118 



THE INDIA RUBBER WORLD 



[December 1, 1915. 



of ;mv one of llicm is insufficient. .And just as plantation or 

 estate rubber must be delivered in original containers, so ship- 

 pers, brokers, and weighers must not put different brands and 

 marks of wild rubber in the same shipping case. The attainment 

 of these requirements is difficnh now. but only because tliey are 

 not generally insisted upon. 



Other important ingredients of rubber mixtures should be sim- 

 ilarly treated. Ordering by specification should be carried out 

 as far as possible, and on all materials tests for approval should 

 be made before acceptance for use. Then each accepted purchase 

 should be assigned a lot number and where the tests on several 

 different containers of the same purchase indicate important dif- 

 ferences in quality, which the manufacturers cannot avoid, each 

 •Quality should be treated as a separate lot with a letter sulifix 

 added to the original purchase lot number. It has been found 

 most convenient to have an independent series of lot numbers, 

 fetginning with 1, for each kind and grade of material. Thus 

 an accepted purchase of, say, sulphur would become lot 1, and 

 differences in quality, if found in that purchase, would indicate 

 lots lA, IB, IC, etc. The next accepted purchase would become 

 lot 2. etc. Cost and stock accounts may be kept on each lot or 

 group of lots, as may be found most practical. 



Not only purchasing and stock-keeping, but also manufacturing 

 by individual lots, should be strictly adhered to. For products 

 of repeated manufacture this involves the following: 

 ARTICLE CLASSIFICATION. 

 .Ml rubber work may be divided into the preparation and manu- 

 facture of the following general classes of articles, each of which 

 should be assigned successive lot numbers. 

 Raw M.\teri.^ls : 



Dried Highland plantation Hevea rubber, lots 1, 2, 3, etc. 



Dried wild Hevea rubber, lots 1, 2, 3, etc. 



Zinc Oxide, grade 1, lots 1, 2, 3, etc. 



Zinc Oxide, grade 2, lots 1, 2, 3, etc. 



Etc. 

 Mixture : 



Mixture 4 (i. e., formula No.) lots 1, 2, 3, etc. 



Mixture 22, lots 1, 2, 3, etc. 



Etc. 



(A lot may contain any number of batches or millfuls.) 



C.KLENDERED ShEET : 



Calendered Mixture 4—18 (i. c. gage No.) lots 1, 2, 3, etc. 

 Calendered Mixture 4—15, lots 1, 2, 3, etc. 

 Calendered Mixture 30—18. lots 1. 2. 3, etc. 

 Etc. 

 Finished Products: 



Lots 1, 2, 3, etc., for each kind, size and shape. 

 P.\CKED Products : 



Lots 1, 2, 3, etc. for each different style and size of pack- 

 age of the same and different finished products. 

 The same raw material may be used in two or more mixtures, 

 the same mixture may be calendered into two or more gages or 

 thicknesses of sheet, and so on right through the complete classi- 

 fied list of articles, so that each article must be a separate manu- 

 facturing unit. The reasons for this will be more apparent 

 later on. 



LIST OF STANDARD OPMK.ATIONS. 

 Each article should have its own complete list of operations 

 or divisions of work, which are made in accordance with loca- 

 tion, machinery, cost and other considerations, and there should 

 be no deviation from this list in the manufacture of successive 

 lots. Thus, in the preparation of a raw material we may have 



a. Ordering 



b. Testing 



c. Preparing (i. c. sifting, etc.). 



The article is then considered complete, and put into stock 

 for such use in one or more mixtures, as may be required. Its 

 cost, ready for use, may be easily obtained. 



Or, in making a mixture we usually go through the operations 



a. Weighing rubber and ingredients 



b. Mixing ' 



c. Refining 



d. Testing. 



The article is then considered complete and ready for use in 

 one or more calendered mixture articles. Or, finally, in making 

 a finished product we may 



a. Make up 



b. Cure 



c. Finish (i. c trim). 



d. Test. 



An operation can be added to any list to cover the same kind 

 of work that has to be done on almost every lot, or regularly 

 upon only a few pieces or pounds of the same lot. 



In contrast with the above, the list of operations in the usual 

 rubber sliop, when there are any at all, runs through the entire 

 schedule of work for the complete process, from the sifting of 

 only as much of the raw material as is immediately needed, to 

 the final packing of the finished product. But it is generally 

 conceded to be good economy to bulk as far as practicable all 

 the same kind of work on the same article, which, in other 

 words, m.eans to sift at one time all the same lot of raw ma- 

 terial, to mix at one time all the requirements of the same kind 

 of mixture for a convenient period, etc. For this reason and 

 also because of shop ordering, cost, stock, and other consider- 

 ations, this detailed classification of articles and the lists of 

 standard operations are very important ; in fact, no complete plan 

 of shop standardization can do without them. 



UXIFORMITY CONSIDERATIONS. 



It is customary in mixing a lot of mixture containing a num- 

 ber of batches to use up one lot of rubber or ingredients as far 

 as it will go, and then to finish the remaining batches with one 

 or more other lots. This may even happen with several different 

 raw materials in the same mixture. Such a procedure ignores 

 the poosibilities that slightly varying qualities of the successive 

 lots of raw materials may cause more or less important differ- 

 ences in the finished mixture. In other words, every batch of 

 the mixture may not be of uniform quality. Of course, the 

 standardization and testing of raw materials will diminish the 

 chances of trouble, but the manufacture of few, if any, of the 

 raw materials, especially colored pigments and rubber, has not 

 as yet reached such a state of quality uniformity in successive 

 purchases that this way of putting them together will produce 

 the most uniform results possible. 



There is a better method, and it requires only a stpall amount 

 of additional advance laying out on paper. When two or more 

 different lots of the same raw material have to be put into the 

 same lot of mixture, they should be so apportioned that each 

 batch throughout the entire lot of mixture will contain ex- 

 actly the same proportion of each lot of raw material. Sim- 

 ilarly, every pound of calendered sheet should be made identical 

 with every other pound in the same lot by the previous blending 

 of any different mixtures or different lots of the same mixture 

 which are to be sheeted out. And in curing, any two or more 

 lots of mixture or calendered sheet of which the pieces are to 

 be made, should be so blended that every cured piece in the 

 same lot should contain exactly the same proportions of the 

 same kinds and lots of calendered sheet or mixture, and hence 

 of raw materials. 



This system of lot manufacture, involving thorough article 

 and operation classification, is not so complicated as it might 

 appear. Its successful installation does, however, require pa- 

 tience, practice, and experience, and until those who handle it 

 acquire proficiency they are likely to want to revert to the old 

 method, because it seems easier and because the new way appears 

 to require extra effort for small and perhaps unapparent dif- 

 ferences. But eventually, if they honestly maintain its integrity. 



