View Full Version : Boundaries - Tool contact areas

02-18-2010, 10:52 PM
I'm in the process of trying to cut some two stroke cylinder exhaust ports on the CNC machine. Normally I'd hand cut these, but in the interest of saving my time I thought I'd give it a try.

Just to put you in the picture I've got a 3 axis machine, so this means that I'll need 3 different settings to get the port cleared to my liking. I've done the 3D model, designed and made the jig, and then fudged 3 mac positions to perform the operation.

The first operation is quite straightforward and I've already done it on half a dozen cylinders. It cam out just as hoped and what would have taken 1 1/2 hours by hand takes 28 mins on the machine with a lovely finish. Now I'm setting up for the next 2 operations.

Anyway, this post is with regards to the boundary selection. At first I just picked the exhaust port exit as the boundary, and this worked fine, but there was a lot of air cutting on the wall that are out of reach from this mac position. Then on the next and final mac positions, using the exhaust port exit again as the boundaries, there's still a lot of air cutting time.

As we're never completely satisfied I was looking for a faster/more efficient option. Selecting faces didn't work. Maybe because there will always be an out of reach face. But tool contact area seems to be what I'm looking for as this produced a much more efficient/faster toolpath.

I'm just running a sim now, and it looks pretty good.

So who else is using this option of boundary selection? What sort of jobs are you using it for? what about settings etc?

Any help much appreciated, and sorry for the rather long post!



Brakeman Bob
02-22-2010, 03:20 AM
Hi Matt.

I use Boundary Selection all the time in HSM; the main ones I use are "User Defined" and "Silhouette". I find it useful to first define a User Defined boundary using face edges, then generate a sketch (right click on the Geometry in the Job Tree) which generates a plane at the exact orientation of the MAC position and the outline of the boundary you selected in the CAM part. Then I edit this sketch to give me the control I desire. Finally I redefine the geometry using the edited sketch.

You can also control the tool with the "Tool on Working Area" which allows you to dictate where you want the tool to cut in relation to the Boundary geometry. The tangent option isn't too clever though.

I have used the "Selected Faces" option but I found it clunky compared to the "User Defined" described above.

Bare in mind that you can miss out a lot of ar cutting by setting the Stock Surfaces on "Edit Passes" tab of the Passes page. I use SolidVerify with "Update Stock Model" set to Manual and save the verified part just before the required job then set the Stock Surfaces to this saved FCT (or STF - I can't remember) file. SolidCAM will then only cut the metal left by previous operations.


03-03-2010, 07:14 PM
Hey Matt,

This is basically the same situation as the "Profile Operation ??" post that we discussed back in January using a combination of boundaries, updated stock & overthickness in "Edit Passes" to control the air cutting as I suggested at the time. In my experience it doesn't matter that the mac positions change because you're using the same stock model. This way you should also be able to use a nice big and simple boundary because the software should only be looking to machine left over stock from previous ops