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Resin 3D printing

Started by Stuart, February 09, 2024, 07:02:14 PM

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Stuart

I'm seeking some advise/help.

For several years I have been creating 3D items in SketchUp and then sending them off to Shapeways (a 3D printing vendor) to have them printed. Shapeways accepts DAE files for printing.  This has been helpful since SketchUp (my 2017 free version) can only export 3D files in the DAE format.  To date I have been reasonably pleased with the quality of their finished product and have gone back to them on numerous occasions to do my 3D printing.

Six months ago I invested in my own 3D resin printing equipment and have been honing my printing skills with STL files available for purchase on the internet.  My printing and slicing program requires STL files so any DAE files I create in SketchUp need to be converted.  I have tried converting some of my old DAE files to STL using free on line sources.  The several I have used appear to work well, at least the rendered images look good, but, when I import the files into my slicing program (Lychee slicer) it tells me the model has structural problems and cannot be printed.  I have gone back into SketchUp and taken a closer look to see if there is something I have overlooked but all seems well.  As I say, I have used three or four conversion programs but, I get the same results every time.  Is there something I am doing wrong?  Is there something I am overlooking?

This is confusing to me since Shapeways has been able to convert and print my files successfully.  Perhaps the free online sources are not up to par and can't meet the demand.  Any suggestions?

   

Lawrence@NZFinescale

You've got yourself a can of worms.

  • It's not that unusual for files to be non-manifold - ie have holes and other errors
  • There are programs that you can use to repair if that's the problem.  Things like Netfabb (which used to be free, but now I'm not sure).  Netfabb will also tell you what the problem is, which may be helpful.
  • Some slicing software under some circumstances is error tolerant.  Others not so much.  Another slicer might sort your problem.
  • Blender will let you import dae and export as stl.  It's free.  Steep learning curve but an extremely useful and powerful tool.

It sounds like to date you've dabbled. If you want to indulge the creativity 3D printing offers there's a price to pay with skill development. You don't need much understanding to print purchased stls, but once you start doing your own stuff you need to know a bit more about what's going on with models as well as what to aim for and how to do it.

Not that it all needs to come in one go.  It may be a suggestion above deals with your dae files and you are good to go.  If not, the old free sketchup is likely not the best software to use in 2024.  Something up to date that spits out stl is likely to cause you less grief, but that may not help with you existing files.

I don't mind having a look at a few files if you want to email them to me.

Cheers,

Lawrence in NZ
nzfinescale.com

Stuart

#2
Thanks Lawrence. 

Actually I have downloaded Blender and have used it to perform DAE to STL conversions.  Unfortunately, those conversions proved to be defective when opened up in my slicing program.  I think you are correct in that I need to bite the bullet and make the effort to learn how to use a dedicated 3D modeling program such as Blender.  My free version of SketchUp has been very useful in many aspects of my model building, but, not as friendly when it comes to creating files for 3D printing.

Can you recommend any on-line tutorials for Blender?  There are some courses provided by Blender Bros. that look to be good. 

Hydrostat

Stuart,

I may have an old free version of netfabb. If you name your e-mail via pm, (and if I find it) I'll send it to you. Netfabb is pretty simple and pretty good in repairing files.

Volker
I'll make it. If I have to fly the five feet like a birdie.
I'll fly it. I'll make it.

The comprehensive book about my work: "Vollendete Baukunst"

Lawrence@NZFinescale

#4
Blender is a great program.  The documentation is poor, but made up for by a plethora of YouTube instructionals.  The thing is that it does so much, there is no need to learn all of it - the 3D modelling and 3D print bits will do.  So you want tutorials that deal with those aspects.  Blender has a 3D print add-in.  It's not active by default so you'll need to turn it on.  Not something I've used to any extent, but does have some error checking and fixing.

Common problems are:
  • Holes (non-manifold mesh).  You can select non-manifold edges (one step) to visualise this problem.  Simply filling them may fix if they are simple, or you may need to do more.
  • Loose geometry.  Unconnected vertices/edges/faces.  You can select these (one step) and delete or reconnect as appropriate.
  • Duplicated geometry. You can merge vertices by distance - removing this and related problems.
  • Flipped normals. You can a) view the normals to see if this is an issue, and/or b) just recalculate them to fix

When needed, I typically look for a video describing a project similar to what I'm doing and follow along.  I can't recommend any particular series.

Blender is good for modelling organic things, I prefer a CAD program for built objects.

