Conveyors, work slides and roll-ways
Every square foot of every workshop carries a certain and inevitable overhead charge, and is hence a debtor to the plant.
The only possible way in which any square foot of any factory floor-surface can be made to pay its existence debt to the plant at large, is to make this square foot of floor surface support a profit-earning load.
There must be shop-floor lines of travel which cannot be infringed upon by direct-profit-earning agencies, there must be floor-spaces which support rough stores only, other floor-surfaces which carry finished components only, and in the great majority of industrial exploitations there must be floor areas of considerable extent which carry merchantable finished product only, this merchantable product being subject to certain fixed charges for every day of its housing before it finds a purchaser.
This last form of unproductive floor-load is almost wholly avoided at the Ford Motor Company's Highland Park plant, where 90 per cent of the entire production is loaded into railway cars and shipped to cash purchasers as fast as completed, and the only finished-product stores space is the open surface of John R. Street.
Otherwise, the Ford shops are subjected to the previously specified indirectly-productive floor-space over-charges, which cannot be escaped by any manufactory whatever.
But there is another and hitherto unmentioned occupation of factory floor-space, which may be relatively large or small in direct proportion to the intelligence, ingenuity, and resourcefulness of the factory manager —that of shop-floor occupancy by components in process of finishing.
This particular form of indirectly profit-earning factory-floor-space occupancy is commonly regarded by factory managers as an inevitable and unrelievable source of added overhead costs of factory product, and one which must certainly be augmented as the factory production is increased.
An increase of total production for a given time must bring more components in process of finishing into the factory; these components in progress must have floor-space to rest upon because they certainly cannot be suspended in the atmosphere between successive operations; there is no place for work in progress support save the factory floor; and consequently, since the ultimate limiting factor of production must always be the floor area available for the placing of direct-production agencies—the workmen and the benches and tools used by the workers— any increase in factory production per day must always result in decrease of factory maximum-production limit. That is to say, the more work in progress, the less the floor-space available for doing the work.
Perhaps not one factory economist in a thousand will find any fallacy in the foregoing summary of factory-floor unavoidable occupancy by components in process of finishing; yet it does contain an error, so glaringly obvious as scon as it is pointed out as to make it seem impossible that even the most conservative of factory managers could fail to perceive it instantly, to recognize its economic significance, to bear this significance constantly in mind, and to exert all his mental powers to avoid limiting his maximum-production possibilities by needless placing of non-paying loads upon his factory floor-space.
The error mentioned lies in the assumption that components in progress of finishing cannot be carried in the air between factory operations , but must, of necessity, be supported on the shop floor.
The enormous increase in the Ford-car demand very early forced the Ford factory management to place workmen and machine tools as closely together as possible on the floor; but it was not until the beginning of 1914 that it was found that, in some special instances, the convenience of the workmen could be served by the installation of gravity work-slides, usually inclined sheet-iron troughs, so placed that the workman upon completion of his own operation could drop the component into a trough, so inclined as to carry the piece by gravity to within the easy reach of the workman who was to perform the next succeeding operation on the component, instead of dropping the partly finished piece into a box or can and having this box or can carried, pulled, or pushed by a laborer to the next workman, and thus become an occupier of non-paying floor-space—with the transporting laborer's time added to floor-space overhead charges, to increase needlessly the finishing costs.
I It was at once discovered that not only were the production labor costs greatly reduced by work-slide installation, but that the floor was cleaned up, making room for more tools and workmen where it was thought the limit of close placing of productive agencies had previously been reached.
At left, inspector and two lathe hands. The lathe hands face each other, and the tail-stock ends of the lathes are set close to the power press. The lathe hands take washers as they come down the slides, with outside and inside edges finished, from the press, face the slides and cut a spiral groove in each side, and then drop the finished piece into the short slide marked 4, seen between the lathe men. The washers slide to the end next the inspector, who stacks them on his table for inspection
Perception of these facts brought instant activities of the Ford engineers to the front in the endeavor to reduce production costs by gravity slides, endless belts, endless chains, gravity roll-ways, and overhead carriers, each one of which as soon as installed produced unbelievable labor-cost reductions, so that, at the date of this writing, October 6, 1914J these means of transporting components in process of finishing through the air instead of on the floor, are the most surprising feature of the Ford shops interiors.
Broadly speaking, it is safe to say that anything in the way of a work conveyor which keeps work in progress off the shop floor, will be found to effect a large saving in direct-labor costs, and to increase the factory maximum-production capacity.
