Ingenious machines, working at remarkable speeds, are used in the large-scale production of modern footwear. Although the craftsman has been outpaced, the quality of machine-made shoes nowadays closely approaches that of shoes made by hand
CEMENT SOLE ATTACHING MACHINE used to attach uppers to the cemented sole. The soles are first placed in the machine and fixed in position. The shoe is then automatically centred and pressures up to 300 lb per square inch are applied.
BEFORE the days of industrial machinery all shoes were made by the craftsman’s hand. He cut, shaped and sewed the various parts of the uppers, he prepared, cut and sewed the soles to the uppers; and he finished the shoe in every way by hand. To-day machinery is used for the production of every kind of footwear.
Mechanical methods of producing shoes were first used in 1810 when the Napoleonic Wars gave rise to a large demand for boots for the men of Wellington’s armies. In that year the versatile engineer Marc Brunei invented a machine for riveting and nailing the soles to the uppers of army boots.
Among the earliest sewing machines made and used for sewing together the parts of shoe uppers was Elias Howe’slockstitch machine, invented in 1841. In 1858 another American, Lyman R. Blake, invented the machine which is generally considered to be the one that instituted the mechanization of the shoe industry. The shoe was fitted to the last by hand, after which the last was taken out and the shoe placed over the horn of the machine and the sole sewn to the insole and upper with a chain stitch. This form of attachment is still extensively used.
In 1872 America again improved methods when Charles Goodyear designed machines capable of producing shoes comparable with those made by hand. The Goodyear welted shoe process is now almost universal in the making of welted shoes. Other methods of manufacture are the Littleway and “cemented” processes, the riveted, the screwed and the stitched forms.
In the production of a machine-made shoe, the various operations are split up minutely and a different machine is used for each operation. Not less than 150 distinct machines are used for the Goodyear welted shoe. The total number of operations in the manufacture of each shoe may be anything between 100 and 200, and each of these is performed by a different operator. Few, if any, articles of everyday use are so extensively subdivided in their production.
The raw material from which the bulk of shoes are made is leather. This is prepared in the tanneries from the skins of, chiefly, the cow, calf, sheep, pig and goat, according to the nature and quality of shoe required. For certain types of footwear the skins of various snakes, and even of certain fish, are used for the uppers, these being suitably treated and coloured as desired. For the soles, especially the bottom or outsole, the best and heavier leathers are used. Rubber is used, either in a specially prepared form for soles of many sports shoes, and for heel tips, or in a form of cement for filling between soles, and for adhesive purposes. Leather is claimed to have the additional advantage of porosity, enough for the foot to “breathe”, at the same time being reasonably waterproof.
The foundation of all shoe construction is the “last”, which, for manufacturing purposes, not only embodies the form of the finished shoe, but also is made of such size and shape as to allow for the particular type of material used. Light leathers and certain materials stretch more than the heavier leathers, and the pattern which is cut from the standard last has to allow for the width of extra material for the seams, for stretch and so forth. The measure of successful production of tens of thousands of shoes depends on the skill and accuracy with which the original patterns are designed and cut out. These patterns are first cut out in paper and from these is built up a complete series for all the sizes required of that particular model. This grading of sizes, as it is called, may be done by hand, or much more quickly, cheaply and accurately by a pattern-grading machine. From the paper patterns, permanent ones of sheet metal or cardboard are made. Separate patterns are made for each piece which goes to make the upper, as well as for the soles and for the linings.
The next operation is to cut out all these separate pieces for the upper from the skins. This process is known as “clicking” and is done mainly by hand. For large quantities, however, a clicking press is used. Considerable skill and knowledge of the various factors which enter into the question are necessary.
Folding the Seam Edges
The thickness, substance, amount of stretch and quality of the leather used are not uniform over the whole area. Skins from female animals produce better and finer leather than those from males. The methods of tanning and finishing the leather affect its stretching nature, and sundry other features bear on the question of from where certain parts of the shoe should be cut. To make the utmost use of the whole skin with the least possible waste, the placing of the patterns requires much care. Brand marks and flaws have to be avoided.
