Cuts are not as designed

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27 Sep 2020 00:17 #183904 by Aldenflorio

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27 Sep 2020 09:21 #183950 by tommylight
Replied by tommylight on topic Cuts are not as designed

Tom, Just curious, when does direct drive with steppers become unworkable? As in when do you need a reduction stage?

That will also depend on the drives used to drive the motors, some drives do very smooth microstepping, while some do not and tend to "drift" when the motor gets to the edges of the magnetic field.
As a general rule, getting 15 to 25mm per motor revolution with no microstepping is the best solution for plasma cutting, then adding X4 or X8 microstepping would smooth the vibrations further so the cuts will end up very smooth.
Also as a general rule, rack and pinion = never without reduction as the pinions are quite big and end up having 125mm of travel per motor revolution for a Mod2 rack and pinion, so way to much, although i do have a machine using that setup with Nema 34 steppers and Lam technologies drives set at X128 microstepping that works perfectly fine, but it did not work with any type of other drives.
If buying rack and pinion for plasma, choose helical gears as they produce much less vibrations during movement and the difference in price is small, and they are much quieter when moving.
Personally i would not use anything over 45mm of travel per revolution with very good drives, and on the subject of good drives, the cheapest drives from ebay marketed as "TB6600" do not use that chip, they use some other smaller chip with TBnnX109 (do not recall the nn and X) that do very smooth microstepping so i got several of them and they have proven much better than 6600 or 6560, do not produce that whiney noise from the motors and even disconnecting motor wires while powered did not kill them, so for 12$ a piece very nice drives for up to 3A. BTW i would not power them with more than 27V although they are rated at 40V. Do not expect record braking speeds from them, for that use Lam Technologies drives ! :)
The following user(s) said Thank You: thefabricator03, Aciera, Aldenflorio

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