How to print without supports?!

Hello guys, first time on here. I am currently using the formlabs 2 printer to work on a research project at my university, in specific the dental school. There is a design I would like to print out: it is basically 4 rectangular boxes that are hollow, with a lattice in between, I am not sure how to describe it any other way besides that it is sort of like a bridge. The inside of it must be hollow as we are planning on doing pressure testing and other sorts of things on the boxes. Now the issue does not arise when I am creating the design on blender, but when I go to the preform software; as soon as i go to print it puts the supports on and the supports cut right through the middle of the boxes. Is there any way around this? Any way to print without supports or a way to print without the supports jutting through the middle? I have already tried to change the contact points of the supports manually but to no avail. Any help would be greatly appreciated, thanks guys.

Post a screen shot of the object. Impossible to understand what you’re describing (at least, for me).

PreForm will not put supports through objects unless there’s something wrong with the objects. However, if you’re printing hollow boxes, PreForm will probably want to generate internal supports inside the box, which might look like they’re going through the box I suppose… You can turn off the “internal supports” checkbox to see if this is what’s happening. But you probably won’t be able to successfully print your box that way.

But you have a bigger problem. You cannot print an enclosed void with a Resin printer. At a minimum you will trap resin inside the object. But you can also get print failures resulting from the hydraulic pressure that is generated when the open-at-the-bottom object is submerged in resin for the next layer to print. You need a hole in the box at the closest point to the build platform to let air out as the print is submerged, and also to act as a drain to get the trapped resin out after the print completes.

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I’ve never had it try to add supports without clicking the option to generate supports. If you don’t have supports and you go to print it should pop up a warning that there are no supports but it shouldn’t try to generate any.

For the Form2 printer, the issue with enclosed parts is not really a problem, the change compared to the old printer with how it now slides the tray and lifts up to separate the layers doesn’t have much of a pressure issue that the old printer had with the tilt and peel method. You would still have the issue with resin being trapped inside though.

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I work with dental printing also and it IS possible to print using only user selected supports. Just select the supports button and then edit. Do not “Generate”. I use this technique for orthodontic bracket placement tabs. If you want, post your model as an STL. I would like to try to support it and send it back.

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You knew there would be someone who said “ah, but” didn’t you?

I’ve got a ring model that Preform insists upon putting supports through. Model seems fine with all the tests I’ve put it through, but this is an area where there is pave setting so there are holes through the model - best guess is that it’s trying to put it through one of the holes (which would be cunning) but the hole is too small to allow for that.

Prints fine once I’ve done the supports manually though.

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Also, some times with auto-generation it will put a support point within the print, if you have separate parts that are intersecting sometimes it doesn’t realize the part is attached to a larger part and it tries to support it.

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OSU dental project design 2.stl (205.2 KB)

OSU dental project design 3.stl (201.1 KB)

Here are two designs I made up to try to get around the supports. design 2 is the one I would prefer to have printed. I appreciate the help greatly. thanks

Please do not tell me it is impossible to print this thing without supports jutting through it. The first picture is the design i would prefer working with, as I would like to keep the inside lattice intact with nothing in between it. thanks alot!!!

I tried putting the supports in manually but it still stuck right through the model.

I think that is my problem. Do you think there is anyway around it.

If there’s supports going inside, then you have to use the slider on the right of the screen to go through the layers while in edit mode, go through where you see the odd supports showing up and you should be able to find the blue sphere on the inside so that you can remove it.

Are the vertical supports and solid base part of your design or just for support?

part of the design, what we really need is just the boxes with the lattice in the middle, we plan on cutting off those supports as soon as it is printed.

I did that, and manually inserted supports as well, but it did not work, supports still stuck through the middle of the structure.

Looking at the object you’re trying to print–that’s not going to print–first it’s way too small, but even if you scale it up it’s likely to not work because those pieces are too thin, and the flat parts wouldn’t print without adequate support anyway.

