	Seat nailing
	47	Heel attaching	Heels
	48	Re-lasting
	49	Heel trimming
	50	Edge trimming
	51	Bottom finishing
	30*	Last removal
Upper finishing	31*	Upper finishing operations and packing	Packing materials

The operations marked with (*) are discussed in the section dealing with leather-upper, cement-lasted shoes with cemented-on soles.

II.2 Sole preparation (Operation reference No. 37)

Small enterprises which sell their footwear at the lower end of the local market may find it unnecessary to subject soles to the full sequence of operations described below.

II.2.1 Sole cutting

(i) Description of sole cutting techniques

Hides used for soles come from the largest animals. Some manufacturing concerns only use the portion down the back of each side and either use the remainder for other applications or re-sell it. The cutting pattern is usually regular and disregards all but the very largest blemishes since it is considered more economical to discard defective soles than break the pattern to avoid damaged areas. Due to its thickness, sole leather can rarely be cut cleanly the whole way with a mechanical press. Consequently, soles are cut oversize and are then edge-pared before being attached to the shoe. Soles can also be hand clicked, and then hand pared.

(ii) Sole cutting equipment

Equipment for this operation includes beam presses with heavy cutting knives. Often, only one knife is used, the hide being turned over in order to make both left and right soles.

II.2.2 Evening

Highly mechanised factories use automatic evening and grading machines. These machines, in a single cycle sense the thickness of the thinnest part of the sole and' reduce the thickness of the remainder part to this thickness. They also stamp on a number corresponding to the final thickness. It is then simple for the operator to sort the soles into boxes or piles. On simple evening machines, it is necessary to adjust the thickness manually. Evening can be also carried out manually.

II.2. 3 Tempering

Tempering involves immersing the soles in clean water for an extended period to increase their workability. The operation can be greatly speeded up if a pressure vessel is used. In some systems, as much as a 100 bars pressure is used to force water into the soles. It is important that the temper is maintained until the soles have been attached.

II.2.4 Edge paring

The purpose of this operation has been described in the sole cutting section. Machines called planetary edge rounders can be used. They employ a vertical knife and two wooden templates (i.e. cum-clamps which grip the sole between them). The knife automatically follows the contour of the lower template and produces a clean edge. Performing the operation by a hand held knife requires effort and some skill to maintain a smooth, square edge.

II.2.5 Waist reducing

To give the soles a light appearance in the waist, the outside edges can be tapered in a manner similar to that used in skiving. Usually, about a quarter of the sole thickness is removed at the outside and the 20 mm. down the middle is left at full thickness.

II.2.6 Grading

This is an inspection operation in which the flexibility, grain, size and general quality of each sole is assessed, and suitable lefts and rights are matched up.

II.2.7 Channel cutting

(i) Process

To prevent the stitching on the grain side of the sole from rubbing against the ground, it is recessed in a channel with a lip cemented over it. The channel is cut at an angle to the sole bottom from near the sole edge back in towards the middle. A small groove is cut at the bottom of the slit. The 'flap' is lifted before stitching and cemented back in place afterwards. As an alternative, to a channel, an open groove can be cut so that the stitches can be seen on the finished shoe. Care is required to keep stitches in the groove. More latitude is possible when stitching chanelled shoes.

(ii) Channel cutting equipment

The equipment used for channel cutting is a hand cranked machine through which the sole is fed by a pair of rollers past a blade fixed at the required angle. By depressing a pedal, the operator can alter the angle at which the knife cuts at different points round the waist and forepart. Both the machine method and cutting with a hand held knife in a manner reminiscent of hand skiving require considerable skill.

II.2.8 Conforming

This operation moulds the sole to the shape of the last so that it fits snugly on the finished shoe. The alternative methods of doing this job are similar to those available for moulding insoles in the cemented-on construction.

II.2.9 Sole cementing

The upper, flesh side of the soles can be cemented at this stage with a neoprene or a resin based latex solution, and then dried.

II.3 Insole tacking (Operation reference No. 38)

Insole tacking is carried out in a similar fashion as for cemented-on sole shoes, except that the last bottom has a steel plate over it which clenches the tips of the lasting tacks back into the top surface of the insole. Holes are left in the plate at the seat, waist and on the forepart so that insoles can be temporarily attached by tacks driven into the wood. Some experience in placing the tacks is required since the holes in the plate cannot be seen during the operation.

II.4 Tack lasting (Operation reference No. 39)

Although many shoes of this type are now lasted by other methods (e.g. cement-lasting or combinations of cement-seat, tack-side and cement-forepart lasting), this section describes techniques and equipment for tack-lasting the complete upper. Tack-lasting combined with stitched-on soles results in stiff, and rather inflexible foreparts. To compensate for this, additional 'toe spring' is often allowed for in the last used for this construction.

II.4.1 Manual lasting techniques

(i) Back tacking

Footwear is usually hand tack-lasted with a round vertical steel peg, or lasting jack, inserted into the socket on top of the last. In this position, the bottom of the insole provides an upwards facing surface ready for tacking. Pincers, incorporating a hammer head, similar to those used for cement-lasting, are normally used for this operation. After lining up the back-seam, the upper is tacked to the seat of the insole by one or two tacks.

(ii) Pulling over

Any lining material must always be pulled tight before pulling on the upper itself. Normally, the first lasting pull is straight over the toe. The pincers lever the lasting allowance of the upper over the toe of the insole. The thumb of the free hand holds the material while the pincers push a tack into position. The tack is then hammered down. This is basically the method used to insert all tacks, although in some cases it is necessary for the pincers to pleat and twist the margin to obtain a smooth feather-edge line. When soles are to be stitched-on, tacks are placed well back from the insole edge to leave room for the stitching. Tacks are inserted on either sides of the toe to stretch the upper forward from the heel over the toe. The seat and forepart just ahead of the waist are then tacked.

