3D Resin Printing 00 Model Trains #8
3D Resin Printing 00 Model Trains #8
Identifying and fixing Chitubox mesh issues with failed wheel prints
Design #10
Let’s go!
Post #6 had quite a lot of wheel print failures and is when I decided to move on to chassis designing. There’s no point in wasting lots of resin, print hours and design time trying to investigate and fix wheels I’ll likely never use.
However, I’ve since noticed some oddities with Chitubox which explain why the prints failed. Some issue are quite obvious, others will take a bit of investigation.
Unnoticed Mesh Errors in Chitubox
This is my mesh in Maya and Chitubox:
Looks fine, right? If a face is reversed in Chitubox, that would be facing inwards instead of outwards, it appears dark blue. The entire mesh is light blue. It should be good.
The problem arises when the mesh is sliced. Something I’ve never considered looking at before. I’ve always saved the export immediately to a USB stick and tried printing. But if I look at layer 253:
The right of the image is the 2D layer being printed and the left is the 3D preview of it. This would explain why my prints either collapsed or the central part printed with supports, but independent of the outer hub.
PrusaSlicer doesn’t have this issue but my printer can’t read exports from that program. I need to slice in Chitubox so I need to adapt my meshes.
What’s wrong With my Meshes?
Buggered if I know. It seems to be a Chitubox issue that I need to work around. I’ve tried exporting the mesh as both individual pieces and a whole object, yielding the same result each time. So it’s either a face issue or object collision.
My initial consideration, that it might have something to do with the way faces are triangulated as seen at the top of this page, was wrong. I triangulated the faces to be more uniform and the issue still occurred. So let’s start by ripping the mesh apart.
I’ll admit it’s not the best way to make a model, but I was unaware Chitubox would be so anal.
Part ‘B’ appears to be the issue. As far as I can tell, everything else is printing fine. Is this inner torus causing issues because faces around the edge, which form a circle, are inside of the outer hub mesh? I’ve done this before on models and it wasn’t a problem. Let’s try removing them…
Nope, same issue.
Maybe I messed up something with the inner mesh? I deleted it, created a cylinder, scaled it up, created a second cylinder, used it to boolean intersect a hole through the middle of the first cylinder, exported from Maya, imported into Chitbuox, sliced and the same issue as before.
The only solution I can think of is to boolean union the 2 meshes together. I don’t like doing this because it makes them harder to work with. Scaling and movement can become a headache if trying to maintain a structure uniform. Let’s see what happens when the meshes are boolean uniformed…
Damn it, that worked. I figured it would as everything is now a single mesh rather than individual objects combined together.
What will happen when the remaining objects are exported without being boolean intersected? That highlights another problem; the mounts under the rivets have a weird cross section:
Is it because I did something wrong when mirroring the meshes? For starters they were duplicated and rotated, not mirrored. I also deleted them and created them again, just in case. Same issue.
While designing these meshes I’m still in the mindset of low poly video game modelling; if a face isn’t visible, remove it. My initial belief with the first issue, inner hub not slicing properly, was that the additional faces around the edge were causing it.
That was wrong. However, maybe the lack of faces on this mesh are causing issues with the slicer?
So I did something:
Which fixed that issue:
We’re not done yet!
The raised inner hub penetrates the entire mesh and acts as a final housing for the axle. Without it, the hole in the center would be too big.
I don’t want to keep welding the mesh together, so I’m taking the longer route:
Fill the hole in the main wheel
Cut a hole the right size for the axle
Split the central hub in to 2 sections; front and rear
Combine everything, don’t boolean unison
Export
Win
Which worked. Trust me bro. There’s no point adding a screenshot when there’s nothing to show.
I’ve learnt a little more about Chitubox and preparing 3D models for printing. Mostly that I have to check the sliced output rather than relying on the preview render. I’m happy that it wasn’t entirely my fault, not so happy that my models will need a lot more preparation in the future.
Now let’s hope it prints!
…in a future post. Once I fix my other failed wheel prints.