Machining undercuts 1

[John2025]

Can anyone help me figure out how to machine the undercut areas of this part in 7.0 or 7.5 with a 3-axis machine? In I-deas I would have used a T-slot cutter with a profile cut but in NX I can't get anything to hit the undercut regions.
Thanks, JohnK

 

[raysapp]

If I'm seeing it correctly it looks like 2d work, in which case planar milling would do fine. You'll want to go to the "more" tab in cutting parameters and make sure "prevent
undercutting" is toggled off. Also, "part safe clearance" determines how close the system will allow the shank to get to the part. If you can post your part with the tool you want to use I'm sure someone would attach an operation for you.

Ray S
NX 7.0.1.7
www.appliedprecisionproducts.com

 

[John2025]

Sadly, it's not 2D as the bottom surface is spherical and the undercut tabs are curved. I tried planar and it wouldn't accept the non-planar faces. Hopefully I'm just missing the boat on this and someone can get me straightened out. Here's the part. Thanks.

 

[raysapp]

NX handles undercut surface contouring just fine. Fixed contouring/surface area is the best choice I think. I'm attaching a sample I downloaded off gtac. It's something to look at while you wait.

Ray S
NX 7.0.1.7
www.appliedprecisionproducts.com

 

[John2025]

Dang it, that looks like what I want and I tried Fixed Countor, Surface Area but couldn't make it work. I need to study the example to see where I went wrong. On a side note , where did you find that on GTAC? I can't seem to find this kind of thing on their site. Thanks a million, at least now I can see that it can be done, I was starting to worry.

 

[wmalan]

If the undercuts are cylindrical I'd still use Planar Mill - Profile. Create a face or plane for your Floor (since the face is slightly non planar. Use the edges for Part. I assume you're going to finish real floor the with a bullnose anyways?

--
Bill

 

[raysapp]

When I say gtac, I mean the user group. I've had to deal with a lot of undercut issues so when anyone ever uploads a file with a solution I grab it and save it in my own database.
As for your struggles, surface area has to be worked. Projection vector is usually the issue.
The problem with surface contouring your feature is the sharp corner at the top of the undercut, requiring a special tool that NX probably wouldn't support for surface area. Speaking of which, I noticed both top and btm edges of feature are planar, even though the face is curved. It appears to me you could cut that with a custom form tool and use planar profile. Maybe you'd rather not hassle with that, but I think the sharp corner poses a problem.

Ray S
NX 7.0.1.7

http://www.appliedprecisionproducts.com

 

[raysapp]

Duh ... Bill's right. I should've looked closer.
Take a look at this.

Ray S
NX 7.0.1.7
www.appliedprecisionproducts.com

 

[raysapp]

Of course that doesn't address fillet at btm. I'd use a std ball mill for large surface and a lollipop style cutter for undercut fillet.

Ray S
NX 7.0.1.7

http://www.appliedprecisionproducts.com

 

[raysapp]

Here's a surface area op for btm fillet. It's programmed for a lollipop/barrel cutter (found it in Harvey Tool catalog), but will also work of course with relieved ball mill. Motion looked right at first but upon closer inspection looked a little squirrelly at points. Ran through verify and sure enough it qouged at .004. Reduced in/out tol and had no effect.

Ray S
NX 7.0.1.7
www.appliedprecisionproducts.com

 

[John2025]

Thanks guys, you've been amazingly helpful. I think I'm starting to get a handle on this. Now I just need to buckle down and iron out the details.
Thanks again,
John