Dual Z bed leveling question.
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The message means what it says. In order to guard against damaging your Z axis if the probing gives incorrect results, there is a maximum amount of individual leadscrew correction that the firmware will apply. This limit defaults to 1mm if you don't specify it.
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That makes sense. I manually adjusted the bed and ran the G32 again and was able to get it to work repeatedly however the adjustment apparantly did not survive a power cycle as after doing power cycle I started receiving the error again. It doesn't look like the lead screws are moving when I power down so I'm not sure what is happening to cause the problem.
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@tletourneau said in Dual Z bed leveling question.:
That makes sense. I manually adjusted the bed and ran the G32 again and was able to get it to work repeatedly however the adjustment apparantly did not survive a power cycle as after doing power cycle I started receiving the error again. It doesn't look like the lead screws are moving when I power down so I'm not sure what is happening to cause the problem.
Stepper motors are more or less guaranteed to move when you power down, typically by 1 to 2 full steps. But that probably isn't enough to account for the imbalance you are seeing.
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It seems this thing can drop the bed a fair amount when powered down. I think it may just be weight related, it's a 500*500mm build surface with a 6.35mm thick piece of glass on it. I'm still investigating a bit but that may be it.
The next thing I'm trying to figure out is how to use both automatic bed leveling and mesh compensation. When I define the area and points for the mesh it just does the ABL points.
On a completely unrelated note I was able to get the mini IR sensor to work by putting parchment paper between the glass/silicone and the heat bed. I thought I'd add that for anyone looking far an interface to use that can't bake high temp paint onto the plate.
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@tletourneau said in Dual Z bed leveling question.:
The next thing I'm trying to figure out is how to use both automatic bed leveling and mesh compensation. When I define the area and points for the mesh it just does the ABL points.
Use G32 for bed levelling using the leadscrews. Use G29 for mesh bed compensation. In Duet Web Control v1.x, to run mesh bed probing, press the arrow next to the Bed Compensation button, and select Mesh Probing from the drop-down list.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 said in Dual Z bed leveling question.:
@tletourneau said in Dual Z bed leveling question.:
The next thing I'm trying to figure out is how to use both automatic bed leveling and mesh compensation. When I define the area and points for the mesh it just does the ABL points.
Use G32 for bed levelling using the leadscrews. Use G29 for mesh bed compensation. In Duet Web Control v1.x, to run mesh bed probing, press the arrow next to the Bed Compensation button, and select Mesh Probing from the drop-down list.
Thanks, I'll give that a try. I've noticed that the bed will drop even with the power on prior to homing. I've got 1.5 amps going to Z now and I'm not sure how much these motors are rated for as they are TronXY branded PN:SL43STH60-1684A. Does the system assign each driver the configured power in a parallel axis configuration or does that need to be specified per driver in the config.g somewhere?
Also, could someone recommend a decent 60mm NEMA 17 motor for a 600mm Z axis?
Thanks for all the help!
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@tletourneau said in Dual Z bed leveling question.:
Also, could someone recommend a decent 60mm NEMA 17 motor for a 600mm Z axis?
There's this beast: https://www.omc-stepperonline.com/nema-17-stepper-motor/nema-17-bipolar-18deg-65ncm-92ozin-21a-336v-42x42x60mm-4-wires-17hs24-2104s.html
I use this one to lift my 10Lb bed with 2:1 gearing: https://www.omc-stepperonline.com/nema-17-stepper-motor/nema-17-bipolar-59ncm-84ozin-2a-42x48mm-4wires-w-1m-cable-and-connector-17hs19-2004s1.html
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@phaedrux said in Dual Z bed leveling question.:
@tletourneau said in Dual Z bed leveling question.:
Also, could someone recommend a decent 60mm NEMA 17 motor for a 600mm Z axis?
There's this beast: https://www.omc-stepperonline.com/nema-17-stepper-motor/nema-17-bipolar-18deg-65ncm-92ozin-21a-336v-42x42x60mm-4-wires-17hs24-2104s.html
I use this one to lift my 10Lb bed with 2:1 gearing: https://www.omc-stepperonline.com/nema-17-stepper-motor/nema-17-bipolar-59ncm-84ozin-2a-42x48mm-4wires-w-1m-cable-and-connector-17hs19-2004s1.html
Thanks! I guess I could go with a shorter motor and build a bracket. Gear reduction, I hadn't thought of that. Do you think it could help with the Z drop I'm experiencing?
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@tletourneau I used lead screws with a smaller pitch to reduce the bed drop potential. Tr88 is rather steep. I chose Tr81 which has a much flatter thread profile. The torque required is also reduced.
