Print wont adhere

Hardware issues, problems and solutions
Eddie
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Print wont adhere

Post#1 » Sun Mar 31, 2013 11:55 am

Hi All,

I just installed B9 but my print won't adhere to the build table.

I carefully adjusted the build table to make sure it is flush to the vat because the table would suction to the vat. So I assume it is perfectly adjusted.

My problem is that the print won't adhere to the build table even with a large bottom support. The support would slip away instead of stick to the build table.

After reading posts on the forum, I realize that my resin might be old and I have failed a few prints so there are debris in the vat though I clean them up with a strainer?

Any other suggestions?

Thanks,
Eddie

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mikej
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Print wont adhere

Post#2 » Mon Apr 01, 2013 3:06 am

Yes, the resin should be free of debris, but "old" shouldn't be a problem. I assume it's creating rectangular "floater" layers that should have attached to the build table but that are instead found in the vat?

Sounds like the build table zero level is too high (too big a gap between the PDMS and build table for the first layer to attach).
Measure Twice, Cut Once.

b26354
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Print wont adhere

Post#3 » Mon Apr 01, 2013 7:56 am

couple of things I've seen:

1: exposure of initial layers too long can cause the support layer to stick to the PDMS so it'll slide off the build table when the vat closes. This usually happens on the second layer and you can hear the motor straining to move the vat. Exposure too short and it won't stick at all.

2: not enough waterfall in the PDMS. The PDMS will expand slighly with the heat of the projector. If the PDMS was cured at room temperature it can be quite flat - the deep end will expand more than the shallow end - so you can end up with it even flatter - or worse, a slight hump. The tell for this is the vat will be sucked up on the first few layers when the build table rises after the shutter has closed. Accelerating the PDMS curing in an oven is essential.

3: build table flatness - I think my build table isn't completely flat so it's hard to level consistently. I've made some acrylic tables which are flat(er) and the surface can be roughened up with sandpaper to improve adhesion.

4: clean the build table thouroughly with isporopyl (or acetone - just to be sure) and make sure it's dry. I've noticed on a couple of prints that there is a film of uncured resin under the bottom support layer when it's removed. I think any residual stickyness or oilyness on the table can inhibit the curing of the resin.

5: spread some resin very thinly over the table and cure it in sunlight or under a UV lightsource before printing.

thejewww
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Print wont adhere

Post#4 » Mon Apr 01, 2013 5:34 pm

Hi, I'm having a similar issue. First off, our support layer exposure time is set around 10 seconds and our normal cure time is set around 4 seconds. At first, this seemed to work great with the resin that didn't have pigment in it. After adding pigment, 10-15 slices into a print the support layer detaches from the platform. If we increase the times on either of the exposure times it just attaches to the tray and jams the motor.. everything appears to be working other than it just randomly coming off after 10-15 layers.. would taking sandpaper or roughening the platform help?

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mikej
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Print wont adhere

Post#5 » Tue Apr 02, 2013 1:04 am

There's no need to sand the platform, something else is wrong with your setup. You don't appear to be using our resin so I can't really comment on what it is?

But, to have a great attach your first 4 layers (no more than that or it may curl a bit and fall off) should be a large rectangle. From there grow supports up to your object. See this example:


Image
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Eddie
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Print wont adhere

Post#6 » Tue Apr 02, 2013 3:31 am

Now I have adjusted the hard-press-down and up-to-flush to 1.27 and 0.9 respectively and the base support (a plate) adhere to the build table. I am printing the model Knight by Andreas www.thingiverse.com/thing:59725.

However the pole supports failed to adhere. How should I adjust the exposure time?

Thanks!


Quote from mikej on April 1, 2013, 09:06
Yes, the resin should be free of debris, but "old" shouldn't be a problem. I assume it's creating rectangular "floater" layers that should have attached to the build table but that are instead found in the vat?

Sounds like the build table zero level is too high (too big a gap between the PDMS and build table for the first layer to attach).

Eddie
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Posts: 12

Print wont adhere

Post#7 » Tue Apr 02, 2013 3:34 am

Thanks a lot! I found the first point very helpful as I reduce the exposure time of 1st layer back the default 40s. And the first layer adheres.

