[FiveSpindleCam]

Hello all. In programming a part with a oval keyway in the OD to run on a Mazak 18-MSY mark 2 with a Maztrol T Plus control.

I'm using the MGV milling function, trying to cut a .408" wide slot with a .313" endmill. My slot looks 95% complete, but one end of the slot has an incomplete radius. Instead of a full radius blending smoothly into the long straight walls, one corner has a distinctive blend mark from a smaller radius. If I were programming in EIA, I would think that I inadvertantly turned tool comp off too early, because the endmill seems to be pulling too tight a turn going into the last corner of the slot. The resultant radius measures about .360", which is not the tool or the programmed part geometery.

My process parameters are as follows:

MODE: MGV OUT
Mode #: 3-0
GRV-WID: 0.408
DEPTH: 1.08 (through the part)
FINISH: .010
RV: 120
FV: 180
R-FR 1: 0.0008
R-FR 2: 0.0005
R-TOOL: 9
F-TOOL: 9

SEQ:1
SPT-R: 0.535
SPT-O: -90.0
SPT-Z: 0.625
FPT-Z: 0.640
ROUGH: .001

Any idea why this slot is not comming out oval? I'd program it as a MMP (Manual Milling Process), but I only have +/-.0025 on the slot width, and then the operator would need to edit the program to size the slot instead of comping the tool diameter. I'd like to avoid that. Any help would be apreciated.

[MrMazak]

I would check the parameters for ramp in and out. That is a pretty tight fit and big clearance will cause some problems with entry/exit. Check U3,U4,U5,U6. Change them to .005 with TPC and see if that helps.

[FiveSpindleCam]

Thanks MrMazak. That advice definitely got me looking in the right area. What I thought was an incomplete slot, upon further inspection, was actually being undercut in one of the corners as the endmill over-shot the far end of the slot before pulling out. I dug thru some books, and it turns out that user parameter U14 controls how much overlap there is on a Y-axis milling path to ensure a smooth transition from the start to the end of a cut. My machine was set U14=787 or .0787" of overlap. That's a problem when my slot is only elongated .015". I set U14 to 100 (.010") and my slot looks oval again. Thanks again for the timely help.