I'm not sure if the gearing would help reduce bed drop. I'd have to think about that. if 2:1 reduces the torque to drive it one way, does it increase the torque to drive it the opposite way?
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@phaedrux I hadn't considered the pitch of the lead screws. The change to compensate for the change in pitch is to change steps per rotation, correct? Can you point me in the direction of a supplier? If I'm changing the lead screws I may look at ball screws as well rather than use the anti-backlash buts I use now. I'm also replacing the LM12's it came with for ones that are about twice as long hope that will help stabilize the front to rear tilting. I have some videos showing some of the challenges.
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@tletourneau https://www.aliexpress.com/store/product/T8-100-150-200-250-300-350-400M-T8-Pitch-2mm-lead-12mm-Lead-Screw-8mm/2882163_32826081042.html If you scroll down the page there are link to other lengths. Buy twice as may as you need incase they come bent
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@phaedrux said in Dual Z bed leveling question.:
@tletourneau https://www.aliexpress.com/store/product/T8-100-150-200-250-300-350-400M-T8-Pitch-2mm-lead-12mm-Lead-Screw-8mm/2882163_32826081042.html If you scroll down the page there are link to other lengths. Buy twice as may as you need incase they come bent
Thanks, I've been looking at them, bangood, and Amazon and haven't had any luck finding single start 1 or 2mm t8's 675mm or longer (I can have it cut if needed).
What about a 5/16" 18tpi threaded rod? I can get those locally in 304 stainless steel with a flange nut. 18tpi is about a 1.411mm thread pitch.
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@tletourneau said in Dual Z bed leveling question.:
Thanks, I've been looking at them, bangood, and Amazon and haven't had any luck finding single start 1 or 2mm t8's 675mm or longer (I can have it cut if needed).
I've ordered my lead screw from this shop. The following link leads you to 750mm long ones. They do have shorter and also longer ones (1500mm was the longest I spotted so far):
Manuel
Duet 3 6HC (v0.6) with RPi 4B on a custom Cartesian
with probably always latest firmware/DWC (incl. betas or self-compiled)
My Tool Collection -
@wilriker said in Dual Z bed leveling question.:
@tletourneau said in Dual Z bed leveling question.:
Thanks, I've been looking at them, bangood, and Amazon and haven't had any luck finding single start 1 or 2mm t8's 675mm or longer (I can have it cut if needed).
I've ordered my lead screw from this shop. The following link leads you to 750mm long ones. They do have shorter and also longer ones (1500mm was the longest I spotted so far):
Thanks! I don't know why I couldn't find it, maybe getting search burn out. Next question, 1mm or 2mm single start T8?
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@tletourneau I do use 2mm single start. But since you have a huge bed and obviously issues with keeping it at where it is, 1mm might be the best solution. But then again they are so cheap you could just order both types. Advantage of 2mm would be double the speed compared to 1mm which might be helpful for long movements after a tall print.
Manuel
Duet 3 6HC (v0.6) with RPi 4B on a custom Cartesian
with probably always latest firmware/DWC (incl. betas or self-compiled)
My Tool Collection -
@wilriker said in Dual Z bed leveling question.:
@tletourneau I do use 2mm single start. But since you have a huge bed and obviously issues with keeping it at where it is, 1mm might be the best solution. But then again they are so cheap you could just order both types. Advantage of 2mm would be double the speed compared to 1mm which might be helpful for long movements after a tall print.
That's a thought, get each to try. Would anti-backlash buts be recommended as well?
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@tletourneau The weight of the bed removes backlash, those nuts aren't need. Misspelled words sure do change things.
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@stephen6309 ha, oops!
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@tletourneau That's definitely some wobble there. Two lead screws like that will always have instability. You may want to look into a 3 lead screw arrangement. Check the printer in my signature to see what I did to solve the issue on the Dbot. I could probably stand on my bed and it's not going anywhere.
I think 2mm lead would be a good compromise. The 1mm lead is rather slow for movement and you end up having quite a bit of rotational momentum so slow acceleration and deceleration is needed. For normal printing it's irrelevant, but if you're going to be jogging the bed a lot then 2mm for sure.
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@phaedrux Yeah, I've thought about adding a third Z. I think I'll order four 700mm T8*2's in case one is bent to give me the option of adding a third screw in the future. I like the idea of parallel motors so I'd be looking at adding a Duex 5 to get more drivers to drive a third axis.
Are there any concerns cutting the lead screws to the correct length?
