AUTOMATIC MACHINES, machines which function throughout their cycle of operation without the intervention of human effort. Special types are used in many industries for two main reasons; to reduce the necessity for manual labour and to secure uniformity of product. The rapidity with which automatic machines are developed and used depends largely on the cost and quantity of manual labour available. This is shown by the rela tively slow introduction of special types of automatic machines into countries where labour is cheap, and the wide-spread use of such machinery where the wage rate is high, as in the United States. The great advantages of uniformity of parts lie in the saving of labour in assembling parts together and in repair work, and so is also closely related to the general wage level.
Machines can be designed and built to perform any operation normally done by hand. Some movements are difficult and re quire intricate and costly mechanisms. But given an output suffi ciently large and labour costs high enough, the machine will be forthcoming. Unfortunately the designer and builder rarely profit to nearly the same extent as the user of the machine, unless the machines are leased, either on royalty or at a fixed charge per month or per year.
Automatic machines are now in use in nearly all industries, from the making of food products to the forming and machining of fairly heavy metal parts. Notable and interesting examples are to be found in the making of parts of watches and clocks (q.v.), cigarettes (q.v.) and in the wrapping of such products as chewing gum, soap and safety razor blades. Incidentally, the razor blades themselves are punched, ground, tempered and sharpened in machines that are almost entirely automatic. In some industries such as flour milling, automatic or semi-automatic machinery has almost entirely replaced human labour. Few men are to be seen, even in the flour mills producing hundreds of barrels of flour per day. Recent steel mills also have machinery so nearly automatic that many men are relieved of much of the back breaking labour that was formerly necessary.
The full automatic machines are much more intricate and re quire greater care in designing. This is largely because of the mechanism required to feed the material into the machine, to hold it firmly while the operations are being performed, and then release, or even eject the finished piece so as to make room for the next cycle of operations. When the work is to be performed on plain bars or rods that can be fed through the work spindles; in punch presses where the material can be fed through the ma chine in strips; in textile machines where the yarn or thread is continuous, the feeding mechanism is comparatively simple. But the problem is far from simple where the machine must pick up pieces of paper, as in an automatic job printing press, place them on the platen, and remove them at the proper time and pile them suitably ; or pick up a safety razor blade, place it in the grinding machine correctly, so that the edges will be ground at the proper angle ; pass it to another machine which automatically strops it and then finally to the machine that wraps it in waxed paper, without touching the sharpened edge in any way. In this sort of work, suction cups are frequently used to pick up flat pieces. Another intricate problem is the sorting of screws, pins, etc., so as to insure their going into the machine in the correct position. These are usually dumped into a hopper which must sort them and direct them, singly, into the chute or slide that feeds them into the machine itself.
The same basic principles, however, are frequently applied to widely varying materials and purposes, but often in a strikingly similar manner. An excellent example of this similarity is to be found in the machines for making lead pipe bends or "traps" for plumbers, and those which turn out "elbow" macaroni for large food product manufacturers. Although there is a vast difference in the material used and in the size of the product, both machines are identical in principle. Both extrude a plastic material (lead or dough) in the same manner and control the flow of material in such a way that more is fed to the outside of the bend, forcing the extruded tube to assume the desired shape. When the curve is completed both materials are automatically cut off in the same way.
One of the most important points in designing automatic ma chinery is in securing the proper sequence of the different motions and the requisite time between the different movements. In "tim ing" the movements the designer must consider the time con sumed in moving the work, the tools or the fingers into position, the actual time of the operation itself, and of moving the tools out of the way and replacing the completed work with a piece that is unfinished. Every movement of this cycle must be carefully laid out, both to avoid the loss of time and prevent the interference of various movements. Designers who have been brought up in this line of work follow the various steps from force of habit, but a novice will spend much time in studying out the next move.
