Bed dropping when powered off
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I have quite a heavy 8mm 300x300 bed on a new corexy I've built.
When powered off the bed has enough weight to turn the dual z motors and goes all the way down.
I've heard if you connect the dual z's in series, the bed won't drop.
But this should already be the case on a duetwifi, as the dual z connectors are already in series.Is this correct?
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You should change the lead screws to ones with a much shallower angle. The typical TR8*8 lead screw with an 8mm 4 start lead is much too steep for heavy beds as you've found. Using a lead of 1 or 2mm with single start threads reduces the tendency to rotate since it's almost flat.
Something like these: https://spool3d.ca/lead-screw-8mm-1mm-pitch-1mm-lead/
Using anti backlash nuts can help as well since the springs they use increase the friction on the thread.
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Thanks, no doubt I'll have to follow your advice.
I was hoping for a cheaper option (e.g. wiring steppers in series) as a pair of 1000mm lead screws comes to about $50, which I not need to buy twice!
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A leadscrew with a 2mm pitch will help you in more ways than one, if you use a 2mm pitch you can utilise a full step number at multiple layer heights. And the added bonus is that the bed won't drop, the price of leadscrews means its a very cheap (but extremely worthwhile) upgrade