The clicking press is made to cut out the parts by specially shaped knives or dies. The leather is laid on a wooden block, and as the operator moves the cutting dies over the surface a horizontally swinging beam is made to descend and press the die through the material. When the various parts have been cut out, they are assembled in their appropriate pairs, and the sizes are marked on each piece either by painting in representative colours or by stamping. The skiving machine reduces the substance of the material at the edges where they are sewn together, or the seams would be thicker than the rest and uncomfortable to the wearer. Some skiving machines use a cylindrical knife revolving at high speed and at right angles to the direction of the feed. Others have a disk-shaped knife which works at a tangent to the feeding surface.
The next operation is the folding of the seam edges, as most of the seams in the uppers are made with a folded edge. The inside surfaces of the fold are coated with a rubber solution cement. The turned-over edges are then hammered down flat and smooth.
The toe caps of many types of shoes are perforated along the edge. This operation may be done in a perforating machine, using a single tubular punch or group of punches and making the perforations in series, or it may be done by a complete set of punches, set to the shape of the design, which punch out the whole' ornamentation at one stroke.
WELTED SHOES in the making. The toe of the upper shoe illustrated is being lasted, the pleated upper having been pulled over and being temporarily held by a piece of wire secured to two tacks. The welt, in the lower shoe, is a strip of leather sewn through the inside “ lip ” of the insole and through the upper.
The various parts which go to form the uppers are cemented or sewn together. Several kinds of seams are used, depending on the style of the shoe and the nature of the material. After the seam has been sewn the resulting surface is more or less uneven and needs smoothing down. This is done by a seam-rubbing machine, or by hammering, according to the type of seam used. “Lap” seams are hammered, as the friction of rubbing would damage the stitches, and plain seams are rubbed, or they would be liable to burst open if hammered. Before the upper is placed on the last for attaching to the bottom, eyelets of appropriate size, shape and colour, for laced shoes, are put in by a machine which punches out the holes, feeds the eyelets into the holes from a hopper, and then clinches them. Another machine laces the upper with strong twine and ties it, so that the upper will not open out when it is stretched on the last.
The needles and threads used for the different types of sewing and stitching have to be of a special nature for each class of work. When used for leather the needle point should be chisel-shaped, because when a round point is used the leather is inclined to close up round the hole, and make it difficult for the thread to pass through.
The first operation on the soles is to cut them out to shape in a cutting press. For this purpose special knife forms, or cutting dies, are used. The knives are made from a strip of steel of a wedge section, bent to the shape of the article to be cut and then welded at the joints.
After the soles have been cut, the leather has to undergo preparatory treatment. The ordinary shoemaker soaks the soles in a tub for some time and then allows them to dry slowly to mellow, or temper the leather. Modern methods have to be much faster. The soles are placed in a machine which impregnates them with clean soft water, or other suitable liquid, using a pressure up to 1,500 lb. to the square inch, and completing the operation in a fraction of the time formerly needed.
The hides are not of uniform thickness, but it is absolutely necessary for the sole pieces to be of uniform thickness. It would be laborious work to gauge each sole by hand, and an ingenious machine has been made to do this automatically.
After this the soles are moulded between shaped metal moulds to give them the contour of the last. The machine is so arranged that while one sole is under pressure the other of a pair is being placed in the mould.
Drafting, Pleating and Tacking
In the Goodyear welted process of shoemaking a channel of special shape is cut along the outer side of the inner sole about half an inch from the edge. Another channel also is made along the surface parallel and simultaneous with this, but a little farther inwards. Both channels are cut in one machine, and the “lips” of the channels are then opened up in another machine to act as a guide for the welt sewer and to allow the stitch to penetrate to some depth into the substance of the leather. The next series of operations is known as “lasting”. The insole is first placed on the last and tacked to it with temporary tacks which can afterwards be withdrawn. The shoe upper is then fitted to its appropriate last, right or left hand, and temporarily attached by an assembling tack at the back. These temporary tacks are made to close limits of tolerance in size.
