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Creating hollow parts and semi-hollow parts

I would love to see a feature that can shell a part (option of shell thickness), automatically generate an internal support structure (option for density and possibly internal structure geometry), then finally allow for semi automatic placement of resin exit holes and air entry holes (automatically oriented and sized for optimal part quality). This would make the printer more affordable for some people who don’t need fully solid parts.


I was going to make a new topic on this matter but since it’s already been brought up the i’ll bump this up.

It would be highly beneficial if we could get this kind of feature within PreForm. Having to work through meshmixer and then to PreForm really slows done the workflow. Being able to optimize the way prints are hollowed per resin type for best printing compatibility within PreForm will allow for more time printing and making and less time fighting with Meshmixer to get the desired results.

Additionally, if it were within PreForm it could better suggest vent holes based on the print orientation for best draining of resin. This would help prevent resin waste and speed up clean up.

I’d love to see something like this.


Shouldn’t have a need to print solid parts except in rare cases such as a prism or lens or something that requires volume. Many software packages do have offset surface function and when not possible Meshmixer does work but I find it cumbersome. It is free and does work so can’t gripe too much.

I don’t see why down the road Preform couldn’t have that function. It would be handy to have and save hop scotching applications to get a job done.

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I was also about to request this same feature in a new thread. It would be really nice if PreForm could allow the user to set a simple wall thickness that could default somewhere in the 3mm range. Then have it automatically place vent holes that could be edited just like the Supports.

Thanks in advance Formlabs.

This is something we’re considering but we’re also wary of inflating the capabilities of PreForm and raising the learning curve for new users. In many cases, it makes sense to modularize tasks like this; containing mesh modifications in programs like Meshmixer and print setup in PreForm. Our strategy thus far has been to educate users on the various tools that can be used for mesh modification and make PreForm the best it can be for print setup. We have a tutorial on hollowing parts in Meshmixer if you’re interested.

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Nice tutorial but its been 3 years and meanwhile Prusa come up with this option in their slicer :stuck_out_tongue:

come on folks, this would be so great to have in Preform, let’s go!! chop chop!



The last comment was in 2020? Formlabs, what is going on? Any progress?

Every slicer that supports SLA printing has this function, except PreForm. The old excuse that “we don’t want to bloat our software, or we don’t want to increase the learning curve”, simply doesn’t cut it anymore.

This is not different that the excuses we got years ago when we asked for the ability to mirror a part. It only took 3 years for that to materialize.

I understand being a little behind the times, but then again, maybe their programmers are not as good as we think they should be… Just sayin’… [hint, hint]


What are you folks printing that would benefit from this?

I mostly just print my own designs, so it’s easy to hollow them out appropriately, during the design process, if I need to.

To me this option would appear to primarily appeal to people that are printing designs made by others, where it might not be quite so simple to hollow out the interior, if all you have is an .stl file and not the underlying data used to generate the .stl.

I print both my own designs and STLs obtained from other sources.

I use Solidworks, and hollowing parts out using the “Shell” command sometimes works simply and effectively, but other times, especially on more complicated geometries, with parts that were joined (Booleaned) together can be a never ending cause of frustration.

I also buy models from places like CG trader or downloaded them from other sources like Thingiverse. On those models all you get is the STL or an OBJ file. Most of those models, depending on the size you print them at will require hollowing, and that’s when programs like Meshmixer come in.

But then again, Meshmixer would require the model be imported then hollowed out, holes placed strategically, then exporting the model back out for printing. Another issue is the model’s complexity and size (number of polys). Meshmixer might take a loooong time to import the model, and manipulate it.

I know that on many occasions I got models that were 5M to 10M polygons, and opening those in Meshmixer and working with them is a real pain.

On the other hand, being able to import the model in Preform, and hollowing it out right there without the import, export, fixing, etc would go a long way to help streamline the work flow.

I use ChiTu Box to import my models, arrange and rotate them as needed. I then hollow them out, ad the drain holes, and finally generate the support. All in the same app, and it’s 10+ times faster than anything I’ve been able to do externally.

So, if Chitu software developers were able to do this, why can’t the FormLabs team do the same?

Fusion 360 had its Mesh area completely redesigned a few months back and now hollowing an STL / OBJ is not only simple but also way faster than their long abandoned meshmixer. Holes still need to be manually placed (AFAIK) but the hollowing is now easy and fast.

You can then either simply export the hollowed mesh or convert it to a Fusion 360 body and make all necessary changes before exporting back to STL / OBJ.

No idea if they’ve used and improved the same engine they had on meshmixer but it’s definitely highly optimized now, almost instant on a MacPro.