Labor-Cost Reductions Gained by Gravity Work-Slide Installation
Surprising labor-cost reductions invariably follow the placing of work-slides, although the first gravity slides were installed merely with a view to the advantages gained in the way of transportation of components in process of finishing from one operation location to the next; but, as before mentioned, it was at once made plainly apparent that gravity work-slides vastly increased each worker's efficiency. In every instance of work-slide placing there was a gain of from 30 to 100 per cent in the production volume, with the same methods, machines, small tools, and men; seemingly nothing done to decrease labor costs, yet large savings shown immediately.
The labor savings were due, as is now fully understood in the Ford shops, to giving the workman a fixed place of reception for work leaving his hand, and a fixed point within his easy reach where he could pick up the next piece, thus avoiding thought, delay, and fatigue of the workman caused by breaking into the volitionroutine of his movements.
Where a workman can perform absolutely similar successions of movement , he very soon gains great skill combined with great rapidity of muscular action; but if the routine of the workman's movements is broken, he must inevitably call his brain into action to find the best means of bridging his troubles, and must lose some time in devising and executing his unusual line of procedure. All of this seems too obvious to demand detailed specification, but it is certain that in very many factory operations great time losses are the rule rather than the exception, while it is also certain that a very large part of these time losses can be avoided by the placing of work-handling conveniences of insignificant cost.
These conveniences fall into the following classes, which will be
- 1. Gravity work-slides.
- 2. Gravity roll-ways.
- 3. Slides on which work in progress is moved by hand.
- 4. Endless belts, power-driven.
- 5. Endless chains, power-driven.
shown and described in the order of mentioning:
My attention was first drawn to the labor-saving powers of gravity work-slides by the example shown on pages 273 and 274, front and side views of a group of three power-driven machines, a press and two engine lathes, employed in finishing a babbitt friction washer, now obsolete. The machines were placed as closely as possible—so closely that the work-slides placing seemed an absurdity. The three workmen, one press hand and two lathe hands, stood close together; the washers (babbitt-metal castings) were first passed through a die working against a spring plunger die and ejector in the bolster, this operation finishing the washer hole and the washer circumference, and leaving the washer about 3 3/4 inches outside diameter, hole 2 1/4 inches, and were then faced in the two lathes to about 3/16 inch thickness and had spiral oil grooves cut in their sides.
Before the work-slides were placed, the regular production for the three workmen and three machines was 800 washers per 8-hour day; this rose to 1,100 washers per 8-hour day—or 37 1/2 per cent increase—as soon as the work-slides were used.
On page 275 are shown gravity slides which take the pistons from four drillers on which four men ream the piston-pin holes in about 4,000 pistons per 8-hour day, doing away with two truck men.
Many more gravity work-slides might be shown, as these transportation facilities appear in every direction in the Ford shops, but one or two examples are enough to direct the attention of the intelligent and aggressive shop manager to these cost-reducing agencies, since every installation of this character is a job by itself and copying is not feasible.
It is enough to say that the best placing of any gravity work-slide must be preceded by a careful motion study of the movements of the workmen who are to make use of it^that most men are wiser after the fact than before it, and that no competent workshop official will hesitate to change his own work if he thinks he sees a way to better it.
Gravity-operated roll-ways for moving components having finished circular outlines are very much used in the Ford shops, and have the very desirable feature of moving work with but little roll-way inclination.
Work-slides in general—mere sheet-iron troughs which do not fit the individual pieces which they are called upon to move—must have considerable "slant"; but a roll-way which is fitted to carry a certain finished piece can be built up from rough angle-iron bars so that the work will travel surely with only a very small drop of the delivery end below the level of the receiving end. An example of such a construction, used for transportation of a flanged sleeve, is shown on this page, end view, showing how two widths of angle bars are combined with a sheetiron bottom to produce a roll-way to fit.
Three illustrations of a roll-way for handling the Ford Model-T fly-wheel are here shown, with particulars of savings gained. The Ford fly-wheel is a comparatively large and heavy component and has a large number of holes drilled and tapped in it to take the fly-wheel magneto.
The Ford Fly-Wheel Finishing Line of Tools
Weight of Ford Model-T motor fly-wheels, T-701, gray iron: rough, 41 pounds; finished, 35 pounds. Finished by 16 operations. The general specifications of the Ford fly-wheel, T-701, finishing, here follow , with three illustrations of the roll-way which reduced the flywheel finishing time from 31 minutes to less than 20 minutes.
