Object comes loose from bed towards the end of the print

Hey, everybody. I have recently been trying to do about a 30 min print of a small 25 by 35 mm part. Towards the end of the print at about the same time each time I have tried the print pops off bed and I have to stop it to save it from melting through the existing part. I am using just a glass plate as the print bed. Is this poor adhesion to the bed or are there other factors at play here? I have tried adding mickey mouse ears to my sharp corners which works great to prevent corner curling but it did not solve my overall problem. I'm thinking that the bottom layers have cooled off too much by the time the upper layers are being printed and it loses its adhesion.

I have read in other posts that white glue, a glue stick, or hairspray may work to help adhesion.

The thing is that the print adheres great in the beginning and it prints just fine for the first 30 layers so. It seems like it would come off the bed earlier in the print if it was going to do so at all.

Edited 1 time(s). Last edit at 09/21/2014 01:36AM by jtoombs.

Hi,
I assume you use ABS for printing?

I also tried some tricks on it.
a) using hairspray works better then pure glass
b) I also tried a carbon plate instead of glass

Both versions give better adhesive to the print but none is really rock solid compared to PLA on blue 3m tape.
With ABS the wrapping will pop out the print from the plate, especially if the part has a small foodprint.

Printing a huge brim (5 - 8mm) makes it slightly better, but also no 100% solution.

I also found that the temperature of the room has also evidence to the result. Some printers therefore have a closed housing to tune temperature of the printing area.
I read about up to 70°C.

Good luck.

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RepRap Electronics, Mechanics, NEMA 17, Filament you find here: [www.my-home-fab.de]

I've never had good luck printing ABS on plain glass. I've used hairspray which worked well until I started printing large objects which warped. I switched to purple elmers glue stick and it works really good as long as there's a good coating of it on the glass. Once you have a good layer of glue on the glass, you can just keep adding more where you did the last print. Eventually if it starts to be too thick, I'll scrape it off with a putty knife or wash it off with water and then start again.

I guess I should have mentioned it in the first post. I'm actually printing in PLA. I;m going to have to try some sort of adhesive still though. I think that maybe it was because my printer was on my basement floor. I moved it into a corner of my bedroom. It seems to be doing better. Is a change in ambient temperature of like 5 to 10 degrees really going to make that big of a difference though?

Edited 1 time(s). Last edit at 09/22/2014 01:51AM by jtoombs.

Do you have a heated bed? I print PLA on plain glass (cleaned in hot soapy water initially, and primed with vinegar between prints) kept at 65C, and with most PLA filaments I don't have any adhesion problems unless I let the bed temperature drop during the print.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

No heated bed. Is vinegar used as an adhesive agent or a cleaning agent?

With no heated bed, you need to print PLA on blue painter's tape, or on an adhesive e.g. solvent pipe cement, hairspray, or PVA. Direct printing on glass only works if the glass is heated. The vinegar seems to improve adhesion.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].