Undercut when using leftover--HELP

[Larry Westgate]

Whenever I use leftover or pencil to clean up small radius, I am getting a .010 to .060 under cut. The tool offset is correct, the undercut is

not consistant. The mold finishers are about to linch me because of the extra time and fill.

Any ideas?

[Fig sign]

Do you use check surfaces ?

[Thad]

Larry,

 

Are you using resharpened ball cutters? Are they ground to a the correct radius? If you touch off the tip of your tool to set the length, but the radius isn't ground correct (.510 rad ground on a 1" dia cutter), that will undercut your part as the walls become more vertical. We've had this happen.

 

What about the wrong insert in the tool? We have some metric and english tools that are close in size (M12 and 1/2, M20 and 3/4). Could the wrong insert be in the tool?

 

Thad

[Larry Westgate]

Yes to check surf, all ball cutters are new GARR TOOL solid carbide .250

[Fig sign]

But no undercuts in verify .

If so ,that`s your tool stressed to much from cut and gets inside the mold

[gcode]

Are you using filter on the toolpath?

[doyleg]

tool offset set to tip or center? its still probably what iskander said

[88Matt]

How much material is left for the .250 ball to cut? What machine r u cutting on? Is it in z, XY, or both?

[Larry Westgate]

Machine is a Multiax router OSAI controller- using ball tip- material left is from a .500 ball end mill - the undercut is evident on all axis-filter is set 1 to 1- I am cutting foam board so cutter whip should not be a problem especialy with light cuts

[Larry Westgate]

I also get a mismatch when the head rotates from one side to the other, sometimes as much as .050 but average is around .020 .025. The machine people keep telling me it is Master Cam giving me bad code.

[malibu]

sounds like you have a machine problem.

if new, send it back !

[Larry Westgate]

That's what I think also, this machine does not have ballscrew drives it has a rack and drive gear. the rack is spring loaded so "there is no problem with backlash" I have used Master Cam for 12 years or so and the only time I had bad code was my fault, garbage in garbage out. This is a

continual problem, I dont belive the machine can do any better than .020 .025 repeatable.

[Matthew Hajicek - Singularity]

I'd say write some code manually for a few test cuts to see if things line up. Maybe tilt 45° one way and cut a corner cube, then tilt 45° the other way and cut an opposing corner cube, and see if the two line up and are the correct distance apart.

[Colin Gilchrist]

Do a Circle, Diamond, Square test, then rotate the C axis and re-cut the same part. This will tell you how much your head is out.

[Larry Westgate]

I will try some of these tests and let you know what happened

Thanks for your imput