Some initial comments now I can see what you’re trying to do…

First, I think it’s a mistake to try and print something this way. My recommendation is that you break the object up in to a base and individual lattice files that you print separately. The stanchions the lattices are perched on could mate with holes in the base, so you can “plug in” the lattices individually to assemble the “brick”.

Why? Because this is a challenging object to print due to the small size and delicate nature of the structure. Breaking it up in to separate pieces means you don’t throw everything away when one particular area doesn’t print quite right. But also, I think a single lattice will be easier to position and print with a minimum of supports compared to the much higher complexity required to support and print all 5 lattices at once.

Second, this object geometry is not “built” correctly. It looks to me like you modeled the lattices by just placing separate pieces of geometry next to or on top of each other. If I go in to your STL file and select any Polygon, and then I tell my CAD software to select all other polys that are connected to this poly, nothing happens. None of the polys are connected, even when they have overlapping vertices.

This may be an artifact of the STL export function of the CAD software you’re using. You’re going to have to figure out why that’s happening and correct it.

If I tell my CAD software to merge all the vertices in your model that are fully coincident, it finds 1902 points that are coincident with other points in the model file. After I do this, if I click on one of the polys on the cross members of the lattice, or on the top or bottom “plate” of the lattice, and tell my software to select all other connected polys, it highlights (almost) the entire component.

But there are other problems with the geometry beyond merging common vertices.

Even though each “piece” of the geometry now (after merging vertices) looks like a solid component to PreForm, the pieces themselves are not actually connected. This is probably the reason PreForm is putting supports through your object. The pieces look connected visually in your CAD software because they overlap each other, but they’re not really joined together, they just intersect each other’s boundaries. PreForm doesn’t see the object as a single entity, it sees many overlapping individual components, all of which need to be supported (PreForm doesn’t appear to understand how an object that’s partially embedded in another object gains support from that overlap). So you can’t just overlap parts to join them. They must be combined using a CAD feature called “Constructive Solid Geometry”.

So before you can go any further, you need to clean up your CAD file so PreForm has valid geometry (you did get a warning about errors in your file when you loaded it in to PreForm, since I did when I tried it). PreForm’s ability to repair things is somewhat limited. You should not rely on it to fix bad geometry for you. Instead, download a copy of NetFabb and use that to pre-check the model before bringing it in to PreForm (PreForm uses a subset of NetFabb’s software). If there are only a few simple errors reported by NetFabb, let it fix them before importing to PreForm. But if there are many errors, you should go back to your CAD file and fix them there. The Standalone NetFabb is smarter than what’s embedded in PreForm, but even it will trash a model file if there are a lot of errors.

Third, this lattice is small. Really small. As you no doubt observed in PreForm, the supports are huge compared to the object. This is going to present a challenge of its own even if you get satisfactory support placement. You might get it to print and find you cannot successfully separate the print from the supports without damaging the print.

Without knowing why you chose the dimensions you are using, specific advice is hard to offer. But I would look to make everything thicker. The printer will print at very fine resolutions but from my own experience, features with less than 1mm of thickness come out very delicate and easy to deform/break. If the internal dimensions are what’s important, you could maybe grow all the external surfaces outward to make them thicker, and in so doing improve the odds of printing success.

I took the liberty of reconstructing your lattice using “CSG” so it’s one solid object. PreForm support placement is better on this than when I tried your original artwork (pared down to a single lattice), but it’s still not perfect. But maybe with some manual placement it’d work for you now…<a class=“attachment”

href="//discourse-cloud-file-uploads.s3.dualstack.us-west-2.amazonaws.com/business4/uploads/formlabs/original/2X/b/beeac0b7e5e8b79482f1a6876763d6491f737b32.stl">Lattice (repaired).stl (98.3 KB)

Here’s what happens when I make things thicker. The internal dimensions are unchanged, only the thickness of the exterior faces of the lattice were increased.

Lattice Thicker.stl (102.9 KB)