Prusaslicer adding layers to my model?
I'm trying to model and print a housing for a fan and filter for an enclosure for my mk3. (The model contains two objects, with the top designed to slide in after I've wedged the fan and filter in, and the bump on the top is a cable channel.) I modeled this in Blender, and I'm aware that it's not a perfect model -- both because I ran the Blender plugin that analyzes models for printability and because prusaslicer/netfabb think the model is problematic. But I'm not a Blender expert so I don't really understand the problems -- let alone know how to fix them. Having said that, I don't mind an imperfect model as long as it slices and prints. And if I don't "fix" it with netfabb and turn infill to 0%, it slices the way I'd like it to -- except that it adds about 4 horizontal layers at a couple of points in the model. Why is it doing that? Is there a way to disable those added layers? If not, any tips for how to fix the model? Or should I just treat this as a bridging test and manually remove the added layers (if they bridge) after printing?
Thank you in advance!
RE: Prusaslicer adding layers to my model?
Sorry for the double-post, but I realized after the editing window closed that I may have uploaded the wrong file type (and that I typo'd the name). So here's an STL.
RE: Prusaslicer adding layers to my model?
That model is so broken. I use blender myself so if you want to learn just ask.
As a quick run down though, for a model to slice properly it must be Manifold. You can think of manifold as water tight. So basically each mesh/object must be closed with no holes into the interior of the model. Yours is most definitely not. The bottom and the top are sort of mildly ok but the entire middle that connects the 2 ends is just a mess. You also have some walls that are mathematically thin as they are the same place inside and out so wouldnt actually produce any slice wall thickness.
Even though slicer tries to repair it you can see its not correct as there are large portions coloured in dark green on the actual model before you even try to slice it.
I also loaded the stl into Blender. You have sections that don't even have faces, so have no chance of printing as is. If you are running Windows 10 then you can take advantage of the right click and fix through netfabb option to repair the model. It looks like it does an ok job on it but without knowing the ins and outs of all the model its hard to tell if there are still any actual errors in it. It does slice with infill too though at least with my settings. If you aren't on Win 10 then you can use netfabb online but with you mentioning netfabb I'm guessing you are on Win 10.
That's another thing, when debugging issues its usual to save your project (File>Save Project As) and then zip up the .3mf file created. That's because the .3mf contains not only your model but all the settings you are using to slice it, as well as any modifiers, the part orientation etc. Just as many issues can be caused by faulty settings as a faulty model. Although in this case nearly everything is down to the model.
However instead of using a tool to bail you out I would learn in Blender just why your model is wrong so that you don't make the same errors in future. If you want to post the original blend I can take a look at that too. Its difficult to see how you tried to construct that stl file. Oh and you can export specific parts from Blender, so the slide in panel doesn't have to be part of the same stl file as the rest.
I have attached a zip file. It contains a Blender file with the fixed model (done in v2.92), stl exports of the filter and the panel exported separately and finally a 3mf project file with the orientation I would try first as well as the needed support enforcers for it. There are a couple of tricks to print those nut pockets on the main filter part without supports but those could wait till later. Hope you find it useful.
Personally I would also have modified the slots for the panel as they are a single perimeter thick so will break easily. If you move those slots further in and position the tongue that goes in the groove the same distance I think you could print the panel without supports too while making it stronger overall.
RE: Prusaslicer adding layers to my model?
Ran out of edit time but here is the re positioned tongue and groove I mentioned. I've also added a little bit of clearance as there is none on the original. So I don't think you will be able to slide the panel in on the first one. Just the stl files this time.
RE: Prusaslicer adding layers to my model?
Wow, thank you. I do want to get better at Blender but don't want to impose further, so if you have any resources you could point me to that would help me understand the kinds of things you did to fix this I'd appreciate it.
The original blend is in my first post. If I had to guess, I'd say the cause of most of the issues is the "creative troubleshooting" I did to fill in certain areas and/or create faces in certain areas. Using 'f' to fill in faces seems to sometimes yield non-manifold geometry, and I'm not totally sure why. And when I wanted to create the raised cable groove in the main part, I got creative with adding small "faces" that I could manipulate. Not really sure what the best way to do those sorts of things would be. And in the future, I'll post a .3mf and/or my blender file.
As far as the nut pockets -- I'm printing this for the prusabox enclosure; I've already printed a bunch of parts with similarly designed nut pockets without supports, and while there have been some cosmetic issues, they're been functional. And I was thinking of printing the sliding part vertically (with a brim) to avoid the need for support material; do you think that's a bad idea? None of this needs to be particularly strong, as (if I've designed it right) it'll be resting on the same surface as the enclosure.
RE: Prusaslicer adding layers to my model?
Double-posting again to respond to your edit -- I was aware of the clearance issue but wanted to err on the side of too little and file away as needed after printing, because I do want this to be airtight. But I'll check out the modified design; thanks again!
Edit: I see what you mean about the tongue, and I do think that's a better design. Thanks for the tip.
RE: Prusaslicer adding layers to my model?
Sorry I skipped the first attachment when I saw the second. I'll try and have a look in Blender after work this evening.
On the clearance front Id be adjusting outwards so you only have one edge against the slot. The surface area of 3 faces, all with layer lines on them sliding over each other just wont work. Trust me, Ive been through the pain of that already lol. Too much friction. Also when adjusting the tolerance you can print just a small cross section to check fit and once you have sizes that work then print the full part.
You tube is full of blender tutorials. Admittedly most of them don't apply for the purposes of 3d print model design. However any that list 'hard surface modelling' can be quite useful and there is a content channel called MakerTales who has a series on precision modelling in Blender that is very good.
RE: Prusaslicer adding layers to my model?
Thank you again -- really appreciate the help and advice. That's a cool idea about testing tolerances. And I've watched a number of blender tutorials on youtube; generally the ones aimed at 3D printing have been very basic, and the more general ones have been mostly irrelevant to what I'm looking to learn. So I'll definitely check out MakerTales.