(iii) Seat lasting

Strains are taken and tacks inserted alternatively at approximately 5 mm. intervals round one half, and then the other half of the seat. Small pleats are produced between each tack.

(iv) Toe lasting

The same procedure as for seat lasting is also used for toe lasting. More skill is generally required to remove puckers over the toe and to pleat the material neatly than is needed for seat lasting.

(v) Side lasting

Tacks are generally spaced at about 10 mm. intervals down the sides. Much less force is required for this operation than for lasting the seat and toe.

II.4.2 Tack lasting machinery

Small footwear manufacturing enterprises will not find it economical to invest in elaborate tack-lasting machines. However, where output levels exceed one hundred pairs per day, there may be a case for investing in relatively simple, manually-powered drafting and lasting machines. With machines of this type, the tacks are individually driven in by the operator. Two such machines cost approximately US$8,000, and may also be used for cement-lasting if necessary. The essential difference between these two machines is that pincers are used on the drafting machines to take the initial strains over the toe, while wiper plates are used to assist toe- and seat-lasting on the second machines. Side tack-lasting is carried out by hand in either of these machines.

A type of machine which is used for side and waist lasting by large-scale enterprises can also be used to completely tack-last shoes. In these machines, the operator holds the work up to the machine so that the lasting margin is gripped by a pincer. A knee operated lever can twist the pincers to the left or right as required and a wiper holds the margin while a tack is automatically driven. Simplified versions of these machines are available for tack side-lasting.

II.5 Bottom pounding (Operation reference No. 40)

The lasting margins of stitched-on sole shoes do not need to be scoured. However, after cutting off any excess material inside the tack line, the pleats around the seat and the toe must be flattened. Special purpose machines are available but the operation can be carried out with a hammer having a large, slightly-domed face. To avoid damaging the feather-edge, the blows should be directed so that they have a slight inwards component.

II.6 Bottom cementing (Operation reference No. 41)

The purpose of this operation is to hold the sole against the shoe bottom during sole stitching. This is done through the application of a latex solution usually applied by brush. The soles can then be loaded onto racks where the cement dries naturally. (See operation reference Nos 18 and 27 for Type 1 footwear).

II.7 Sole laying (Operation reference No. 42)

The object of this operation is to attach the sole to the shoe bottom by adhesive and to form the sole round the lasted bottom so that they are in close contact during stitching. It is important that leather-soles are mellow during this operation.

Sole presses identical to those described for attaching cemented-on soles can be used. Alternatively, soles can be tacked or stapled in position with the fasteners positioned near the edge of the channel. Thus, they can be avoided during stitching and will not leave visible holes in the finished shoe once they are removed after stitching.

II.8 Last removal (Operation reference No. 43)

The methods available for last-removal were dealt with in connection with cemented-on shoes. However, in this case, there is no sole to provide support to the bottom and the lasts used are normally of the hinged type so that they 'break' at the waist. The use of such lasts reduces the risk of damaging insoles, particularly when they are made of fibreboard.

II.9 Sole stitching (Operation reference No. 44)

II.9.1 Channel opening

The channels round the edge of the soles are opened up at this stage. Machines are available, but opening can be carried out by hand after the top surface of the lip has been moistened with a sponge to increase its plasticity.

II.9.2 Stitching

(i) Stitching techniques

All stitching machines have a swivelling horn placed inside the shoe and through which waxed thread is fed. The wax, which may be pre-heated, helps waterproof the sole. In chain stitching machines, the needle is hook shaped so that it can catch the thread when at the bottom of its stroke. It then pulls the loop through the layers of insole, upper and sole on the upstroke. It then links the loop into the chain with the proceeding loop.^l Considerable skill is required to keep stitches vertical and the line of stitching in the bottom channel, particularly around the toe curve. After traversing from the waist round to the other side of the sole, keeping about 3mm. from the edge of the insole, the operator cuts off any excess thread.

¹ Stitching configurations are illustrated in Appendix I(Glossary of terms).

(ii) Equipment

Although machines have been used in this operation for over a hundred years, they are still expensive. Both chainstitching and lockstitching machines are available.

New motor driven chainstitching machines can cost up to US$4,000. Alternatively, small enterprises may buy less expensive used machines.

II.10 Sole levelling (Operation reference No. 45)

In this operation, the channel and lip are cemented, usually with brush applied latex. After drying, the lip is moistened to soften it and is then rubbed down with a metal bar. The shoes may require re-lasting before this operation, using a last smaller than the making last. The metal bar should be rust proof since iron can leave rust stains on the damp leather. Alternatively, this operation may be carried out with machines fitted with a rotating indented wheel. These machines reduce considerably the time needed for this operation.

To restore the curve of the waist, the shoe can then be mounted in a sole press with a female mould to compress the layers of material on the shoe bottom. Special purpose presses are available for this purpose whereby the shoe is mounted on a cast iron footform. It is then forced into a concave mould made from a non-corrosive alloy. Any press with a force of about four tonnes which may be gradually applied may be used for this operation.

II.11 Seat nailing (Operation reference No. 46)

The back of the sole is attached to the shoe by a semi-circle of nails driven from the outside. The nails pass through the sole, the lasted margin of the upper and the insole and are finally clenched on a flat topped iron horn on which the inverted shoe rests. The operation can be carried out by hand or on a special purpose nailing machine.

Surplus material is then trimmed from the edge of the sole around the seat. This rough rounding operation can be done manually with a knife. Alternatively, the excess material may be ground away with an abrasive covered wheel or on a special purpose disc knife. The wheel or the disc knife may be incorporated into a seat nailing machine so that both operations are carried out simultaneously.

