I am working on a new maze for cylindrical puzzle (seen on thingiverse under “Blind Puzzle Box”) and have encountered something strange when I import the stl file into Luban. Initially after loading the stl file into Luban it looks normal. But when it generates the g-code there are horizontal gaps in the model.
Some background: I’m using SketchUp to create the maze as a flat maze and then using the TrueBend plugin to turn this flat maze into a cylindrical maze - with the maze on the inside of the cylinder.
Interestingly, I imported the same object with the orientation of the cylinder on its side rather than on its end, and did not get circular gaps shown in the image above. I got gaps running along the side of the cylinder.
I have spent several hours trying to find some problem with the SketchUp design, but have not been successful in finding a reason why the gaps occur. I have tried a number of different STL viewers: Autodesk drive, MeshLab, Sharecad, STL Viewer, STLView, ViewSTL and 3D ViewerOnline. I won’t show what each one shows, but they are all consistent in the way they show the object (i.e. no gaps). Here are a couple:
I am at a loss for why the Luban slicing is showing the gaps I see. Could this be a bug in Luban? Or is it actually some issue with the STL file that has been generated?
So I am looking for any tools that might help me figure out what the problem is. I would like free tool if at all possible. Or a fix for Luban is that is the cause.
Those areas are probably too thin.
If your nozzle size .4mm and the thickness is less than that, it won’t print it.
A slicer is always trying to figure out how best to reproduce the stl provided. It’s always a bunch of compromises and interpolations. Sometimes this can result in strange errors.
It doesn’t know what to do with items smaller/thinner than it can print.
So it just doesn’t even try. It just eliminates those portions and/or averages it out.
An easy way to check is to scale the model up. If it renders those areas at 500% but not at 100%, then they’re too thin. That doesn’t work if the sections have 0 thickness though.
+1 about thinness. You could also try using superslicer and the “thin walls” setting, it does a good job of printing walls that are only 1 layer wide.
But if you only have 1 layer width, it’s probably better to just add some extra material to the outside, should just be a simple extrude and maybe a boolean operation to bump up that out wall thickness.
Thank you to those who replied about the potential thickness problem. But that did not turn out to be the issue. The outside shell of the object is almost 3 mm thick and the maze pattern lies on top of that with another 1.5mm in height.
After posting here and doing some more research (which I probably should have done before I posted - mea culpa!), I found out about ‘meshmixer’ which was able to show me that there were issues with the both the flat version of the maze and the cylindrical version of the maze. Meshmixer was not able to automatically fix the issues, but it did give me a method to see “how bad” the object was after making modifications to it.
Rather than just leave you with an “I solved it” comment, I would rather share what I learned. What I learned was the following:
Some hidden geometry was causing issues. That has to do with how I created the maze itself. Starting with a flat, solid rectangle, I was creating the maze passages that were in a rectangular pattern. I would then “extrude” these rectangles by 1.5 mm to make the maze. But since I was going to be printing the cylinder on it’s end, I needed to add a taper to the lower part of each horizontal section of the maze so that it would 3D print nicely. I found out through trial and error that removing the hidden geometry was causing most of the problems I saw in Luban after generating the g-code. I also verified this with Simplify3D and Cura slicers. Not sure why STL viewers didn’t see this as a problem, but Meshmixer did. After a couple of hours of removing the hidden geometry I had a flat version of the maze that didn’t cause problems with the slicer. Here’s what the flat maze looks like:
The TrueBend plugin (in SketchUp) which turns the flat maze into a cylinder was also causing some issues. Since it makes a cylinder that has a finite number of segments around the circle (I used 48 segments - instead of the default 24 - to make it smoother), there were some places where the location of the segment would cause issues at the end or sides of some maze objects. Again, I had to do some manual editing of the cylindrical maze to patch these.
I now have an STL file that does not have gaps after generating the g-code. Here’s what the sketchup model looks like:
Awesome that you diagnosed, I’m assuming by “manually fixing” you meant using meshmixer’s hole repair to make sure you had complete surfaces on your model?
No, actually I didn’t use meshmixer’s hole repair. There were so many issues that meshmixer just couldn’t seem to handle them - or I just don’t know how to use it effectively.
I started out removing some of the hidden geometry, then saving the sketchup file as an STL file, then importing it into meshmixer. I could see that it made things better, but there were still lots of issues highlighted by meshmixer. So I manually removed the hidden geometry by hand - an admittedly painstaking process, but when I was done I had a file that meshmixer didn’t complain about and one that the Luban slicer didn’t choke on.
