Prints stopped attaching to build plate

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jon_bondy
Posts: 78
Joined: Tue Jun 16, 2015 10:55 pm
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Prints stopped attaching to build plate

Postby jon_bondy » Fri Sep 18, 2015 9:41 am

The last 3 times I tried to print, the prints failed to attach to the build plate, entirely. I re sanded the build plate, but no joy. I switched to a fresh batch of resin, but no joy. The petri dish is used, but not excessively.

I have never felt as if the build plate could be leveled properly. The build instructions called for 2 grommets between the plate and the 3D printed part, but there was not enough room for 2, so I used 1. I cannot adjust the gaps at all using the original approach. So, perhaps part of the build plate is not close enough to the petri dish. I have been putting paper shims between the build plate and the 3D printed part.

At this point, the printer is totally useless, and I have a customer with a tight schedule.

Any support would be appreciated. My current evaluation of the LittleRP is that it is the most unreliable of my 5 printers. I wish I did not have to say this. Very frustrated.

goopyplastic
Posts: 236
Joined: Sat Mar 29, 2014 6:16 pm
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Re: Prints stopped attaching to build plate

Postby goopyplastic » Fri Sep 18, 2015 12:35 pm

Sorry you are running into problems.

The two grommets is more for the folded metal arm as it has a little more variance than the printed are. You can get away with one grommet typically with a fdm printed z arm.

I would first relax the 3 leveling screws so they are barely snug, then loosen the 4 z arm m5 screws, you should be able to wiggle the z arm around a bit now this will give you extra room for leveling.

If you are coating your own dishes and not using a level enough of a surface, rotating the discs will change the angles the pdms surface is at compared to the build plate. I would mark the front of the dishes so they stay in the same orientation when removing / inserting / recoating etc. This will help with leveling.

Lower the z arm to the pdms surface first (z arm is now somewhat loose because the 4 bolts are loose) the z arm should level itself somewhat now, after this is done tighten the 4 screws.

Now tighten each of the 3 leveling screws one full rotation so they will be somewhat snug.

Now loosen the build plate knob a few turns while the build plate is on the pdms surface this creates a gap between the build plate and the the z arm spacer (you might need to raise the z arm a little for the gap to form) You can then tighten the leveling screws to even the gap front/back/side/side.

The best way to fine tune the leveling is with an opaque resin in the dish. by looking through the mirror you can pretty easily see high/low spots as areas of no resin, or lots of resin on the build plate.

The base layers should be seen as sacrificial and a cost of build plate adhesion, so increasing your base layer times a bit may be useful. One of the more useful aspects of the flex vats are that you can use obscene first layer times such as 60 seconds to make sure you get an excellent bond.

You might try stripping your build plate with acetone and some steel wool in case it has become fouled by some unknown material affecting adhesion as well. You can try sanding the build plate with sandpaper on t a piece of glass to make sure the surface is level as well.

If you are recoating your own petris, I would double check how level they are and start parking the 'front' of your petris so they are always in the same orientation during curing and use. The leveling process of the arm only levels the arm to the pdms layer, and there are other factors that can affect how consistent the pdms layer level / angle is.

Which resin, base/layer times, layer height projector etc are you using?

jon_bondy
Posts: 78
Joined: Tue Jun 16, 2015 10:55 pm
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Re: Prints stopped attaching to build plate

Postby jon_bondy » Sat Sep 19, 2015 12:01 pm

Thanks for taking the time to write up things in so much detail. I re-leveled the build plate, and managed to get a print out. I wonder if the print that failed may have had too large a surface area, and was having trouble getting sucked down by the petri dish. Not sure how to measure the cross sectional area of a print in order to tell if I'm close to the limit.

Scatterplot
Posts: 119
Joined: Mon Jan 12, 2015 12:09 pm
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Re: Prints stopped attaching to build plate

Postby Scatterplot » Mon Sep 21, 2015 3:41 pm

Post which model you're using (if you can- maybe just a screenshot?) and we might can tell you just based on eyeballing it.

jon_bondy
Posts: 78
Joined: Tue Jun 16, 2015 10:55 pm
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Re: Prints stopped attaching to build plate

Postby jon_bondy » Wed Sep 23, 2015 7:22 am

Thank you. The models I am printing are proprietary, so I cannot post them, unfortunately. I was told that a rule of thumb was not to exceed 1 square inch. It would seem a very simple thing for the software to compute that; not so easy to eyeball.


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