This topic contains 64 replies, has 17 voices, and was last updated by 
poju 1 year, 7 months ago.
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Hi.
First of all. i must appologise for any misspelling and bad grammar. English is not my first language.
I have followed this forum for a while and have noticed that one of the one of the most common problems we roboxers have, is the PEI bed.
I had the same problems in the beginning, but the last 1kg printing material that has passed through my printer, has been sticking to the bed like crazy.
This is how i did it (I can not promise that that the solution will work for you).
- I noticed that my PEI bed was flat when cold, but when heated to 115°C it was bulging in the center of the bed.
That was a easy fix. Everything expands when heated (except water), so i figured that the PEI bed was cut to precise in the bed frame. I took some P80 grid sandingpaper, and carefully sanded all the edges on the PEI and making it a little bit smaller (maybe 0,5mm on each side)
Now the PEI bed was flat at 115°C- Next thing i noticed was that the innermost left corner of the aluminium bed was lower than the rest of the bed.(maybe it is bent a little bit, i dont know)
Hmm.. how to fix that.
I printed a large flat square that i found on thingiverse (http://www.thingiverse.com/thing:13053) and measured the thickness in all the corners.
I found that my left inner corner was 0.2mm lower that the rest.
I took some household “standard” aluminium foil and filled my “low corner” between the bed and PEI sheet. Remeber to NOT put everything in a big stack. You have to taper the foil nicely.FYI. i measured the temperature on the PEI bed, after putting aluminiumfoil and found that at the “foiled” area it was 10-15°C colder than the “unfoiled” area.
The stickiness of the printbed had increased, but after a few testprints i still wasn’t satisfied.
So i tried the “glue stick trick” (Office paperglue). And that was like applying magic 🙂
The parts are really stuck to the printbed now.I bought my glue stick at a local Biltema shop, but i imagine that it works with any PVA based glue stick
The difference i see after the glue stick trick, is that the print bed temperature needs to be under 50°C before i can try to remove the part.
/ Looserx
Very resourceful and ingenious!
Happily I’ve had no such problems.
I’ve only run ABS and have found that a brim width of 8 (or larger, I haven’t tried smaller yet) gives a pretty good result. The base is not perfectly flat, there is slight lifting right at the corners of those articles I’ve printed but it’s acceptable. And the article comes off the PEI very easily once it’s cooled down.
Are you using the glue stick with PLA, or ABS or both?
Mike.
I was getting along fine with the prints that the Robox produced. Initially the intermittent quality was I felt due more to the original CAD file than the printer. But after my latest successful print, the filament will not stick to the PEI bed. As I’ve only had the printer for a few weeks I am using the PLA that it came with and see no reason to change. However the problem of the filament not sticking is an annoyance. I don’t understand why it prints perfectly and then on the next it has lift problems. It’s so bad that none of the filament sticks now, it just flows in mid-air and I have to cancel the print right at the start. I have used a PrintrBot which is a far more basic printer and doesn’t come with a heated bed (not the one I used), but you had to cover the bed with printer’s tape and the filament stuck fine to this. I am wondering if it would be okay to try printing on the Robox with the same method. I haven’t tried this yet as I wonder if the heated bed would almost weld the printer’s tape. Can anyone advise? I did clean the Robox PEI bed with the supplied wipes after every attempt but it hasn’t made any difference.
It sounds like your nozzle height needs re-calibrating if its printing in the air? The PEI bed has been great for my prints once the first layer’s set-up to the right height. If the auto height calibration isn’t giving you a nice smooth first layer, you can adjust the height manually in the settings?
When I say it’s printing in mid-air, what happens is that it starts off extruding the filament onto the PEI as a kind of anchor. Then as it moves to complete the path, it pulls the filament off and so it’s no longer adhering. Thus it is then printing in mid-air. Yes I will recalibrate, but the point is that it had produced a perfect print and I was not expecting any problems. All I did was clean the PEI with the alcohol wipes as directed and nothing else. So while I accept that although I will now have to adjust the nozzle height, how is it that it’s completely perfect one day and yet totally zero the next without any adjustment?
Something similar happened to me on Saturday - I spent around 30 starts before got filament to stick to the bed… again!
At the end, after filling tabs to ensure PEI is not bulged in the middle, calibrating nozzle, re-calibrating it, and manually adjusting it to oblivion, I had to leave PEI to cool down completely, clean it again (as cold!) with 99% IPA and restart print. Only at then it worked.
Oh, not only because I clean it cold, but because previously I re-adjusted nozzle height. Now, I have first layer slightly squashed on most of the board to get it to stick and get proper height on the edges - but at least it works and bottom side of the prints look quite nice.
Just as a possibility do you think the offset between nozzles is causing certain prints to stick? You can choose which nozzle is used on the first layer and maybe one is calibrated higher than the other so the filament is not squashed as firmly to the bed. I can’t remember if the different quality settings changes the nozzle used for the first layer.
I think if you can get the PEI bed as flat as possible and then calibrate you wont have any problems with adhesion as any prints I have done to this point have been glued solid to the bed (Not to say this wont change in time!) and the first layer always looks perfect so this could be the defining factor.
@paulsroom: if it’s pulling the filament away, in such a way that the new filament is under tension, then it’s possible not enough filament is coming out for some reason. I would recommend you do a Purge Material and post up some photos. It might sound like Purge Material is meant to be a maintenance operation (it is!) but it’s also a fairly useful diagnostic procedure. Read more: http://roboxing.com/purge_material
I’ve got exactly that thing - filament would bind to part of the bed and then it would just continue extruding it in the air over the bed pulling it under the tension - not really too much of tension - but it seemed that as it cooled rapidly (as it wasn’t touching the bed) it shrunk… Lowering nozzles, cleaning bed, etc., helped it…
@gid The calibrate nozzle, purge and eject material operations are greyed out and I can’t access any of these routines. Also the make arrow is not appearing as it did before. This seems to have happened overnight! In the attached pictures the spinning top was a perfect print that I did on 6th November. I had calibrated everything to the AutoMaker instructions in the manual. I also cleaned the bed with the supplied wipes. The picture showing the status and a column object to print is what it looks like today. Once again I’ve simply switched everything on without doing anything further (other than load a file). However after the spinning top print was done, AutoMaker updated when I next opened it. So at the moment I can’t print any trials or make any adjustments - do I need to reload AutoMaker?
for me I have also noticed that the filament, particularly ABS sticks better as the ambient temperature gets closer to the required temp, so it is something to watch out for as well. I have not tried PLA as I do not have any, but Taulman Bridge, does not have any sticking issue, regardless of ambient temperature.
@paulsroom, i do not see the eject button on the image of the reel, this typically indicates that while your reel is plugged in, the filament has not been fed through the extruder, check it and re-feed, if needed you can trim the tip of the filament at an angle or trim off a few inches of the filament and re-feed to make sure it is gripped properly.
Moh
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