A producer of rubber products for the automobile industry was not using batch inclusion bags. The production workers poured powder additives onto a conveyor belt which led to the mixer. On the way, small amounts of the powders spilled over the sides of the belt onto the floor. When the additives reached the mixer, they were dumped into the opening, but this created dust which was absorbed into the dust collector. The company re-worked the material collected in the dust collectors as a filler. Over time, the company realized there were significant differences in the mixing time and quality of the rubber from batch to batch. The main cause was variability in the amounts of key accelerators and cure agents that were added to the mix because some of these ingredients fell onto the floor or accumulated in the dust collector. Secondly, when they re-worked the material from the dust collectors, the cure time varied because of the presence of accelerators and cure agents in the "filler." When the company began using batch inclusion bags, they saved money by virtually eliminating the loss of expensive additives on the floor and in the dust collectors. They also improved the quality of the rubber they produced and uniformity from batch to batch because the key additives were added to the mixers with much more accuracy.
CASE A major tyre producer used one large batch inclusion bag for the additive weighments. When we toured their plant, we noticed that much of the time they only put a small amount of material in the large bag. We also realized that, on some of the production runs, they could use a second type of bag with a higher melting point. We calculated that, by using the higher melting (and lower cost) bags on some of their batches and switching to three bag sizes, the customer could save over Rs.100,000 per year. To avoid using the bag with the wrong melting point, we color coded the higher melting bags blue for easy identification. The customer instituted these changes and reduced their batch inclusion bag costs significantly.