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Benefits of Reduction Gearing?

Posted by GrahamCracker 
Benefits of Reduction Gearing?
June 02, 2017 07:29AM
Would reducing the X and Y axis by 2:1 and dropping from 1/16 micro step to 1/8 micro step have any advantage? I would imagine that you would have more achievable accuracy at 1/8th step due to having more torque and you would still be able to drive at "1/16" step. The question I really have is would this be negligible?
Re: Benefits of Reduction Gearing?
June 02, 2017 08:58AM
Using the 2:1 ratio on my "Hlidskjalf" CoreXYU, only because will be using it as a CNC mill eventually.

Most 3d printers will not benefit, as masses are low.
However, gear ratios allow you to use smaller steppers, and since print speeds are relatively low, there is no sacrifice.
Re: Benefits of Reduction Gearing?
June 02, 2017 10:38AM
Why not just use a 400 step per rev motor instead?

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Re: Benefits of Reduction Gearing?
June 09, 2017 02:51PM
Why not just use a 400 step per rev motor instead?
Because 1:2 gearing also increases torque, so the motor should theoretically be able to hold a position more accurately, however this has to be weighed against any backlash in the gearing system, and theoretically also against additional inertia in the now fater spinning motor itself.
Lower microstepping resolution could also make the motor louder.

Though i can't tell (yet) which option is better, i haven't experimented with that yet tongue sticking out smiley
Re: Benefits of Reduction Gearing?
June 09, 2017 11:06PM
You are confusing holding torque (which is the torque that can be provided before the motor misses steps) with torque per unit angular error (which determines how accurately the motors can position the print head).

Reducing microstepping doesn't affect either unless you go to full steps.

Changing to 0.9deg motors of the same length reduces the holding torque a little (you can see how much by looking at the motor data) but almost doubles the torque per unit angular error. So it improves positioning accuracy.
However, if your X and Y steps/mm is around 80 at x16 microstepping, then your motors probably provide more than enough positioning accuracy already, because the typical extrusion width of 0.5mm in much greater than the movement per microstep, even if friction in the system means that it takes 2 or 3 microstep to create any movement from rest.

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