Re: [CAD_CAM_EDM_DRO] Re: Just How Accurate Is CNC?

> reputedly achieve positioning and repeatability in the neighborhood
> of 0.0001". As I said earlier, he is estimating only 0.001 on his
> machine.
> It appears to me that his modifications were not too successful.
> Any thoughts or guidance?
> Regards to all,
> Another John

I've never heard of Nantong before, but 0.0001" is a fairly tight tolerance
to hold. The 0.001mm tolerance I mentioned is the tolerance claimed by the
very newest machines. 0.01mm is a fair tolerance to hold on a part, 0.001mm
is really pushing it futher out. You are essentially trying to machine to an
accuracy of a single micron, which is quite something when most micrometers
can only just about manage to read that level of accuracy.

If you must achieve these kind of accuracies, you should be looking at
machining quite small work areas if you want to do it within any kind of
normal budget. I believe the machines mentioned above between a quarter and
half a million dollars each - having a work area of a few metres cubed
usually.

It is much easier to achieve higher tolerances if your work area and forces
involved are smaller.

You should also ask whether or not you even need those tolerances. If you're
building an engine, there is no way you can realistically expect it to
function to micron accuracies. As soon as it warms up, it will rocket right
passed those kind of accuracies. So in this instance, thermal modelling
plays a much bigger role than actual machine accuracy at this level.

I would doubt a standard knee mill would ever manage a single micron
accuracy. I think they're probably quoting the specifications of a single
part of the mill, like a surface finish on the ways or something similar.

If I wanted to make something with micron accuracy at home I'd probably use
linear stages designed for and a dental drill for the spindle.

What is it you'd like to make?

Best wishes,
John