Strange cutter path finish

[Bazzer]

Does anyone have any ideas on what might be causing this strange finish on an aluminium tool that we are machining?

The stepovers are .1mm so we were expecting to get a really nice finish. Machining stratergy is 'Planar', there is stock left at 0.25mm and semi rough cut of 1mm stepovers, the rough cut image is also attached.

The 3D model seemed smooth when viewed in a number of CAD packages, the model that was imported into BobCAD is in the attached ZIP file.

Any pointers would be gratefully received.

Regards

Barrie

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[CNCMAN172]

Bazzer,
Is that surface smooth? It looks rough and it appears your spindle is out of tram. Did the same machine do the machining on the outer rim which looks good?

Russ

[Bazzer]

Bazzer,
Is that surface smooth? It looks rough and it appears your spindle is out of tram. Did the same machine do the machining on the outer rim which looks good?

Russ

Hello Russ

Yes all done on the same machine which is a Dugard. The machine produces good work, lots of precision aerospace stuff and the machinist is very good.

We have done full 3D paths before but not had this problem.

Where I think you are suspecting out of tram is actually some wide bands where the 4mm ballnose cutter has bunched say 100 passes together and made that horrible fore and aft band, then it has moved on and done the same again.

Baz

[jrmach]

Try Equal Distance for finishing

I cannot open your file,,but also use the largest radius tool possible

Also reduce you CAM tolerance in settings

[Bazzer]

Try Equal Distance for finishing

I cannot open your file,,but also use the largest radius tool possible

Also reduce you CAM tolerance in settings

Ok I will check these out.

Thanks

Barrie

[BurrMan]

I wouldn't define that surface as "smooth" but I wouldn't call it terrible either.

I think it's a numbers game and not the surface. The part is 514 whatevers with a stepover of .1 with the tolerance set at .0127... Just not enough and it is allowing those gaps.

I set part prefs 3d tolerance and also feature tolerance to .0001 and it smoothed the toolpath. Took about 6 minutes to calc.

I think that is very small in metric. I didn't check how low to take things to still produce a good path...

A good think would be if deviding that 514 with .1's, you want to allow for enough calc room on the surface to not variate, or "Jump" far off....

[Bazzer]

Hello BurrMan

As is often the case you pointed me in the right direction, it was the tolerance that was wrong.

We ran a trial cut and it seems good, going for the whole job tomorrow.

Many Thanks

Barrie