Lines in recesses and on flats?

We’re having a recurring problem with most things flat, and especially if its at the bottom of a recess.

I’ve attached a photo to show what I mean - I’m thinking export issue, but in Preform everything looks fine. It’s often bad around embossed text. Anywhere where 2 surfaces intersect really.

This one isn’t too bad, but we recently did a cathedral model sample in which every window looked fine in preform, but the print came out REALLY bad., and really don’t fancy sanding all those on the real one!

Any suggestions?

(Most our flat surfaces are exported from Rhino, but the problem isn’t software specific.)


What printing orientation are you using?

I orientate to minimise the amount cleanup on visible surfaces, which is different for every job.

The caps got lines on the underside of a near vertical surface, the cathedral on the top side of a near horizontal one - I’ll happily be wrong, but I’m not convinced orientation has much impact.

Hello there @mep

Thanks so much for taking the time to post! This is a great question, and luckily it’s one we’re pretty confident about the underlying cause.

It’s an odd characteristic of PreForm that, if you have zero-thickness gaps between two parts of a model, these lines will extend out across the entirety of the part. As you can see in the pictures you attached, all these lines come directly off the intersection points. I’m guessing the thin ribs and the surface under them are just barely touching(technically both touching and not touching, “zero thickness gap”).

The solution for this is pretty simple! You’ll just need to have the two parts intersect a little more so you get some more overlap. Once you do that, I suspect your next print will come out just fine. :slight_smile:

I hope that’s helpful! If you’re still having problems please don’t hesitate to reach out to our support team at the link below and we’d be more than happy to give you a hand.

Oh ok - cool, I’ll give it a go!

I do a lot of designing stuff for layering up of laser cut or CNC sheet, so snapping things to faces is kind of a motif!

The good news Is I’ve got my next really complex architectural detail already modelled as a single boolean-ed/trimmed solid - should that print ok?

Another good question!

In my own experience(I use Maya myself) with Booleans and printing, they typically don’t play nice unless the resulting mesh is very clean. If you don’t have any ambiguity about faces it should be fine.

I’m sure you’re familiar with that “flickering” look faces can get if it’s not a clean Boolean. I’ve found areas that display like that in your modeling software don’t usually print super well.

I’m happy to take a look if you’d like, but hopefully that helps.

I’m using Rhino which is NURBS based and the proper mesh generated by the export settings. Fingers crossed it will be fine (at least from the random lines perspective).

And thanks! I’m dreading January slightly less now :slight_smile:

Good luck!!

What version of PreForm are you using? We added some improvements to how the coplanar case is handled in PreForm 2.19.0. If you’re running an earlier version, you might try upgrading.

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Nice one! Was still on 2.17 - must have missed the update notification!

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Did that fix it?

I first reported that bug way back. Make sure you use obj format for models that made of multiple parts and the parts need to intersect. STL format will treat the intersections as hollows. OBJ supports multi mesh models.

If you want to spend a little $$$ FormZ handles Booleans really well and has an object doctor tool that fixes many issues with prints that Preform can’t fix. I did have meshmixer for a while but ended up junking it, found it awkward to work with but that is just me, others find it useful.

Thank you for your report a while ago. This issue should be fixed in PreForm 2.19.

Will 2.19 support the F1 machines?
Trouble with co-planer faces is it may be difficult to have a fix for that which is the cause of the streaks. It resembles the flickering of a polygon you would see in a video game but a static representation.

You should be able to fix the hollows issue, perhaps have a tolerance or maybe a fix brush tool where you could paint in areas you want to be filled? OR have the software create a shell may be using an offset surface function with 0,0,0 distance. Offset would be handy for people printing parts that need clearance adjustment on their models such as threaded parts and press fit parts. These are often very difficult to adjust for and the factors such as orientation and layer thickness effect fit.

Yes, Form 1 is still supported in PreForm 2.19.

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