Accumulating Efficiency

June 2004

multipage

As such, the product accumulation is continually increasing and decreasing in size. Sometimes there are more accumulated products on the conveyor, sometimes less, depending on the pattern of machine stoppages.



This process is, of course, controlled by sensors and computers, or by PLCs (programmable logic controllers).



While accumulating conveyors are the preferred approach to implementing an accumulation process, they're not fundamentally required. Some manufacturing lines have implemented the process using manual means.



When a machine goes down, trained workers quickly take products off the upstream non-accumulating conveyor, and pile them onto a pallet or drop them into a bin (hence the term "pile down").



When the downed machine comes back online, the workers manually reintroduce the products back onto the production line. It's an error prone, time- and labor-intensive process, but certainly better than no accumulation process at all.



Automated accumulation is, in my opinion, the better choice. It is far more time- and cost-efficient than manual methods, plus it keeps workers free to concentrate on other tasks.



By installing automatically accumulating conveyors between key machines, such as a perfect binder and a trimmer, plants can increase throughput by up to 30%. Once done, an entire production line will rarely be idled when one machine goes down.

Deciding to install an automated accumulation system is the first step towards further increasing productivity. Properly sizing the accumulation capacity is the second step. It's a balancing act that requires careful adjustment of rates, machine capacities, mean time between failure, mean time to repair, and the number and duration of delay occurrences, based on empirically derived data.



Floor space and capital budgets must also be considered when optimizing accumulation capacity. And, as you might expect, there is a point of diminishing returns on downtime coverage.



An accumulation capacity large enough to cover 80% of stoppages makes better sense than one sized for 100% of occurrences. That's because some stoppages can be a few hours long. The accumulation required would be so large (and rarely used) that it would consume most of a plant's floor space.



That said, for production organizations seeking to increase throughput beyond established operational productivity initiatives, automated accumulation is an exciting, often overlooked process worth considering.

-Christopher Arthur Brumm

Christopher Arthur Brumm is paper market segment manager for Shuttleworth Inc., in Huntington, Ind. He can be reached at C.Brumm@Shuttleworth.com.