Problems levelling TAZ 5 bed

My borosilicate glass cracked. While waiting for the heat bed assembly to be available in the UK warehouse I got some 30x30 IKEA mirrors to try to print without a heated bed.

The problem comes when trying to level the bed. It seems impossible. I first thought I might need to re-level the X axis. However, it seems some sort of cross-axis problem. I have unscrewed the front-right levelling screw as far as it will go without becoming completely unscrewed from the aluminum bed, and the printhead is still too high. However, the rear-right screw is completely tightened and it’s at the proper level. The rear-left screw is not as high as the front-right, but is also quite high, while the front-left is not as tight as the rear-right, but almost. I’ve attached a few pictures which will hopefully show the problem.

In summary, front-left and rear-right seem to be too low, while front-right and rear-left are too high.

Any ideas?

Thank you.

That mirror isn’t think enough for the corner mounts to engage it. thats allowing it to push the mounts in and out. it also looks like dimensionally it’s slightly too large so it is forcing one of the corners out of perpndicular, which is causing your leveling issues.

Lower the Z-endstop if possible. If still too low, get longer M3 socket cap and print spacers to help the spring.

If that doesn’t work, let me know how far you are. I have the corner mounts in SketchUp, I can make a taller mount.

I’d be careful with the mirror… borosilicate is heat resistant. Usually made in Germany…

@kcchen_00 I´d previously used IKEA mirrors as a build base on my old Prusa i3, that usually worked. Thank you for the offer for the replacement mounts, but see below.

@piercet thanks for the tip. Since I mistakenly ordered a new glass plate (without the heated bed) thinking that, like the RepRaps, the heater could be separated from the plate, I’ve put it in without the heater, to try PLA on a cold bed with hairspray. The glass being the correct thickness made all the difference! Dimensionally the mirror is actually a couple of mm smaller than the borosilicate bed, so that might have factor in.

One thing that worries me. It’s now been 2 weeks and the heated bed assembly isn’t available in LulzBot’s UK warehouse. They have offered to ship me one from the US (US$60+ shipping) but that has me concerned about parts availability if something else breaks down. The sales people have NO idea when it will be available. It worries me that, if something else breaks down (or if I crack the bed again after I get it), it might be complicated to get replacement parts.

The bed heater is one of the parts that is pretty specific to the Taz. There are very few other 12" bed printers out there, and most of those others use a different type of heater bed. It’s actually an industrial panel heater of some sort, possibly designed to heat oil sumps. If you can find a 24 volt 12" silicone adhesive heater from a different source, it should be compatable as they are all somewhat standard. You might also check and see if will ship one to Europe for less.

The only other part that should be difficult to source for replacement would be the Rambo controll board itself. If you were worried about failures, i’d have a bed heater, a bed plate, a rambo board, a set of heater core and thermistors, a set of the tiny grain of rice rambo board fuses, 2 sets of printed gears and 2 idler arms on hand. Your chances of needing any of those except the gears in the long term is minimal though. Gears are a wear part and with heavy printing can wear out in 2 years.

If you still have your old cracked bed, you can remove the existing heating element and install it on new glass. Stick the old broken glass bed in a sealable plastic bag and put it in the freezer for an hour or 3. Then carefully (wearing gloves to avoid glass splinters) peel back the adhesive heater and set it aside. If it still won’t go, you can use a citrus based anti adhesive, such as goo gone or orange oil to remove the bed. You will have to then clean the residue off and reapply the bed. if you were able to just use the freezer method, it should stick right on. if you had to use adhesive remover, you may need to use a high temperature contact cement to reinstall the heater core.

Thanks again @piercet. I tried the freezer method and was able to unstick the corners, but just a little bit in the putty knife I was using to unstick started to cut into the silicone, which I think is not good. I’ll try some antiadhesive but I’m concerned that now some of the silicon on the glass side has been sliced off (with some remnants left stuck on the glass).

The heater pad itself is actually available from the UK warehouse, it’s just the full assembly that isn’t. I was waiting to get the full assembly to save myself the work of gluing the pad and the PEI sheet on without bubbles, with perfect alignment, etc., but the way things are going I’ll probably just order the heater and do it myself (I have the glass and the PEI). Any suggestions so I get good adhesion without bubbles, and also so that I can remove the heater later if I crack the glass again?

The best heated bed replacement suggestion I can offer is to not replace the heated bed with glass, but instead find a 12" x 12" x 3/16" thick aluminum plate and use that. It spreads heat much better than the glass ones do. You’ll need to print a different set of bed mounts to attach it, and finding a truely flat plate is apperently a bit of a challenge (i got mine on the first try, other people report problems) . The corner clips are available here if you want them: you’ll also need to source 8 M3 heat set inserts for them. You stick the heater core on the bottom, stick the PEI sheet on the top, then print as normal. No firmware changes.

If you have to replace the glass anyways, that results in a far better heated bed.

To get good adhesion without bubbles. use a glue roller and work in from the corners to the center, slowly peeling the paper back as you go. If you adhere it to a metal plate, removal becomes very easy later, you just pull it off heh.

Thanks again piercet. I am now waiting for the new heated pad. I’ll have a look at how easy it would be to source the aluminum plate here in Germany (without speaking German, it might be a bit complicated).

What adhesive would you recommend to glue the pad to glass? And to aluminum? Preferably something that can somehow be unglued if of disaster strikes again.

I’ve also ordered a Zebra Pad. I’ve read really good things about it, and I hope it will prevent something like this from happening again.

Also, any particular grade of aluminum that you think is best?

The Taz heater pad is self adhesive, as are most of the other aftermarket ones. You don’t need to add any other glue to it. Contact cement would work if you had to re-adhere it or it doesn’t come with adhesive for some reason. The spray contact adhesive variant would probably stick with a bit more chance of removal if necessary.

The aluminum plate you want is going to be a 3/16" thick (5mm) 12" x 12" (300mm x 300mm) aluminum plate. prefferably a cast aluminum tool plate, but those are going to be hard to locate. Finish doesn’t really matter, as both sides will be covered with adhesive things, but flatness does. You want the stiffest alloy you can find. 5052 will work and should be easier to find, 6061 or 7075 would be prefferable but difficult to source and not that much of an improvement.