Prints being knocked off suddenly  

Re: Prints being knocked off suddenly

Hi Craig

As you have done all the standard stuff, possibly the next thing to look at is calibration (again), bed preparation, more heat and printing with a brim.

Calibration - try to get a slightly tighter fit with the card (or whatever you are using). Ensure the card is 0.22 to 0.23mm thick.

Bed prep - clean the glass thoroughly and apply 2 layers of glue, allowing it to dry in between layers.

More heat - increase the temp of the bed by 5 or 10 degrees (I have printed with PLA up to 65 degrees).

Brim - when slicing, include a 3mm brim to increase adhesion.

Something in the above should get you printing again (I hope!).

Peter

Re: Prints being knocked off suddenly

I’m far from an expert (pretty new at this myself) and you undoubtedly thought about this (but you did not mention it): any changes in the environment in which you operate the printer? Has it become colder/warmer with more/less humidity perhaps etc… ?

Re: Prints being knocked off suddenly

Thanks for the suggestions, I'll try them one by one and update. I've tried a few of them but I'll try again with fresh eyes....

As for the temperature/humidity, they only thing I can think is the room humidity has gone down, its been pretty cold here recently so the heating has been drying the air out but the temp is around the same.

Re: Prints being knocked off suddenly

Hi Craig

I think that the only problem that humidity would cause is if you are leaving your filament out, then it may be soaking up moisture which could possibly cause extrusion issues.

Not sure that would affect adhesion.

Peter

P.S. I also have spells where things won't go right for me; I get to the point of almost giving up and then, after hours of trying to find a problem with the printer, I find that it's something really simple that I have done wrong. Something like having a piece of melted plastic stuck on the underside of my feeler gauge.

Re: Prints being knocked off suddenly

Ok, deep breaths! I've just spent another hour trying to get the bed level, so I'm treating this as progress!

What appears to happen is I get three corners the of the bed the right height and then the fourth is wildly out normally way too high or too low and I can't fix it. I'm also getting a lot of binding on the bolts when leveling which is causing some misleading results, If I remove the binder clips when the bed is warm the PCB is far from flat.

I tried the light bending of the pcb (as I think was commented by Mr Prusa) but that didn't seem to make any difference, using less or more blinder clips didn't help as well.

I'm leveling the glass by going to each corner in turn, using feeler gauge 0.2 to try and get something vaguely level, hindsight I should have checked the middle as well. I've checked the corner feet and they are all dead flat on the ground.

Any ideas what I can do to get the bed level on all four corners? I'm thinking the reassembly of the y carriage probably didn't help things.

Thanks for you time, normally a patient person but this is soooooo frustrating. 👿

Re: Prints being knocked off suddenly

Hi Craig

Firstly, do not use a 0.2mm feeler gauge. The default firmware is set for an initial nozzle gap of 0.23mm.

The bed wobbling usually denotes a twisted frame, but you have mentioned that you have already resolved that possibility. So can you do the following:

Remove the heated bed and remove from that one of the 4 corner screws. Use that screw and screw it into the aluminium chassis holes, one at a time. WHen it gets to the end, do one more turn. Before you have unscrewed it filly from each hole, get a pair of pliers and pull (wiggle) the screw out. This will remove any excess paint in the holes.

The screws should now fit the holes snugly.

Now, replace the screw in the heater and loosen the locking nuts under the bed by half a turn.

Replace the heater into the chassis and heat the bed up to about 70 degrees. Now tighten up all 4 lock nuts. Care not to burn yourself!

Turn off the heater, replace the glass and the bed should be ready for levelling, hopefully without the issues you previously experienced.

Peter

Re: Prints being knocked off suddenly

Hi Peter,

I was using a 0.2 feeler just to get rough height, I'll try and find something that has a thickness of 0.23mm for future use, the card that came with the printer is now well used and past its best!

Followed the steps you suggested for clearing the bed holes out, the holes took quite a few attempts to clear them out but now the bed moves up and down easily, much better thank you.

After that minor success I then did the steps to loosen the bed, heat and tighten (no burns!), it took a matter of seconds to get the bed nearly perfectly level, all four corners touching at the same time, something I've never managed to do! No obvious rocks or tilts so I thought I'll do a quick Marvin and that finished without knocking over and was very well stuck at the end.

Thank you for your help, it has been greatly appreciated. I'll probably not have any time to use the printer for the next week but I'll update when I can.

Thanks again.

Craig.

Re: Prints being knocked off suddenly

Hi Craig

That's great news, thanks for letting us know.

With regards to the feeler gauges; it is better to be slightly closer than further away, although the first layer may be rough.

