Problem- ? VF-3

[littlerob]

Hello everone, I have never seen (or maybe noticed) this problem before. I like to run my tools above the part before I make stuff. Monday one operator tells me this machine is way off, OK right lets see what the problem is (your an idiot) so we run it above the part 300 IPM it is creating oval arcs on the Y axis....by 100 thausandths of an inch approximately, checked the backlash (thanks Geof), thats OK. Corner rounding is toleranced at .005, Has any one had a similar problem? Let me say again 100 thousandths, WOW. The machine has been run to it's limits for a period of time, about 6 months. When run at reasonable feeds in 1018 it's fine. Thanks, Robert

[Geof]

I had a thought. (Dangerous stuff thinking, have to be careful I don't hurt my head.) And this is a crazy thought.

You did not check the backlash under load; you can't the machine has to be stopped.

Maybe there is something loose in the Y ballscrew, but not completely loose; think of how a floating tap holder is held between opposing springs, no load no movement.

When running an interpolation at 300ipm I bet the inertia loading is greater than the cutting load.

So increase or decrease the inertia load, i.e. mass on the table and see if it changes the ellipticity. Take off all the vises, etc and do a test then fill the table with enough stuff to get to its maximum load capacity.

I have already admitted this is a crazy idea.

[littlerob]

That is a good idea and coincidetally it has an APC maybe I could figure out a way to run without the entire table, I don't think it will, but it's worth a try, and if thinking is dangerous we all need to be put away, I just "think" that we need to think before we over think. Thanks, Robert

[Gravey57]

We had the same problem with a vf-4. The machine would not read ahead correctly at a high feed rate such as 300 ipm. When run under 100 ipm or less it was fine.

[littlerob]

But what was the solution? To me it seems unacceptable, there are times that we machine that fast.

[Donkey Hotey]

What year is the machine? Does it have the HSM option? Have you tried turning HSM on (trial period) and checking the results? Have you called Haas and talked to them?

[littlerobb]

Contacted the local Haas tech he is on the way, I am not familiar with HSM, and it is a 2000. Thanks, Robert

[littlerob]

The problem was that we were creating an ellipse at a high feed rate. To go more into detail I was allowing the operator the opportunity to learn how to generate a single line that would produce a helical pocket. He figured it out but I didn't notice that he had put a finish Y value into the line, instead of putting only I, and , J values while in G91 mode. My fault. This caused the machine (not to the fault of the machine) to incrementally move to that Y position. Just thought I would let you guys know. Robert