As an example of how some of these various elements are com bined in actual machines we show an outline of the movements of a type of riveting press used in the huge automobile frame assembling plant of the A. O. Smith company in Milwaukee (for photographs of this plant see Plate I.), taken from the patent specifications. Starting with the electric motor A (fig. I) we follow the drive through the pinion and gear to the worm B, which drives the disk C by means of the worm-wheel, in the direction of the arrow. The disk carries the crankpin D and the cam slot E. Crank D drives the connecting rod F and the crank-arm G, that rocks about the shaft H. To the right of H is another small crank I that moves the ram J of the press up and down for head ing the rivets in the frame. Simultaneously the lower part, or anvil K, moves up and down so as to head the rivets and return to the open position at the proper time. The movements of the anvil are effected by the cam slot E in which is a roller at L, in the end of lever Al. This lever, being pivoted at N, moves the wedge (or cam) 0 under the plunger supporting the anvil K, and so raises and lowers it at the proper time under control of the cam slot E. By following the revolution of the disk C, it will be seen that before the riveting ram .1 gets far on its down stroke, the wedge 0 has raised the anvil K into the position shown. The cam holds the wedge in this position until the ram J has headed the rivet and then withdraws the wedge for a little more than half the revolution of the disk C.
During this time, the ram J is being raised and the next frame is being set in position for rivet ing. This is only one of many mechanisms in this huge as sembling machine, a description of which may be found below ; but it shows one application of all the elements, if we consider the worm B as a screw, which it really is. Similar combinations of these four elements will be - - -- found in most of the modern types of automatic machines.
Two types of parts going to make up a frame are side-rails and cross members. Due to their different peculiarities and lengths, they each have a separate system of machinery leading to the far end of the building where one large unit takes care of the final assembly.
Let us first follow the side-rails. The pickled steel entirely handled by conveyors passes through the side bar press line (see Plate I., fig. 2) with its four operations. First, the straight strip is kicked up in order to as nearly as possible follow the desired con tour of the side-rail. Next, the numerous rivet holes, gauge-points and other openings are pierced, separate presses for right and left hand rails being required. Next there operates a single blanking press which trims the blanks, whereupon two more presses take care of the forming operation, i.e., the folding up of flanges to obtain the conventional channel section. The feeding and unloading of each of these presses is done entirely automatically, and all the movements are timed and synchronized in a single unit, which does not require labour at any point. The side-rails are automati cally deposited in crates, which move to the next unit by crane.
Before the side-rails can be assembled into a frame, there still remains a great deal of work to be done on them. A number of spring hangers, brackets and other attachments must be riveted on; but first the ends must be clipped (see Plate I., fig. 3) off and certain holes drilled and reamed with extreme accuracy. This is done in the single large unit called the "side-bar parts assembly" (see Plate I., fig. 4). Right and left hand bars are handled in pairs simultaneously, and loaded on to trucks automatically. The assembly is about 3 5of t. long, has 38 trucks and i 9 stations, at each of which adjustable automatic machines are performing the various operations required. The finished side-bars are auto matically removed from the trucks at the end and inspected before being delivered to the adjacent general assembly unit.
Going back to the point where the strip steel enters the manu facturing building, the steel intended for cross members is depos ited by the monorail cranes at the loading ends of four crossbar finishing lines (see Plate I., fig. 5). Each of these is equipped with blanking, piercing and forming presses, very similar to, although smaller than, corresponding machines for the side-bar press line described above. Like them, the crossbar presses are fed auto matically and all handling is done with automatic machinery.
Following the press-line is a continuation, which has a purpose similar to the above mentioned side bar parts assembly line. How ever, much less work has to be done on crossbars, requiring pro portionally less space. At the end, the finished crossbars arrive at the general assembly unit in a manner similar to the side-bars.
The general assembly performs two important functions and does both automatically. It collects all the required parts for the frame, assembles them and puts in all the rivets (see Plate I., fig. 6), finally setting each rivet by forming the rivet heads, as was described above. One conveyor system with trucks called the hand-loader line takes care of the first function. A so called nailing machine assembles the frame and puts in the rivets, while another conveying system equipped with other trucks handles the last function of riveting. All three sub-units are synchronized and operated with one single motor.
When the frame is stripped off its truck at the discharging end, it is delivered to the painting machine. On a conveyor, running the full length of the building, it travels back to storage. While on the way, it is carefully inspected and if any part is missing or defective, it is side-tracked, fixed up on a special repair line and then sent on its way again.
