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barkest

Solid or generic solid

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I just started 3D printing.

I have been converting the whole object to a solid before export.  I saw in the video that generic solid is preferred. Is there a reason for this and is it worthwhile converting at all?

 

thank you

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You should definitely try it first without converting to generic solids to see how it goes. The main issue is when you put the model into a slicer, some of the older slicers were not able to handle separate intersecting objects they expected one solid figure and they would choke on it sometimes.

 

However more and more recently I have not run into problems by skipping the generic solid step. I mostly use Cura these days.

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How are you going to print? I would recommend creating a solid addition myself so any touching objects become one "shell". Multiple shells can cause issues depending on your print method.

This model was printed in 1/4" scale by Shapeways. I made the whole thing into a single solid addition before turning it into an STL file.

Kevin

 

Hay_Fever.jpg

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What Kevin mentions is key, it doesn't always have to be a Generic Solid but often making sure it is ONE solid matters. For instance, in many slicers if I export two spheres that partially overlap, they will assume the overlapping mass should be hollow rather than solid, which leads to weak parts at best but complete print failures at worst.

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Thanks guys.

I am restricted to what the University provides. We use Preform software (slicer) to generate the 3D code so its a given that we use this. Over the summer we introduced 4 'self-service' printers with 3 different materials. The printers use a liquid and print upside down so the software produces the supports. I do this manually in the software now because the auto generate supports is awful.

I have done several tests some of which have been quite poor, especially door panels which are far too thin and come out as a patchwork of lines. With little to go on I just naturally converted to a solid and on simple models this works fine. I watched Jim's video (thank you) and he converted parts to a generic solid.

I think from what you are saying that I will convert to solid before export to STL. I have found the Preform software pretty inflexible but we have no choice but to use it. In reality I have not used other slicers so have nothing to compare it to.

The max size for these printers is 145mm x 145mm x 175mm (height) which is fine for us.

With regard to 'thinness' do you have any experience of how thin you can go?

 

thank you

 

 

3dprinters.jpg

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I have no 3D print or STL experience.

But as it also tessellates into Meshes, my FBX/C4D experience.
Generic Solids work well, welded vertices and correct face orientation, face normals
pointing to the outside of the volume.
Extrudes do not work as they have their top cap flipped, face normal pointing inward.
(So also happens for Slabs, Stairs, ...)
Solid Additions and Substraction also work well. I don't see any quality differences
between Generic Solids or Solid Additions.
(Solid Additions will also heal Extrudes)

As Kevin also said, I think you don't have to reduce to a low level Generic Solid,
You can use a final Solid Addition to pack all geometry without losing your
models editability.

Edited by zoomer
upgrade
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Nice print lab! I would follow the guidelines in the Formlabs design guide - http://formlabs.com/media/upload/formlabs-design-guide.pdf or the ones on Shapeways.com for a similar material. I suspect the Shapeways guidelines will be slightly more robust. I use a version of netfabb to check my models before printing to confirm there won't be any issues.

When printing on an FDM (filament based) printer, you can often trick it to print thin items like doors since it defaults to a single layer thickness in the Z direction. The slicer will round up to a single thickness when it sees something thinner so with a little trial and error you can discover what thinness will still print. For other printer types you need to follow the guidelines because they are a lot more accurate.

Kevin

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Thanks.

As it is a formlabs printer then I will follow the guide and do some more test printing. I agree it will be trial and error and given its zero cost for me this won't be an issue.

Good point about normals. Not sure how that affects the printing but making the object a solid addition would solve this. I am not sure but I believe I can only see the normal direction if the object is NURBS which it won't be.

Apart from removing the history does generic solid do anything to the mesh?

 

 

 

 

Edited by barkest
change

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Yes, you can't see face orientation directly in VW. You need a Polygon Modeler.

I did a test with an Extrude and exported by STL to C4D.
STL is triangulated and the Face Orientation of all triangles is correct.

Seems only FBX/C4D is effected.
So Extrudes are safe for STL, if that is the format of choice for printing (?).

[OT]
BTW it is the bottom cap, not the top cap.
So the former original 2D geometry that is wrong orientated because it should be flipped
when creating the extrusion. C4D keeps Quads, which is fine.
FBX gets triangulated unfortunately. So even more strange the the bottom triangles are
flipped also.
[/OT]

Edited by zoomer
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I have been testing for a while with OBJ from C4D to VW and have had normal issues. It all looks fine in C4D but is flipped in VW. On export to OBJ from C4D I flip the normals as part of the process and all works fine. This fixed an earlier issue with the UV Map which I though was the problem but turns out it was the normals. Not sure how VW is handling things but in my case it needs looking at.

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