region toolpathing in PW3D

[Steve Howden]

Hi All,

This is my first post here. I've had a BT48 Alpha running for few months now and I must say I love it.
Cutting all manner of materials in 2D for signage and it runs flawlessly.
We are also cutting lots of foam in 3D for props and models and again all behaves very well.
But now I've bumped into a problem I could do with some help on (this is a recreational job, not business, so no urgency).

I have modelled a new rudder for my sailboat. It consists of the foils shape in 3D and planar horizontal and vertical sections. See attached image.
The model is about 13mm thick and stock is 18mm thick.
I want to mill the 3D section by toolpathing in PW3D but I want to do the planar sections in 2D to save the damn thing doing miles of additional finishing work with a ball nose cutter where it shouldn't. I 'd also like to stop PW3D from cutting any vertical sections........ and THAT I can't work out.

I realise that regions aren't supported in PW, but I thought maybe some of the gurus here may have a strategy to deal with this.

Failing that, I suppose I'll have to stump up for a better CAM program, so I'd love to hear any suggestions and experiences.

All modelling is done in Rhino 5, so I've considered both MadCAM and RhinoCAM.

If anyone wants to have a go, here is a link to the model as a DXF

http://www.3dinflate.com.au/3D/JB_RUDDER_v2.dxf

BTW, this is a shape I have used before and it is VERY fast. It's a NACA12 section. Any sailing shopbotters are welcome to use it ;-)

Regards, Steve

[Steve Howden]

Ooops, just remembered you are mostly Americans and use those funny old inches as units ;-)

Units are mm.

[shoeshine]

Steve,

I would simply slice out the section of your model that requires 3D machining in Rhino. (as sort of a pocket type cut) Pull that in as a 3Ddxf to partworks 3D. Export the portions that are to be cut in 2D as a seperate DXF to get the outside vectors. Layer the two imports in partworks and create seperate toolpaths. You should be able to run your 3D cutting and then cut out the form using vectors.

make sense? if not I can mock up a quick example.

Chris

[Steve Howden]

Thanks Chris,

That makes sense. Now, I'm just trying to imagine a pocket that will prevent PW3D from roughing and finishing the vertical sides of the pocket. I'll model up something quickly.

Steve

[Steve Howden]

Chris,

Sorry, my brain hurts. Every solution I try just creates more machining of planar surfaces. Actually I should be more specific. Importing the 3D toolpath into partworks and cutting the vectors in 2D all makes sense. It's just the "pocketing type cut" in 3D that is giving me grief.

An example would be hugely appreciated.

Thanks, Steve

[shoeshine]

Hey Steve,

My thought is to create an inverse of your form (the "pocket" if you will) in a 3d model of your blank. Then let PW3D remove material. It will mill around the perimiter, but only to the dia. of the bit.

I'm running out of steam tonight, and not sure if I am thinking clearly, it's midnight here...

But I'll have a crack at it tomorrow.

Chris

[tony_mac]

Hi Steve,

In PW3D / Cut3D the machining region can be limited by specifying negative (-ve)
Machining margins around the model as shown in the attached image.

I hope this helps,

Tony

[Steve Howden]

Thanks Tony,

That is good information. It still leaves me with lots of excess machining though. See attached.

Looks like upgrading to Aspire, Visual mill or MadCAM is the only solution to limit machining to boundaries?

I originally cross posted this thread on the Vectric Forum under Cut3D General, so to save duplication I'll continue there only.

Cheers, Steve

[tony_mac]

Steve,

If you are modelling the part, would it be possible to create a 3 mesh for
just the 3D area you need to machine?

If yes, the option to limit the toolpath inside the model Silhouette might work.

Tony

[shoeshine]

Nope, here is an example of limiting machining to just the areas you need it in PW and PW3D

I just took the section into PW3D created the toolpaths for the 3D area(limiting machining to model silhouette as tony said) and then pulled it into PW to do the 2D cutout.

http://www.schaie.com/shopbot/rudder.jpg

[Steve Howden]

Hi Chris,

Thanks for looking at this. I really appreciate the way people help around here, nice community :-)

I presume this approach means that the roughing and finishing paths are still plunging around the perimeter and the finishing pass is machining the planar horizontal section or am I just missing something obvious.

See attached.

Regards, Steve

[shoeshine]

Nope, I isolated the 3D portion so the passes only cut where needed.

[shoeshine]

Or perhaps this would be clearer, previews of the cuts in order

[Steve Howden]

Dear Chris,

Thank you. I really feel like a dope here. I still can't get a roughing path that doesn't cut the end off. The finishing path is fine, but the roughing path wants to chop the end of the 3D section off.

Just to make sure we are on the same page:
* In Cut3D I pull in just the 3D section of the model.
* Check Use Model silhouette and Symmetrical at 0.0
* Create roughing toolpath and finishing toolpath
* Pull the whole lot into PW as .v3d and do the profiling stuff

Everything works EXCEPT my roughing toolpath. If I choose Z level X or Y, I get the end chopped off. If I choose raster for roughing it works ?????

Please see attached.

Sorry to turn this into such an epic. I'm sure I'm doing something incredibly daft.


Steve

[shoeshine]

Hmmn, I honestly dont know why the roughing pass would be off where the finishing would not. In theory they should use the same envelope to calculate the cutting parameters.

Shoot me your email addy to chris(at)schaie(dot)com. And I will send you a copy of the file as I have it set up. (too big to post through the forum) I did use z-level raster in X for the rough. Hopefully you can compare settings and figure out what's going on. But you most certainly should be able to do this in PW/PW3D.

Chris

[Steve Howden]

Hi Chris,

Yeah weird eh?

You have mail.

Steve

[Steve Howden]

After much head scratching and some great help from everyone, especially Chris, I'm now much wiser on this subject and have also discovered an odd bug. So for those of you who may bump into this here goes:

Totally bizarre. If the symmetrical model slhouette boundary is set to 0.0 it machines the vertical faces at the boundary (which it should't). If set to the radius of the cutter or less it behaves as expected and of course if greater than the cutter radius it again machines the vertical faces at the boundary.

However! If you are useing a ball nose bit and you set the boundary to the cutter radius it "rounds off" the top next to vertical edges. Creating a toolpath for finishing with an end mill fixes that. I'll be interested to see what happens if I use a ball nose in the machine with the end mill finishing toolpath. I'll keep you posted.

Cheers, Steve

[steve_g]

Here we are a year later... I knew I had seen the answer to this problem before. what a great resource the forum is!

Steve