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.
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/xfacepalm.gif.pagespeed.ic.EBDwh1hCfo.png)
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
![ThumbsDown :--](https://www.eevblog.com/forum/Smileys/default/icon_thumbsdown.gif.pagespeed.ce.D027Y9gZ7m.gif)
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-