Trouble getting a decent surface finish on arcs

[maxine]

I am moving this discussion to it's own thread. I have been trying to program the toolpaths for this part in Mcam X MR 2. I am using the genereic Haas post that was with Mcam X and I am using a new TM-1 with less than 100 cutting hours on it and all brand new Kennametal tooling. The part is being cut from a 3.5" diameter round of 6061 aluminum. The part was drawn in and exported from Alibre Expert, then read into Mcam.

I am just learning CAM from scratch and I am having a real hard time getting a decent surface finish. I bought the surfacing CD from "Tips for Manufacturing" and I have been through the lessons over and over but I still can't get it right. The issue is on the arcs I get a real choppy surface. The post comes out with a whole mix of arcs and short line segments. I tried setting my tolerance down to 0.0005 with arc filtering set at 2:1, one way arcs, xy arcs only. My min radius is 0.02 and max is 99.9. When that wouldn't work I have tried setting the tolerance up and down, setting filtering from off to 1:1 to 3:1 and changing the min radius all over the map. When that wouldn't work I tried turning filtering off and set the tolerance as low as the program would let me. In all cases when I post I get a choppy mix of short line segments and arcs as small as a few degrees to arcs as large as 180 degrees but not consistent in how they are intermixed with short xy moves. Note that at the suggestion of someone on the Cnczone Haas forum I tried hand programming several different size and radius arcs and circles and cut them on my machine to make sure it was not machine adjustment or machine control issues that were hanging me up. When hand coding arcs or circles the machine cuts a beautiful flawless surface. Same if I use the conversational programming option on the Haas. So here is what the part looks like. I'll post some specific questions in a separate note. I could really use some help as I am getting so frustrated I am ready to just give up.

Maxi

[maxine]

Here is an example of the post produced for one z level cut around the larger pocket on the top side of the part. Not the o-ring groove, that was programmed with finish flowline and it is the only toolpath I can get to work OK. The top side is shown in the first 2 pictures on the left above. Tolerance 0.0005, filter arcs 2:1, one direction, xy arcs only.

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[Matt@RFR]

Your pictures look like the part is all 2D, so if that's right you shouldn't be using surfacing tool paths at all. Am I not seeing your part correctly?

[Steve Arteman]

I'm not sure why you are changing the filter tolerence to .0005 on a rough pocket. what post are you using? very rare ocasions do I ever use filtering for roughing out surface pockets. leave some stock .05 maybe then come back with a finish blend or contour to finish the sides of the pocket, then try filtering. The tolerence .001 to .0005 will be the lowest I go with a HAAS, How much should you filter with your machine. I have seen if you filter too much you take away to much from the program and your part is affected.
I agree with Matt many areas can be cut using 2-d pocket and contour but I would like to see the part. If you can send it I will look at it.
Here is a example video on this link below of a 3-d surface part I showed how to create curves to machine the part using 2-d toolpath, this is in v9 but same concept.
http://www.cad2cam.net/v9wireframe/v9wireframe.avi.html

steve@cad2cam.net
Steve
www.cad2cam.net

[cadcam]

We need to see your file and what path you are using.I fully agree with Matt that part is 2d.