Model Blow out Hole / rough lines

See attached, but I’ve been experiencing a few blow out issues on models. Wondering how to best avoid holes in the model. Tank doesn’t seem to have excessive clouding.

For every “hollow” part you carry “full of resin” when Z tilts, you need to add a draining hole, with suitable software like meshmixer for example.

Thanks for the response.

It does have 2 drain holes see the 2nd pic.

Always figured they were for air.

But from what your saying I may need to make sure they’re oriented differently and always at the bottom of the print?

The ragged edges seems to me that your resin has some partially cured lumps in it that might be the cause of the blowout. I would check the resin and make sure it is clean. Dust on mirrors and worn pdms can be the root cause of the lumps causing the cascading fail.


The face pointing towards the build platform needs a relief hole. Without it, any concave surface relative to the resin tank direction creates a vacuum pocket with the pdms and puts extra load on the work piece and the machine. Even if there are relief holes later, as you have here, until they are formed you will get suction problems.

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@sigmazero Thank you that explanation helped immensely. It’s almost as though the pressure continued to build up until the hole was formed and any further layers seemed to print fine thereafter.

In your experience do you use multiple relief holes or just a single hole?

Depends on the geometry of the object. But as a rule each local “cavity” (and keep and mind that a hollow object might have one large “cavity”, but multiple ‘local’ cavities as it is being printed) needs a drain hole.

(Forgive my crude paint drawing)


Light blue are your relief holes, red is the object.
Notice that until the print reaches the dark blue line, there are 2 cavities that each need a relief.
Now, not every single tiny cavity needs to be handled like this, but as many large-ish ones that can be accommodated in this way will greatly increase the chances of success.


A blow out would be more likely if the wall thickness was minimal. There isn’t that much pressure when layers are formed to be the cause of the blowout on that part. It is more likely the pdms is clouded and/or the main mirror has a fleck of dust that is enough to foul the laser beam at which you would have a region that is partially cured and resin around it being partially exposed causing lumps.
I would strain the resin and check the tank. If the pdms looks clear then inspect the
Typically the more remote the failure then the obstruction is closest to the part, More dispersed ragging across an entire part no matter where the part is situated or oriented is usually dirt on the galvos.

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Thanks for diagram @sigmazero. That all makes sense.

@KenCitron Thanks for the reply. Wall thickness is 2mm and current drain hole size is 2mm.

We’ve had the printer a year. So it could no doubt be dust. The reason I don’t think it is, is because this issues only arises probably 5% of the time. With shell thickness and hole and orientation all being consistent on the other successful prints. Which is why the issue must be in the orientation in some way.

Another issue we’ve been experience is cracking. I’ll see about documenting next times this happens. But this seems to be in the post process of this material. As castable material seems to be very fragile.

IPA does deteriorate the resin so try to minimize it’s use on critical parts or swap to a water based system for cleaning. I haven’t tried castable resin since I use the clear mostly for making master parts. In general I personally like the water based method for cleaning my parts since many are flat and prone to warping.

Check your pdms layer, good chance is it is starting to fog.

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@KenCitron Is the water method something encouraged by form labs? Haven’t heard of this process. Little envious of you lol. Clear has been by far the easiest material to print with it seems, love how it can basically air and room light cure.

This castable resin remains tacky for a frustratingly long time. With some prints requiring over night cures… Forcing swaps of the ipa way too often. Not to mentions parts of the model cure at different rates if not exposed to even light.

Let me know if you happen to have found any good documentation on the water method. Something I’d like to try.

Formlabs loves their IPA method even with all the drawbacks, Few of us have migrated to a far less toxic method you can read here: Replacing Isopropyl Alcohol with Yellow Magic

I haven’t tested Yellow Magic with castable resin but assume it would work fine. You can get YM from Z-Vat industries.

As far as the parts remaining tacky, that is actually oxidation on the resin prohibiting it from fully curing. You can easily overcome this by post curing your part while it is submersed in plain water. If you don’t have a post curing unit you can use a plastic container or ziploc bag filled with water and toss it in the sun. I use a reptile lamp that seems to work fine. There are slew of home made boxes and FL has one too.

I have the same issues + holes filled in with V3 Black Its not dust. Try a bit more yaw, rotate orientation perpendicular to the X axis and a smaller resolution. The lines don’t go away, but are finer. Never had this issue with V2 Black. I run the same print in V3 Grey, tough and durable with NO problems. Word on the street is the matte white isn’t good either. Can’t say for true as I haven’t used it. Have fun!

If that is material specific then maybe the exposure settings are wrong for the material. Can you test the part with a standard gray, clear or one of the basic resins?

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