How to edit Supports

I’ve had my Form 2 for about 5 months and using almost every day with great success on my projects, but what I need help with is editing those supports. Many times I let the software generate the supports automatically, but a lot of times the connection points land in areas that are difficult to reach and finish. So I go into the edit mode and move the points, sometimes only a fraction of an inch and then the parts fail. I also check very carefully as I move each point if the area shows any red color as a warning, and if it does, I either shift the point or even add an extra one. But when everything looks good, no red areas and I print the model, sections either don’t print or they drop into the tray.
Are there any rules to follow to ensure that moving the points won’t ruin my print?

Ken_Weiland, It might be a problem with the normals in your model. That happened to me when some of my normals were inverted, although it looked OK in the PreForm software, a couple of supports were placed on the inside surface.

Try recalculating the normals to see if it helps.

After you place your supports and accept the edits, scroll the layer slider on the right side of the PreForm window one layer at a time and look for areas of the model that “air print”, meaning they start printing on a layer where there’s no connected support. I’ve noticed that PreForm doesn’t always see overhangs. And PreForm also doesn’t always do the best job of understanding “stress” during printing. I had a model with some long “rods” that PreForm though would print fine, but they came out all bowed.


I think we need a video tutorial on how to adjust supports for different kinds of prints. The one on Formlabs Support section is good but not enough to teach you how to deal with certain cases.

I noticed that sometimes Preform adds little supports on some large surfaces and my print ends up not perfectly flat.

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Hmmm… My experience has been that support placement is more an art than a science. PreForm is somewhat indiscriminate about placement, meaning its priority is ensuring the model will print and not that you’ll be able to separate the model from the supports without wrecking the print. When I go to print something with a minimum of supports, I manually place the object, then I let PreForm auto-generate my supports (typically at some lower setting like 75% density), and then I go in and edit. Where the object is symmetric about a given axis, I look to ensure supports are arranged symmetrically on both halves of the object. Then I scroll through the layers looking for layers that have a large printed surface area. If I’m not satisfied there are enough supports I add more. If I think I can get away with less, I remove some. Then I look for areas where there’s a high density of supports touching the model. Often times, I find I can get away with fewer supports spread out more. And since the whole point of 3D printing is that you can fabricate shapes with arbitrarily high surface complexity, I finally check for areas where the supports will be difficult to remove and I try to make adjustments to correct that problem.

Unfortunately, you can’t “route” supports (which would be a really handy feature) so moving support contacts is the only option. Where the support touches the model dictates how it will route to the base. So sometimes, I have to iterate the process, making small changes to the model’s orientation and starting the support editing exercise again.

I’ve gone from prints that PreForm would have rendered virtually impossible to remove from the supports (using auto orientation and auto support generation with default settings) to prints that had fairly sparse support networks that literally peeled away from the print with a minimum of effort. But there’s no set of rules I could articulate. I could offer you advice for a particular model, but each model is different. You have to make compromises in terms of where and how much support you need (for example, I’ll orient the model to sacrifice the back side of a print, meaning more supports there, to improve the quality of the front side of the print, meaning fewer if any supports there), and you just sort of have to experiment to figure it out.

Could you please explain what “normals” are? I’ve heard this used, but am not sure what it means.

Your 3D model is comprised of 3-sided polygons. These entities are two dimensional, they have length and width but do not have any thickness. Every polygon also has a direction in which it is facing. The “normal” defines this direction. Your 3D modeling program may have an option to display normals on your model. Like the dotted line in the image below.

A 3D model must be water-tight in order to print, which means it has a continuous outside surface and you cannot reach the inside via any path you can draw on the outside (the object above cannot be printed because it has no thickness. Think of a simple cube). Because 3D models have to have this property, there is never any ambiguity about which side of a polygon is the side that faces outward. Object surfaces have thickness (or they’re solid throughout) and water-tightness means you can’t get between the walls. All the polygons that can be “reached” are outward facing by definition regardless of the direction the poly is facing. But they don’t always get modeled that way.

Many slicers (programs like PreForm) ignore the polygon normal. It’s not clear to me if PreForm does actually care. But you can eliminate doubt by running your model through something like NetFabb and fixing flipped polys before importing to PreForm. Though PreForm actually uses a subset of NetFabb functionality to fix models, so it might already be correcting this and an extra NetFabb step might not do anything,

You have to look at how the layers are going to be printed to understand why PreForm is putting supports where it puts supports. With that understanding, you can reorient the model manually to adjust where the supports are needed. The printer doesn’t like to print large flat surfaces, so orienting the model with large faces parallel to the build platform will result in “dimpled” surfaces from the supports. Models print best when oriented so each layer is the minimum surface area…

Here’s a model I positioned manually. I didn’t want any supports to contact the front of the object (it’s a cylinder for a dummy radial aircraft engine for a model airplane). PreForm’s auto orientation did a terrible job. But I let PreForm generate supports. Then I went in and manually edited them, moving them to places that would be easier to reach to break them free, arranging them symmetrically where the object is symmetric. It took me a couple of iterations to get right. PreForm didn’t complain about the lack of supports anywhere (no red) but I still had some areas that printed poorly until I made some adjustments.

I can print this entire dummy motor as a single monolithic object (9 of these cylinders, a crankcase and an exhaust ring/manifold), the Form2 is just big enough for the ~140mm diameter. But I designed it as pieces that I could print separately (even though I can’t print everything at once this way) since this gives me more options for iterating on positioning the objects to get the supports where I wanted them without printing the entire ~150ml object and then discovering I had to scrap it.


What he said. (Thanks, Randy_Cohen),

You can tell if your model’s normals need fixing when some of the bases of some supports go through the surface of one side of the model and touch the inside wall of the other side. When you edit the supports you won’t see the ball marker of the support because it is on the inside, and you can’t delete it.

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I have had what you describe happen. Thanks so much @Macro and @Randy_Cohen. I appreciate your time to explain in such detail!

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Another thing to consider is whether separating the model into different pieces can give better results. For example, I’ve got a round engine piece with lots of detail, some of the details are separate pieces which I will attach later, some large sections can be printed well in one orientation but other sections can print better in a different orientation. For details, you want to try and make the details face upwards to get the best results, anywhere the supports touch will need to be sanded down. Things that are facing more downwards will end up not looking as sharp.

I’ve been making prototypes for some 40 years and I find that it is always easier to sand an outside surface than an inside one. So when I look at the supports, I do take this into consideration. Many times I glue a full sheet of sandpaper down so I can rub a large flat surface to get a smooth finish. I have several of these sanding boards made up in different grits.

That’s one thing to consider as well, some details I make separate because it’s easier to sand a smooth surface and glue it on later than to try and sand around details. Though sometimes you can’t avoid it, I have a part that took hours to sand because I had to go all around the details with a file

Exactly my point, with my post above. The inclination is to print an object as a single monolithic object. But that can significantly increase the complexity of the supports required, which makes it much harder to finish the print after it’s printed. Instead, I break larger objects in to smaller pieces and print them separately. Not only does this afford more flexibility in setting up supports, but it also means you can print pieces of the model individually and fine-tune those components without wasting resin on parts you aren’t interested in tweaking…

For what its worth, when I first started printing I tried printing in as few pieces as possible, with experience I now routinely break up models as the smaller cross sections reduce peel force and it’s easier to place supports.

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