II.12 Heel attaching (Operation reference No. 47)

When heels are built from stacked leather or leatherboard, they can be cut and built by hand with nails. However, the best results are obtained if a heavy load is used to compress the stack before nailing.

Since the shoes are unlasted at this point, they can be attached by nails driven from either inside or outside the shoe. Usually, the nail heads are on the inside of women's shoes and on the outside of men's shoes.

The nails attaching the heel can be driven manually or by special purpose machines. Heel attaching nails usually have rows of corrugations round them which helps provide a firm grip. Top pieces can be nailed or stapled onto the heel.

II.13 Re-lasting (Operation reference No. 48)

In this operation, lasts are put back into the shoes. Hinged lasts smaller than the making lasts are usually used to simplify their subsequent removal.

II.14 Heel trimming (Operation reference No. 49)

The uneven edges of built heels can be smoothed and shaped by rough scouring on a emery covered wheel. Alternatively, a special purpose cutting machine called a heel parer can be used. The latter is preferred when heels with backward sloping concave curves are required on women's shoes.

Heel paring machines are fitted with rotating cutters consisting of a pair of knives shaped to the required contour. These cutters rotate at a very high speed. The top piece and the sole top edge act as guides for the shoe on either side of the cutter blades during paring.

II.15 Edge trimming (Operation reference No. 50)

The edge of the sole around the forepart is trimmed, back in preparation for the finishing operation. The edge is moistened to aid the operation.

Excess sole leather can be removed manually with a knife. Alternatively, special purpose machines costing about US$300 are available. These machines have a guarded rotating knife. The operator guides the edge of the upper past this knife.

II.16 Bottom finishing (Operation reference No. 51)

Unless soles and heels are prefinished, a substantial amount of work remains to be carried out on them. The operations involved are described in some detail, since the view that a consumer forms of the quality of leather soled shoe is possibly influenced as much by the finish on the sole as by that on the upper.

The traditional bottom finishing sequence is very elaborate and includes several variants. However, it is rarely followed completely. A comprehensive sequence of operations is described below. Whenever appropriate, simple alternatives to the types of machines that are employed in large scale factories in developed countries are described.

II.16.1 Heel scouring

This operation removes marks left after heel paring, and polishes the surface. Usually, rough and fine grades of scouring paper are used. The work can be done by hand, or, preferably with a rotating wheel fitted with a felt backing on which is placed the scouring paper.

A number of machines, equipped with steel wheels that open into two halves to permit the ends of the felt and paper to be gripped are available. Sometimes, felts and paper are contoured to the heel shape and cut to a width that corresponds to the heel height. Square heels require only flat papers and felts. These can be cemented to the circumference of a wooden wheel, belt driven by a small motor (see figure II.11). A bicycle can also be adapted to provide the drive by removing the rear tyre, and clamping the frame in an upright position. A continuous belt drive taken around the back wheel and then around a small pulley on the wheel shaft completes the adaptation.

II.16.2 Heel dyeing

A spirit based dye of the required colour is applied with a fine hair brush. Sometimes, a wide brush is used for the heel and a narrow one for the top edge of the sole. Since the heel fibres open when wetted by dye, a second coat containing a small quantity of filler may be applied.

II.16.3 Fine heel scouring

Very worn fine scouring paper can be used at this stage to restore the surface roughened as a result of swelling during dyeing.

II.16.4 Edge inking

A soft toothbrush may be used to ink the top, flesh and surface of the sole next to the upper. The ink has more filler than that used for dyeing. To avoid the inadvertent application of ink to the upper, this operation is sometimes carried out before sole attaching.

II.16.5 Edge setting

This is an important operation since unset leather sole edges are very porous. Hand edge setting involves applying melted stick wax or wax in an emulsion with water to the sole edge. It is then rubbed with a pre-heated iron back and forth to polish and force the wax into the edge. Often, the process is repeated to obtain the desired degree of smoothness and water resistance. Flat edges can be set using any hard and smooth round object.

The irons used for rubbing the wax have their nose shaped to a slightly exaggerated reverse contour of the trimmed sole edges in one plane , and are sligthly convex in the other plane. For flat edges, a wooden or plastic disc that is free to rotate on a length of bar, or even a round glass bottle, will suffice. Machines with heated oscillating irons are available. Irons are also often fitted to finishing machines that are used by repair workshops in developed countries.

II.16.6 Heel burnishing

Heel burnishing involves a number of operations, including: applying a hard wax to the heel with a rough cloth, producing a dull polish with a finer fabric; and finally producing a high polish with a brush or mop. Alternatively, a simple machine with three driven wheels carrying progressively finer cloths may be used for these operations.

II.16.7 Seat wheeling

This is a traditional operation that only performs a decorative function. It is now only applied to expensive men's shoes. The result of the operation is a narrow line of small vertical indentations round the seat at a level that overlaps the sole and heel. It is carried out with a handle carrying a freely rotating wheel with a milled edge. A lip to register against the upper edge of the sole acts as a guide.

II.16.8 Bottom scouring

The purpose of this operation is to produce a smooth clean surface in preparation for finishing the sole bottom. Two grades of scouring paper are used. They can be either mounted on the circumference of a driven wheel or wrapped round flat wooden blocks. When scouring by hand, a circular motion should be applied in order to avoid a grained effect. On some machines, the rotating cylinders reciprocate from side to side to produce a similar effect to hand scouring. If the leather is dry during this operation its surface structure can be damaged.