The 16 finishing operations on the fly-wheel and the machine tools used in performing them, were as follows:
- Operation 1. Rough-turn, finish -turn, face engine side complete, ream two diameters, and finish. Machine tools used are Potter and Johnson automatics.
- Operation 2. Face transmission side, on Reed-Prentice lathe.
- Operation 3. Face transmission side of hub on Reed-Prentice lathe.
- Operation 4. Drill six holes on Foote-Burt, one-spindle driller with Foote-Burt spindle head, to drill six holes at same time.
- Operation 5. Ream two .436 holes on Cincinnati drll press, one spindle, with Ford head to ream both holes same time.
- Operation 6. Counterbore three .6755 to 5/i6 inch three-spindle head; counterbore three holes at once.
- Operation 7. Drill three 41/64-inch holes on Foote-Burt, same as operation 6.
- Operation 8. Ream three .6755 holes on Foote-Burt, same as operations 6 and 7.
- Operation 9. Drill sixteen 21/64 winch holes for 3/8-inch diameter, 24 per inch tap, on special Foote-Burt; drill sixteen holes at once.
- Operation 10. Drill sixteen No. 6 holes, for 14 tap, 24 per inch, on same as operation 9.
- Operation 11. Counterbore sixteen holes, 1/2-inch diameter, on same as operations 9 and 10.
- Operation 12. Counterbore sixteen holes, 3/8-inch diameter, on same machine as operations 9, 10 and 11.
- Operation 13. Tap sixteen holes at same time, 3/s-inch, 24 per inch, on special Foote-Burt tapping machine.
- Operation 14. Tap sixteen holes, 14, 24 per inch, on Foote-Burt machine, same as operation 13.
- Operation 15. Tap four holes, 7/i6-inch diameter, 20 per inch, on Cincinnati single-spindle driller with Ford four-spindle head to tap all four holes at once.
- Operation 16. Balance on Rockford Tool Company's balancing machine.
This fly-wheel finishing line is 120 feet long, and includes 27 separate machine tools. The roll-way covers full length of the line, but is in three sections; first, north to south, page 279; middle one, page 278; south section, page 280. Number of men when fullhanded , eighteen; some men attend more than one machine.
Before placing the roll-ways the best one 9-hour day production was 350 fly-wheels, with two truckers, 20 men, total, on the fly-wheel job. With roll-ways, the production was 460 per 8hour day, with no truckers, floor cleaned up.
Before the roll-way placing two truckers were kept busy in transferring the fly-wheels in process of finishing from one machine to another and piling them adjacent to the next operation machine, never in the best place .for the workman's convenience.
The tools were closely placed and the piles of fly-wheels at each machine and the constant journeys of the two truckers made the flywheel job a place to avoid if possible. Worst of all, the straw boss could never nail, with certainty, the man who was shirking, because of the many work-piles and general confusion due to the shop floor transportation.
As soon as the roll-ways were placed the truckers were called off, the floor was cleared, and all the straw boss had to do to locate the shirk or operation tools in fault, was to glance along the line and see where the roll-way was filled up. As more than once before said in these chapters, mechanical transit of work in progress evens up the job, and forces everybody to adopt the pace of the fastest worker in the gang, and the roll-way had the expected effect of reducing the labor-costs by better than 33 1/2 per cent.
Slides on Which Work in Progress is Moved by Hand Placing work in progress on a slide-way and moving components along by hand as they are placed on the slide-way after an operation completion has the same effect on pace as that obtained by the moving assembly and the gravity roll-way. All the boss has to do to spot the slow man infallibly is to seek the forward end of the congestion of units in transit. This invariably results in increased labor-hour-production , besides cleaning up the shop floor and dispensing with the trucking labor.
Page 281 shows the hand-moved slide-way for supporting the aluminum -casting transmission covers, T-826, between successive milling, drilling, reaming, and tapping operations. About 1,200 pieces are handled per 8-hour day, 20 operations on each piece, 33 workmen, single shift. The tools used are one Ford Company's design special milling machine with two horizontal working spindles, one Ford Company milling fixture applied to a Cincinnati driller; twelve Cincinnati drilling machines, of which two are fitted with special Ford tapping fixtures; and four Foote-Burt special machines, two of which are fitted to drill holes in three directions, while the two others are fitted to drill holes in four directions, simultaneously.
This was one of the first slide-ways to be installed in the Ford shops, and it has now been in use about one year. Previous to the use of this slide-way, 594-hours work finished 1,000 covers. Now, with no change in machines nor small tools, but with the slide-way, 264 labor hours produce 1,200 finished covers, thus more than doubling the labor-hour production, with no change in tools, method, or class of labor employed.