The necessary stiffening pieces, known as the “counter” at the heel and the “toe box” at the toe, are inserted between the shoe lining and the upper leather. The counter is inserted before the upper is fixed to the last, and the toe stiffening afterwards. The counter is generally made of fibre board, and the toe box of fabric impregnated with waxes or celluloid.
The firm securing of the upper to the insole while on the last involves three main operations — drafting (or pulling over), pleating and tacking. The object of the pulling-over machine is to pull the upper close down to the last, so that it conforms to the contour of the last, and to draw the projecting edges over the insole, firmly holding them in that position while the edges are tacked down. The machine has generally three sets of pincers, so placed that one operates at the toe end and two at the sides near the toe. Round the outside of these pincers are a number of polished metal “wipers” and the tacking mechanisms. In the space between the pincers is the insole rest, which serves to resist the pull of the pincers.
THE SHOEMAKING ROOM in a factory at Kettering, Northamptonshire, one of the chief centres of the British shoemaking industry. Mechanization of the industry has become so complete in the last eighty years that as many as 200 mechanical operations may be carried out in making one pair of shoes.
In performing the operation of pulling over, the operator guides the upper down into the pincer jaws until the insole reaches the insole rest. He then depresses a pedal which starts the machine, and causes the upper to be gripped by the pincers. As the machine continues its cycle the upper is pulled down to the last. By hand manipulation of the pincers the operation is able to correct the disposition of the uppers if necessary.
Then, for a second time, he depresses a pedal and the pincers move inwards towards each other, drawing the leather tightly round the last. At the same time, tacks are automatically driven in on either side and at the toe, to hold the upper securely in position. These tacks are not fully driven in, as they are withdrawn afterwards.
The most difficult operation of all, that of completely lasting the shoe, now follows that of pulling over. When a piece of flexible material, such as leather or fabric, is pulled over the corner of a more or less rounded shape, the turned-over part gets into folds or pleats. This adds to the difficulty of getting the surface of the main portion of the material, such as that forming the upper, to lie flat, particularly when that surface is of an irregular shape. The material has to lie close down to every portion of that surface, and the pleated parts have to be finished flat and evenly to present a uniformly flat surface. This is particularly difficult at the toe and heel ends of the shoe, where the curved edge is of smaller radius.
Toes are next lasted, the usual method in Goodyear welted shoes being by a machine which incorporates a pair of centrally hinged plates which wipe the whole of the upper material at the toe into place simultaneously, the pleated upper being temporarily held in position by a short length of wire secured to two short tacks.
Heel-Seat Lasting
The heel-seat lasting machine deals with the problem in a different manner. The last is placed on a peg held by a jack, and the shoe thus held is swung into a moulded cramp. The machine pedal is then depressed, and the following cycle of operations performed. The jack is locked; the band closes round the upper and exerts heavy pressure to bed the upper and the counter to the last; a pair of hinged wiper plates moves forward over the back, and at the same time closes over the sides, thus folding the upper over the heel seat. The plates are now withdrawn, and the operation of wiping is repeated after the shoe has been slightly elevated. This exerts a heavier pressure and flattens out the pleats caused by folding the material round the circular end of the last. While the wiper plates are still closed and holding the material in position, twenty-one tacks are driven simultaneously through holes in the plates. The tacks pass through the upper, the counter and the insole, and clinch on a metal plate fixed to the last. Finally the parts return to the open position of the machine, and the machine stops. All this takes place in less than two seconds.
The uppers being now securely fixed to the insole, the surplus leather and ragged edges projecting beyond the tacked-down portions have to be trimmed off. This is done by a machine fitted with a pair of fast revolving knives which cut away the excess.
