Full Version: Gunstock design with MOI3d

Finally getting back to the gunstock design and carving (CNC 3+1) project.
I have some gunstock I will be designing from scratch, some existing stocks I will be having scanned and making minor alterations before carving.

From what I have read,, MOI will give me a simpler, more streamlined interface, less of a learning curve?

I believe MOI will be fine with the solid, curvy surface of a gunstock, but a few questions:

Does MOI have tools to create very precise layout for the "inlay" cut out, where the gun lays in the stock,, this would be added to the solid model, I am assuming this would be the final step after the solid surface design is completed.

Any issues importing a scanned existing stock and working with it? I assume this would be a STL file?

Thanks
Nick

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Hi Nick,

re:
> Any issues importing a scanned existing stock and working with it? I assume this
> would be a STL file?

There are a lot of issues with converting triangle mesh scan data into CAD surfaces and solids.

That's a process called "Reverse Engineering" - for that you will likely need a tool that is specifically focused on that area of work which MOI is not.

Some links to previous discussion here:
https://moi3d.com/forum/index.php?webtag=MOI&msg=11684.4


> From what I have read,, MOI will give me a simpler, more streamlined interface, less of a learning curve?

It depends on the characteristics of the model. MOI works best on mechanical part type models that are defined by 2D profile curves.

Models that have more freeform organic type shapes are a lot more difficult and have a higher learning curve.

Probably a polygon mesh editing type program would work better for your type of work rather than a CAD program like MOI.

- Michael

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Michael,

I will check with the person scanning my existing rifle stocks,, I am assuming they could provide that service.

I was under the impression that a NURBS based CAD, that is better with free flowing designs, not 2D mechanical type.
Did I have it backwards?

When you say a Polygon Mesh program, are your referring to a "Parametric" style program such as Fushion?

Thanks,
Nick

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Hi Nick,

re:
> I will check with the person scanning my existing rifle stocks,, I am assuming
> they could provide that service.

That's a pretty big assumption. You may need to be careful how you how ask them, like if they say they can deliver it in a CAD file format like a .step file, will it be a big pile of little triangles in the STEP file or actual NURBS surfaces.


> I was under the impression that a NURBS based CAD, that is better with free flowing designs, not 2D mechanical type.
> Did I have it backwards?

Pretty much all CAD software is NURBS based.


> When you say a Polygon Mesh program, are your referring to a "Parametric" style program such as Fushion?

No, I mean a sub-d modeling program like Blender or Cinema4D. Using this type of geometry:
https://www.youtube.com/watch?v=ckOTl2GcS-E

- Michael

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Hey Nick,
I have a bit of input for you...

Here is a quick mockup from your image. I left the construction curves so you can see
See if this gets close to what you had in mind.
(If its not something you can follow, I should be able to recreate it pretty quick for you)

I didnt use any real world dimensions. Just winged a visual then resized the final solid to be closer to an actual size. If I was doing a real item, I would use very specific dimensions.

Regarding the "scan data" I would only use this as a reference to rebuild the item in NURBS, which is best for your CNC process. Most CAM packages will prefer NURBS data to work with. Some stuff will work with poly's, but you will be limited. This depends on your CAM package and machining process...

If you need organic stuff added to the stock, like deforming things or adding image "Emboss" type work, this will be done with other software. For us, our CAM package has the "Embossing" built into it. There are other "specialty software made for that (Think Vetric). Either way, it is a process "AFTER" you have modeled the part in CAD.

Think of the CAD part of the process as creating the precise piece and dims. (Your lower receiver cutouts, etc) Then using something else to "Paint" it. (The "paint" being modeling you cant/shouldnt do in CAD)

Attachments:
stock work.3dm

Image Attachments:
stock setup.jpg 

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After posting my model and re evaluating the image you posted, i realized there is an error in concept that can make it harder to do with this method. The transition from the butt to the grip ismore or less tangent in the image. Mine is “smooth” but there is a definite shift in size.

I am currently out but will re look at a different way for you to achieve a good NURBS result to move forward

The rest of what i said still stands

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