Decrease of laser power? Seperated Resin? prints still liquid inside


I am having an issue with prints not beeing fully cured on the inside. The outer skin of the models seems to be cured well enough. But on the inside sometimes are huge hollow areas. Sometimes the complete model. This does not only occure to the model itself but also to the raft. (The arae underneath the letters is barely cured)

I haven’t used the printer for 2 weeks. After that the first prints came out perfectly. Currently the printer is running nearly 24/7 and the prints are getting worse and worse. I print quite a lot of small models at the same time. Therefore a lot of support structure and raft.

I know that the laser power of diodes decreases over time and operating temperature so could it be that the diode has become too weak?

In my understanding the support, raft and outer skin of models is cured for a longer time than the infill of a model. Therefore these areas are cured well enoughl. The infill on the other hand is cured for a shorter time and (in my case) remains liquid.

I am using a new LT tank, mirrors and glass plate are cleaned.

I had that same problem middle of last year. After 6 weeks of email conversiation with different people from formlabs support they told me that they don’t know what is the reason. They can only offer me a repair for 900€.
They also told me that formlabs is using a laserdiode that does not get weaker over time and temperature. To be honest I dont belive this. Does anyone of you have a similiar problem or a solution? Can I increase the curing time in open mode?

Are these models solid or just shells?

They are solid. Just take a look at the raft. It should be solid but is liquid in the middle.
Do you have similiar expieriences?

Can you share a form file?

Sorry, I can’t share the form files. But as said before. Just have a look at the raft. This is created by preform and the same on every printer / print. The raft is still liquid on the inside under the letters.

This is an issue I would absolutely recommend talking to our support team to solve because they have the ability to investigate these issues a little more closely on an individual basis. :slight_smile:

Hi DKirch,

I did. Middle of last year. I had an email conversation and several phone calls over several weeks. I did a lot of testprints, cleaning of mirrors and replacing the glass plate. Nothing helped. They also told me that they can not check the strength of the laser on the 4 sensors because these sensors seem not to respond. They then told me the only option I have is to send the printer in and get some parts replaced/recalibrated for 900€. But they couldn’t assure me that this will fix the problem. So overall there was no solution.

If you have a contact at Formlabs that is willing to help me with this issue I am very happy to get in contact with them again. But I just want to avoid to have to explain everything again, making all the tests and then stop with no solution in the end.

Totally understandable! Always keep in mind that we should have those previous conversations on record, so it’s worth mentioning if you get in touch again that you’ve spoken to us before and that our support team should read through that to familiarize themselves with what’s going on.

I think you would get an effect like that if Preform was trying to support both the exterior and interior faces of a shell. What the rafts show is not a single raft with a void between the inner and outer faces, but two superimposed rafts, one from the outer shell face and the other from the inner. If your theory was correct you should find evidence of a void the parallel to the base of the raft.


Okay, I will give it a try.

@ bilb:

I dont think so. Because of two reasons:

  1. in case preform would support the outer and inner faces of the shell it means that it would create two rafts. To have these rafts running parallel with a small void in between around a single point of support structure is not possible. The angled part of the raft is created X ammount of mm around a support structure collumn. Therefore these rafts would overlap by 100%.
  2. In case there would be an additional raft for the inner shell of the support structure, it would also have the letters a second time. And there is only one set of letters per raft. This set of letters is in the middle.

Also check the pictures where the rafts are overlapping: In this area the middle part is not liquid. This area was hit by the laser 2 times.

I Just had a look at the different prints and failures from the last days. And I found a pattern in the failures. They are all located in the upper left corner (preform view) or upper right corner (printer view). This is also the place where the new resin enters the tank.

Could it be an issue with the resin? Not mixed properly?

I know from PU csting that one of the resin components seperates after some days. This might explain why the first prints after some pause were all good. One component of the seperated resin was at the lower level of the cardgridge and used first and cured well. Then the other part of the seperated component was used and didn’t cure properly. Now with a new (properly mixed) cartridge I am slowly getting to the correct mix ratio again. Therefore the prints should get better.

This would also explain why I had an overall bad print after cleaning the mirrors and filtering (and mixing) the resin from the tank. The print quality of the print was overall quite bad but had no hollow models.

Has anyone similiar experience with not proper mixed cardgidges or printquality drops after a long (3 week) pause?

Just try using the slicer in Preform to see whether these are shells…

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