Tech Talk
What has changed in woodworking machinery?
In more than one hundred years of existence the woodworking machinery industry has designed and built so many types of cutting, shaping, sizing and profiling machines it's hard to imagine anyone coming up with anything brand new. Improving the technology, of course, this is a never ending task in every industry. So why would anyone bother to try to build a custom machine? The most common objective is to do 2 or 3 processes at once, or in sequence without buying 2 or 3 machines. The sequence is often unique to an application and may not require the diversity of standard equipment. Saving money is another motivator for building a custom machine. Standard machinery has to be adaptable to a wide variety of applications in as many factories. This can add cost, and if the task in question is singular and simple often a less complicated and less costly machine can be built employing the design principles of the tried, true and experienced machinery. The other reason for starting from scratch is the notion that somehow it can be built better and cheaper.
The types of custom machines vary but the most common are saws - of all kinds. For example wide band resaws. There is this mistaken idea that Resawing machines can be built a lot cheaper and better than standard ones. I call this a mistaken idea because almost everyone who attempts to build one thinks they are nothing more than big bandsaws. In fact, they have little in common. Trying to resaw on a bandsaw will probably lead to disappointment. There are strengths and features designed in to resaws that insure that the blades built for them will cut straight, fast, stay on the machine and run true and safe. This is rarely the case with custom machines. Inevitably the blades will not stay on properly, or they will wear prematurely and/or crack or break easily. There is not too much experience out there building custom resaws because they are seldom attempted twice. The factory built machines have tensioned, crowned and tilted wheels that hold the blades straight in the cut and firm on the machine. Without these features the blades will wander in the cut and wander off the wheels. Blade life is terrible, and the poor guy that supplied them is often left to explain why.Custom built Circular saws can vary from gasoline driven Cordwood saws to PLC driven multiple blade Ripping machines to Mitering machines for a huge variety of materials. We have even tooled saws for trimming vegtable stalks, in bulk. Every application for a custom circular saw has it's own problems to overcome, but from the standpoint of tooling these machines, the problems we run into usually begin with being ignored at the design stage. Once the need for a custom machine is recognized the process of figuring out how begins. This usually involves determining the type of machine, and this is where a lot of custom jobs lose focus. The concentration is on the job at hand and the machine. Too often, how the machine is going to be tooled is not brought to the floor until it is half or even fully built, and this can be a costly mistake. If, at the design stage the saw blade people were brought in they would focus on how the blade, the machine, and the material were going to interact. This interaction is too often taken for granted, but won't be by the guy who is going to be called when the cut or production from the blades is unsatisfactory. He will look at the spindle speed, clamping system, blade diameter, drive method, for either the blade, the material, or both. The other thing he will look at, that is too often taken for granted, is the areas of adjustment. It is amazing the number of machines that have been built with no allowance for blade wear. The blade has to be fully adjustable, as does the feed system, if for no other reason but to give you some flexibility. Custom machines have been designed and built with feed rates that were set from pure guess work and set up so that adjustment could only be made by either a programmer or, by a major modification to the machine. How the blade is mounted is also very important. In the worst case I can remember a customer was very proud of the fact he had built a fool proof and safe saw for his one function. It was sturdy and would do exactly what he required. What he forgot to consider was that saw blades get dull and have to come off to get sharpened. In order to remove the blade he had to break down the machine, including removing the motor. It was a source of never ending frustration and costly downtime that should have been avoided. In another case, I recall a machine that was built and fixtured with a specific position for the blade. The problem was they built it assuming they could put a blade on that was over 20 inches in diameter and as thin as the thinnest 8 inch blade he had found, and there was no room for adjustment, or to modify it. The material thickness should be no more than one third the diameter of the saw that cuts it, but every once in a while someone builds a machine with allowance for a 12 inch blade to cut 5 inches of wood, forgetting the blade has a one inch bore, not to mention a support collar.Hold down is another big issue. The rule is zero tolerance for movement during the cut. Light springs or pneumatic pressure wheels don't work. If you don't hold the wood firmly it's like throwing it in a blender, and you will likely destroy or damage the blades as well.Never under power your machine. Too little horsepower will transfer too much load to the blade. It will bog down, overheat, warp, wear prematurely and may break, and of course, it will do a lousy job. Geared or pully driven blades offer more adjustment for tunning the relationship of power, feed and speed, as well. There are many custom saw builders who can probably foresee most, if not all potential problems as they pertain to the saw blade. The problems usually arise with builders that have limited experience building saws. But no matter who is designing the machine, if it's purpose is to cut or shape the material the important thing is to get everyone, from the ducting people to the tool people, involved, before it is built.These observations are merely a portion of all that have to be considered. Each project would invite it's own set of circumstances, questions, problems and solutions. Here I have only dealt with saws. There are other types of custom woodworking machines that present challenges to tooling people and the same rules of early consideration are absolutely necessary. by: Doug Reid, President, B.C. Saw
