Thanks for linking to those videos branadic. I'm considering an Anycubic Photon at the moment.
As I tend to make structural rather than decorative pieces, how easy is it to get accurate dimensions? I saw 7.1% shrinkage mentioned for one resin. That can't be right - it would be almost unusable.
After some tests we performed I can now state something to the dimensional accuracy, even though test's are still in progress.
First of all, z-axis was fully misaligned. So we disassambled z-axis and found that the mounting surface looked like it was sawn and filed and thus fully out of angle.
We removed 0.2mm with the milling maschine, reassembled the z-axis and it's now perfectly in angle to the red anodized platform in each direction. Anycubic should have spend this little step during their fabrication of the printer
We then started our tests. Test object is a cube with 10mm feed size arranged in 8 different angles on the plattform, with an 8mm circle being 1mm deep on one of the surfaces, an equal-sided triangle of 8mm height with 1mm depth as well as an indication number on a third surface. These cubes were sliced with the following parameters:
- layer thickness (mm): 0.05
- normal exposure time (s):10
- Off time (s): 6.5
- Bottom exposure time (s): 50
- Bottom layer: 8
- Raft: 1mm + 1mm support structures
- Resin: Anycubic Gray
What we found so far is, that there is a compression of the part in z-direction of ~0.41µm per layer, resulting in an overall compression of the printed part of 170µm along 20.7mm length. The website states a z-accuracy of 1.25µm, but it's not mentioned wether this is an absolut accuracy or a relative accuracy. I guess it's the latter and means that the deviation per layer adds to a total error that we observe.
Since there is currently no possibility to correct for that by an average offset error per layer we can't compensate for that.
We have a last test running right know. We found a spreadsheet about
Anycubic Photon Resin Settings. So we changed parameters to values given in the spreadsheet today and started the job:
- layer thickness (mm): 0.035
- normal exposure time (s):14
- Off time (s): 1
- Bottom exposure time (s): 90
- Bottom layer: 8
We will see how that turns out tomorrow. If nothing helps we will contact Anycubic for support and ask for a new firmware with the additional average offset value per layer, which would be a neat feature as you only have to print a dimensional part, measure the difference and divide the difference by the number of layers you printed.
-branadic-