Can not figure how to limit toolpath - help please...

This forum is for general discussion about Cut3D
Post Reply
ddoughboy
Posts: 4
Joined: Sun Feb 22, 2009 6:20 pm

Can not figure how to limit toolpath - help please...

Post by ddoughboy »

Hello,

I just purchased the Cut2D and Cut3D package and am now wondering if Cut3D is going to do what I need. I am a student and am trying to cut a 3D trophy out of 3/4" acrylic. The design is very simple, it is basically a sloping scallop down into the thickness of the acrylic. A few images are below. The two frustrating things that after many hours of trying various approaches and reading many posts on the forum, I for the life of me still can not figure out. I'm hoping that it is not a limitation of the software as the relatively low price of the software in the CAM world is still a lot of money for me on my student loans... anyway, here is what I am trying to do, any help is appreciated.

The first problem I am having is keeping Cut3D from running a full finish toolpath across the top most flat surface of the acrylic. If the top surface of the imported model is coplaner with the Z zero plane, I don't understand why it assumes it should be toolpathed, especially if the setting for "Depth of Model Below Surface" variable is set to 0. As the images show, the only machining that is needed in the design is a depth cut in the shape of the "D", yet Cut3D forces the finish toolpath to raster across the whole surface. This of course isn't what I want since I want the factory polished surface of the acrylic to stay as it is. The only way I was able to get around this is to fake the Z zero point on the CNC machine a little higher than the surface, though this seems like a mickey mouse way of working around the issue. (Please see the last image that goes along with this issue.)

The other way I tried to work around this problem was to reduce the imported model (I'm modeling in Rhino) to just the cut "D" scalloped part, with no top surface into Cut3D. I thought that this might reduce or eliminate top surface toolpath issue. The problem then, is that it assumes a rectangular boundary around the rounded, non-rectangular shape of my model. It then insists on rough cutting and finish cutting any space between the boundary of my non-rectangular model and the rectangular bounding box that Cut3D assumes. (please see images 6-9 for this attempted fix).

Any thoughts if there is something I'm missing in terms of settings in Cut3D or a better strategy of how I model the piece? Again, thanks for any help on the matter, I'm starting to pull my hair out! :)

Best, Rob Ley
Attachments
Model as first imported
Model as first imported
Rough tool path, everything is alright at this point.
Rough tool path, everything is alright at this point.
Finish Toolpath.  Here you can see that the top flat surface is being cut in the tool path.  How to prevent this?
Finish Toolpath. Here you can see that the top flat surface is being cut in the tool path. How to prevent this?
Final Preview.  Top finish toolpath isn't shown, though it does show in the final cut part if Z is set to flush top of surface
Final Preview. Top finish toolpath isn't shown, though it does show in the final cut part if Z is set to flush top of surface
Here is the first actual cut test.  I artificially pulled the Z zero plane 1/8" above the actual surface of acrylic to prevent cutting, though this can't be the only work around.
Here is the first actual cut test. I artificially pulled the Z zero plane 1/8" above the actual surface of acrylic to prevent cutting, though this can't be the only work around.
Attempt #2.  reduced model is imported in, this time without the top plane surface.  Rough toolpath now goes outside of the non-rectangular model. Space between actual model boundary and the boxy imposed boundary is being cut.  This doesn't work for my part, either...
Attempt #2. reduced model is imported in, this time without the top plane surface. Rough toolpath now goes outside of the non-rectangular model. Space between actual model boundary and the boxy imposed boundary is being cut. This doesn't work for my part, either...

User avatar
metalworkz
Vectric Wizard
Posts: 2463
Joined: Mon Mar 31, 2008 3:26 am
Model of CNC Machine: SX3 CNC, DIY 24x20 & 48x60 routers
Location: Modesto, California 95358 USA

Re: Can not figure how to limit toolpath - help please...

