Bed gets stuck near Y=0, Y limit switch not reached

Hi everyone!

I've had my Robo3D a few months now and I've done about 20-25 successful prints with a few minor mishaps. (I've gone through the nuts problem, how to calibrate the Z-limit switch screw, how to adjust Z-height when the print starts, how to make the print stick to bed etc..)

After a print, sometimes it happens that the bed gets blocked when going to Y=0. If I press Y home the bed doesn't even get close to the limit switch (about 1-4cm short), instead the whole bed is blocked and vibrates until the boro glass pops out of its clips. That is unless I manage to hit the emergency stop in time.

Similar symptoms as in this case: http://forums.robo3dprinter.com/ind...t-and-robo-vibrating-on-y-axis.833/#post-3418

However, my limit switch is undamaged and I can activate it manually with my finger.

When I move the bed manually with the motors off and with a light hand, I'm unable to make the bed reach the Y limit switch at Y=0.

I can fix it temporarily (when motors are off) by carefully but firmly pulling the bed toward Y=0 until the limit switch clicks. Then I can move the bed without effort and I can start a print.

I've tried to see what it is that blocks the bed but I really don't know what to look for.

Any ideas what this could be?


Regards, Daniel

 

Sorry for the late follow up and my ignorance here but what do I need to disassemble in order get to the set screw on the Y axis pulley?

Regards, Daniel

 

Thanks Mark, that's great! I'll do it at the first convenient time!

 

Hi again!
Thanks again Mark for the removal guide.

Now when the bed is off I see and feel that the belt pulley is in place and it sits really firmly on the axis. It's nicely aligned with the two bearings just as described in the the Middle Plate Assembley Video so I don't think this is the problem.

However, when I removed the bed, looking at the sliders I noticed that the "bearing holder" had slid so that the sliders stopped about 5-8 cm before they could reach their natural endpoints. I had to pull the sliders with the same amount of force and with the same mechanical feeling as I described in my first post and force the "bearing holder" to get the sliders to the endpoints.

I really don't know why the "bearing holders" slips in this way but but IMHO this seems most likely to be the problem.

I have the ABS with PCB heatbead and boro glass. The bed is mounted to the sliders with four flat head screws inserted from the top to make place for the heatbead+boro clips. There are of cource spacers between bed and sliders and the lock nuts sit on the inside of the sliders.

I tested putting the screws back on the sliders without the bed in place and it seems that the nuts hit the "bearing holder" about 1 cm before the sliders hit the endpoints. It doesn't feel likely that this is the root cause but it might be worth trying to replace those nuts with thinner nuts so that they won't hit the "bearing holder".

Apart from that I can only say that I'm not really comfortable with how much the sliders move up and down on the z-axis. I'm probably wrong but my gut feeling is that the printer loses a lot of precision there when it comes to bed leveling. For instance, when the bed was mounted and set at Y=0 I could easily move the other end up and down at least 5mm. But then again, I might be missing some crucial design idea here.

Any ideas on the root cause to why the "bearing holder" slips are most welcome!

Regards, Daniel

 

Ok, I think I've found a possible root cause. My birch wood bed is warped at room temperature. Is it supposed to be like this?

Regards, Daniel

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Yeah, the birchwood beds are bad, mine was badly warped also, I didn't have any binding problems with the sliders though. I made my own glass bed out of 1/4 glass. My sliders also move up and down on the about a mm or two, and this does effect leveling the bed, one of my sliders is also 2 mm higher then the other. I'm slowly working on a replacement for them.

 

Only thing I see you could do is replace the bed, that is horribly warped. Contact the Robo guys via the email and ask about purchasing the glass bed it is 100% better then the birch. The slides are the next thing to go I think after the birch bed. I JUST finished replacing mine with heavy duty slides and we will see how that works. If the slides look bent or have too much play in them I think replacing is the only way to go.

 

Thanks guys! Apart from the play, the sliders seems quite fine but I'll look for a bed replacement.

@robo team, what's your deal the glass bed? (I know they might not read this, I'll contact them directly

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Hi All,
I had this same problem with mine (PLA / ABS) and after reading this thread, it gave me an idea what might be wrong.
DA91 mentioned the sliders and that's what I focused on.

I removed the belt clips from each end of the bed and then I pushed the bed all the way back. Then, gently but firmly, I applied a little pressure and the bed slipped back a little. When I thought I had it back enough, I re-attached the belt clips and manually checked the action. Now the clip hits the stop switch before it reaches the end of the slider.

I fired up Repetier Host and did a manual control home of the Y-axis and it worked as it should.
I will do a print and see what the results are, but I expect no problems.

 

sounds pretty much like my problem. I didn't remove the belt clips before I pulled the bed tho. However after a few prints the problem came back again and again. If it come back for you as well I'd recommend you to remove the bed and check if it's warped. In my situation I'm quite convinced that was the root cause to the slider problem.

Regards, Daniel

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I have the same repeating issue with one slider. I disconnect the bed from that side, pull the slider through it's travel, all the way in both directions. this sets the bearing block back to where it belongs. reassemble and carry on. This "fix" lasts 10 or 15 prints.

 

I also had the same problem, but instead of taking the whole thing apart, I was able to push the rack/cage that holds the bearings back with a small metal rod. You have to move the bed back and forth while doing this though, or else the bearings will not move. Hope that this helps with time and effort.once we tried it this way it was like a two minute fix.

 

I had the same issue with my y axis not being able to reach the limit switch. I took the bed off and was able to push the black drawer slide bearings all the way to the end of the slide. I put the bed back on and all is good.

Is this part something that I should be greasing to prevent this issue?

 

Mine just started doing this today... Confused the heck out of me to start with. I finished one print and everything was perfect. Go to start a print a couple of hours later and it can't reach the y limit. Looks like yet another partial tear down tomorrow!

 

When I reported my warped birchwood bed to Robo3D, they sent me the new glassbed with integrated heater. Since then I've only had this problem once and I fixed it by simply pushing the bed by hand towards Y=0 slightly harder than usual. Be careful!

N.B. As of today, I still have the old sliders and not the new Y-axis linear system.

Regards, Daniel

 

Just an update, what I've seen happen is that the "carriage" or bearingsholder (as in the thing between the slider part that is fixed to the printer and the one that holds the bed) gets misplaced in relation to the sliders. Therefore, as a temporary solution it "should" be safe to just push the bed towards Y=0. However if you have a wooden bed and this happens a lot I'd recommend check if the bed is warped.

Regards, Daniel