Now you have a level bed, you can always amend the firmware to fully home the extruder (to zero) which is what I have done. I home, raise 0.2mm and use feeler gauges.

Peter

Re: Prints being knocked off suddenly

Hi Peter,

Thanks for your help, I managed to get quite a few prints now with nice smooth bases and no failures from the bed (probably about 8 hours in total) but I've just had to re-level the bed again using the instructions you said previously as the bed started rocking again. 🙁 is this normal?

Craig.

Re: Prints being knocked off suddenly

Hi Craig

Have to say that when I got things level it has been pretty stable since, so I would suggest that it's not normal, unless there is a problem elsewhere.

Make sure that the nuts holding the Y frame to the Z frame are nice and tight (and square). Don't move the printer around too much.

Other than the above, I am out of ideas, sorry...

Peter

Re: Prints being knocked off suddenly

Hi,

I'll give it a week or so and if it goes again I'll contact support to see if they have any ideas.

I'll double check and make sure the nuts are all tight and stable, the printer has a permanent home now so I can rule that out.

Thanks for your help though, it is highly appreciated, I wouldn't have got this far otherwise.

Craig.

Re: Prints being knocked off suddenly

I had this issue as well, until I decide to investigate until finding the solution.

In my case the root cause was that the Y-axis was slightly twisted, but you cannot see it until you remove the soft pads under the corner. These pads are nice to reduce sound, but compensate small level variation and hide twist.

So this is what I did:
- Removed pads from the 4 corner of the Y-axis.
- Put 5 business card under each corner.
Here I was able by checking the friction when moving the business card under the corner that something was wrong, one corner didn't touch the business card at all.
- Loosen every external bolts on each corner, as well as the ones blocking the aluminium frame. For the frame you can very gently shake it with one hand while tightening the bolts with the other hand. Did not touch the internal bolt of the corners to avoid changing the alignment.
- Gently shaked/moved the printer to ensure the weight is equally applied on each corner. Just move the business card under each corner to ensure the friction is the same.
- Tightened every bolt by hand, all at the same force at the same time (do it by cycling doing cross, not turn-around). For the frame you can very gently shake it with one hand while tightening the bolts with the other hand.
- Checked friction under each corner, restart loose/tighten if something went bad.
- Tightened every bolt using spanners, all at the same force at the same time (do it by cycling doing cross, not turn-around)
- Did it step by step by checking at each time the friction remain the same, restart loose/tighten if something went bad. (I had to do it several time when tightening too much on single corner).
- Once everything properly tighten, after checking your corner are properly aligned, you can remove the business cards and reapply the pads.

In my case, this procedure completely fixed my popping heatbed corner

Re: Prints being knocked off suddenly

Thanks for the suggestion, The felt feet barely stick now I've had them off so many times! I like the idea of the cards as I'm pretty sure my y-frame is perfectly flat now by eye but that will show any further twisting. I did see any idea with some sticks to check the distances are all perfectly square and level as well which I might as well try.

I'll try soon as I've had another day of partial prints after being stable for a few days. 🙁

Re: Prints being knocked off suddenly

I would just replace the glass.

You mentioned that the PCB was not flat when heated, but do all 4 corners stay in place when the glass is not clipped to the PCB?

That was the case for me and I just replaced the glass. No problems since.

Re: Prints being knocked off suddenly

Sorry for the delay in replying, had some success for a few days, cleaned the glass and had a unlevel corner again and after trying to fix it for a few hours I throw in the towel for a few days.

Managed to get a few hours spare monday (and feeling calm!) took the printer apart and removed the Y assembly completely from the Z frame and using paper sheets (couldn't find any business cards).

I found two corners where not taking the same amount of pressure. All four were touching down just two where lighter on the pressure, strangely enough the two corners opposite I've always had trouble with. Looks like the y frame was out by a tiny amount after all.

Followed the instructions from christophe.p around 5-10 times until I was happy with the corners, then added the Z frame back in, rechecking each time, then measuring carefully with calipers the attachment was straight and level.

Rechecking after every step and it looks so far good the initial bed level was very easy, took seconds to get very close, slowly refining the height.

Fingers crossed it was just the Y being out by a tiny amount that you couldn't see but could feel.

Thank you all for the suggestions and assistance, I think I've got there in the end. I'll give it a while and I might try this pei stuff...

Re: Prints being knocked off suddenly

I'm glad it helped you !

Another "lesson learned" I had with this issue, is that you must tigthen the bolt holding the heathbed only once this one is hot, so that everything is in place when dilation from heat occurs.

Re: Prints being knocked off suddenly

Mmmh, changing the mail in the shop website created a new forum account, strange ...