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Rack & pinion

Posted by Emmanuel 
Rack & pinion
October 01, 2017 04:59AM


This idea was put aside for production reasons back in the days (easier to buy belt in 50m roll), but I can implement it again now smiling smiley
(so you can use belt or printed rack, both are compatible with the x-carriage once the little protrusions for the bearings are removed)


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Re: Rack & pinion
November 16, 2017 10:34AM
What’re you doing about backlash?
Re: Rack & pinion
November 24, 2017 01:08PM
The back of the rack have a wave shape that act like a spring to compensate that smiling smiley

[reprap.org]


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Re: Rack & pinion
November 25, 2017 03:57PM
Some progress on the ends, to ease the correct setup (no lateral play but still one degree of freedom for the spring effect)



The second is better than the first.
I have yet to try the third in real conditions, but it seems better when playing with it mounted on a profile.

Edited 1 time(s). Last edit at 11/25/2017 03:58PM by Emmanuel.

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Re: Rack & pinion
December 12, 2017 02:33PM
I wonder what printing speed is achievable using this rack & pinion system? Have you tried it?
Re: Rack & pinion
December 14, 2017 06:00AM
Same as with belts.

The speed limit is reached either from :
not enough motor's torque
acceleration (too high)
step rate generation (at 1/32 microstepping, a 8 bit cpu will quickly have problems following the "consumption" of step pulses)

That said, I print at 30 or 60mm/s (small or big objects), usually 40mm/s

Beside XY movement speed, the printing speed mean nothing, the important factor is the volumetric speed (how many mm3/s you can lay down).
e.g.:
7.5mm3/s
= 0.5mm width 0.25mm layers at 60mm/s
= 0.5mm width 0.30mm layers at 50mm/s
The layers being thicker you need to slow down.
(I just want to say that every time someone claim to print at xxxmm/s, with very thin layers yes it is easy)

Edited 1 time(s). Last edit at 12/14/2017 06:06AM by Emmanuel.

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