II.16.9 Naumkeaging

The purpose of naumkeaging is to scour the curved waist of leather soles. The equipment for this operation is often mounted on a vertical shaft at one end of proprietary finishing machines. It consists of a conical wheel round which scouring paper is secured. For hand scouring, the scouring paper can be wrapped around a suitably shaped piece of wood.

II.16.10 Bottom staining

Shoe bottoms can be finished in several ways, but only staining is considered here. In small enterprises, the stain - which can contain some wax - is painted on with two or three strokes of a soft wide brush.

II.16.11 Bottom burnishing

Once the stain has dried, the bottom of the sole is burnished with wax and cloth in a manner similar to that employed to burnish heels.

II.16.12 Bottom inspection

Some rectification of the bottom finishing work may be required. Melted wax and heated irons can be used to hide minor defects. After last removal, the soles may be branded on the waist or forepart. As described in the context of insole marking, the impression can be produced directly with a heated metal die or with embossing foil.

II.17 Tables of technical data

Tables III.5 and III.6 provide estimates of the needed workforce for the selected four scales of production, and the type, number and cost of the pieces of equipment required for each scale.

Table III.5 Workforce allocation at each output level for Type 3 footwear

(Jobs are shared by operatives in some cases)

Op. Ref No.	Operations	Scale 1 8prs/8hrs	1 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 splitting				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/cementing				3 us
9	*Stitch 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/eyelet insertion				1 us
14	*Temporary lacing			3 s	2 us
15	*General fitting and puff insertion				2 ss
16	*Upper trimming				8 s
36	Insole preparation	1.0 s	1.0 ss	3 ss	4 ss
37	Sole preparation				4 ss
38	Insole tacking		2.0 s	2 us	1 us
20	*Stiffener insertion				1 us
21	*Upper conditioning
39	Tack lasting			4 s	10 s
23	*Tack removal and inspection		1.0 ss	2 ss	2 ss
40	Bottom pounding				2 ss
24	*Heat setting				1 us
26	*Shank attaching	0.2 us	0.5 us	1 us	1 us
27	*Bottom cementing				2 us
28	*Bottom filling	1.0 s	2.0 s	1 ss	1 us
42	Sole laying				3 ss
43	Last removal				1 us
44	Sole stitching			1 s	2 s
45	Sole levelling				1 ss
46	Seat nailing			3 ss	3 ss
47	Heel attaching				2 ss
48	Relasting				1 us
49	Heel trimming	0.5 s	2.0 s	1 ss	1 ss
50	Edge trimming				1 ss
51	Bottom finishing			2 s	8 s
30	*Last removal				1 us
31	*Upper finishing	0.5s	1.0 s	4 s	14 s
	TOTAL DIRECT WORKERS	5	15	49	151

*See Type 1 equipment specifications for these operations,
s = skilled (4 months training)
ss= semi-skilled (3 weeks training)
us= unskilled (1 week training)

Table III.6 Methods and equipment specifications for Type 3 footwear

Output per day: 8, 40, 200 and 1000 pairs

Type: Leather-upper, tack lasted shoes with machine-sewn leather soles

Op. Ref No.	Operations and Major Equipment required:	Equipment source1	No. required by scale2				Estimated unit cost ($)
			1	2	3	4
1-16	See Type 1 footwear at same scale
36	INSOLE PREPARATION
	- clicking bench	local	OP1	1	2	1	30
	- clicking board	local	-	1	-	-	15
	- mechanical swing arm clicking press	Sup. list 1	-	-	1	1	2,200
	- press kmives	Sup. list 1	-	-	30	-	40
	- insole moulding and
	sole conforming mach.	Sup. list 17	-	-	-	1	8,000
	- insole bevelling machine	Sup. list 17	-	-	-	1	2,500
37	SOLE PREPARATION
	- clicking bench	local	OP1	1	1	-	30
	- clicking board	local	-	1	-	-	15
	- tempering tank	local	1	1	1	1	50
	- paring and channeling knives	local	-	5	5	-	6
	- mechanical swing arm clicking press	Sup. list 1	-	-	OP36	1	2,200
	- bench for waist reducing , bottom cementing and channel cutting	local	-	1	1	1	30
	- sole evening machine	Sup. list 37	-	-	1	1	1,800
	- sole rounding machine	Sup. list 37	-	-	-	1	7,000
	- manually powered channel cutter	Sup. list 37	-	-	-	1	1,000
	- mechanical swing arm clicking press	Sup. list 1	-	-	OP36	-	2,200
38	INSOLE TACKING
	- tacking bench	local	1	1	1	1	25
	- tubular steel jack	local	1	1	1	2	5
20-21	See Type 1 footwear at same scale
39	TACK LASTING
	- lasting bench	local	OP38	1	1	2	25
	- jack (mounted on bench)	local	-	-	1	2	5
	- lasting pincers hammers and knives	Sup. list 22	4	-	20	-	4
	- hand tacking tool	Sup. list 22	-	-	1set	1set	1,000
	- manually operated drafting machine	Sup. list 22	-	-	1	-	3,000
	- manually operated lasting machine	Sup. list 22	-	-	1	-	5,000
	- back part moulding machine	Sup. list 22	-	-	-	1	10,500
	- pulling and lasting machine	Sup. list 22	-	-	-	1	18,000
	- tack side lasting mach.	Sup. list 22	-	-	-	1	6,000
	- tack seat lasting mach.	Sup. list 22	-	-	-	1	15,000
23	See Type 1 footwear at same scale
40	BOTTOM POUNDING
	- lasting bench	local	OP38	1	-	-	25
	- lasting jack	local	-	1	-	-	5
	- scouring buff without dust extractor	Sup. list 25	-	-	1	-	400
	- bottom roughing mach.	Sup. list 25	-	-	-	2	2,400
24 , 26,28	See Type 1 footwear at same scale
42	SOLE LAYING
	- bench	local	OP26	1	1	1	25
	- manually powered sole press	Sup. list 29	1	1	1	-	1,900
	SOLE LAYING
42	- twin station hydraulic sole press	Sup. list 29	-	-	-	2	8,000
	LAST REMOVAL
43	- tubular steel jack	local	1	1	1	1	5
44	- bench	local				1	25
	SOLE STITCHING
	- lock stitch insole sewing machine (This operation could be performed in a central facility serving several small enterprises)	Sup. list 44	1	1	1	2	6,000
	SOLE LEVELLING
45	- manually powered sole press using sole levelling plates		OP42	OP42	OP4	2 -
	- twin station sole press with sole levelling plates	Sup. list 29	-	-	-	1	8,500
	SEAT NAILING
46	- bench	local	OP26	1	1	-	25
	- tools for nailing and edge paring	Sup. list 1	-	3	5	-	7
	- loose nailing and rounding machine	Sup. list 46	-	-	-	1	3,000
47	EEL ATTACHING
	- bench	local	OP26	OP46	-	-
	- manually operated heel attaching machine	Sup. list 47	-	-	1	-	1,600
47	HEEL ATTACHING
	- heel nailing machines for heel building and heel and top piece attaching	Sup. list 47	-	-	-	1	9,000
48	RELASTING
	- bench	local	OP26	OP46	OP46	1	25
	- tubular steel jack	local	-	1	1	-	5
49	HEEL TRIMMING
	- trimming bench	local	1	1	1		25
	- heel paring machine	Sup. list 49	-	-	-	1	4,000
50	EDGE TRIMMING
	- trimming bench	local	OP49	OP49	OP49		25
	- sole trimming machine	Sup. list 50	-	1	1	-	300
	- edge trimming machine	Sup. list 50	-	-	-	1	1,200
51	BOTTOM FINISHING
	- bottom finishing mach. with edge irons scouring wheels, mops and brushes (can be shared with small-scale ent.)	Sup. list 51	1	1	1	4	5,500
	- hand work bench for drying, inking and staining	local	-	1	1	1	25
30-31	See Type 1 footwear at same scale

