Accumulating Efficiency
June 2004
So your organization has flirted with or even implemented Enterprise Resource Planning, Lean Manufacturing, Kanban, Total Quality Management, Six Sigma, Kaizen, Taguchi, Feng Shui, and a host of other quality and productivity initiatives.
What's next? How do you squeeze more productivity from a plant when the operation is, theoretically, already optimized? There is a proven method. It's called Automated Product Accumulation.
Initially, "product accumulation" might sound like a problem, not a solution. Certainly accumulating product in the general sense of the term would work against efforts for increased throughput or productivity gains.
But for organizations using in-line processing, strategically placed product accumulation can significantly increase overall throughput, especially when the accumulation is automated.
Think back to operations management class, where throughput or productivity were defined as "the value of outputs divided by the value of inputs." A common way to measure this is "units produced per unit time".
For example, with book binding, there are typically several machines working together to produce the finished product. These machines might include a gatherer, binder, saw, trimmer, stacker, cartoner, palletizer. Together they're components of an in-line process. If you line the machines up end to end, the output of one directly feeds the input of the next.
This system works until one machine shuts down due to a jam, misalignment, or other issue. Since each machine's output feeds a downstream machine's input, one machine going down anywhere in the lineup stops the entire production line.
The upstream machines must stop feeding the off-line machine. The downstream machines stop cycling because they lose their input feeds. The cascading effect is immediate and all encompassing.
In live production environments, some machines must be shutdown thousands of times a year. Sometimes a shutdown consumes just a few seconds, to allow a quick adjustment. Other times it requires minutes, hours, and in crisis situations, days.
Even a few seconds of downtime is enough to require other in-line machinery to stop. Automated accumulation helps solve this problem. It enables all other machines in a line to keep running when one goes down.
Automated accumulation requires conveyors that transport products directly from the discharge of one machine to the infeed of the next. The process can be flexible in the quantity of units retained, and accept more in-process products without having to offload any.
This particular ability is called "accumulation" or "buffering". When the downstream machine is off-line and the upstream machine is still discharging, the products accumulate while waiting for the downstream machine to come back online.
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.
What's next? How do you squeeze more productivity from a plant when the operation is, theoretically, already optimized? There is a proven method. It's called Automated Product Accumulation.
Initially, "product accumulation" might sound like a problem, not a solution. Certainly accumulating product in the general sense of the term would work against efforts for increased throughput or productivity gains.
But for organizations using in-line processing, strategically placed product accumulation can significantly increase overall throughput, especially when the accumulation is automated.
Think back to operations management class, where throughput or productivity were defined as "the value of outputs divided by the value of inputs." A common way to measure this is "units produced per unit time".
For example, with book binding, there are typically several machines working together to produce the finished product. These machines might include a gatherer, binder, saw, trimmer, stacker, cartoner, palletizer. Together they're components of an in-line process. If you line the machines up end to end, the output of one directly feeds the input of the next.
This system works until one machine shuts down due to a jam, misalignment, or other issue. Since each machine's output feeds a downstream machine's input, one machine going down anywhere in the lineup stops the entire production line.
The upstream machines must stop feeding the off-line machine. The downstream machines stop cycling because they lose their input feeds. The cascading effect is immediate and all encompassing.
In live production environments, some machines must be shutdown thousands of times a year. Sometimes a shutdown consumes just a few seconds, to allow a quick adjustment. Other times it requires minutes, hours, and in crisis situations, days.
Even a few seconds of downtime is enough to require other in-line machinery to stop. Automated accumulation helps solve this problem. It enables all other machines in a line to keep running when one goes down.
Automated accumulation requires conveyors that transport products directly from the discharge of one machine to the infeed of the next. The process can be flexible in the quantity of units retained, and accept more in-process products without having to offload any.
This particular ability is called "accumulation" or "buffering". When the downstream machine is off-line and the upstream machine is still discharging, the products accumulate while waiting for the downstream machine to come back online.
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.
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