Wear offset G41

[GPTech2444]

I don't seem to get the result i was expecting with the wear setting. 

Say I bore a 10mm hole and it measures 9.7mm, I put -.15 in the wear offset on the Fanuc controller, and I rebore the hole and I get a 10mm hole.  That's all good but when I do outside 2D contour and use the offset I get an undersize part.  

So the wear compentsation works for in inside cut but not for an outside cut.

Any ideas?

[LibertyMachine]

There are many factors that could contribute to this issue. First off, is it mechanical, how old is your machine, is it a retro-fit or homemade mill? This could be the culprit, but not altogether likely.

The next area I would look at is the G code and the CAM file. Would you mind sharing it? It might be the case that you have a value in your "Stock to Leave" dialog box. Hard telling without seeing the file. 

[fredsi]

GP

If you run the same bore, but drop your feed rate by half, do you get the same result?

On our CNC mills we will do straight contouring at standard high feed rates, but when circular interpolating a hole, we drop the finish feed rates dramatically and add a spring pass. If we used the 'recommended' high feed rates for all the cutting and the outside contour was spot on, the holes that we circular interpolated with the same tool would be significantly undersize.

As gearsoup mentioned, would be helpful to know the machine, material being cut, feeds and speeds, etc. to comment futher. Thanks.

Fred

[fonsecr]

Just to clarify, there is nothing that Fusion does differently with repect to running on the outside or inside for the same compensation settings. So as long as you have selected one of the Wear options you will get G41/G42 in the NC program. You can double check that you see this in your program as a first step.

[GPTech2444]

The machine is a1992 mori seiki mv40b and the controller is a fanuc 0m.

I had the leave stock option off. And I checked the code to make sure the G41 was being applied to each contour.

So as long as the cut is a climb milling operation the G41 wear offset should be correct regardless of an inside or outside contour?

[fonsecr]

Yes, both inner and outer contours will be machined with Climb milling and the G41/G42 will be the same for both. So you should get the exact same result. The CNC doesnt know what is inside and outside either (it just follows along the toolpath offseting to the same side) so not use why you would get a different result.

Try to machine a simple rectangle on the inside and outside and measure the difference from the desired wall on both contours.

[jeff.walters]

GPT two questions: I don’t intend to sound insulting but what does the hole on your modeled part measure?  When you say bore what operation type are you using?

[fredsi]

GP,

Thanks for the info. Solid machine, with box ways I suspect (given the table weight it can handle). Based on my limited experience, I'm sticking with the assumption that the servos can't keep up at high or moderate feed rates if the hole is being cut with circular interpolation. René's suggestion to cut inside and outside rectangular profiles (plus some circular inside/outside ones) would help diagnose the inconsistency.

Fred

[GPTech2444]

Thanks everyone for the replies, I'll have time today to make some circular and rectangle cuts and compare. I'll post up the cam I used and the results.
Grant.