Pockets Not Correct

[Atomic_Sheep]

Hi,

I'm making a spoilboard, so I routed round holes where the T slots are. Problem is, the diameter of the holes turned out to be too small and I'm not sure how to troubleshoot the problem.

The spacing between the holes appears to be spot on so I'm pretty confident Mach3 is setup correctly in relation to my my motors.

I had two hole diameters planned. 8.5mm and 10mm, in the end I got 7.8mm and 9.6mm respectively. These figures don't make much sense to me i.e the differences between them aren't proportionally different, so something really wierd is going on.

Any ideas?

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[ger21]

Flex in the machine.
Small holes are one of the most difficult things to cut accurately.
Try cutting them very slowly, and see if it helps.

[Atomic_Sheep]

I think my holes look perfectly round at least perfect enough for me. If there was any flex, I think the circles wouldn't be round.

It almost seems there's something wrong with my arcs.

I' m cutting MDF at 1.5mm depth, it looks like it goes through it like butter.

What's more, I already cut these holes once before and they came out pretty much spot on. I ran the program again and the only thing that I can imagine that I changed since the last run was my post which I've tried updating and reverting back to the one I used before, but still the problem persists.

[Atomic_Sheep]

Have some additional information on this issue.

A month ago, I made my first cut after setting up Mach3 to work with my machine and achieved a very nicely made rectangular pocket with an island. I don't remember the exact dimensions as shown on my calipers but it was something like 100.07m and 40.04mm so it was pretty darn close to my CAD 100mmx40mm.

Then something changed and suddenly my circles were wrong.

I have now made another rectangular pocket in the same material as my first one and this time I got a pocket of 100.7 x 41.1. My CAD model requested an island of 100 x 40.4 so my dimensions were off my exactly 0.7mm on the X and Y axis. Here's where it gets even more bizzare. I measured my endmill and it was 3.16mm vs 3.175mm, and the G code requested a rectangle of 100.315mm x 40.715 which is obviously 0.315mm off what I wanted to do.

This is at least consistent with my circular pocket problem i.e. my circular pocket is smaller than requested and the rectangular island is bigger than requested, so that's consistent, however everything else doesn't make sense to me. Does anyone see a pattern I can't?

EDIT: forgot to mention, the G-Code for circles appears to be correct i.e. the generated G-Code requests circles consistent with my selected endmill, so why the G-Code for rectangular pockets is coming out incorrect is befuddling.

[Jim Dawson]

Is it possible that you have cutter comp turned on? Maybe ''stuck'' in Mach3? You might try adding a G40 to your code and see if that makes any difference.

[Atomic_Sheep]

I think I found the problem, I think I was sold an endmill that was 0.7mm smaller than I anticipated. Still looking into the issue. Wasted 2 weeks on the issue.