operation cnc

[Jonathan]

Jonathan I've had to correct stuff you made because the **** things weren't square or correct so don't give me that ****

Yes you have once because the machine started off not square and I didn't realise. When it finished cutting I'm sure it was just as far out as when it started! If the machine had gradually lost 'squareness' then the cutter would have broken and the finish would have been terrible since they were so far out. Since then I have corrected the problem.
Also, I should add that the customer you're referring to didn't even tell me there was something wrong with the parts before asking you to fix it. If anyone has a problem with something I make, then I will do my best to fix it, but I can only do that if they tell me there is a problem. He also lied about where he'd sent the parts, but that didn't take much working out.

Even then if motors are tuned anywhere near close to the edge, esp regards Acceleration, they can easily lose steps without realising on jobs just a few hours long.

Easily solved - don't tune them anywhere near close to the edge. If you need to do that then you should have bought better motors or drivers.


There is an easy way to check how square the machine is once it is assembled and working:

1. Set the machine to drill 3 holes of the same diameter at the corners of a right angled triangle in some scrap, with one side parallel to X.
2. Push drills or bar the same diameter into the holes.
3. Measure using digital calliper the side lengths of the triangle by measuring the centre distance of the drills.
4. There are now various ways to find how off-square the machine is. You can draw the triangle (which will be scalene if the machine is not square) in a CAD program and measure the angle that should be 90° to find how far off it is. There are of course several ways to calculate this angle, or you could just use Pythagoras' theorem to see if the hypotenuse is longer or shorter than expected, then at least you know which way to compensate.
5. Correct for the error, then repeat until error is acceptable.
6. If two motors set the home switches appropriately if you have them, or you can put marks on thepulleys you can accurately align.

I got mine within +-0.01° using this method, but that was with a 600mm calliper. Still with a 150mm digital calliper you can get it very close. Also when measuring the hole spacing parallel to X or Y you should find they're within a few tens of micrometers:



There will be a slight error due to the lead error on C7 ballscrews, but as the images above show, at least in my case, this is very small - about 0.01mm in 600mm.