Optimizing Material in a Lean Woodworking Environment
By Spencer Dick | Posted: 03/12/2012 11:41AM
Lloyd's Custom Woodwork
With raw material costs continuing to climb, manufacturers are incorporating a variety of methods to maximize their output while minimizing waste in the process.
At first glance, optimizing material usage in a lean environment seems to run counter to the lean concept of single piece flow. Material optimization typically relies on having as large a pool of parts to maximize the number of combinations the computer can look at in order to minimize the amount of material used. Producing one piece at a time would, on the face of it, make optimizing essentially impossible.
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To balance material costs against labor and overhead in a lean environment, the manufacturer will need to create a pool of parts that is not so large as to cause a bottleneck in the plant, nor so small as to loose the benefits of optimizing. Breaking the order into small batches that allow the cutoff department to manage and sort parts so that they deliver them sequentially to the next process or assembly is generally the goal.
Optimizing systems are presumed by most buyers to be created equal, giving results that are the optimal use of material. Nothing could be further from the truth. All optimizers must balance between time and results. Even if we build every product to order, we are limited in the lengths that we will cut. These limitations can be because of shipping, material properties, product range, etc. This means that the potential pool of parts has limits.
On the raw material side, lumber is graded and these grades yield specific lengths. With both a confined input (raw material) and a limited output (finished lengths), by experimenting with pool sizes you can find a quantity of sizes and lengths that will give the majority of the benefits of optimizing; and at the same time can be practically sorted and handled.
The single biggest issue with any optimizing system is how to manage the parts and ensure that they go to the correct product. This has been solved in a number of ways. The first is labels with information printed part by part. Less effective in terms of ease and space are sorting systems that kick off pieces, by length or job, into specific bins. With this, a great deal of space is given on the outfeed side of the optimization system. And while some systems can combine both labeling and sorting, these are generally better suited to secondary remand plants than those doing mass customization.
Influence of Mass Customization
Mass customization flips the logic of the manufacturing environment upside down. Instead of bringing the work in large batches to the processing area, you bring the processes to the work. The result is a dramatic decrease in the physical movement of product through the plant.
With multiple processes occurring in the same work cell, you do not have the room to support large fixed process equipment. You must find smaller solutions adapted to the space limitations, including methods for optimizing or reducing raw material use as related to cut-to-length work.
"The single biggest issue with any optimizing system is how to manage the parts." — Spencer Dick, president, TigerStop Critical to the cutoff process is the ability to reduce the number of error points and produce consistently sized parts, avoiding miss cuts and rework along with related issues in down line processes and assembly.
The tried and true method of measuring, marking, positioning and cutting rely on the skill of the operator. It introduces multiple error points and causes a high variability in produced parts.
Manual stop systems can be an excellent solution. A well-designed stop system has the ability to compensate easily for when the blade thickness changes on the saw; the traditional fixed tape on the bench does not allow for this to happen. The simple solution is to attach a block that the saw can cut through, setting your tape back to compensate for this added length on the stop block. Then when you change your blade you place the stop indicator on zero, then advance the block or change it to a longer block and cut the block. Now your measurements will be accurate. If this is done systematically, you can get good results from such a system. But you are still reliant on operator accuracy.
Another method is a numerically set gauge or stop systems. The advantage with these systems is that it does not matter who cuts the part or when, as long as they enter the correct value and hold the material firmly against the stop.
However, with all these systems is the opportunity for operator error. And, there is little real optimization that can be achieved.
A compact solution is a smart gauge system, which allows the downloading of cutting lists. The user needs only to enter the usable material length and the system takes over, deciding which parts to cut out of the given usable material. It sets the stop to position, the operator makes the cut, the system prints a label and then resets the stop to the next position. All while keeping track of the number of parts cut and optimizing the material usage.
At the next level is a system that allows the throughfeed of material, with infeed and outfeed tables. Information on defects is fed into the computerized system, which creates an optimized cut pattern. The operator then places the material in front of the pusher, at which point the material is pushed to the saw and successive cuts made. Finished parts pass out of the machine and onto the outfeed table. Though typically faster, these systems require a bigger footprint and are more complex and expensive. Often for the same price manufacturers can purchase multiples of smaller optimizing systems that will also allow processing of multiple jobs and materials simultaneously, thus avoiding a potential bottleneck in production.
Source: Spencer Dick is president of TigerStop. For information, visit TigerStop.com or call (360) 254-0661.
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