RE: [CAD_CAM_EDM_DRO] Timing Belts?

Hello Tom,

Glad to see you step out an announce yourself!

Belts are a pretty common element in a CNC system. While you are correct
that there is a certain amount of inaccuracy inherent, I think it falls into
the ego range (you know, the my machine can do 1 micron, well mine can do
.5). The reality is the errors are so small that they will be unnoticed. If
you study how a stepper works, you will have inaccuracy due to the way they
overshoot and return on any given step. We are talking very small amounts
here. There are so many things that can affect your accuracy. Some of the
ones that come to mine and are totally unrelated to the machine are:
metal expansion do to heat from the cutter
setup rigidity
cutter sharpness, geometry, concentricity
toolpath strategy
etc. . .

I think it was Ballendo that brought up the point that marketing and ego
will drive us to want higher levels of precision and accuracy than are
realistically needed. Remember, we sent a man to the moon with 1960 era
technology and machining methods.

My recommendation is build a machine and start learning what it will do.
Don't stress over all the little things of what if. You will quickly learn
that this is actually a pretty straight forward technology.

Tim
[Denver, CO]

> Hello-
>
> This is my first post to this facinating group. I am am jewelry model-
> maker and hope to build a cnc mill sometime in the future. I have
> plenty of questions to ask but I'll keep this post brief.
>
> If I ever learn enough to attemp to build my own machine, I would
> like the machine to have the following qualities: moderate speed,
> high resolution, and accuracy. I have been reading about micro-
> stepping as a way to getting higher resolution, however I am
> concerned that the micro-steps are really not that accurate.
>
> The alternative to micro-stepping is either gearing down or using
> timing belts and pulleys. I realize that ordinary gears can introduce
> a certain amount of back-lash into a motion system, and I imagine a
> set of gears that reduce or eliminate back-lash can be very
> expensive, so I would like to find out if pulleys and belts should be
> considered in designing a "tight" system. I have seen steel
> reinforced belts, so I imagine stretching of the belt is nothing to
> be concerned about, however I am wondering if the teeth on the belts
> can introduce some flexing ( resulting in inaccuracies) into the
> system?
>
> Thanks for your time-
> Tom Murray
>
>
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