Uneven base thickness, base doesn't stick to platform

General Discussion
1

As documented in another thread I had some success with my latest printer. However the model I’m currently trying to print fails every time.

The base comes out uneven, it’s very thin on one side. That side also doesn’t stick to the build platform, see photos. It sounds a bit like the issue discussed in this thread: https://support.formlabs.com/entries/38561208-Testfile-didn-t-print-succesfully-Base-plate-too-thin

I played around with the z-offset in diagnostic mode. The reason why I even tried this is that I got the impression that on this printer the platform gets lowered too low initially. With previous printers, when the platform was lowered for the first layer, I could still see a very small gap between the metal of the platform and its reflection. On this printer, the two are completely together, no gap. Also, the print platform’s plastic sides are bulging outwards, and I *think* they didn’t when I got it, so I wonder if they got pushed out by too much force/pressure.

For that reason, I tried z-offsets of -0.2 and -0.7, that didn’t help and the latter actually made it worse. On the attached photos, you can see that the first print failed and the right side sags downward a bit, and the hole isn’t circular like the one that’s near the middle of the model. When I printed with -0.7 it was worse, that’s the second photo. However, with -0.7, it seems to me that on the side where the base is thicker, it’s actually closer to the intended thickness, it is about 1.8mm at the thickest location. Unfortunately the opposite side is still way too thin, I measure it at about 0.3mm. You can see that in the photo.

About the orientation of the model, I not only tried it in this orientation, pointing straight down, I also tried it with auto-orientation and 0mm z-offset. It failed in the same way, parts of the base didn’t stick to the platform and the model sagged in two locations. That’s the photo of the model with the metal thread inserts.

Another print I did at 0mm offset is the one with the cat, you can see that part of its base also didn’t stick.

It seems that the part of the base that comes out too thin and doesn’t stick is always towards the back of the printer.

I’m currently printing the butterfly test file at 0mm z-offset to see how that goes, and I’ll open a support ticket. I was wondering if anybody else has a fix for the models not sticking to the platform.

2

Hi Marc,

I can think of two things happening there - first it’s very interesting to see your warped build platform - someone else posted about that in the very early days on this forum. So I’m guessing this might be a refurbed printer perhaps with one of the early build platforms.

Have you tried laying a metal ruler against the build platform surface to check it for flatness? if the build platform is bowed - then that might explain your issue.

Alternatively - it may be that your resin tank is far from level - as per my thread where you demurred to running the printer with the cover open.

As I said in that thread I’m running a test print that will confirm how level my resin tank is, in response to Formlabs warning about adjusting the levelling nuts ourselves. I’ve been delayed by several new issues, FL white resin seems to cloud the PDMS much faster, my Z-axis galvo suddenly started expanding, and my build platform was taking in and leaking resin - but hopefully I’m back on track - currently running the print again.

Here’s the form file I’m using now - the pieces are printed vertically and perpendicular to the build platform - this means you can check your resin tank alignment with the Z-axis, by checking that the external square angles are in fact square.

Kevin.

vertical_windows_right_and_rear_b.form

3

course that’s a silly typo above, there is no “Z-axis” galvo, I meant Y-axis.

4

Thanks Kevin, I’ll try your test file and I’ll check the flatness of the platform with a square, good idea…

5

The other way to check squareness is to tape a ruler to a piece of paper, lay the test print against one edge of the ruler - draw a vertical line, then rotate the piece 90 deg lie it against the ruler again and draw a line against the next edge, close to the first line; if they are parallel - then the piece printed square.

It’s a bit more effort, but will be less fiddly and should be clearer than judging by eye with a set-square.

You may also need to trim the corners a little - I haven’t managed to finish printing my 4 (one each side) yet because of my recent printer issues - but some of my earlier versions of that part had “flaring” at the top corner due to peel stress.

6

course I suppose it’s no good if the test part bases separate from the build platform as well …

The other thing you could do is run the first part of my resin tank levelling procedure - without actually touching the adjustment nuts; just look at them to see how much air there is between them and the resin tank carriage.

You don’t need to worry about using a magnet to run the printer with the cover open either. Just undo all the hex screws - but leave the cover on; then start your print, wait until the build platform is fully descended, the resin tank is back level (tic-tic-tic), then interrupt the print by lifting the cover. Then lift the whole upper casing off with the cover. Now you can check the position of the adjustment nuts. I don’t think you need to remove the front and back if you’re only going to look at the nuts and not adjust them.

If you can see clear thread (anything over say 1/2mm) between nut and resin tank carriage on one or more of the nuts, then that will explain your issue.

Once you’ve checked the nuts, you can put the casing back on - cancel the print, replace the screws - and no harm done…

7

Thanks again Kevin, I’ll try that check when I have some time.

In the mean time I looked at the butterfly test print, which, fortunately or unfortunately, didn’t fail in the same way. Of the 5 prints only the middle one had some failed supports, the others look pretty good.

I also checked the flatness of the print platform. I do see some gaps there, but I don’t know what the expected precision is.

8

I tried another print, this time positioning the model at the back of the platform, where I noticed that the bases were thickest. This failed again, one side failed to stick to the platform again.

Then I tried to *lower* (instead of raise) the build platform in the Fine Tuning dialog, by 0.1mm, and I got an almost perfect print right away. I tried to lower it this time because the latest release notes for PreForm mention that if the model doesn’t stick to the platform, that might help. I never tried that before and instead just raised it because I thought that the thin bases on part of the model meant that the platform was too low, not to high.

I’ll try some more in the other areas of the print platform (this print was towards the back only), and hopefully that fixes it.

9

Hi Marc,

Did you finally find a solution to your issue ?
I have a form 1 first gen and i am running into the same kind of issue.

Slightly uneven build platform, thin base (not fully hard when you touch it), fail of the print.
I will probably submit a ticket but having your feedback could be great.

Victor

10

Hello all!

I think I may have a solution as I had a similar problem with prints:

IMG_20150727_103620.jpg2688×1520 1.01 MB

I thought it was odd that the prints did this in the middle more often than not and when I ordered a new build platform it was slightly bowed (not as much as my old one but enough to rule out that being a problem.

IT WAS THE RESIN TRAY!

I prodded it a little and I could just see the thick non-stick surface bow up. So I started a new one and as I poured the resin into the new tray from the old I could see the sides were torn and despite only being a little bit of a bow when prodded it’s probably enough to mess up a print.

I’ve not had this problem since so thought I’d share my potential fix with you all.