Quote from b26354 on April 1, 2013, 13:56
couple of things I've seen:

1: exposure of initial layers too long can cause the support layer to stick to the PDMS so it'll slide off the build table when the vat closes. This usually happens on the second layer and you can hear the motor straining to move the vat. Exposure too short and it won't stick at all.

2: not enough waterfall in the PDMS. The PDMS will expand slighly with the heat of the projector. If the PDMS was cured at room temperature it can be quite flat - the deep end will expand more than the shallow end - so you can end up with it even flatter - or worse, a slight hump. The tell for this is the vat will be sucked up on the first few layers when the build table rises after the shutter has closed. Accelerating the PDMS curing in an oven is essential.

3: build table flatness - I think my build table isn't completely flat so it's hard to level consistently. I've made some acrylic tables which are flat(er) and the surface can be roughened up with sandpaper to improve adhesion.

4: clean the build table thouroughly with isporopyl (or acetone - just to be sure) and make sure it's dry. I've noticed on a couple of prints that there is a film of uncured resin under the bottom support layer when it's removed. I think any residual stickyness or oilyness on the table can inhibit the curing of the resin.

5: spread some resin very thinly over the table and cure it in sunlight or under a UV lightsource before printing.

Eddie
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Print wont adhere

Post#8 » Tue Apr 02, 2013 3:36 am

I am guessing my problem of supports not adhering is because when the slider moves, it breaks the not yet hardened support. All other setting remains default. Any suggestions?

Thanks!

Quote from Eddie on April 2, 2013, 09:31
Now I have adjusted the hard-press-down and up-to-flush to 1.27 and 0.9 respectively and the base support (a plate) adhere to the build table. I am printing the model Knight by Andreas www.thingiverse.com/thing:59725.

However the pole supports failed to adhere. How should I adjust the exposure time?

Thanks!


Quote from mikej on April 1, 2013, 09:06
Yes, the resin should be free of debris, but "old" shouldn't be a problem. I assume it's creating rectangular "floater" layers that should have attached to the build table but that are instead found in the vat?

Sounds like the build table zero level is too high (too big a gap between the PDMS and build table for the first layer to attach).

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mikej
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Print wont adhere

Post#9 » Tue Apr 02, 2013 3:42 am

Confirm your XY calibration is for 75 microns, correct? Can't talk about exposure timing without knowing your settings, but since you're printing the knight downloaded from thingiverse then you'll need to have the same XY calibration for it to work.
75 micron exposure timings of 10 + 2 is what I used on that knight print.
Measure Twice, Cut Once.

Eddie
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Print wont adhere

Post#10 » Tue Apr 02, 2013 3:58 am

Damn....... my XY is 100 microns. And I change the setting to 100 micro in the print setting. Does it work this way? I thought different calibrations will only affect the print scale but didn't realize it has something to do with the energy/exposure time.

I will try it now.

Quote from mikej on April 2, 2013, 09:42
Confirm your XY calibration is for 75 microns, correct? Can't talk about exposure timing without knowing your settings, but since you're printing the knight downloaded from thingiverse then you'll need to have the same XY calibration for it to work.
75 micron exposure timings of 10 + 2 is what I used on that knight print.

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mikej
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Print wont adhere

Post#11 » Tue Apr 02, 2013 4:53 am

XY calibration is performed by changing the physical location of the projector, which makes a huge difference in print exposure times.
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DennisH
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Print wont adhere

Post#12 » Sat Apr 27, 2013 3:47 am

So this build table issue has happened to me recently more...
I will try to calibrate build table with NO resin but i do kinda fear pulling the build tale of a dry PDMS layer. I had success with a lubricated calibration step previously so....

Then the other thing I will try is to return from the default 50 down to 40 for 3 instead of 4 attach layers.

Finally I have no problem using Dans trick of spreading a tiny amount of resin on build table and curing in sun if in fact this solves for this.

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behold3d
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Print wont adhere

Post#13 » Sat Apr 27, 2013 4:23 am

add some water in the vat if you are concerned

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DennisH
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Post#14 » Sat Apr 27, 2013 5:01 am

I guess so...I thought the purpose of removing liquids at this step was to get no gaps...the closest fit.
Wouldnt water prevent a flush placement as well?