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 the operation where the equipment is used for the first time.

III. Type 4 footwear: Welded synthetic upper, string lasted shoes with moulded-on soles

Type 4 footwear is a welded synthetic upper, string lasted shoe with moulded-on sole. It is a substitute for leather upper shoes with cemented-on soles, to which it bears a superficial resemblance. As an upper material, PVC has a number of disadvantages: it is impermeable and does not therefore absorb sweat or allow it to escape, and lacks the wear resistant qualities of leather.

A process route for this type of footwear is outlined in Table III.7. Operations already dealt with in relation with footwear type 1 are marked with asterisks.

Usually, the PVC sheet that forms the upper material has a woven fabric backing. The seams are produced by means of high potential, high frequency electrical power under pressure. Rapid changes in the polarity of the particles that make up the material causes internal friction. This friction heats the material to above its melting point, and weld layers together.

Table III.7 Stages in the production of welded synthetic upper, string-lasted shoes with moulded-on soles

Production stages	Op. Ref.	Operations	Major materials
Upper cutting and welding	52	Cutting and welding uppers	PVC uppers and lining materials
	53	Upper welding
	54	Lasting string attaching	Lasting string
	14*	Temporary lacing	String
	17*	Sock cutting	PVC or board socking
	6*	Sock embossing
Lasting and moulding	20*	Stiffener insertion	Heel stiffeners
	55	String-lasting and moulding-on	Sole raw materials
	56	Sock insertion	Socks
Upper finishing	31*	Upper finishing operations, packing	Packing materials

The operations marked (*) are discussed in the section dealing with leather-upper, cement-lasted shoes with cemented-on soles.

The output capacities of the equipment described in the remaining part of this section are relatively high. Thus, although capital investments are also high, unit production costs are generally low. This type of shoes may, therefore, be particularly suitable for low to middle income groups in developing countries although the manufacturing processes are relatively capital-intensive.

III.1 Cutting and welding upper components (Operation reference No. 52)

(i) Processing techniques

Upper components may be cut in the conventional manner with knives. Alternatively, heat cutting and welding can both be performed on a single machine. The machine can be fitted with a material roll feed unit enabling two thicknesses of material to be cut to shape as well as welded together during the operation. Thus, the back parts of the upper can be welded to a lining material round their top lines to form pockets for stiffeners. Similar arrangements can be made to locate toe puffs.

(ii) Equipment

Typical machines of the type described above have open fronted twin station welding areas approximately fifty centimeters square. Two work stations can be arranged on the table so that an operator can unload work at one station while a welding cycle takes place at the other. Power requirements on such machines are three kilowatts for the press and ten kilowatts for the generator needed for the high frequency welding operations. This type of machine is often operated for two or three shifts a day in developed countries.

III.2 Welding upper components together (Operation reference No. 53)

The type of machine used for this operation works on the same principle as the cutting and welding machine described above, but is smaller and consumes a total of about four kilowatts. Operations performed by this type of machines replace the conventional closing operations on shoe uppers performed by means of stitching. A variety of welding tools is required for operations such as side and back seam welding and for tongue attaching.

III.3 Lasting string attaching (Operation reference No. 54)

Lasting string is made from strong, loosely twisted cord. It is held in position around the lasting margin of the shoe by a run of overlock chainstitch loops. This allows the string to run freely through them.

Specially adapted conventional stitching machine or stitchers of the type used for glove manufacturing are suitable for this operation.

III.4 String lasting and moulding-on of soles (Operation reference No. 55)

Shoes with directly moulded-on soles can be string lasted immediately before sole moulding on metal foot-forms attached to the machines. Usually, stiff socks-cum-insoles, which cover the whole bottom, are inserted after moulding.

