PreForm ability to control Wall thickness and infil for solid objects

With my Robo3D I used Sinplify3D, When printing with that you could control the thickness of the shell and the type and density of the infill. It would be really nice to take a solid object and create a shell and infill in PreForm, this would drastically reduce print time and the amount of resin used.

As I understand it, printing with a patterned “closed cell” infill like is common with a FDM printer creates problems on a resin printer. An infill pattern like for instance a honeycomb creates individual cells which are sealed at the top (near the build plate) and open at the bottom (where the “business end” of the print goes into the resin). When the print is positioned for the next layer to print, the submerged cell end wants to fill the cell to the same height as however deep the resin tank is filled. If this happened, when the cell was finally closed off by the last layers of the print, there would be resin permanently trapped inside. While I’ve never experienced the problem myself, I am led to believe that what usually happens is that the hydraulic pressure as the cell is submerged causes features of the print to rupture and you end up with a failed print. The term used is “blow out”.

At least as far as I know, with few exceptions, for any additive manufacturing technique (powder or liquid), if you want the interior to be less than 100% filled in you have to design-in ways to remove the leftover material captured in the interior during the printing process.

I don’t think there’d be much interest in a feature that required you to let it poke holes in your model… Not something you want the CAM software doing on its own. Better to design it yourself.


The infill could be something open- think geodesic dome.

Have you considered using your software to hollow the shell then letting preform fill the cavity with internal supports as needed? Youbcan get much better/stable shell prints with SLA that. With FDM

I’d be interested in something like this too. Even if will create visible holes in my model, I think it will save some time and potentially good amount of resin.

If such a feature is to be implemented it should allow us to control the model’s thickness, number of holes, their location and their diameter. This way you can ensure no liquid resin is stuck inside your model and the holes are placed in spots that don’t ruin the look of the print.

I am currently doing the hollowing myself. It was just really nice to have the software do it for me on the FDM printer. I would be ok with internal supports. PreForm will already do that on projects that are hollow already so they would really just need to hollow the object and allow for a predictable wall thickness.

I would also be willing to allow weep holes as long as we could choose the placement.

You still have the problem of an exterior shell that’s closed at the top and open at the bottom, being submerged in resin as each layer is printed. So geodesic internal supports wouldn’t necessarily trap resins but the overall object still will. You still get that “hydraulic” action each time the growing object is resubmerged.

And think about printing a sphere. The object is submerged for the last layer to print. The sphere fills up with resin to a height equal to the depth of the resin in the tank. That resin is trapped inside when the last layer closes up the object. So you still need holes in the exterior shell to drain it out, even if the hydraulic pressure doesn’t cause a blow out.

I wouldn’t want PreForm to automatically punch holes in my designs, so I might as well “engineer” the internal supports I need at the same time I’m poking holes in my hollow object to let the trapped resin out.

good points, I guess I am still thinking in FDM terms.

I started with FDM myself. Still use my trusty old’ Replicator Dual. So when I got my Form1+ I asked all the same kinds of questions you’re thinking about, which is why I (think I) already know the answers.

I would love to see a print shell option as well. Meshmixer is hit or miss for me. The current part I was trying to hollow with it comes in solid to PreForm which is really disappointing. True the shell would have to have an option for holes too - but I don’t see that as a problem if they could be either manually placed and/or moved.

As for internal closed cells not working, the internal structures would just need holes in the walls - I don’t see what the issue with that would be.

As it is now, we are at the mercy of 3rd party software to print hollow which is less than desirable.

If you import an enclosed shell like a hollow sphere to PreForm, it ought to show solid. There’s no such thing as a 2-dimensional surface (a wall with no thickness). Everything has an outside and an inside, and everything on the inside is printed solid.

Also, PreForm runs a model through a subset of NetFabb when loading. If you got the warning that there were problems with the model that PreForm could try to repair, it got processed by this software. I use a standalone version of NetFabb all the time. NetFabb removes “internal” shells from objects. So it’s possible when you loaded the model in to PreForm, the inner shell got “optimized” out as not being printable.

Unless you already tried this, I bet if you poke a hole through the shell so there’s an opening (tube) from the exterior to the interior, it works. That makes the inner surface an “outer” surface like the actual outer surface. It won’t be ignored or optimized-out.

Note: It’s late and I’m too tired/lazy to actually try this for myself to see what happens… sorry.

Awesome, thank you. I thought I had added holes - in MeshMixer - but I somehow didn’t. You are correct, that did the trick. I appreciate the explanation too.

I still would love to see a shell and infill percent built into PreForm though. But thanks again!

Thanks Randy.
I just had to realize this matter. I modelled an enclosed hollow space (with flipped normals of course) to a model but it came out solid.

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