What does triangles not closed imply?

I’m working on my first print, first one just stopped probably the instant I left the room. How did it know? Anyway, many of my first downloads from thingiverse generate a “triangles not closed” message. Should I immediately give up on those models and move on? Or is there a threshold or does the form software usually compensate ok? As an example, see  http://www.thingiverse.com/thing:55332

Thanks, and I’m looking forward to many long nights of printing!


I too am interested in this. I have now completed about 4 prints on mine and had a range of success/failures. A lot has to do with the complexity of my part but I wonder is some has to do with this error.

I have printed items with anywhere from 72-174 open triangles and currently have one printing right now with 174. should know how it turns out in 9.5 hours :slight_smile:

Hi George, RJ,

This type of message is a warning that the STL file you are attempting to print has some problems and you may not get what you expect when you print it.  A bad STL can have a wide range of negative effects on how a model prints, so it makes sense that you’ve had some bad prints from the file.

This particular error is letting you know that the model does not appear to be “closed.” That means that Preform may have difficulty figuring out the inside and outside of the model. You can find a bit more information here on why this can be a problem for 3D printing:


You will have much more reliable printing if you correct the problems that Preform is alerting you to in the STL file. You should check out the support page here on how to go about repairing STL models: http://support.formlabs.com/entries/23384387-Repairing-STL-Files for advice on ways of fixing your files before printing.


Thanks for the reply!

I had seen the support page you listed and downloaded Netfabb and tried it out. With Netfabb I was able to make this warning go away when importing however the part in Preform looked WAY more coarse than my STL out of Solidworks. Maybe this is me just not knowing the Netfab software well enough but I punted on it at that point.

Anyone here know more about this or have seen the same issues with STL’s out of Netfabb?


So I decided to try the Cloud Netfabb upload site and see if letting them do the work produced a better looking STL that imported into Preform with no issues. You know what happen?? I worked Great! Model Looks nice and smooth and loaded into Prefrom with no issues what so EVER! Not to mention it was pretty quick and I had to do basically NOTHING! Other than upload and download the model that is.

I will be giving this model a try on the printer once the current one is complete. still about 7.5 hours to go!

Last Print came out the best of them all here! This one had 174 open triangles. It still has some very slight pitting on the inside of a tube and a slight delamination of the inside of the tube as well.

On the printer now is the same model cleaned up by the Netfabb Cloud so we will get to see how they compare side by side.

Any more news Ryan?

Woops, RJ Lynn. Doh. Sorry.

Todays update.

The Print that finished this morning is the Netfabb Fixed print and it Does look a lot better. However I again had the issue of one of my .065" passage ways through a .12" wall clogged again and I could not get the partially cured and uncured resin out. It clogs about 3" in, which is too bad because it only has about another inch to go! I have gotten 1 of these to print successfully.

I have also printed a couple smaller trinkets all processed through Netfabb(Cloud), as each one of the native STL’s out of Solidworks had issues loading into Preform. All came out great.

The Netfabb Cloud service is fantastic and I am not sure how long it will stay free but I will continue to use it that is for sure! Especially since it seems Solidworks is incapable of creating a STL that opens in Preform without Open Triangles. Unless I have something screwy in my options…

Also all have been printed at the .05 Grey Setting. I have not tried to print at .025 again recently as my first couple of prints(8.1 Preform) were terrible. Although I need to try it again with 8.2. But who can stand to wait 20hours! :slight_smile:

RJ Lynn,

Great to hear!  Unfortunately, Solidworks does have some known issues producing good STLs for more complicated objects.  As far as your “clogging” issue, you may find that you have better results with that when using Clear Resin settings.


I will have to try that again as well, that is the Clear Settings.

Also I have been using some compressed air from the garage to try and blow out the channels in addition to working some copper wire through them to clean them out. The channels are not straight at all!

I just picked up some small desktop cans of compressed air with the small straws to keep next to my finishing kit to try and blow them out as soon as I pull them from the printer. It seems the longer you wait the harder it is :slight_smile: which of course makes sense :slight_smile:

Well the Clear setting produced some delamination of the outside layer on the outside of the part in the same spot on two different prints. The first one was not bad at all so I tried to reprint it on the clear and it was significantly worse.

Reprinted the EXACT same part with same orientation and same support settings on the Grey and it comes out great. I have printed 2 in a row that have come out perfect. #3 is printing as I type this.

This part averages around 50ml of resin per part. I need to deliver 3 GOOD parts to my client. I will have printed it 12 times…

Needless to say I am a little under water on this job and I have another bottle of Resin on order.

I chalk it up to a new cutting edge product with a learning curve that everyone is on, including those at Formlabs, and my glutton for punishment to start with my very difficult customer part on Print #2.

All in all I have very high hopes for the machine. 1 Week in 1 Bottle of Resin down…

Any chance we can see the models? Both failed and successful?

Unfortunately I cannot share these prints. My customer’s patent is not all the way through yet.

I Will try and take some close up pics between the two print just of the affected area.

And The 3rd Printed on the Grey Setting had the delamination issue! Man this is frustrating.

I am going to try and post some pics later.

Oh bummer. If you can’t show us, can you show parts of it to FormLabs? Maybe they can help.

But what a waste of resin. Ow!

Ok I will Start putting up pictures, of the last 5 Prints starting with the oldest, first of the 5, first.

1 of 5 latest of design Netfabb Cloud Cleaned .05mm Clear 2mm Base 2.5mm supports on 3.5 spacing.

2 of 5 latest of design Netfabb Cloud Cleaned .05mm Clear 2mm Base 2.5mm supports on 3.5 spacing.

Thought the last little bit might be a fluke so I tried it again with a slightly different orientation. Obviously the delamination got much worse but in the same area.