by Nicholas C. Weidhaas
"Production Tips" courtesy of Woodworking International
(Editor's note: This is part one of a three-part series.)
Evaluate your potential "cost savers".
First consider "targets" which are bottleneck operations or those which have broad of multiple applications such as "materials handling", or "overall level of plant efficiency", and potential savings which can be quickly achieved such as lumber yield improvement in your lumber cutting department.
Focus on the handling of parts at the machine.
Typically, many different machine operations involve a series of handling operations which are very similar (even though the machining operations are different). A common sequence of operations is:
- Extract the finished part from the machine.
- Turn and step to deposit the finished part of the finished parts truck.
- Put the finished part on the finished parts truck in such a way that it does not fall off the truck.
- Turn and step to the rough parts truck.
Locate small work tables or platforms at the machine.
These permit the operator to "handle stock in handfulls" from the rough parts truck to the table, and then bring a single piece to machine and collected on the table until a handfull quantity is accumulated which can then be brought to the finished parts truck. In effect, the operator works back and forth from the table to the machine with the single pieces. All activities to and from the trucks are with handfull quantities. The concept of "handling in handfulls" is extremely important.
Keep the machines operating by doing the handling while the machine is running.
Hoppers, and automatic machine cycling devices help to accomplish this, but often there is still lost time when the machine is loaded and unloaded. A few ways to minimize this type of lost time include:
Utilize multiple loading stations, such as the type found on many shapers. While the machining operation takes place at one work station, another can be used for loading or unloading.
Preposition the stock as close as possible to the loading point considering all safety factors and in correct orientation to speed loading and minimize the unproductive time of the machine. This can take some preplanning, such as orienting the finished part on the truck at one operation in such a way as to minimize loading time at the next operation. How many times have you seen an operation where the operator first had to turn the part over or end-for-end before it could be worked on Ė while the machine stood idle?
Eliminate as much of the handling as possible.
A few examples of this include:
For non-critical parts, eliminate handling by tossing the part into a box rather than carrying it to and carefully placing the part on a finished parts truck. Automatically discharge the part from the machine into a box.
Use scissors lifts to avoid the very time consuming "bend and arise" which are necessary when the operator must secure stock to work on from near the bottom up a stack of material.
Install movable "end" and "back panel" devices which can be either attached to the factory trucks or be moved in next to the materials handling conveyors as needed. These panels provide a "stop" or "wall" which the parts can be piled against. This makes the loading of the trucks much easier (and faster), particularly for small parts which tend to fall off of the truck, since much of the careful positioning which would need to take place in the absence of the "walls", is eliminated.
Install quick-acting clamping devices if clamping devices are necessary to hold the stock during machining. Avoid clamps entirely, and time consuming "careful positions" when safety is not jeopardized and other factors permit.
While the part is at the machine perform as many operations on it as possible.
In effect, this reduces the handling component of the job, since "one handling" might service two or three operations.
Focus on "balance" problems.
In most woodworking plants, a tremendous amount of productive time is lost due to "balance" problems. Usually, balance problems are not hard to find if you look for them. Typical examples are:
The boring machine is set on automatic cycle, and the operator is much faster in his handling operation than is the cycle of the machine. How can the machine cycle and the operators handling cycle be made to more closely coincide or "balance"? Could the machine cycle be increased? What additional work could the operator perform rather than to "wait for the machine" and lose valuable productive time. An excessively long machine "stroke" often contributes to this type of imbalance.
One operator frequently waits for the other operator in a team operation. Often "job assignments" need to be redistributed to reduce this type of imbalance. Sometimes, team operations should be broken up, and each operator should work independently.
Conduct a work sampling study
Although this sounds a little academic, it is not. This procedure can be one of the most revealing approaches that you can take in your efforts to improve operating efficiency.
Hereís how itís done: the supervisor (or engineer) simply walks through his or her department with a pad and pencil, looking mostly at the floor, or away from the workers whose activities he is going to analyze. Then suddenly he looks up at one of the workers and observes what the worker is doing at the instant of observation. Usually the supervisor simply checks off which of the pre-established categories of activity the workers activity falls into at the first instant of observation.
Typical categories are: working, idle, missing from job, and trucking materials. Observations can be further broken down to include the reasons for the idleness such as waiting for machine to complete cycle, or waiting for another team member to complete his assignment.
At first it is usually best not to get too complicated, and have too many categories of activity. The analyst observes first one worker, and then another and another. . . As he casually walks through the department, noting category of each workers activity.
After about twenty trips through the department, which should be made at random times over a one to three day period, the analyst can summarize the observations for each of the operators. His results will show something like this (but with more workers):
The analyst then evaluates the data and asks such questions as:
- Does 62.5% overall working time suggest a reasonable level of efficiency?
The technique is simple, but very powerful and revealing. Try it in your operation!
Find your bottleneck or limiting operations.
There is one operation in your entire plant which controls the potential output level of the plant. True, this bottleneck operation can change depending on the mix of products which is going through the plant at any given time. But the concept of a bottleneck or "most limiting" operation deserves serious attention. Think for a moment . . . If you can eliminate a bottleneck by improving the most "limiting operation" then the output level of the entire plant can be increased . . . until the next bottleneck is encountered. If this new bottleneck can be overcome, the output level of the entire plant can be increased again . . . etc. If improvements are made in this stepwise manner, the entire plant output can be increased with only the cost of overcoming the bottleneck. In other words, the return on investment for the entire plant can be increased through only the increased investment associated with overcoming the bottleneck. This is a most powerful concept to understand.
For more infomation, including videos, books, and training programs, visit the: The International Productivity Center Web site at http://www.woodvideo.com/. Their products are designed to assist manufacturers of lumber, furniture, cabinets and similar wood products in their machine operator and supervisory training efforts.