Dual Z bed leveling question.
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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):
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@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.
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@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?
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@tletourneau just be sure to protect the threads and you'll want to bevel the edge after you cut it.
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Well I ordered a pair of 670mm 8mm T8x2 Lead Screw Trapezoidal ACME w/ Small Delrin Anti-Backlash Nut kit from ZYLTech. The parts were significantly less expensive from
aliexpress but once you add the shipping cost it came out fairly even although I'm only ordering two they have it in stock and I ordered it second day air.Here is the link to what I ordered.
http://www.zyltech.com/8mm-t8x2-lead-screw-trapezoidal-acme-w-small-delrin-anti-backlash-nut-kit-custom-length-up-to-1000mm/