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 Post subject: Doctor Skewb Version 2
PostPosted: Thu Oct 03, 2013 1:02 pm 
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Joined: Thu Dec 02, 2004 12:09 pm
Location: Missouri
During the past 20% off Shapeways sale I figured I'd rebuild my supply of some of my own puzzles. I sold my last Doctor Skewb over a year ago and wanted another. However the puzzle is hard to assemble and takes for ever to break in and is almost impossible to take apart without breaking pieces so I figured I'd redesign the puzzle a bit before printing more. Basically I moved the pin and grove mechanism up one layer in the shell model and this now makes the feet of the pieces much simplier.

However I just recieved notice from Shapeways that they can't print the new model. They stated "The file contains shells which are inside one another. " and they sent me this picture:
Attachment:
DrSkewbV2.JPG
DrSkewbV2.JPG [ 48.92 KiB | Viewed 1029 times ]

The only thing I can think of is that I used Tom's piece packer to pack the pieces and I'm now wondering if it stuck one of the pieces inside the big void in the center of the core. I'll check that when I get home. If that isn't the problem I'm really not sure what they are talking about.

If that is what I did this is a very good catch by Shapeways and I sort of look stupid for failing to check that before I uploaded the file. I'll post again after I'm home and can check some of my files.

Carl

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 Post subject: Re: Doctor Skewb Version 2
PostPosted: Thu Oct 03, 2013 1:32 pm 
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Joined: Thu Dec 31, 2009 8:54 pm
Location: Bay Area, California
The nested shell issue can happen when two copies of a part are stacked on top of each other.

Holes in the mesh or non-manifold edges can also cause issues. Try importing the STL with Meshlab and run some of its checks.

You may also want to go back to Solidworks and re-export.

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 Post subject: Re: Doctor Skewb Version 2
PostPosted: Thu Oct 03, 2013 2:34 pm 
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Yes, this almost happened to me, too. Tom's tool has a minimum hole setting you need to tweak to keep parts from landing inside others. His web page for the tool explains. I had success using that feature and pushing the camera clipping plane into my core to make sure it was empty after awhile.

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 Post subject: Re: Doctor Skewb Version 2
PostPosted: Thu Oct 03, 2013 7:59 pm 
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JasonSmith wrote:
Yes, this almost happened to me, too. Tom's tool has a minimum hole setting you need to tweak to keep parts from landing inside others. His web page for the tool explains. I had success using that feature and pushing the camera clipping plane into my core to make sure it was empty after awhile.
Yes. I was aware of this potential and even how to check for it and fix it. I had checked for it on my Bubbloid123 core I just had printed as well and there were no pieces inside that core. If my rush to finish version 2 of the Doctor Skewb it does appear that I failed to even check for this as I now see there is an edge inside the core I sent Shapeways. Though after reading Brandon's post I'm not certain that is what Solidworks found or not. If that is all that was wrong with my model Shapeways still could have printed it and I just would have had a piece trapped inside the core. Though I've had them move things around in the past so I guess I might not have even had that issue if they moved that edge out before printing. Still that is what the problem was I'm glad they stopped and gave me a chance to fix it.
bmenrigh wrote:
The nested shell issue can happen when two copies of a part are stacked on top of each other.
Holes in the mesh or non-manifold edges can also cause issues. Try importing the STL with Meshlab and run some of its checks.
You may also want to go back to Solidworks and re-export.
Ok... I just downloaded the latest version of Meshlab. Its been probably a year and a half since I've played with this and things look different. I can import the mesh and have... that is how I found the edge inside the core. What is the menu option I need to select to have it run its tests again? I want to make sure I don't have other issues before I re-run tom's piece packer and make sure that nothing ends up inside the core this time.

Carl

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 Post subject: Re: Doctor Skewb Version 2
PostPosted: Fri Oct 04, 2013 12:09 am 
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bmenrigh wrote:
Try importing the STL with Meshlab and run some of its checks.
Did you mean Netfabb? I found this link:
http://www.shapeways.com/tutorials/how_to_use_meshlab_and_netfabb
which walked me through the process. Though now having done that I think the only real issue was the edge stuck inside the core. If that is correct... I'm really impressed Shapeways caught that and didn't just print the file as I had sent it to them. I'm pretty sure it was printable as it was and yes I wouldn't have been happy with the result but I wouldn't have been able to blame anyone but myself. I know they have printed parts inside others in the past (as I've read about it before, not personal experience) so maybe this is a sign Shapeways is getting better about how they check models.

Carl

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 Post subject: Re: Doctor Skewb Version 2
PostPosted: Fri Oct 04, 2013 2:25 am 
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I think that Shapeways are doing a few more manual checks to verify the model. On my latest design, I didn't want to have any external holes in the shells of the pieces, but I didn't want to pay for the trapped powder, so I used the "tiny hole which fuses during manufacture but fools the checking software into thinking the part is hollow" technique, which has worked in the past. But this time they caught it at the manual check stage :( so I had to add some correctly sized holes.

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 Post subject: Re: Doctor Skewb Version 2
PostPosted: Sat Oct 05, 2013 12:58 pm 
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Interesting... I just spotted another issue with my new core. 4 of the 8 corners are solid and were NOT shelled by the shelling shelling operation. It took me a while to fix this but the key was to notice that the original corner and the 3 which were rotated into position were all shelled properly. To make the last 4 corners I mirrored the first 4 and it was these that didn't want to be shelled. I have no idea why that didn't work and I've now gone back and rebuilt the whole thing... this time rotating ALL corners into position and now they are all shelled properly. Again I'm not sure if this was something Shapeways noticed as I would have though it should have been possible to print with solid corner pieces. Now that I have caught that issue and fixed it, the printing costs should come down a bit.

Carl

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