Large Support Base Issues

I have on many occasions had prints fail because the vacuum between the base and bottom of the vat is too strong for the motor to overcome. I am wondering if having some flow channels that break the base up into smaller cross sections would help with this.

Maybe an option to create flow channels in the support base could help with this? Otherwise, re-homing the z axis if skipping is detected may help, at least for the base section. I can see where re-homing during the actual part would cause some inconsistencies in the part.

Another side effect I have run into with large bases that did not cause the z motor to skip, but were too large to allow adequate re-coating before the z moved back down. Therefore no resin was present between the previous layer and bottom of the vat. I think some flow channels may aid in this as well.

I suspect this might be because the surface of the tank is already worn out. Does this happen on a new or used tank?

I have experienced these issues on both. The support base on the recent incident is about 11 cm in diameter.

Large support bases will definitely have that issue, part of the problem is that there’s some prints that could be more efficient in how the base is made–for example if you print a cylindrical shape you would expect a hole in the middle where there are no supports but currently it will not do that and that creates a large base.

The raft does tend to require the greatest peel force due to higher compression and over-exposure but it shouldn’t be causing the motor to skip. If you’re noticing skipping, it may be caused by over-compression and raising your Z offset via fine tuning can help. You might try iterating upwards by 0.2mm in Z fine tuning until the skipping corrects. If that doesn’t help, get in touch with our support team so that we can help to troubleshoot further.

I can’t say I’ve seen inadequate re-coating before using Formlabs materials. What sorts of artifacts are you seeing in your prints?

Thanks for the Z suggestion. I will have to try it next week. I should note that the motor skipping is an issue that I have seen occur between two different machines now. Neither of which I ever touched the fine tuning adjustments on.

I recently had my original machine replaced so my “recoating” issue may have actually been due to insufficient laser power to provide a good cure depth. Thinking way back, the laser problem may have started early enough that it caused several things that were wrongly attributed to other causes. I will describe what I (and someone on the support team) thought was happening though.

The issue manifests in the form of very large layer shifts. I have seen this happen on support bases as well as part layers. Unfortunately, I do not have a picture of the example I am thinking of and I long ago threw out the part. But this occurred on a part that had a large cross section and was admittedly not a great design for SLA but I was printing it for a customer. It looked like there were regions where a layer was cured out, but there was not quite sufficient resin to wet between the part and the bottom of the vat so as the lateral movement of the peel process was executed, the layers shifted relative to one another. Then when the next layer was supposed to be printing it somehow cured out enough resin between the layer stuck to the bottom of the vat and the existing part layers. That way they stuck together and the cycle seemed to repeat.

Are you printing parts with hollowed out cavities? We don’t often see poor layer registration on the raft layers but if there’s a hollowed out cavity that doesn’t have any drain holes for resin to escape, there’s a suction cup effect that will cause something similar to what you’re describing. In the case of hollowed parts, we recommend adding drain holes or orienting parts in a way to ensure that resin has a path to escape. If you upload an example .form file that’s causing issue, I can take a look and let you know if there’s any modifications that should be made.