Processes Characteristic of Modern Practice. Heat Treat ing.—Twenty-five years ago little was known about this subject, whereas to-day steels are treated for strength and wearing prop erties in a highly scientific manner, thus providing against break downs and ensuring a longer life for the car. There has been a great change from the old "batch" type of furnace to the present day continuous furnace, at one end of which the operator loads the constantly moving conveyor with forgings. Forgings travel through the annealing furnace, through a quench, then through a drawing furnace without any labour. This principle is applied to pre-heating furnaces in the forge shop, where billets are loaded at one end and travel to the outlet, gradually acquiring the forg ing heat. In these cases time, labour and fuel are saved.
Plating.—The first automobiles were equipped with brass head lamps. Along with the development of the electric lighting system for automobiles, nickel plating came into use on lamps and other outside trimmings. Later, radiators called for nickel plating, which necessitated enlarging of this department in the factory and putting it on a progressive basis. Nowadays, chromium for plating automobile parts such as radiators and lamps is being used by most manufacturers. This plating is not as easily scratched as nickel, and will not rust or tarnish. The plating of rims, usually galvanizing over a copper strip, has not changed much except in method of handling the work. Rims can now come from the forming rolls and sizing machines to conveyors which conduct them through tanks to inspection without manual labour.
Painting.—Painting as applied to automobile bodies has under gone a great many changes. At the beginning of the century bodies were made entirely of wood, and were painted by hand with a brush, pushed around on trucks by hand, and stood up on end to dry after each coat was applied. A good paint job required approximately 24 major operations and 14 drying periods ranging from six to 24 hours, the whole taking about 21 days from start to finish. With the introduction of steel body panels, drying ovens could be used which speeded up the time of drying. With
the flow system of applying varnish together with conveyors, more time and much labour were saved. Increasing use of quick drying nitrocellulose lacquer finishes or synthetic-resin enamel finishes, and spray guns has further speeded up the work and re duced the labour cost until the time needed for finish-painting bodies is measured in hours instead of days. Synthetic-resin enamels are high-lustre paints composed of pigment, solvent, and binder or non-volatile vehicle made of synthetic resin. Enamel ling of wings, or fenders, and other sheet-metal parts pre sents another advancement. For years these parts were dipped by hand in the bath, hung up to drain, transferred to a truck and pushed into a drying oven, which had to be brought up to the proper heat after being loaded. After baking, the oven had to be opened and the parts cooled off before preparing for the next coat. To-day the preparation of the parts is about the same, but they are now hung on a constantly moving conveyor, run alternately through several baths and baking ovens, inspected and conveyed direct to the car assembly line. Here again is a big saving in la bour, material, fuel, floor space and inventory.
Foundries.—Only in comparatively recent years have found ries been operated on a strictly progressive basis, and the transi tion from hand labour to machine and conveyor has kept pace with improved methods in other branches. Machines are now used for ramming cores and moulds; sand is mixed and conveyed to moulding machines mechanically; moulds are made, cores set, castings poured, cooled and shaken out while in motion. Cupolas are charged mechanically. Here again is a great saving.
Machine Shops.—Modern machines have reduced labour, speeded up production and reduced inventory. Not only have they made closer limits possible, but in some cases have made pos sible improvements otherwise impracticable economically. Typi cal from a production standpoint are multiple drills for drilling more than Too holes in all sides of a crankcase casting at one time. Centreless grinders are used considerably to speed up the grinding of certain parts. Special machines are used to balance crankshafts, fly-wheels, and other rotating parts. A recently developed finish ing process produces a finish, accurate to a few millionths of an inch, in a short time. The finish is produced by abrasive stones that are given three or more simultaneous motions under light pressure in conjunction with a lubricant.