Looking for suggestion for 2 sided machining (3D) in Vcarve Pro 9.0!

[Eric-James]

Hello!

I am looking for some suggestions on how you might tackle my 2 sided machining (3D) issue in Vcarve Pro 9.0.

I have been working on getting the right 3D model parameters, and the correct toolpaths to machine out a wearable mask.

The following two images show the 3D modeled mask in Vcarve 9.0 when I first selected import 3D model (STL file).

Here is the front of the mask:
Front of mask image 1.JPG
Here is the back of the mask:
Back of mask image 2.JPG

The next following two images show my initial attempt to roughing / finishing tool paths for both the front and the back of the mask in Vcarve.

Front of mask tool path rendering:
front of mask rendering 1.JPG
Back of mask tool path rendering:
back of mask rendering 1.JPG

As you can see, the front of the mask tool path turned out great (using a 1/4'' ball nose for all operations), but the back of the mask tool path stops where the Zero Plane was in the modeling settings....

My question....Is there a way that I can get the backside tool path to machine away material so 1/4'' thickness is left. This would give me a wearable mask that was only 1/4'' thick, and that was smooth on the inside / back of the mask as well...

I've tried offsetting my outside vector of the model by 0.25inches until it reaches the middle using a fluting toolpath, but that gave bad results, now trying to make the offset by 0.001inches to see if there's a difference.

Thank you very much for your time!

-Eric-James

[srwtlc]

Without having the file to test with, I think that instead of creating both sides in one import, you'll have to create the other side with a second import with bottom orientation and use the same size settings as the first time and drop the cut plane to the bottom.

Another possibility that might work right is to chose bottom orientation instead of top and then try to create both sides. I've done this before, but it depends on the actual model. If you can share the model, I can try to dig into it some.

[Eric-James]

Scott,
Thanks for those suggestions. I will give them a shot asap and see what happens..

I have also sent you a Google Drive link to the mask STL File to your PM.

-Eric

[Brady Watson]

Scott points to it....

Just import the model concave side up. Create a toolpath that will hollow/dish out the cavity. Zzero to the top of the block. Flip the material over.

Import the convex side, being sure that it is aligned properly in the material. Zzero to the bottom of the material/top of machine bed. Machine the outside.

Since there will be very little surface area for hold down, you may wish to add some 3D tabs as 3D geometry so that you have space to clamp, screw or glue/tape the outside portion.

Depending on wall thickness, don't machine too aggressively as the material will have a tendency to flex and give more than a solid block on the 2nd side. Crank the RPM up...

-B

[Eric-James]

Scott and Brady,

I took your suggestions over the past day or so, and got some final results! I made a smaller version on some scrap poplar I had, then a larger full-sized one on a good piece of poplar (both 1.75'' thick).\
I set up 2 different files (loaded the model twice) and switched the orientation for each file. One with mask faced up, and the other with the mask faced down.
I then had the modeling feature produce a vector around the mask so that my roughing / finishing 3D tool passes would only cut out the mask and not the rest of the material. (Had to make sure my tools were long enough to go deep into the mask cuts).
I followed TJ's 2 sided machine introduction video for the method I used to hold down the material and accurately flip it over using dowels as indexers.
Video found here: https://www.youtube.com/watch?v=9EeJN9KIh6I
20171030_132604.jpg
20171030_132615.jpg

Still a bit of tweaks that need to be looked at in future projects....
1. It took a lot of time to complete the back concaved side (I think it's because it had to go over the eyes and mouth, even when it didn't need to..not 100% sure..I did everything in Vcarve 9.0)
On the back side, the cuts repeated themselves over and over until it got to the deepest part where it did a few cuts then repeated itself.
4.5 - 5 hours or so to complete the mask (front / back)
2. On both the front and back, I noticed what sounded like the tool slightly running / bumping into some the raised / recessed features before it climbed /descended over it (such as the markings above and below the eyes - see above pictures in initial post)... not sure what was going on there.

Other than those, seems to have run well.

Thanks guys!!

-Eric