Weired issue( just started) Cnc realted or not

[Rainman229]

Well since I have been recently been doing more with the cnc I have a problem that just started to show it's face. ( just so you know it hasn't happened running the cnc before just reared it face on the last 2 or there runs).

What's happening is when it go's to the next cut depth on multiple passes of the same cut pattern. It steps out a few thousands each pass all the way around the pattern. Making it the right size at the top and wider at the bottom. So on the last Project i cut that was a 1/2 depth the diference from the top and bottom was about .005+ at the bottom. You could see the steps and where each pass depth was. The out side off the material it was cut out from came out perfect.

Is this just me and did I screw up the g-code and have my cutting direction messed up. or did my machine mess up some where?

I've checked backlash. That seems fine. But backlash would cause it to be off more or less one way. and can't see how that would effect it if it on continues path all the way around.


Thanks for any input.

[HuFlungDung]

Worn or damaged tool?

Since the tools typically get used only for a small fraction of their depth, on the end, it is possible that edge wear will produce a step pattern.

Drilling a hole with an endmill can also cause corner damage to the tool if a plunge entry method is used. Or recutting of chips can also damage a tool.

[Switcher]

You need to post the g-code file, first, So we can check that out.

If the g-code is good, than you will know it's your machine,

[Rainman229]

Oh it's defiantly the machine finally noticed what was going on when manually cutting. I cut a path going straight on y and when i went to cut the second step down the end mill shifted about .010. So i have major column issues it seems. Do's the same thing on x cuts too.

Just put a dial indicator on it. With a collect in and measuring at the Colet i have .010 play side to side and on the column it seems to .004 , So i would say my issues are the claim and the bearings.

Nows the question is how do i fix it? Figure snugging up the bearing should take care of that. But the column play? Snugging up the column lock only takes out .001 , But i don't want to tighten it to much cause it will bind the z and eventual break the casting. So what do i do?

[Rainman229]

Tightened the bearings helped a little. The finish of the cut is nicer now. But still drifts off to the side when cutting deep pockets.

noticed something odd when cutting to if i let the end mill sit in one spot it would drift/sink making a hole. So after seeing this i put the dial indicator on the bottom face of the head. Pushed down then up. Dial showed .040+ of movement. Any way to fix that or ball screw the only fix?