Dimensional Accuracy - What Happened?

Good day everyone, first and foremost I would like to say I really enjoy the Form 2 forums its literally like a family in here and I know there are many talented and gifted people in this forum. I need a little assistance with understanding what is going on.

I’m working on a project to create a device and I had to split the device in to several pieces due to print build volume. All of these pieces were created in SolidWorks and they are dimensionally accurate. I had to be a little tricky with how I orientated the parts to print as many of them just barely fit.

After printing all of the pieces, about 1 Liter of resin* I can’t lie, I expected the parts to fit together like a laser cut jigsaw puzzle. Thats not what happened. Please see images after crude assembly. Now grant it I could always do post on this model but this is for prototyping so I found internal part misaligned that sanding would do no justice if I’m to achieve the ability of functionality testing.

Here are my questions. What went wrong? Was it the orientation of the parts and even though they all printed successfully they still bended a bit? Our curing staton “Meccatronicore BB Cure” was out for a moment being replaced so we did not cure these parts. I might add if it is not obvious we are using white resin v2. After removing the parts from the IPA they seemed to only need to be allowed to dry in order to cure. Was I wrong about this and should have cured all the parts? Should I use another resin? Is white not really used for this type of thing? Was a wrong altogether about prototyping with the Form 2 and I should look for other options to print a dimensionally accurate version of something this big? Thanks in advance for your response.

*Cost is not a concern when this works, however, if something is printed that I cannot use then eventually these mounting resin costs would be a concern.

Click to see complete image

Very cool model. Can you post pictures of how the parts are oriented and supported. It might tell a more complete story. Are all the parts off or is it possible that one mis-print is causing most of the issues?

If you couldn’t get the part oriented properly due to the size of the part, you may want to break that part up into smaller ones and then assemble those to create the larger parts. You may find that orientation is more important then printing off each larger part at once.

With optimally oriented parts you should be able to use white. When they printed the white violin it was with the new white and it came out beautifully. I don’t see why you wouldn’t be able to get the results you are looking for.

Thanks for taking a look here are some screens of the part orientations. I did choose less support options over the wizard.

I would add more supports. Some of the models I would add a lot more. Someone with a Form 2 can chime in to let you know how many more supports you should add but from my experience, I would add a bunch. Specifically running up the edges where the dimensional accuracy matters.

You should be able to scale the model down 50 - 75% and do a small test fit to save a whole bunch of resin while you figure out the best way to orient the parts. I gather at that scale / size, you would get a good preliminary good test fit based upon the orientation. Then you can scale up to full sized to see if you should chop the models up into smaller pieces to get the best orientation for optimal print quality.

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Orient all pieces of a given assembly the same way, meaning if you had a sphere and you split it in two to print it, ignoring any surface details that might distinguish them, both pieces would look the same in PreForm. This will ensure that any tolerance variations will be generally in the same direction.

Orient the parts so that the surfaces that need to mate are positioned as close to the build platform as possible. In the example of a sphere above, they would be positioned with the open end of the sphere half pointing mostly downward in PreForm. This will put supports on the mating surfaces, so those surfaces will have blemishes that will need post processing to clean up. Doing this also puts most other support contact points on the inside surface of the print, which means less post processing for that part.

If you want the part to be as good as possible don’t reduce the support density. You might even need to go above 100%. You can reduce the point size a little to reduce the size of the blemishes and make it a bit easier to get all the supports off the print.

If you don’t want the part to warp and deform, it has to be cured while still attached to the base/supports. The print will deform a bit with time if you do not post cure. I’ve had parts that came off the printer looking perfect that I didn’t post-cure, that were useless after a few days sitting on a bench.

I also agree with David’s advice. Print a smaller version to play with orientation and when you get that to work satisfactorily scale the successful orientations back up to and print the size you need.


Be careful of your cross sectional areas. When the resin is cured, fat sections will shrink more than thin ones so there will alway be some warping if the cross section changes too much. The other place to look out for warping is on ‘L’ shaped sections. Her the apex of the ‘L’ tends to shrink more than the edges, making thin sectioned box shapes problematical.

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Some parts can flex as it prints causing dimensional problems, but also any downward facing surfaces will be a little bit thicker than they should be due to light bleed

If something is simple enough, then I think an FDM printer is a better solution since you can usually get a large build volume and the amount of detail isn’t as important.

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Thank you so much for this, also thank you @DavidRosenfeld

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