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Help: Axis alignment of fused scan for two part 3-axis cnc

Help: Axis alignment of fused scan for two part 3-axis cnc

Postby gene » Fri Aug 30, 2013 4:21 am

Feel free to move to another forum if this is in the wrong place. It seemed more of a software type of question as in what to use.

I've used structured light to scan some gun stocks that I've made by hand. I'm trying to reproduce them using a 3-axis cnc router. The scans themselves are perfect representations of the stocks but I'm having problems getting the planes of the model perfectly symmetrical before slicing/dividing the model in half for cutting. When cutting, one end of the stock is coming out thicker/the other end thinner than it should be. When flipping the piece of wood over to cut the other side this causes the two sides to not perfectly match up (and requires a lot of hand sanding). I was wondering how to go about getting it aligned perfectly in the x/y/z plane before slicing it in half so that the two sides are seamless and match the models measurements after cncing. I'm currently using Rhino/Rhinocam to try to align the scan correctly in the x/y/z axis before importing each half of the model into aspire 3 for 3d cnc programming.

Eventually I hope to go to a 4th axis rotary attachment so I don't have to deal with it. Any one have any ideas on how to get this perfect? As it stands now I have to trial and error the model until it's as close as I can get it

Pictures below. The unfinished stock is an older one before i did structured light scanning but shows the problem
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby dangre » Fri Aug 30, 2013 1:45 pm

Gene,
I have a bit of knowledge in the CNC world but I have not done 2 sided 3-axis before so use my advise accordingly. I have noticed that most machinist with similar problems have found the error to be with how they align the stock (pun intended) in the cnc. If your model looks good in software (and the two halves align properly using Rhino) then it is most likely how you position your work in your machine (and set your X,Y,Z to the 'flipped' part). Can you add alignment features such as holes or such and create a work holding fixture that aligns to these holes? I.E. create two holes that are in exact axial alignment with either side of your part? I don't have the money to afford Aspire, I use MeshCAM and they have a 2-side explanation here:
http://www.grzsoftware.com/users/larryw.html
Your best source of answers will be in the Aspire forums. Good luck, awesome project.
Dan
DAVID-CAM-1-C, Acer K11, Macro lenses for K11, Logitech Pro 9000, EOS 40D
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby gene » Fri Aug 30, 2013 6:26 pm

Thanks for the reply. I'm gonna give meshcam a shot and see if it can handle the 3d contouring better. The problem with aspire is it dumps the model below the cutting level so it's very hard to line it up. I don't think aspire is really intended for 3d work. More 2d based. I'd love to get my hands on Mastercam but talk about expensive
gene
 
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby dangre » Fri Aug 30, 2013 7:13 pm

Gene,
I don't think MasterCAM is all whats its cracked up to be, especially its price ($15k+ US). You will be amazed at what MeshCAM will do. Is it perfect?, no but at $250 US with no maintenance fees, hmmm. I think the annual maintenance fees of MasterCAM is $1500 or more. I work with a machine shop that uses MasterCAM and it looks like it tries too hard to do something simple. For simple 3D stuff I can import, create CAM paths, and export code in less time it takes MasterCAM to just set up.
Dan
DAVID-CAM-1-C, Acer K11, Macro lenses for K11, Logitech Pro 9000, EOS 40D
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby Bobby » Sat Aug 31, 2013 1:33 am

Most stocks don't slice evenly down the center because they are not truly symmetrical. They usually have a little bend in them to favor the shooter. At least this is true for all the stocks I have scanned.

My advice would be to NOT try to program this as 2 different halves. Rather, use CAM that lets full 3D model be present for machining. Cut3D is around $300 USD and would work well for this. As Dan points out material registration and prep are very important on 2 sided parts. Y and Z dimensions must be exact or you will have errors in the finished part size.

See this, very easy & cheap software: http://www.vectric.org/video/cut3d/Gett ... ooster.pdf
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby gene » Sat Aug 31, 2013 2:49 pm

Cut3d doesn't have enough features to select the areas I want to machine and you can't import the models really once you work with them in cut3d (the workaround of importing your cut code and building a model out of that sucks). Also tried meshcam and I'm not sure if it will work for what I want. Wish it had profile cut and some other functionality.
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby MagWeb » Wed Sep 04, 2013 7:30 pm

Hi,

I'm using MeshCam for such two sided jobs without any problems.

Just in case you wish to stay with the well aligned separated parts, maybe MeshMixer can help.
I made a short tutorial pdf.

Gunter
Attachments
MM_Cut_Align_tut.pdf
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby dangre » Thu Sep 05, 2013 5:04 pm

Gene,
I think MeshCAM does do profile cuts if you 'trick' it. See:
http://www.grzsoftware.com/users/2d/
Dan
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Re: Help: Axis alignment of fused scan for two part 3-axis c

Postby gene » Mon Sep 09, 2013 2:18 am

I'll check out both those tutorials tomorrow after I get off work. Thanks guys
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