Modern Production Methods

Procedure in a well-known Midland Works

An article published in the January, 1924 edition of The Automobile Engineer

At the present time four distinct types of Sunbeam cars are being produced, these being their 14, 16, 20, and 24 hp. models. The average output of the factory is 45 cars per week, rather more than 3,000 work people being employed. It may be noted that the firm have their own extensive non-ferrous metal and iron foundries, and also that the coach building, painting, and finishing departments are very considerable in extent and provide employment for a large number of persons.

The site on which the works is situated is on the outskirts of the town of Wolverhampton, and is in many respects ideal. Ample land is available for future extensions, and in laying out the works there has been no necessity for cramping, and therefore wide gangways, that assist considerably in facilitating the transportation of the work through the factory, have been provided between the various buildings.

Apart from the supply of drop forgings and various specialised components, such as magnetos, wire wheels, etc., all parts are made in the works, the factory comprising a self-contained unit. Every precaution is taken to ensure that the quality of the raw material employed conforms to specification, and a particularly extensive laboratory, equipped for both chemical and physical examination, has been installed. When the raw materials are received from outside sources, the bulk is placed in the stores, and remains in bond, as it were, until samples, tested in the laboratories, have been passed as satisfactory. Until the report of the laboratory superintendent is received, under no circumstances is the raw material issued to the works for production to be commenced.

Both iron and non-ferrous castings are produced, and, in addition to the ordinary sand castings, the die-casting process is employed to a very considerable extent, both in connection with aluminium and also with aluminium bronze. When melting aluminium considerable trouble is often experienced through the corrosive action of the molten metal on the cast iron pots used for melting. In order to obviate this difficulty, the Sunbeam Company coat the interior of the pots with a mixture of ordinary water glass and whiting, it having been found that by painting the pots daily with this preparation they last almost indefinitely.

Immediately adjacent to the foundry is an extensive fettling section, a general view of which is shown in fig. 2. Band saws are provided for removing the gates or runners, and pneumatic hammers are employed for chipping purposes. This department is also responsible for carrying out the necessary water-pressure tests on cylinder blocks and cylinder head castings, etc.

As numerous jigs, special tools, and fixtures are employed for machining practically every component, the Sunbeam tool room is naturally an extensive department, and in addition to the necessary jigs and fixtures, a large quantity of standard and special cutting tools are made in this section.

The machine shop comprises a modern and well equipped department, as may be seen from fig. 3, gravity operated runways being employed for the transportation of the heavier components from one operation to another.

With regard to the layout of the machines, as far as possible the shop is grouped in various sections, each of which is completely equipped for the efficient production of a given component or unit. For example, fig. 3 shows the section in which cylinder block castings are machined.

Commencing with the rough milling operation at one end of the line of machines, each casting travels along and undergoes successive operations until it reaches the far end in a completely finished state. There is no possible doubt that this arrangement constitutes a most efficient production method where fairly large quantities of parts are required, for it reduces the necessary progress or routine staff to a minimum and also enables the work of the operation inspectors to be considerably facilitated.

Practically the only exception that is made to this method of machine arrangement in the Sunbeam works is in the case of the automatic section, where, on account of the highly specialised labour that is required for setting-up and operating these machines, it is considered advisable to group all tools of this class together. It may be mentioned that the Sunbeam Company operates one of the largest batteries of Potter & Johnson automatics in this country, these machines being almost exclusively employed for the machining of such parts as gear blanks, brake drums, pistons, etc.

In practically every works a certain amount of trouble arises on account of the difficulty of distinguishing one class of steel from another, after it has left the stores for use in the works. A widely adopted scheme is to paint the various grades of steel with distinctive colours in the form of a strip an inch or so wide extending the length of the bar. In the course of time, however, the colours are apt to fade or rub off, and hence confusion arises. In order to overcome difficulties of this nature in the works under consideration, a scheme has recently been introduced by which every individual piece of bar stock is stamped for the whole of its length with a distinctive description, such, for example, as
3 per cent nickel, mild steel, etc.

Fig. 4 illustrates the device employed for stamping the bars, from which it may be seen that the stamp, in the form of a circu1ar disc having the necessary lettering cut on the periphery, is mounted on the arbor of a small horizontal milling machine. On the worktable of the machine are arranged two lengths of channe1 iron, forming an approximate guide for the bar, which is actually supported on rollers on the underside, minimising the friction to the greatest possible extent, thus enabling the bar to be conveyed along merely by the rolling action of the circular stamp.

To accurately centre the bars in relation to the circular stamp, a pair of rollers located in the vertical plane are provided. These are operated by a self-centring mechanism actuated by the hand wheel to be seen in the illustration, and are closed in on the bar, which is thus automatically centred. The necessary degree of pressure is obtained by raising or lowering the worktable of the machine, and the device is designed so that it will accommodate all sizes of bars used in the works.

The water-cooled detachable cylinder heads are of cast iron, and considerable care is taken in the foundry to ensure the correct position of the numerous cores that are necessary for moulding. In machining, the first operation consists of milling the lower face to provide an efficient bearing face and location for the subsequent operations.