This slide-way is a steel-tube construction, as were all of the early Ford shop slide-ways. The pipe construction is now abandoned in favor of gray iron supporting members and steel angle-bar sliding-ways.
Four examples of endless-belt work conveyors are here given, with illustrations, one from the radiator job, one from the fender job, and one from the sheet-steel-working department, which takes the work from two long lines of power presses, set back to back, so that the punchings drop from the press work-slides onto this big belt and are all carried to one end, where three pickers-off and sorters place similar pieces together in receptacles for transportation to points of storage or assembling.
The fourth example of endless-belt transportation is from the motorassembling department, and shows an overhead endless-belt carrier, close up to the roof beams, which takes components finished on the fourth floor, and transfers them through long gravity slides, to the two widely separated lines of motor assemblers, delivering components to
one line or the other as governed by a switch overhead, the switch being changed on signal from assembling line.
This page shows one of three belts in the radiator department, working together and placed at right angles to each other, to take assemblies made ready for soldering from a bench line of assemblers and carry them a considerable distance and then automatically transfer the assemblies to another belt at right angles, which carries them under a solderer's bench.
The belt used is sewed canvas, the same as in all the other beltconveyor installations shown in this story. The Ford Company has purchased these canvas conveyor belts from Hethick Bros., Toledo, Ohio, the Sawyer Belting Company, Cleveland, Ohio, and from the Gandy Company.
Collier Smith, "quick-work" sheet-metal tools, Detroit; about nine men in each gang are placed at right angles to the belt; mud-guard assembling begins at the far end, and is finished when the mud-guard reaches the belt; the last operation man lays the fender on the belt to be carried away from the job. This belt makes a direct saving of two truckers, and a very considerable indirect saving by moving the fenders as soon as they are ready to move, and so keeping the floor cleaned up and the whole job in tidy shape.
Page 284 an illustration from the motor-assembling floor, and shows two gravity chutes for conveying brake bands supplied by an endless belt placed on the roof beams. The brake bands are made on the fourth floor and are dropped down chutes to the endless belt, 192 feet long, which carries the brake-bands to a switch, overhead, midway between the two lines of motor assemblers. The switch is placed by signal from the assembling lines. This belt saves one trucker, and gives far better service, besides keeping the brake bands off the floor while in transit.
The illustration on page 286 is taken in the pressed-steel department , and shows a belt placed between two lines of power presses, set back to back, to receive both work and scrap.
Work-slides from presses to belt convey all the press product to the belt as fast as it drops from the dies, and the scrap is also placed on the belt. The belt is 192 feet long, 30 inches wide, speed 80 feet per minute. Two men handle scrap, and three men sort the multiform products into receptacles at the end of the line. This belt receives the product of sixty-five presses; it was installed in December, 1913, and saves the labor of about fourteen men. Former practice was to take the press product away in barrels, by truck men, to the craneway, where the barrels were piled, to be taken out of the pile and work handled into cans and trays to go to assemblers. Scrap was collected by laborers, and piled on trucks for disposal.
A great number of endlesschain carriers are used in the Ford shops, some for driving assembling lines and some for elevating and carrying.
Only one example is here illustrated and described, that of the transmission and magneto assembly transfer from the finish end of the magneto assembling line to the two motor-assembling lines.
The magneto and transmission are assembled on a line located at a considerable distance south of the two motor-assembling lines.
The last operation man on the transmission and magneto line places the assembly on an inclined chain elevator as shown just above. The chain serves two gravity chutes, seen close at the left of the workman's head, these gravity chutes delivering the transmission and magneto assemblies to either one of the two motor-assembling lines, according to bell signals from the lines, the one workman shown changing the switch by the pedal shown on the floor, right front, in the upper picture on this page.
The lower view on this page shows the delivery end of one of the transmission and magneto chutes. As this assembly weighs The chain seen in the picture above is used for elevating only.
The delivery is by gravity and includes a brake, 300 lb. spring loaded, which retards the assemblies just before they are brought to rest against the sliding bail in front, which has about 6 ins. movement against heavy cushioning springs. A man receives assemblies and places them in racks, within ready reach of the motor assemblers 98 pounds, a strong brake and spring buffer are required when delivering
. For particulars see the legends under the illustrations. The cash saving effected by this chain elevator is about $20.00 per day, besides the indirect saving due to the removal of travel obstructions on the floor.
It is of little use to give the conveyor belt and chain speeds because in each installation there is some consideration which fixes the speed.