Blender can certainly fix your dae file issue, but Netfabb might be an easier way short term.  Netfabb was consumed by AutoDesk.  You can get a free trial and I believe the basic version persists after the trial expires.  You can also download the basic version elsewhere.  The fixing is often relatively trivial.  Determining the problem can be the hard part.  Given that your issue is consistent and that the dae files are printable, it's likely that a similar issue exists with all your files and that once you know what's going wrong there will be a common procedure to sort it out. You likely won't have the above issues randomly sprinkled through your models.

I would import your dae to blender and then export as stl.  If that works, great.
If it doesn't, then you could start selecting for the items above to light up areas that might be causing issues and/or use the 3D print add in to troubleshoot.

In my experience 3D modelling/printing is about workflow.  It starts as difficult with various hurdles, but once you've navigated methods that work for your needs/software/hardware it becomes much easier and most problems just vanish.  Navigating those hurdles can involve some heartache though.  So while you might want to move on from Sketchup, I'd find out what's wrong with your current workflow.  It may be an easy fix, which means you can print your current models and upgrade your software at your leisure. Once again, I'm happy to take a look to help you identify the problem.
Cheers,

Lawrence in NZ
nzfinescale.com

finescalerr

You guys seem to confirm my hypothesis that 3-D printing is almost a hobby in itself. -- Russ

Stuart

Thank you Volker for you generous offer of providing a copy of Netfabb.  You should be able to discover my email address by clicking on my profile but if not, it is stuartgfx@hotmail.com.

So, it seems that simply learning and creating 3D models in Blender and exporting an stl file will not necessarily produce or guarantee positive printable results. I have already learned that a model needs to be "water tight" with all vertices connecting (no holes) and that the model interior needs to be clear of structures that would prevent a completely open cavity.  However, I am not familiar with what it means to have flipped normals. 

Lawrence, it would be very kind of you if you could have a look at some of my models to see what the problems might be.  Would you need dae or stl files or both?  If you can provide an email address I will forward a few items to you.

Again, thanks Lawrence and Volker for your wiliness to offer assistance to a fledgling 3D modeler/printer.  And Russ, I believe you are correct, 3D printing may prove to be a hobby all unto itself.

Stuart   


Lawrence@NZFinescale

A link to my email is below my avatar in this post.

A normal is a direction perpendicular to a face (triangle in an stl).  Essentially it indicates which of the triangle's faces is to the outside of the model.  As you might imagine, the software can struggle if some, or all, of the normals are flipped.

I've never had flipped normals from CAD software converting solids to stl.  However, using software such as Blender to stitch surfaces into solids will often have this problem.  Depending on your software this may, or may not, be something that need concern you. It's really simple to find and fix.  The problem is that you need to remember to check for it as it isn't often obvious.  Blender does shade positive and negative normal faces slightly differently, but I find it's too subtle to be a reliable indicator of a problem.

Cheers,

Lawrence in NZ
nzfinescale.com

Lawrence@NZFinescale

Quote from: Stuart on February 12, 2024, 11:05:01 AM...the model interior needs to be clear of structures that would prevent a completely open cavity. 

That probably depends on your slicer.  My experience is that multiple overlapping closed solids work reliably on most software.  Solus Contour software was amazingly error tolerant and seemed to sort all sorts of problems - but you can only use it with Solus hardware.

It's a good policy to produce error free models though.  It means you can exchange them and reliably run them on different platforms.
Cheers,

Lawrence in NZ
nzfinescale.com

Stuart

Lawrence,

After reviewing your list of the possible problems one might encounter in creating printable 3D models, I went back to my SketchUp program to investigate how to correct reversed normals.  Of all the items you listed, reversed normals was unfamiliar to me.  Sure enough, that turned out to be the problem.  Fortunately SketchUp makes it pretty easy to identify where the problems lie and with not too much effort I have been able to make the corrections.  The models saved correctly as stl files and the few I have printed have turned out successfully.

So thanks again for your expertise and helpful suggestions. 

Stuart

Lawrence@NZFinescale

Cool.

Unfortunately slicer errors tend to be of the 'bad file' variety.  Succinct, but unhelpful for troubleshooting.  Flipped normals catch me out from time to time.  They happen infrequently enough (for me) that they are not something I normally check for.  But if a file is problematic, they are a common culprit.
Cheers,

Lawrence in NZ
nzfinescale.com