III.4.1 String lasting

String lasting is becoming increasingly popular for lasting light leather upper materials onto conventional insoles, using wooden or plastic lasts, prior to cementing-on sole units. Lasting involves pulling the two ends of the string tightly so that the lasted margin bunches in over the sole of the last and stretches the upper down onto it. The lasting string may run either once around the lasting margin or twice around the forepart and once around the seat. Operators should wear a leather glove for protection when lasting is performed manually. Pneumatically powered string hauling equipment is available.

III.4.2 Moulding

The lasting margin of synthetic uppers is solvent wiped prior to moulding. The sole moulding process is similar to the one described for conventionally lasted shoes with moulded-en soles.

Equipment

Moulding machines are used for this operation. They are often single or twin station machines, having two or three metal footforms per station. One footform is used for string lasting while the second footform moulds-on the sole. Soles may cool on a third footform if one is included. The footforms are indexed between moulding cycles. The waists of the footforms may have magnetic inserts so that steel stiffening shanks placed on them can be incorporated into the upper surfaces of the soles. Alternatively, arrangements of spikes can be used to locate wooden shanks.

III.5 Sock insertion (Operation reference No. 56)

In situations where the soles are to be moulded-on immediately after string lasting, insoles need not be lasted into the shoes. Instead, socks of a heavy substance can be used to line the whole inside of the shoe's soles. These socks are cemented to the top surface of the soling material and blank off any cavities moulded into the top of the sole for lightening purposes. Inserting these stiffeners can be time consuming due to their size and stiffness.

Following this operation, the shoe is ready for finishing and packing. This latter operation is the same as that used for the previous types of footwear.

III.6 Tables of technical data

Table III.8 provides estimates of labour requirements for the selected scales of production, while Table III.9 lists the type and number of tools and equipment needed for each production scale.

Table III. 8 Workforce allocation at each output scale for Type 4 footwear

Note:	Where an operative is only required part-time on an operation the work is split.
	This construction is unlikely to be used at output levels of 8 and 40 pairs per day.

Op. Ref No.	Operations	Scale 1 8prs/8hrs	Scale 2 40prs/8hrs	Scale 3 200prs/8hrs	Scale 4 1000prs/8hrs
52	Cutting and welding uppers	-	-	1 ss	2 ss
53	Upper welding	-	-	1 ss	2 ss
54	Last string attaching	-	-		2 ss
14	*Temporary lacing	-	-	1 s	2 us
17	*Sock cutting	-	-		3 ss
6	*Sock embossing	-	-		2 ss
20	*Stiffener insertion	-	-		1 us
55	String last and moulding-on	-	-	1 s	3 s
56	Sock insertion				2 us
31	*Upper finishing and packing	-	-	2 s	7 s
	TOTAL: DIRECT WORKERS	-	-	6	26

*See Type 1 equipment specification for these operations.
s = skilled (4 months training)
ss = semi-skilled (3 weeks training)
us = unskilled (1 week training)

Table III.9 Methods and equipment specifications for Type 4 footwear

Output per day; 200 and 1000 pairs of shoes

Type: Welded synthetic upper, string-lasted shoes with moulded-on soles

Op. Ref No.	Operations and Major equipment required	Equipment source	No. required by scale		Estimated unit cost ($)
			3	4
52	UPPER CUTTING AND WELDING
	- twin station welding and cutting machine, generator and cutting and welding tools	Sup. list 52	1	2*	34,000
53	UPPER WELDING
	- seam welding machine with tools	Sup. list 52	1	2	8,000
54	LAST STRING ATTACHING	Sup. list 54	1	2*	1,600
	- overlock chain stitching machine	Sup. list 35	8	12	2,125
14,17 6,20	See Type 1 footwear at same scale
55	STRING LASTING AND MOULDING-ON
	- sets of moulds and foot-forms
	- preheater	Sup. list 35	1	2	800
	- granulator	Sup. list 35	-	1	1,400
	- single station PVC injection moulding-on machine	Sup. list 35	1	-	23,000
	- twin station PVC moulded-on machines	Sup. list 35	-	2*	35,000
	- last string pullers	Sup. list 35	-	2	1,000
56	SOCK INSERTION
31	- hand fitting and cementing at bench See Type 1 footwear at at same scale	local	1	2	25

*A single machine is needed when used on a two-shift basis.

IV. Type 5 footwear: Stitched synthetic upper cement-lasted sandals and casual shoes with built or unit soles

The type of footwear considered in this section are stitched synthetic upper, cement-lasted sandals and casual shoes with built or unit soles. While the majority of the footwear of this type is manufactured for the women's market, none of the constructions covered are exclusively used for either women's or men's footwear. Shoes of the flip-flop and buckling types, with stitched synthetic uppers and with either flat or raised heels comes under the type 5 footwear. They typically have a PVC coating and a woven fabric backing. However, few changes to the basic sequence of operations would be required if leather rather than synthetic uppers were used, or if men's or children's sandals were to be produced.

In tropical climates, a large proportion of the demand for women's shoes often consists of plastic casual and sandals produced by injection moulding machines. This latter type of footwear - described in the following section of this chapter - is mostly marketed among low-income groups. On the other hand, the type of footwear described in this section are more likely to be marketed among middle-income groups.

The process sequence is shown in Table III.10. Only the five operations that are unique to this type are discussed below since the other operations have already been dealt with earlier.

