Generating Supports added supports below base

I am using Preform 2.5.0 and I went to print an antenna booster for the RC control on a drone. Anyhow, when adding supports, it caused some of the large upright support posts to extend below the base that it had created and raised it all up. Also, it says that some of the model is outside the build volume, but it doesn’t look like it (even the posts, and I zoomed quite far in).

So if I try to print this, it would try to print the bottom of the support posts and then go up a few millimeters before printing the base. Obviously, I can’t let this happen. I ran the STL through cloud netfabb, and I would try playing with the orientation some, but it’s a large object. I assume that downloading my .form file will help show the issue.

Anyone seen this?

It’s probably a mistake to orient the model the way you have it oriented. Besides the simple fact that taller orientations mean more layers mean longer print times, you need to keep in mind that a peel cycle is required between each layer and “tall and skinny” is inherently less stable, meaning you’re more likely to have a print failure. For something like this, you want the print oriented to be as close to the build plate as you can.

Go back in to PreForm and orient the model -45º on the Y Axis and then auto-generate supports. You’ll see you get a lot more supports in this orientation and the problem you saw with your orientation will no longer be present. Also, your print time will drop by close to 50%.

PreForm is not 100% perfect. Particularly the choices it makes in auto-orient, though support generation is imperfect some times as you’ve seen, and PreForm sometimes also highlights an area in red as unprintable when there’s plenty of supports (and if you ignore the red the model prints fine). The solution is to ignore issues where experience (which of course you need to gain some of) tells you PreForm is wrong, and/or change the model orientation and try again. Usually, you only need a small change to make a big difference.

Fred, that looks like a bug. I’ll have our PreForm software team look into it. In the meantime, you should try rotating the part by a small amount (~0.1º) and regenerating the supports to see if that fixes the issue.

Thanks, Randy. I know the best practice is to orient lower. Yes, this model can technically be rotated that far on one axis, but it actually lengthens the printing time due to the amount of support it needs - and it more than doubles the resin volume.

Well, clearly not what I expected!


You’ve got a lot of the print “cantilevered” out from the build platform. And there really isn’t a lot of support structure to hold it out there. You actually want more supports not fewer. PreForm may say it’ll print the 0º orientation faster and with less resin, but if the print fails its print time is “infinite” compared to 45º and you’ve wasted all that resin in the attempt!

The peel operation puts a fair amount of stress on the print. Taller/spindly prints tend to need more support that shorter/squatter prints or you get distortion of the print, or outright failure. Supports mar the print and are a PITA to get off, I try to minimize them whenever possible. But the more “delicate” the model, the more supports you have the more likely the model will print without defects.

Optimizing orientation to minimize supports and resin use is in my experience viable only in rare cases. Probably, at 45º PreForm is generating more supports than it needs to. Cut the support density down. I hardly ever print more than 75%. Let PreForm generate the supports and then go in and edit by hand to add individual supports if/where necessary. Also, PreForm seems to be conservative on support placement. Many times it puts a lot in a small area where fewer will work as well. It’s not unusual for me to remove supports that PreForm auto generated.

I guess the point being I use PreForm as a starting point but generally optimize by hand before printing…

Thanks, you have some good points there. I do have it oriented such that the larger object in the XY plane is also along the sweep path to deal with the peel stress you are talking about. I haven’t tried reducing the density – only increasing it when the analysis shows trouble spots. I’ve played a couple times with adding supports where it looked like a corner would have a problem, and the automatic tool seemed to miss them, and I also decrease the point size unless the object is large and hefty.
Well, I’m going ahead with the print vertically and see how it comes out, but I get the point about infinite print time if it fails. There was an art to FDM/FFF printing, and there is a similar but unique one here.

FDM requires some “organic knowledge”. There are better ways to orient parts for printing, but you need to figure it out by trial and error mostly. Same applies here to the Form printer. It’s not a Star Trek Replicator that only needs a button to be pushed. Some things work better than others and each model has different requirements, and while there are guidelines to follow you still need to do some empirical experimentation to figure things out sometimes.

The print came out perfectly with vertical orientation. While trying different things such as adjusting the support density or editing support points, I’d say half the time it generated those vertical supports that were lower than the base. I couldn’t seem to figure out what things caused it to happen, but I’d go ahead and tweak something and they would not be there the next time.

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