Arriving in the storage building (see Plate I., fig. 7) it first has to pass through a washing machine where grease, dirt, etc., is thoroughly removed in a special automatic machine, using hot alkali solution. Clean and dry it is delivered to the painting machine, where, hung, one close to the other on an endless chain, the frames slowly pass through and special lacquer paint is sprayed on at the rate of 75ogal. per minute; they pass through an oven which bakes the paint, then through a cooling chamber, emerging after one to i hours as a finished product (see Plate I., fig. 8).
A few examples of automatic machinery as used in other in dustries will give a good idea of the extent to which machinery is replacing human labour in nearly all lines of work. The folding of men's collars, for example, is done on a machine such as is shown in Plate II., fig. 1. This is a Sweet and Doyle machine that folds collars to the desired shape, after they have been cut from the cloth at the rate of 12 collars per minute in regular production. Milk, now sold almost exclusively in bottles, is handled by machinery from the time it leaves the cow—some dairies even employing mechanical milking machines. The milk and cream are separated by centrifugal machines, both are cooled by me chanical refrigerators, and they are bottled in a machine such as is shown in Plate II., fig. 2. This is known as the Elgin, and handles i 2 bottles of milk simultaneously. The bottles are car ried on a conveyor, stop long enough to be filled, and are then replaced by the next 12 bottles. From here they travel on a conveyor to the capping machine, Plate II., fig. 4, where the name of the dairy and the date of bottling is stamped on the cap, and the bottles sealed at the rate of 5o per minute.
The machine shown in Plate II., fig. 6, wraps bread or cake in any size of loaf at the rate of from 45 to 55 loaves per minute, the pre cise number depending on the size of the loaf. The machine also inserts a label under the wrapper of waxed paper to identify the make of the loaf.
The pieces to be turned are stacked in the vertical magazine at the back, this being done by hand, although it could be done automatically if the labour-costs warranted. At the proper time, the feed slide below the pile of work moves back so that the lowest piece in the slide can drop into the notches in front. The next forward movement of the slide carries the piece to the centre of the lathe and holds it while the tail canter forces it into position for driving from the live spindle. Next, the tools move into position for cutting and are fed forward the desired distance. The piece is then released, and the tail stock centre recedes, the finished piece drops out of the way and the cycle is repeated.
A typical example of a multiple spindle automatic screw machine is shown in Plate II., fig. 7. This is a National-Acme, five-spindle machine capable of handling Ain. material through the work spindles. There are five of these spindles and five tools at work, with a correspondingly large out put. The indexing time is short, owing to a rapidly accelerating indexing movement. This ma chine is driven by a 5 h.p. motor running at I,800 revolutions per minute and has a net weight of over 3,000 pounds. The spindle speed can be varied from I,o5o to 2,885 revolutions per minute. The production range is from 355 to 2,88o pieces per hour, depending on the character of the work.
An idea of the way in which the work is divided between the five spindles may be had by studying fig. 3. This shows the finished piece at the upper left with its principal dimensions. The other illustrations show the work performed at each tool station. It should be remembered that all five of these operations are in process at the same time on material which is in each of the five work spindles. The first tool is a drill that goes in about of the length of the piece. The next station completes the large hole and at the same time a tool in the cross slide forms the neck at the end. The outside is next turned, using three tools so that only one-third the tool travel will be required. At the same time a high speed drilling attachment drills the small hole clear through the piece and leaves a centre beyond the cutting-off point. The out side is then finished with form or shaving tools in the cross slide, and the hole reamed to secure the desired size. The large hole is also chamfered. The last spindle taps the hole in the end and as soon as the tap has backed out the cutting-off tool comes in and separates the finished piece from the bar. The small drill has left a centre for starting the large drill on the next cycle of operations performed on the same bar of stock.
There are, of course, many more types of special automatic ma chines, but these will serve to show some of the developments and to bear out the statement that automatic machines can be designed and built for duplicating any human motion. In the machine-tool field there are comparatively few strictly automatic machines, if we consider this term as meaning those in which the work is fed to the machine without human assistance. Many machines are called automatic which perform their cycle automatically after the work has been put in place and the machine started by the operator. Such machines run their cycle and stop when it is completed. But they do not unload, reload and start again with out attention from the operator as a strictly automatic machine should do. (See MACHINE TOOLS.) (F. H. C.)