sufrace finish problem on radii

[fergieman]

Hello,
Hopefully someone can help me with this problem, it's driving me mad! I have a recently purchased haas vf4, and when i'm machining radii the surface finish looks like a series of very small flats rather than a continuous radius. I am using a cam package to program the parts, and it makes no difference to the finish if i output the code in G02 and G03 moves or letting the program control the interpolation.
I have programmed other haas machines using the same cam package with the same settings and have not had this issue before. The steps are in line with each other if you machine in a number of z-level steps so i have ruled out the spindle and tool, i have checked the backlash compensation and it is ok, i can't help thinking there is a setting i am missing in the controller.
Straight line interpolation does not show the problem.
Can anyone help?
Thanks.

[automizer]

I understand this problem can happen with the high speed machining option turned off. Did the other machine you ran have this option? There is a 100 hour trial for this option, turn it on try it out then you can turn it off.

[PBMW]

Bet ya a dollar the issue came from the cad system. Tighten up the arc settings in the cam system...

[extanker59]

I had a similar problem and it came from my CAM system (CamWorks). It came out looking like it was faceted instead of rounded. The Cam has a setting to force line moves only. I changed the setting to not force line moves and it was like night and day.
There is a setting 191 , on the Haas, for smoothness. But even at Rough it shouldn't do what I think you're saying.

[maxine]

I have been having the same problem with my TM-1 and Mcam X and I haven't been able to get it to look right even if if set the CAM to filter arcs and try all sorts of different arc tolerances. But I am just learning this stuff so I do think it is me and my use of the CAM that are messed up, not the mill. The best I can get is a series of regular facets like you describe mixed with occasional short smooth arcs that go maybe 10 to 15 degrees of the circle, then more short lines, then another short arc etc. Very frustrating I agree.

[Geof]

An easy way to check if it is the machine is to hand program a simple straight move into a 180 arc and then straight again. Do this parallel to both the X and Y axis and also at 45 degrees and if the arc is smooth and the transition from straight to circular interpolation is smooth there is no problem with the machine.

Running a TM, or at MiniMill at a feed of about 100 ipm on a test like this will give visible ripples in the path following a change from circular to linear interpolation or the other way around. However, these ripples fade away with a short distance. A VF4 should not generate noticeable ripples unless you are feeding much faster.

[maxine]

Thanks I will try that. I have only been running about 45 ipm so the speed shouldn't be the problem.

[fergieman]

Thanks for the suggestions.
I've ruled out the cam system (hypermill) as its exactly the same one i've used to program both the machines that do and don't have the problem. I think it has to be my vf4 in some way, i'm only cutting at 500mm per minute on aluminium, and none of the machines have the high speed option turned on.
I'll try cutting a line blended to a 180 degree arc and post the results later.

[big_mak]

Fergie,

What kind of cutter are you using? Solid or Inserts? If it's an insert tool you may have a tip not seated properly if it is what you describe, or your endmill may not be running 100% if it's solid. Just trying to rule everything out before you go and pull the machine apart!

[fergieman]

Fergie,

What kind of cutter are you using? Solid or Inserts? If it's an insert tool you may have a tip not seated properly if it is what you describe, or your endmill may not be running 100% if it's solid. Just trying to rule everything out before you go and pull the machine apart!

I'm using a solid carbide endmill, but i'd (maybe wrongly) ruled out the cutter and spindle as all of the 'flats' line up with each other on each z-level pass. I would have thought this would be unlikely if it was cutter/splindle related?

[big_mak]

If your cutter is off axis, you may be gitting those lines. It's unlikely, but may be something to rule out.

[Geof]

If it is cutter or spindle related you should see changes if you change rpm or feed.

Do your Z level passes at different combinations of speed and feed, if the flats still line up I would be confident that has ruled out machine issues.