X3 Surface Finish Contour Problem

I am trying to mill a radiused channel. It has a radius of 0.118". Essentially all I want to do is run a ball end mill across my part to make an o ring groove. The problem is the radius is not a standard size. So short of having a cutter ground how do I do this channel in mastercam? The tolerances are tight and using surface operations, mastercam seems to be milling the channel the correct width but the depth is wrong. Also if I choose containment boundary offset to none the ball mill ends up cutting a tiny 0.002" chamfer at the top of the channel, but the dimensions are fine, if I say offset inside it gets rid of the tiny chamfer but the channel dimensions are wrong. Any ideas/solutions?

You may need to post what you've got and see if any of us have a second to help you with it.

Bueller?

Did you get it to work?

WallyL7,
I work the evenings and didnt have a chance yet to follow up with you. I will be generating the nc code tonight and will try to post some pics and stuff of what im talking about.

If you are up against a wall, then post your file also. We may be able to help quicker with the file vs a picture...

So here are some drawings to explain whats happening. The "Shape" pic is what I need to machine and the "Machined" pic is what is getting machined. The chamfer is only about 0.001"-0.002" so the pic is exaggerated. I can see it under a microscope and on an optical comparator so the client isn't accepting the part because it isnt a sharp edge.

If I use a "inside" containment boundary it fixes the problem but the dimensions of the cavity are on the small side. Im trying to hold +/-0.001".

If I use a "center" containment boundary it leaves the chamfer. Do other users see this too? Using center containment seems to machine the cavity correctly for size but leaves the chamfer.

Can you post the actual file? I've never seen it just go ahead and chamfer an edge like that...

Did you use Check Surfaces?

Yeah I did use check surfaces. Im not at my shop but will be later. Ill generate the code and post it.

When you use surfacing operations, do you use center containment or inside? Also if you use center do you start the depth limit at 0 or do you set it for the first depth of cut? I notice if you set it at 0 it always runs a pass at 0, not cutting anything.

Actually, no I didnt use check surfaces. I was thinking about a different setting. Are you thinking if I set the outside of the channel as a check surface it wont do it?

Post the file not the code. I can have a look at it if I get a chance. You may just need to tighten up the filters.

For that type of situation you would probably just use inside containment..


For check surfaces - choose the top 2 surfaces of the part (the one that is getting chamfered)...

Ok ill post the file so you can see the parameters.

Ill also try the check surface idea and see if that works.

I think using center containment, as the ballnose runs up the side and centers the tip on the edge it is just nicking the side on its way up/down.

Thank you for your help!

Quote:

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Originally Posted by moto1965

I am trying to mill a radiused channel. It has a radius of 0.118". Essentially all I want to do is run a ball end mill across my part to make an o ring groove. The problem is the radius is not a standard size. So short of having a cutter ground how do I do this channel in mastercam? The tolerances are tight and using surface operations, mastercam seems to be milling the channel the correct width but the depth is wrong. Also if I choose containment boundary offset to none the ball mill ends up cutting a tiny 0.002" chamfer at the top of the channel, but the dimensions are fine, if I say offset inside it gets rid of the tiny chamfer but the channel dimensions are wrong. Any ideas/solutions?

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My maths work out that 0.1181 = 3mm .... it's not a "special", try a 6mm ballnose along the centreline

as for that chamfer, it is a tolerance setting .... so
- don't let the tip of the cutter go anywhere near the edge of the rad, your start depth for finishing should be a little less that the cutter radius as this is the point that generates the upper size width. as for depth, make sure the cutter actually cuts at -0.118" () sometimes the settings don't allow a pass along the centreline.

Thank you Superman that makes sense. I am machining a similar cavity tonight and will see how it works out.