The next operation is to sew on the welt, which is done in the Goodyear welt-sewing machine. The welt is a strip of leather generally supplied to the operator in a continuous ribbon. Starting where the heel is placed, the welt is sewn right round the edge of the insole to the corresponding spot on the opposite side. The stitch is taken from the inside lip of the insole, and passes through the bottom of the lip, the shoe upper and the welt in a horizontal direction, strongly uniting all three portions. None of the stitch is allowed to penetrate right through to the insole surface of the insole. Thus a perfectly smooth surface is left for the foot tread. To do this special form of stitch, the needle is curved to a radius of about one inch. The thread, as it is fed, passes through molten wax and is impregnated with this to make it weather proof.
IN THE FINAL STAGES the sole is stitched to the welt, the channel is closed and pressed down and the whole of the sole consolidated in what is known as a levelling machine. Then the heels are attached.
THE COMPLETED SHOE, ready for the removal of the wooden last, on which it has been built up by the Goodyear welted process. Before it is removed from the last, the shoe undergoes about twenty separate finishing operations.
Surplus portions of the upper, the insole lip and the welt are now cut away by the inseam trimming machine. A welt-beating and slashing machine now comes into operation, in which a little hammer is vibrated rapidly, and a small knife slashes the welt with diagonal cuts at the edge of the welt round the toe. The purpose of this operation is to make the welt lie parallel to the bottom of the insole, and, by means of the slashing at the toe, to relieve the tension at the outer edge of the welt due to the curve.
As the welt is only a narrow strip running round the outer edge, between the insole and the outer sole, there is a space between the two which has to be filled in to produce a solid uniform thickness. The filling may be of leather, sheet or powdered cork, or of a waterproof plastic compound. This filling is inserted in a plastic condition, and will later adhere to the soles as its volatile component evaporates. The outsole is coated on its flesh side with a rubber cement, and when this is tacky the outsole is applied to the shoe, which is then placed in the “sole laying” machine. Here the shoe is placed on suitably shaped rubber moulds which conform to the sole of the shoe. Pressure is applied for a period long enough for the cement to set, and a solid joint is effected between the outsole, the welt and the shoe bottom.
Another machine now trims the edge of the outsole and welt to the proper contour of the shoe, and cuts a channel near the edge of the outsole similar to that done previously on the insole, but the channel stops short at the front edges of the heel. This channel allows the stitch to be sunk well into it, and thereby protected. After the heel seat has been permanently nailed or pegged to the insole the channel is opened out for the stitching.
Lockstitch Machine
This operation is done in a lockstitch machine, capable of making 1,000 stitches a minute. The time taken for this stitching operation is only ten seconds, compared with the forty-five minutes which a hand craftsman would require to sew a shoe.
After stitching, the channel is cemented and closed, and the whole of the shoe bottom is consolidated in the “levelling” machine. One form of this machine applies the pressure to the sole with a rocking movement similar to the action of walking, between pairs of suitably shaped feet and forms. The pressure applied not only closes the channel, but also gives shape and character to the shoe sole after the disturbances it has been subjected to, particularly in the stitching operations.
Now the heels have to be attached. They are previously built up in layers of leather called “lifts” in the heel-building machine, but, so far, without the top piece, or lift. The heel is attached, while the shoe is on the last, by a machine which uses special nails driven from the outside towards the plate on the last.
The shoe is now completely built up and ready for the finishing operations, which may number as many as twenty. The heel, unless it is a wooden one, is trimmed to correct shape and size by the heel-trimming machine, which embodies a two-bladed cutter shaped to the correct heel form, and running at 6,000 revolutions a minute. The front, or “breast” of the heel, which extends across the sole, is trimmed by a knife operating vertically. The edge of the sole is trimmed by fast-running cutters. It is then inked or stained, and waxed, after which it undergoes a setting operation with a heated iron hydraulically pressed against it, thereby moulding the edge to the shape of the iron and closing the pores of the leather to resist water.
CEMENTED SHOEMAKING is now a widely used process. The operations are much the same as for a welted shoe, except that the soles are not stitched but cemented on to the shoes.