IV.1 Sole and insole preparation (Operation reference No. 57)

Outsoles can be cut to shape from sheets of rubber or resin and man-made composite materials. This may be done by hand or with the assistance of a press. Insoles preparation is similar to that for cement-lasted, cemented-on construction, with the exception of the following: (i) the bevelling of the edge of the insole backpart is unnecessary on open backed shoes, (ii) a binding of fabric or of upper material may be cemented around the edge of the insole if it were to show on the finished sandal, and (iii) the bottom of the insole may be reduced in thickness in areas where straps must be lasted to it.

Table III.10 Stages in the production of stitched synthetic upper cement-lasted sandals and casual shoes with built or unit soles

Production stages	Op. ref.	Operations	Major materials
Upper cutting	1	*Cutting upper components	Sheets of upper materials
Upper preparation	3	*Lining marking
	4	*Stitch marking
	5	*Hole punching
	6	*Sock embossing
	7	*Skiving
	8	*Edge folding and cementing
Upper stitching	9	*Stitching of uppers	Threads and tapes
Stitched upper finishing	10	*Seam reducing
	11	*Taping	Tapes
	15	*General fitting/attaching	Trim, puffs
	16	*Upper trimming
	57	Sole and insole preparat.
Bottom component preparation	58	Heel preparation	Sole units and insole sheet Heels
Making	19	*Insole tacking
	20	*Stiffener insertion	Heel stiffeners
	21	*Upper conditioning
	59	Lasting uppers
	23	*Tack removal/inspection
	25	*Bottom roughing
	26	*Shank attaching	Shanks
	27	*Bottom cementing
	28	*Bottom filler insertion	Felt
	29	*Sole laying
	30	*Last removal
	60	Heel attaching
	61	Sole finishing
Upper finishing	31	*Upper finishing and packing	Packing materials

*The operations marked with (*) are discussed in the section dealing with leather-upper, cement-lasted shoes with cemented-on soles.

IV.2 Heel preparation (Operation reference No. 58)

Prevailing fashions determine if women's casual shoes may have prefinished sole units, wedge or flat soles or separate soles and heels. It is nowadays unusual to carry out the finishing of the heels of women's schoes after they have been attached since most heels are made of wood or plastic covered with material which matches or contrasts with the upper. Even when heels are built from stacked leatherboard, they are prefinished before attaching.

When mould parting lines are not evident (as they may be on some type of plastic heels), heels may be painted by hand or sprayed with cellulose paint. Cementing operations associated with heel covering are, usually, carried out by hand.

IV.3 Lasting uppers (Operation reference No. 59)

Lasting this type of footwear is much simpler than for other types of footwear since open work uppers do not require lasting at the toe and heel. The lasting techniques vary with style, but they only involve the pulling of pre-heated uppers over the lasts followed by side-lasting onto the insoles. For example, they are not needed in cases where the upper consists of two narrow straps fed through slots cut in the insoles and cemented to the insole bottom.

IV.4 Heel attaching (Operation reference No. 60)

When separate heels are used, they are usually attached to the insole by a maximum six nails driven out into the heel through the insole. Heel attaching can be done by hand or by machine. Simple, manually operated machines costing US$700 are available. They can attach a heel in about one minute. Hand nailing takes longer and requires skills whenever high heels are used.

IV.5 Sole, finishing (Operation reference No. 61)

Where laminated sole or heel units are built up, or when pre-cut outsoles or heels are attached to insoles so that their edges are exposed on the completed footwear, mismatches on the edges usually need trimming and smoothing.

Operators require considerable skill to produce a neat finish regardless of the type of machinery used. Simple, inexpensive machines of a type used by shoe repairers in developed countries may be used for this operation. These machines are usually bench mounted and driven by small electric motors. Elaborate machines are also available. Their use may not, however, be justified for conditions in developing countries.

IV.6 Tables of technical data

Tables III.11 and III.12 provide estimates of labour requirements for the four selected scales of production, and the estimated number of pieces of equipment needed for the additional operations used in the production of Type 5 footwear.

Table III.11 Workforce allocation at each output scale for Type 5 footwear

Op. Ref No.	Operations	Scale 1 8prs/8hrs	Scale 2 40prs/8hrs	Scale 3 200prs/8hrs	Scale 4 1000prs/8hrs
1	*Cutting uppers	0.7 s	1 s	5 s	16 s
3	*Lining marking			1 us	1 us
4	*Stitch marking				3 us
5	*Hole punching		1 ss	2 ss	1 ss
6	*Sock embossing				2 ss
7	*Skiving			1 ss	1 ss
8	*Edge folding/cementing				2 us
9	*Stitching uppers	1.0 s	2 s	8 s	36 s
10	*Seam reducing		1 s	2 s	1 us
11	*Taping
15	*General fitting and puff attachment				1 ss
16	*Upper trimming				5 s
57	Prep, sole and insole	0.3 ss	1 ss	1 ss	4 ss
58	Heel preparation				1 ss
19	*Insole tacking	1.0 s	1 s	1 us	1 us
20	*Stiffener insertion				1 us
21	Upper conditioning
59	Cement lasting			1 s	5 s
23	*Tack removal/inspection			1 ss	2 ss
25	*Bottom roughing				2 ss
26	*Shank attaching		1 s	2 ss	1 us
27	*Bottom cementing				2 us
28	*Bottom filling				1 us
29	*Sole laying				2 ss
30	*Last removal				1 us
60	Heel attaching			1 s	2 ss
61	Sole finishing				4 s
31	*Upper finishing		1 s	3 s	10 s
	TOTAL DIRECT WORKERS	3	9	29	108

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

*See type 1 equipment specifications for these operations.
s = skilled (4 months training)
ss = semi-skilled (3 weeks training)
us = unskilled (1 week training)

Table III.12 Methods and equipment specifications for Type 5 footwear

Output per day: 8, 40, 200 and 1000 pairs

Type: Stitched synthetic upper cement-lasted shoes with cemented-on built and unit soles

