Hi Mahmood,

I'm afraid I can't speak to the details of how to operate your machine. But the zeroing techniques you describe are similar to those I use on my CNC machine (in my shop, not my LPKF). But instead of a sheet of paper, I use a feeler gauge to set a precisely known gap between the tip of my bit and the z = 0 plane.

So your friend says the smaller the bit the better? Sorry, but I couldn't disagree more. The angle of the cutting tip of your bit allows you to set the width of the cutting path by setting the depth of the bit. Mine have 90° angles and allow me to set the cutting path width from 0.008" (0.2 mm) to 0.012" (0.3 mm). I can use smaller bits that go as fine as 0.004" (0.1 mm) cutting path, but I never use them. If I needed to I would, but frankly I've never needed to.

Since yours are so acute, you won't have much variability. You'll cut through to the other side (or at least to the next layer) first. That's the first reason I would take exception to your friend's claim that smaller is better. It really isn't. It's just more expensive. Smaller bits not only cost more to buy, but they require higher spindle speeds which means they wear out much faster (my second reason), contributing to their higher cost. You should never use a smaller bit than your job requires.

There will be times when you need to clean out the extra copper from a large area of your board (e.g. resonant circuits, controlled impedances). With the tiny bits your friend recommended that's going to take a lot of cutting. You should have some end mills (flat bottoms and vertical sides) for cutting wider paths.

As for your particular machine/software, I'm sorry but I can't really speak intelligently about either.

Good luck,

Joe