Post by metalworkz »

Hello Rob,

On attempt #2 did you by some chance select 'all' vectors and include the bounding material vectors? I don't see why the roughing pass would go outside the modeled vectors unless perhaps it got inadvertently selected? If you can remove the outside vectors maybe the attempt #2 will do what you want?
If you did not need the gradual slope to come to the surface perhaps you could do a very shallow pocket(.001" ?) for that section and then do the 3D slope from that to the other end? This way you could start the 3D vectors further away from the finished surface and perhaps since they start below the top surface they will not try to cut on that plane? I know it is not per the original design but even a shallow pocket of perhaps .001" might not be so noticeable and could even be fairly easily blended out if needed. Maybe start the shallow pocket a few thousandths in from the final end of that toolpath so it will be close to the model when blended? Hope you find an easy way to get past this.
Best regards,
Wes
wes.spence@comcast.net
Gingery Machines:
Lathe, Horiz. Mill, Shaper, Leaf Brake

ddoughboy
Posts: 4
Joined: Sun Feb 22, 2009 6:20 pm

Re: Can not figure how to limit toolpath - help please...

Post by ddoughboy »

Hi Wes,

Thanks for the reply. I don't see where in Cut3D it even gives the option to select vectors to include. My understanding is that it assumes you are by default going to include and machine the entire part/vector that was imported. Am I missing that option somewhere?

Rob

User avatar
metalworkz
Vectric Wizard
Posts: 2463
Joined: Mon Mar 31, 2008 3:26 am
Model of CNC Machine: SX3 CNC, DIY 24x20 & 48x60 routers
Location: Modesto, California 95358 USA

Re: Can not figure how to limit toolpath - help please...

Post by metalworkz »

Hi Rob,
I'm sorry, I don't have the registered version and I need to download the trial version again to take a better look. Perhaps it does not give you the option to select the vectors to create toolpaths for? I guess the way it did the machining outside of the model is from the rectangular material designation when you start the program? I will try to download the trial version again and see if there is another way around this.
I have the Aspire program and I know I can create a vector to enclose my 3D model and limit the finishing toolpaths to within that vector. Unfortunately that is not an option in Cut3D.
Do you think you can set the Z zero plane up a little bit so as to have the finishing toolpaths above the surface? Then it would cut it all except the surface similar to what you did with it at 1/8" high but just high enough to clear the surface??
Best regards,
Wes
wes.spence@comcast.net
Gingery Machines:
Lathe, Horiz. Mill, Shaper, Leaf Brake

ddoughboy
Posts: 4
Joined: Sun Feb 22, 2009 6:20 pm

Re: Can not figure how to limit toolpath - help please...

Post by ddoughboy »

Hi,

Thanks for the suggestion to raise the z plane by 1/8". That does work if I tell my CNC into thinking its Z is on the surface of the material, but actually making it 1/8" higher, but the problem arises when the angled plunge then enters the material unevenly, if that makes sense.

Based on the documentationo, the Silhouette option for object boundary should work for what I'm doing, but after trying many different values for this, I'm realizing that it appears to be geared to offset OUTWARD only. Thus, if one were milling the car model as shown in the documentation, it would limit the tool path to only the object. That's good if you are machining objects. The problem is when your object is actually a pocket, or a sculpted cut into the material, as is my part (please see photos above). The silhouette offset only want to help limit the cut path outward, not inward.

In essence, no matter what I try, since there is no way to limit or put a boundary around the area that needs tool pathed, Cut3D assumes the user is making an object that the user will want 'cut out' of the material. Not sure if this is 100% the case or if I'm still missing something?

Rob

Cerberus
Posts: 4
Joined: Thu Jan 10, 2008 12:12 pm
Location: Barcelona (Spain)

Re: Can not figure how to limit toolpath - help please...

Post by Cerberus »

Hi Rob,
I had a similar problem, and I'm using a workaround that maybe can help you.

I want to carve a guitar top, that has a center plain surface that I don't want to be milled

If I calculate the finishing toolpath I get this one (2h 1minute)
TEST01.JPG
The height is 12.692mm, so I slice the model at 12.6mm
TEST02.JPG
Then, 2 slices are generated, and I get the first one (12.6mm) and discard the other one (0.092mm)
Now I can calc an 'optimized' toolpath (1h 08min) that differs only 0.092mm (good enough for me)
TEST03.JPG
I hope it helps you
Regards,

Jose

ddoughboy
Posts: 4
Joined: Sun Feb 22, 2009 6:20 pm

Re: Can not figure how to limit toolpath - help please...

Post by ddoughboy »

Hello Jose,

Thank you for the helpful post. I went back and tried your suggestion to use the slice function and it works great! I thought I had tried everything but apparently I didn't consider other ways that the slice model function could be of benefit.

Thanks again, take care.

Rob

Post Reply