Looking for Suggestions on Tilting bed after Leveling

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PTaladay
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Looking for Suggestions on Tilting bed after Leveling

Post by PTaladay »

I can get my HevOrt to print even with this problem, it just doesn't have the quality I want. A lot of my parts are from a previous CoreXY design I was going to do, hence the 2020 extrusions.

I have both Z axis stepper motors hooked up to the Duet 2 wifi shared z axis so they run as one. I have checked the leveling when the bed is all the way down and it is leveling. I had added the anti back lash Tnuts to try and solve the problem with the bed falling down after the motors are disabled. It helps a little, but what happens after bed leveling is the right side starts to sag. It ends up making the leveling useless.

I'm looking for any suggestions. The bed itself is 5mm thick aluminum cut to 500mmx500mm. I'm using a piece of glass mirror as a flat surface since the aluminum was from a second hand store and isn't brand new.

I don't have money right now to pour into the newer z axis design that has come up, so I'm trying to figure out a way to fix this issue.

Thanks.
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Re: Looking for Suggestions on Tilting bed after Leveling

Post by Jhonno »

Do they sag when under power? Have you turned up the idle current?

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by PTaladay »

I haven't noticed it sag under power, just when the motors become disabled after the auto bed leveling. I'll double check that again tonight.

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by PTaladay »

So, I've noticed only the right side dips down. Even if I manually rotate the stepper on the right side up or down the left side stays in place. Keep in mind this particular test was with no power at all. I think I have a spare stepper motor I can try replacing that one with and see if that makes any difference at all.

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by ProtoMon »

I found a thread on another board that may help.
https://www.thingiverse.com/groups/duet ... opic:36887

Might be an alignment issue, seems you could try loosening and then tightening things back to relieve the stress on the bed.

Or maybe keep motors on after the level?

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by Jhonno »

PTaladay wrote:
Fri Mar 19, 2021 4:39 pm
I haven't noticed it sag under power, just when the motors become disabled after the auto bed leveling. I'll double check that again tonight.
What about idle power? If my memory serves me correctly, after leveling the motors should hold it at an idle current, which is a user specified % of the full current.

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by PTaladay »

Jhonno wrote:
Mon Mar 22, 2021 5:00 am
PTaladay wrote:
Fri Mar 19, 2021 4:39 pm
I haven't noticed it sag under power, just when the motors become disabled after the auto bed leveling. I'll double check that again tonight.
What about idle power? If my memory serves me correctly, after leveling the motors should hold it at an idle current, which is a user specified % of the full current.
I checked my idle power and it was only at 800mA. I increased it to 1150mA. That definitely gives a better hold after the G29 leveling. Thanks for that. Now I just need to see about how to keep it from dropping on the one side when powered off/initial power on, or find some way of releveling it after it has done that. I did also go and adjust that whole side to make sure it wasn't some sort to torsion force from it not being level or something along those lines. That seems to be fine. The other side is a like a rock even with no power to the stepper motor. I do notice the stepper motor on the side that is dropping is much easier to turn unpowered than the other. They both came from the same batch. Maybe I should replace it? I also did see another thread about using stepper motors with built in brakes. Pretty pricey though, but I may go that route. Thanks for the help and suggestions everyone.

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by firegun »

I guess that cheapest thing you could do is to swap those motors and see if the issue presents on the other side ^^

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by PTaladay »

Ok, so finally getting back around to playing with this I was able to fix the problem. I stopped using the Z stepper motor driver for both and wired one and then added jumpers to the second to close the the loop. I set the other one up on the extra E1 stepper channel as I only have the Duet 2 and not exspansion board. I added the settings needed in both the config.g and the bed.g to make use of the G32 command. I had to allow the max deviation to be above 5mm in order for it to compensate as that is how much it gets thrown off. Still need to do test prints now, but at least I can see if is level.

Thanks all for the help. The combination of both the idle current for the stepper motor and enabling the independent z leveling fixed the issue. That was driving me crazy so thank you.

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Re: Looking for Suggestions on Tilting bed after Leveling

Post by RHolt51 »

Have you given any thought to geared steppers. they tend to hold their position even when powered off.
Russ from Ocala, Florida

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