Op. Ref. No.	Operations and Major Equipment required	Equipment source1	No. required by scale.2				Estimated unit cost $
			1	2	3	4
1-16	See Type 1 footwear at same scale
57	PREPARATION OF SOLES AND INSOLES
	- clicking bench	local	OP1	1	1	1	25
	- clicking press	Sup. list 1	-	-	1	2	2,200
	- press knives	Sup. list 1	-	-	20	60	40
	- cutting knives	Sup. list 1	3	3	-	-	6
	- cutting board	local	-	1	-	-	15
	- insole moulding mach.	Sup. list 17	-	-	-	1	8,000
58	PREPARATION OF HEELS
	- clicking bench	local	OP57	OP57	OP57	OP57
	- manually operated heel attaching machine for heel building	Sup. list 47			1		2,500
	- heel attaching machine	Sup. list 47	-	-	-	1	10,800
19-21	See Type 1 footwear at same scale
59	CEMENT LASTING
	- bench	local	OP19	OP19	1	3	25
	- lasting pincers and knives	Sup. list 22	3	6	10	40	4
	- jacks	local	-	-	1	6	5
23,25 30	See Type 1 footwear at same scale
60	HEEL ATTACHING
	- manually operated heel-attachment for sole press	Sup. list 29	1	-	-	-	600
	- manually operated heel attaching machine	Sup. list 47	-	1	1	-	2,200
	- heel attaching machine	Sup. list 47	-	-	-	1	10,800
61	SOLE FINISHING
	- sole trimming machine on bench	Sup. list 50	1	-	-	-	300
	- edge finishing wheel on powered buff without dust extraction	Sup. list 25	1	-	-	-	400
	- bottom finishing machine with edge irons, scouring wheels, mops and brushes*	Sup. list 51	-	1	1	3	5,500
	- hand work bench for inking and drying of heels	local	-	-	1	1	25
31	See Type 1 footwear at same scale

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 the operation where the equipment is used for the first time.

*May be shared by several small enterprises.

V. Type 6 footwear: Single injection, moulded plastic sandals

Single injection moulded plastic sandals are typically of the "flip-flops' type, with broad straps across the forepart and completely open backparts and toes. Closed sandal designs are sometimes produced, but may not look attractive unless the tooling quality is very high. The main merit of sandals of this type is that they are inexpensive. On the other hand, they have a number of disadvantages when compared to leather sandals: they do not absorb sweat, are difficult to repair and require a large capital investment in machining and tooling for their production.

The various operations specific to the production of plastic sandals are briefly described below.

V.1 Single injection moulding technique and equipment (Operation reference No. 62)

In the production of moulding, melted PVC is injected into a split metal mould. The process is very similar to that used for the direct moulding-on of soles to pre-lasted uppers. However, in the case of single injection moulding, the moulds incorporate spaces which allow the melted PVC to form both the uppers and the soles. After solidification of the melted plastic, the mould is opened and the finished moulding ejected. The moulding and cooling cycle time varies with the weight of the material injected, the amount of mould cooling applied and the shape of the moulding. Once the best settings and the automatic cycle have been established, it is only necessary for the machine operator to fill up the raw material hopper and to remove any flash from the mouldings. If the range of moulds on the machine does not cover the full range of sizes and styles that are required, it will be necessary to change moulds occasionally. The colour of the PVC granules may also be changed from time to time.

After moulding, sandals have any trim added and are then inspected and packed.

Since PVC is thermoplastic, mould runners, sprues, and flash can be regranualted and fed back into the process.

The moulding operation is the only important operation in the production of plastic sandals, the other operations consisting of packaging and re-granulating of PVC wastes.

Various types of single injection moulding machines are available on the market. The choice of machine will depend on the selected batch and market sizes. These determine which of the available single-station, twin-station or multi-station machines are the most appropriate ones. In general, whenever the product mix is very wide and the batch sizes and total volumes of output are small, single station or twin station machines are likely to be more economically efficient than multi-station machines. The former machines may also be used by large-scale enterprises for the completion of small orders or the carrying out of tooling trials.

V.2 Tables of technical data

Tables III.13 and III.14 provide estimates of the required labour force and equipment. Given the high capital-intensity of the production process, single injection moulding may not be adopted for scales of production lower than 200 pairs per day. Thus, no data is provided for scales 1 and 2.

Table III.13 Workforce allocation at each output level for Type 6 footwear

Note 1: Where an operative is only required part time on an operation, the work is split.

Note 2: One-shot moulding is unlikely to be undertaken at daily output levels of 8 and 40 pairs.

Op. Ref No.	Operations	Scale 1 8prs/8hrs	Scale 2 40prs/8hrs	Scale 3 200prs/8hrs	Scale 4 1000prs/8hrs
62	One-shot injection moulding of complete sandals	-	-	2 ss	3 ss
63	Packing	-	-	1 us	1 us

ss = semi skilled (3 weeks training)
us = unskilled (one week training)

Table III.14 Methods and equipment specifications for Type 6 footwear
Output: 200 and 1000 pairs per 8 hours
Type: Single injection moulded PVC sandals

Op. Ref No.	Operations and Major Equipment Required	Equipment source	No require d by scale		Estimated unit cost
			3	4	$
62	SINGLE INJECTION MOULDING OF SANDALS
	- twin station, semiautomatic injection moulding machine, moulds and racks	Sup. list 62	1		40,000
	- ten-station, semiautomatic injection moulding machine, moulds and racks	Sup. list 62		1	110,000
63	- granulator	Sup. list 35	1	1	1,400
	PACKING
	- packing bench	local	1	1	25