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behold3d
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Print wont adhere

Post#15 » Sat Apr 27, 2013 5:41 am

I do not think the molecules of water would cause that much displacement. Not more then the resin and the pigment just my 2 cents

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DennisH
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Print wont adhere

Post#16 » Sat Apr 27, 2013 5:46 am

Thanks! I'll try that here next print.

sciencelookers
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Print wont adhere

Post#17 » Thu Sep 04, 2014 11:55 am

I have two build tables and two vats. My original build table has a beautiful brushed aluminum finish with the orange anodizing over it. The new one is plain, smooth metal with the same orange anodizing. I spent two days dealing with parts coming loose from the build table and then hundreds of paper thin slices piling up in the vat. I'd clean out the vat, strain the resin and try again. I increased the adhesion layer exposure time, increased the adhesion number to four layers, finally doubled both exposure times. This final adjustment left one part glued to the vat bottom and another broken up in the vat. I switched to the old build table and I just made four good prints of both objects in a row. Can you make build tables with the brushed surface again?

If it helps, the parts being printed are flat endpanels for electronic enclosures. They are big, flat rectangular things with a ton of surface area in contact with the build table. In the past, when I let the PDMS cure for 48 hours at room temperature, printing these caused the PDMS to peel up after one or two prints. I get good results now by baking the PDMS at 150 degrees for two hours and using the brushed build table. I need 75 micron resolution to fit the parts, I slice at 74 micron. I'm using 80 percent cherry and 20 percent red, which tends to control bleed and make parts the size specified in the CAD drawing.

The idea of sun-curing a thin film of resin on the build table sounds good to me, I'll try it on the smooth build table next time and will report what happens. Has anyone else had this experience with the two build tables?

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Robert Howle
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Print wont adhere

Post#18 » Thu Sep 04, 2014 12:37 pm

Did u recalibrate with the table change and does if "float" when the screws are loose with very little or no friction?
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sciencelookers
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Print wont adhere

Post#19 » Thu Sep 04, 2014 2:05 pm

Hi again Robert, thanks for being such a help on the forum.

I don't think the build table was loose. I screwed up a batch of prints with that mistake a while back. The build table was adjusted by lowering into the PDMS and then I press down all four corners before tightening all four screws. I remember tightening the screws really tight because I had forgot that before. That part of the procedure was done as close to exactly the same as I could do it for both build tables.

Your suggestion makes sense though. The time I forgot to tighten the screws holding the two halves of the build table assembly together it resulted in the same symptom, a hundred paper thin layers in the resin.

The other difference between the failed and successful runs is the vat. I had that warped vat that I heated up and tried to straighten out. That was the vat used when the parts turned into individual layers. The good prints were made with the vat you sold me, thanks again for that.

I have the models I need now so I can do some experimenting with the two vats. I'll drain the vat and try leveling the smooth build table to it (and be sure to tighten the screws). Then I'll see if I can make a good print. I'll also try the warped vat with the brushed build table. This should reveal if the problem was the table or the knackered vat. If I get good results with all combos, I'll assume I'm remembering wrong and you were right about the build table screws.

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Robert Howle
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Print wont adhere

Post#20 » Fri Sep 05, 2014 6:58 am

One other thing I forgot to mention, but if u mix your resin by shaking and u add it to the vat too soon (before most of the gas bubbles have dissapated, then your print can fail because the attach layers will be grainy and full of holes. You can eliminate this as an issue by examining the layers in the strainer (when u strain the failed print resin) to see if they are smooth and shiny on both sides. If u have any of the attach layer that are grainy with holes this may be your problem. Just one more thing to consider. I can promise u this can happen. I did it last week being in a hurry. Failed 3 hr print with nothing but attach layers and lots of little bits of cured resin. Restarted print right after straining and no other changes and perfect print. the only diff was the frothy resin. Stupid move, I know better.

I really wasn't concerned about loose screws, although that is def a no no. More about just an accurate table calibration. When I said does the table "float" it is very important that it moves freely (with little or no frictioin) when the screws are loose (up and down). There have been some instances of the black upper part and build table not fitting properly, making it nearly impossible to move freely during calibration. I happen to get one and had to file the thickness down on the black component where the slots are in order to get free movement. When the screws are removed, and u hold the black upper portion of the build table assembly, the red lower portion should fall completely away. Don't drop it on the floor doing this and bend it. Not good.

Robert
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