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Bed leveling: is my unit faulty?

Posted: Wed Oct 10, 2018 1:35 am
by Draazith

I'm new to 3D printing. I received my A10 a week ago and I haven't managed to print anything useful as the first layer won't stick to the bed.

I have tried different settings (see below) but I think the problem it that the bed is "wavy" on the Y axis: when I move the bed from front to back, the distance between the bed and the nozzle varies. It's paper thin at each corner and at about 1/3 and 2/3 of the way, but it between it increases by 1-2 mm. Facing the printer, when the bed goes high on the left it goes down on the right and vice versa. The bed itself is flat though, I have checked with a spirit level.

I have also noticed that out of the four bed wheels, one on each side is slightly loose (if I hold the bed I can spin them with little resistance).

I suspect the problem to be either uneven wheels or twisted bed axis, but then again, I'm new to this so I don't really know.

Any idea how I could fix that?

Settings I've tried so far (using Cura):

Layer height: 0.1, 0.15, 0.2
Initial layer height: 0.3, 0.14, 0.18
Build plate adhesion: none, skirt, brim, raft
Enable retraction: off and on
Everything else is default settings (print temp 200°C, bed temp 60°C, print speed 60 mm/s, initial layer speed 30 mm/s).

Let me know if there's any relevant settings or details I should share.


Re: Bed leveling: is my unit faulty?

Posted: Wed Oct 10, 2018 1:49 am
by BennyBoyW
I had a similar issue with mine.
The wheels under the bed need to be sorted out for you to progress. There should be no "looseness" on the bed at all. The wheels on the left hand side as you look from the front just need to be tight, but the ones on the right hand side are on eccentric nuts/spacers, which means that the hole through them is not central, and therefore can be used to tighten or loosen the beds grip on the central rail.
This takes a bit of getting used to and I still haven't got mine quite right. I will, though. You will need a socket on the nut side and a spanner/wrench to turn the middle part, which is the "eccentric" part. You also have to be a bit careful - my current problem is that the front wheel is too tight and the rear one too loose, which is slightly rotating my bed - not a good thing for levelling. My advice would be to make small adjustments till you get it straight and tight and true.
Beware getting the wheels too tight though as this may stop the Y-axis from travelling predictably. As you can probably gather, this is all a fine balancing act.
Let me know how you get on.

Re: Bed leveling: is my unit faulty?

Posted: Wed Oct 10, 2018 4:38 am
by Draazith
Thanks a lot Ben!

I was wondering why the spacers on the right where a different shape. I unfortunately can't try that now as I lack the tools (and I'm kind of disappointed they are not provided, considering that the unit came with a 18 mm flat wrench I can't find any use for) but I'll try to buy some tomorrow.

I'll give an update once I'm done.


Re: Bed leveling: is my unit faulty?

Posted: Fri Oct 12, 2018 4:20 am
by Draazith
I managed to remove the waving by adjusting the wheels (it took me many hours though), so that problem is solved. I still can't manage to print anything but I suppose it's just about settings and fine tuning now.

Thanks again Ben!

Re: Bed leveling: is my unit faulty?

Posted: Fri Oct 12, 2018 10:10 pm
by aarli
This printer has an extremely soft profile on which the hotplate is sitting. Now add the hotplate, which itself already tends to bend and warp at higher temperatures, and after a while you end up with both of them going more and more out of shape when you over tigthen the diagonals. At least that's what happened to mine in less than 1.5 months.

So to fix it I basically took the hotplate off the printer. Then took the bed (painted aluminim plate on which the heatbed is) to flat surface and realised that it's not level. Thankfully it's an easy fix. Men can even bend it by hands. Or better yet, put it on a flat surfrace and step on it a few times until it becomes straight. After that it's just a matter of re-assembly.

When usually tightening screws you notice that one or some seem to be too loose, un-tighten the screws that are at the ends of an imaginary diagonal that's crossing your diagonal.


Code: Select all

A ----- B
| \   / |
|   X   |  
| /   \ | 
C ----- D
if A or D are too loose, loosen B and C (as vector AD is crossing vecor CB)
if B or C are too loose, then loosed A-D accordingly, etc...
You get the picture :)

At the center of the bed the ideal distance between the bed and tip of the nozzle would be about 0.75 * Nozzle size
Rule of thumb seems to be that with standard 0.4 nozzle the ideal distance (considering that you'd ideally print first layer slowly, at higher temperatures and at slightly lower layer height than the rest of the layers) is when you put a standard (80g/m2 density) sheet of office printer paper between the bed and the nozzle and then lower the nozzle until it starts to slightly scratching the paper (but it shouldn't stop you from sliding it back and forth under the nozzle). Repeat the same procedure with corners and try to find good average, considering the shape and position of the first layer you are about to print..

And now when it comes to sticking to bed, then 2 most (cost) effective solutions:
1) PVA-based conventional paper glue-stick aka Scotch, Pritt, which ever. After printing you can wash it off with a cloth soaked in warm water. Just don't try to scrape it off. It will damage the sufrace.

2) Blue painters masking tape. Printed objects stick to it as well as to glue in #1, yet it's super easy to remove from plate. You don't even have to replace used tape segments after each print...
Just bear in mind that it's highly advisable to let the bed completely cool down before you start removing your 3d printed object(s). Otherwisem when the tape is still warm it doesn't want to let your objects go, as each time you warm the tape the glue re-activates. That's why it's better to let it cool down.

3) Optionally both, such as for extreme cases when you don't want to make the bed too hot and/or you're printing with something that requires extra hot bed (such as PETG and some other printed at 100-110 degrees C bed temperature)

Re: Bed leveling: is my unit faulty?

Posted: Sat Oct 13, 2018 4:08 am
by Draazith
Thanks for the very detailed explanation aarli. I think I actually managed to level the bed now (test print in progress), but that will be very useful if I need to make more adjustments. Which might be sooner than later as I'm now facing another issue: the bed is very off-center. About 1 cm on the X axis and 2 on the Y axis. I have no idea when and how that happened. Not a huge deal for now as I'm not planning to print something large enough, but I'll definitely want to fix it at some point.

I'm also considering the painter masking tape, specially as I saw a video of a guy using small pieces to even the bed before covering it.

Re: Bed leveling: is my unit faulty?

Posted: Sat Oct 13, 2018 10:13 am
by aarli
Meanwhile I experimented on a hunch that masking tape solution can be improved even further. And the winner is combo of masking tape + clear packaging tape on top.
Packaging tape
download.jpeg (10.42 KiB) Viewed 5458 times
And based on my today's experiments I can say that with packaging tape on top there's no difference which masking tape to use. Even cheap white masking tape + packaging tape on top worked just fine ;)

First layer sticks better (and at even lower temperatures than masking tape alone) :!: