December 1, 1915.] 



THE INDIA RUBBER WORLD 



117 



Modern Industrial Methods in the Rubber Industry. 



/(■. .Irmm 



NUT long ago a friend addressed the writer as follows: 

 "Why doesn't the rubber industry in general put a more 

 reliable product on the market? Usually I am obliged 

 to stretch several rubber bands before I can get one that won't 

 break, two out of every live auto shoes I buy have to be returned 

 for credit, because they become unusable before the completion 

 of their guaranteed mileage," and so on with water bags, syringe 

 bulbs, shoes, and other rubber articles he had occasion to use. 

 It was not any one make that he complained of, for he had tried 

 many of the best, and although some proved to be more reliable 

 than others, successive purchases of the best sooner or later 

 proved their unreliability. A certain tirm manufacturing apparatus 

 for hospital use recently installed an expensive equipment, includ- 

 ing several hundred feet of standard rubber tubing which they 

 bought for the purpose directly from a well-known rubber fac- 

 tory. Within a very short time the tubing had become unusable. 

 The rubber factory replaced the entire lot, but the results were 

 just the same, and in both cases the cause of the trouble was laid 

 to improper curing. Such experiences are only too common and 

 have led to general condemnation of the rr.bbcr industry for its 

 unreliable product and its backwardness compared with other 

 industries. 



The manufacturers meet these criticisms by claiming that the 

 art of rubber manufacture is still comparatively young; that the 

 nature of the product itself offers peculiar difficulties not found 

 elsewhere because of the variability in the raw state and the 

 changes which are likely to occur in the finished article after it 

 is made ; that they are spending large sums of money investi- 

 gating and trying to eliminate these troubles ; and, finally, that 

 the many stores in which the product is sold and over which they 

 exercise no control carry rubber stocks unreasonably long 

 before selling. 



To many of those who are acquainted with the manufacture 

 of rubber articles, these claims are readily understood and ap- 

 preciated ; but they do not satisfy the present needs of the con- 

 sumer, and it is a belief held by the writer, as well as by others, 

 that the average rubber shop overlooks two very itnportant weak- 

 nesses, namely : — 



1. An absence of a high standard of mechanical practice 



and precision, 



2. The use of empirical instead of scientific methods in 



the control of processes, and the handling of 



materials. 

 Comparisons of representative shop practice may make the 

 lirst of these points clearer. Contrast, if you will, the usual meth- 

 ods employed in a machine shop with those found in a rubber 

 factory even of the better type. In the former a workman is as- 

 signed a task on a machine — a milling machine, for instance — 

 which makes one or more cuts under graduated control from any 

 desired angle. The material upon which he operates and of 

 which his cutting tool is made — tool or machine steel, hard or 

 soft brass, or whatever it may be — is of practically uniform qual- 

 ity, not only from different sources of supply, but also in dif- 

 ferent purchases over considerable intervals of time. A clear 

 understanding of what is expected of the workman is shown on 

 a detail working drawing made in advance from a complete de- 

 sign, so that the result harmonizes wfth other work on the same 

 or other pieces and is a part of a schedule of operations whose 

 previous consideration, as a whole, assures the elimination of mis- 

 tits and a standard quality which can be repeated as often as 

 desired. Any experienced machinist who can operate the ma- 

 chine and read the drawing, can produce the same result. Xo 

 change in the design is allowed without a reconsideration of the 



Jiihnslon, Jr. 



whole by the designer. The judgment of the lower-priced ma- 

 chinist can have no effect upon the quality of the product so long 

 as he adheres to the instructions on the drawing and the design 

 and di-awing are correct. 



In the rubber shop, however, a workman does his work on a 

 machine— a mixing mill, for instance— where the adjustments of 

 heat application and roll spacing are not under graduated control. 

 He puts on the mill the rubber and ingredients, which are usually 

 weighed out for each batch in advance, adjusts the roll-spacing 

 or gage, applies steam or cold water to the rolls, and handles 

 the mixture in accordance with his sight, touch, and previous 

 experience. He is given few, if any, written instructions to fol- 

 low. Xor does the material which he works on act uniformly, 

 even in different batches of the same kind of mixture. This 

 may be because of quality variations in the crude rubber or other 

 raw materials, or it may be caused by differences in previous 

 treatment due to faulty workmanship or the different personal 

 equation of a substitute workman. At any rate the mill-man 

 takes the materials as furnished him and endeavors to work 

 them into a condition which his experience tells him is about 

 right. Other operations throughout the whole process, except 

 possibly curing and vulcanizing, are carried on similarly; so that 

 there is at best only an incomplete harmonizing of all operations 

 as they affect the whole finished article. In some plants chemical 

 and phj'sical examinations are made to check the resuhs of im- 

 portant operations ; but although they indicate and save many 

 defects, such tests are often difficult and of questionable reliabil- 

 ity. In short, the maintenance of the manufacture of a rubber 

 product of uniform quality, according to present practice, is very 

 largely dependent upon the judgment and personal equation of 

 the more or less experienced workman, rather than upon a high 

 standard of mechanical practice and precision. The result is a 

 product of variable quality, as might be expected. 



It might be well to state here that the writer realizes that 

 among rubber, as well as among other factories, there may be 

 exceptions where a higher state of development obtains; but, 

 unlike the others, the number of exceptions among rubber shops 

 is comparatively small, as evidenced by the condition of the prod- 

 uct on the market. 



Thus far an endeavor has been made to indicate the absence 

 of a high standard of mechanical practice and precision in the 

 average rubber shop by comparing the present existing con- 

 ditions with those of a modern representative of high develop- 

 ment—the machine shop. Hereafter an attempt will be made 

 to describe briefly a few of the better methods of handling ma- 

 terials and of controlling processes. 



In any effort to standardize the rubber shop the first necessity 

 is to eliminate as far as possible the effects of unavoid- 

 able variations in the crude rubber as it is now frequently 

 marketed in small quantities by many different growers or 

 estates. One of the best methods is to include always in 

 each batch or millful a small quantity of the product of each 

 of several of the same reliable growers in the same quantity 

 ratio to each other. The more growers included the less will 

 be the percentage content of each, and the less possible variation 

 from standard quality by occasional failure to obtain the product 

 of one or two of the usual growers. This may involve increased 

 purchasing and weighing costs, but the resulting smoother manu- 

 facturing conditions, fewer defects, and more uniform quality of 

 product will more than justify the extra expense. With the 

 wild South American rubbers the same treatment can be applied 

 to different brands or marks when the usual available quantity 



