change broken trapezoidal screws

djaurora

I have a question, what exactly are the parameters of our trapezoidal screws? The diameter is known to be 8mm, but the thread pitch? Any information on this subject?

Samuel Pinches

• The lead screws are 8mm outer diameter, 2mm pitch, and 4mm lead.

Sorry, I forgot to reply to your earlier thread.

djaurora

thanks a lot for info

djaurora

but, cant see any on amazon ali etc

Samuel Pinches

I'm not sure what length the A5 uses - if you can let me know I can send you some links.

e.g.

http://s.click.aliexpress.com/e/cSuSIPle

Andre

You may bei interested in this:

Its a video about how to change the leadscrews of an stepper motor with integreated leadscrews.

Flexible couplers tend to be not exactly centered, so the leadscrews may wobble around even if the leadscrews themself are perfectly aligned. Rigid couplers are much better. But best of all are stepper motors with integreated leadscrews. I compared it in my tronxy x5, original using flexcoupler. Ever improvemed showed up in the print; rigid couplers reduced wobble by 90%, integreated leadscrews by 99%.

You can get them for about 15€. But these l cheap ones are often with simple packaging and so with a bend leadscrew. As nearly all stepper motor with integreated leadscrews use 4 theads 8 mm lead/rotation anyway, you can use the instructions in the video to change the leadscrew to one with a lead of 4.

You can always use a lower lead, If you change firmware and the nut. A lead of 2mm is optimal, as a stepper motor mostly have 200 full steps per rotation, so with a lead of 2mm you have exactly 0.01mm per full step. On (often used) 0.15 mm layerhight its exactly 15 full steps, while in the original leadscrew its 7 full steps and one half step. As full steps have more torque, a 2mm lead have more precision.

If you integreate a leadscrew, of course  you need a longer one than the original, as it have to reach to the bottom of the motor (and not only to the coupler).

Be aware that stepper motors with integreated leadscrews often have an other pinout than normal stepper motors. So you have to measure the resistance between the wires to find the corespondending ones and swap the pins on the connector (you can loose them with a needle and put them in in the needed order).

If changing a leadscrew seems to complicated, you may also use a lead of 8mm. The loss of precision doesent matter at all if you print 0.2mm layerhight. The precion in x/y increases a lot, as there is nearly no wobble at all. In firmware you would have to halve the steps/cm.