Next the manifold facings are milled, and this operation is illustrated in fig. 5. For this purpose a Hendey double spindle horizontal milling machine is employed, the cutters being of the inserted tooth type. As may be seen from the illustration, four cylinder head castings are secured in the fixture at one setting, and each cutter serves to machine the facings of two heads as the work is traversed past to the cutters.

A particularly simple type of fixture is employed for balding the work, which, briefly described, consists of a box shape casting having two sides only. The work is firmly held in position by substantial clamps which operate at each end of the heads. Subsequent operations on the cylinder heads include drilling and tapping, boring and facing the valve guide holes and valve seats, etc.

For cylinder boring, a special machine, shown in fig. 6, is employed, made by Messrs. George H. Alexander & Co., Ltd., of Birmingham. It will be seen that the machine comprises a horizontal worktable of large area, on which are mounted the necessary fixtures for locating and holding the cylinder castings. Four spindles are provided to drive the necessary boring bars, which are suitably supported at both ends and in between the two cylinder castings by hardened and ground steel bushings.

It may be noted that provision is made in the design of the boring machine to enable the centres of the boring bars to be varied within relatively wide limits, the tool being thus

suitable for practically all sizes of cylinders. After rough and finish boring, the cylinder blocks, which have previously been faced on all necessary surfaces, are drilled and tapped and are finally ground in the bores before passing to the assembly section.

For the milling of the larger aluminium components, such as crank cases, gear

boxes, etc., multiple spindle Ingersoll milling machines of the type shown in fig. 7 are extensively employed, The efficiency of these machines is such that considerable care has to be taken when designing the work holding fixtures to ensure that the actual cutting time is not exceeded by that taken for placing the components in position.

Sunbeam rear axle casings are produced from steel forgings, and after the ends of the forgings have been machined in a lathe, the centre portion is bored and faced by the use of a large centre lathe, provided with special equipment of the type shown in fig. 9. It will be seen that to the faceplate of the lathe are secured two angle plate fixtures, which are fitted with hinged caps that serve to hold the work firmly in place.

Location of the forging is effected by the use of a positive stop operated at one end of the forging, as may be clearly seen in the lower portion of the illustration, whilst one fixed and one adjustable stop make contact with the underside of the centre circular portion of the axle casing and serve to effect radial location. Two studs on either side of the centre of the casing carry swinging clamps, and serve to hold the forging firmly down against the stops, thus preventing either distortion or chatter whilst the machining operation is actually in progress.

It will be observed that special multiple tool posts are employed so that in the first place both flanges of the work are rough and finished bored at one passage of the boring head, while finally both flanges are faced to width simultaneously by use of the four tools held in the second post, which are seen in the illustration.

Considerable use is made in the Sunbeam works of the continuous rotary method of milling of the parts required for the product. There is no doubt that where sufficient quantities of parts are required, this scheme offers the most economical method of production that it is possible to devise, but where only small batches of work are put through at a time, the natural complexity and consequent expense of the necessary work holding fixture, renders this method somewhat uneconomical.

The construction of the work holding fixture is much the same as that shown in fig. 10, the work in this instance being located in suitable vees formed on the upper face of the jig casting, while a number of pins which come into contact with the longer shank of the work towards the bottom extremities serve to control the radial setting.

In addition to numerous modern and standard types of adjustable multiple spindle drilling machines, special heads of this type are extensively used for drilling a number of components.

Fig. 12.  A special multiple spindle drill head.

Fig. 12 illustrates the head and fixture employed for the drilling of rear axle casing covers.

Each drill spindle, together with the main driving shaft of the attachment, is carried on substantial ball bearings, the whole of the gearing being enclosed by a suitable safety guard.

It will be seen that a particularly simple type of work holding fixture is employed, suitably supported on four pillars or legs raising the work to a convenient height, and in order that the same fixture may be employed for drilling other similar parts, which are somewhat longer than those shown.

The cutter spindle is connected by means of reduction gearing to a shaft carrying a pair of circular plates that are provided with numerous serrations on the inside faces in order to locate and firmly grip the nuts being castellated.

A third disc located between the two gripping discs serves to provide a positive means of locating the nuts so that the slots shall be the correct depth.

Fig. 13. An efficient nut castellating machine.

The shafts on which the gripping plates are mounted are arranged so that their axes are at a slight angle, and when the nuts are travelling past the cutter they are firmly gripped on account of the plates being closer together at this point. Immediately a nut has passed the cutter the plates begin to open, and after a short travel the nuts automatically drop free of the fixture. As the empty spaces again rotate towards the cutter, an operator standing in a convenient position places further nuts in position, and thus the operation is entirely continuous.

To prevent any spring of the gripping plates, two rollers are provided, which may be seen in the illustration immediately under the cutter arbor, and these serve to hold the circular plates or discs firmly in position, and to rigidly grip the nuts.

Great care is taken in the assembly of the various units that comprise the Sunbeam chassis, and individual tests are carried out in connection with each engine, gear box, rear axle, etc.

A particularly extensive department is devoted to the final assembly operations, and a general view of this section is shown in fig. 14. After leaving the assembly shop the completed chassis undergoes further exhaustive tests on the road, and when these have been satisfactorily passed, the chassis is handed to the coach building department for body fitting, painting, etc.

In conclusion it may be mentioned that the standard of workmanship and procedure generally in the Sunbeam shops is of particularly high quality.