Help newbie with linuxcnc on stepper wizard

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28 Jul 2019 17:27 #140818 by Carrball05carrball05@
I have setup my machine and I got motion but I am trying to figure out the configuration on this. I am coming off of Grbl with my router but I am trying to find out what the pitch and revolution for a rack and pinion setup? I have stepper motor with a 12 tooth pinion with no reduction just 1:1 on a 20 pitch gear rack. Can someone help me out with this?

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28 Jul 2019 19:59 #140834 by Todd Zuercher
You may want to consider adding some reduction between the pinion and motor.

The math will be #steps per rev times 20/12. So if your drive is set for half stepping you will have 666.667 steps/inch.

Also are you sure your rack and pinion are in pitch. I thought they usually went by diametral pitch, which is the number of teeth that fit on a 1" gear, or module, which is the ratio of mm diameter to number of teeth on the pinion. Either way it adds a factor of pi to the calculations.

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28 Jul 2019 21:04 #140837 by Carrball05carrball05@
Well it’s my first machine that build using rack and pinion and the size of table is 4x2 I don’t want to do crazy speeds it will be just strictly plasma. The motors I have are 425oz nema 23. Maybe in the future I will add a reduction system or if I build another one I kind of just wanted to see thing work and get it functional. So then how do I plug in these numbers on the wizard?
Driver microstepping : 2.0
Pulley teeth 1:1 ??
Leadscrew pitch 666.667 rev/in ??
Maximum velocity: what’s your recommendation
Maximum acceleration : what’s you recommendation

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28 Jul 2019 21:31 #140843 by tommylight
What drives are you using, what is the module of the pinion/rack?
If you want to use direct pinion drive you will need microstepping drives set at 1/8 or 1/16 as a minimum to reduce the vibrations.
You can also draw a line on the rack and pinion, rotate the pinion one full turn and draw another line on the rack, measure the distance on the rack.
Then you put in the stepconf:
microstepping 8 or 16 :1
pulley:teeth 1:1
leadscrew pitch " the distance between the two lines on the rack"

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28 Jul 2019 23:34 #140850 by Carrball05carrball05@
The drivers I am using are tb6560 and I could move them down to 1/8 step cause yes they are vibrating when I run a test gcode. The pinion is a 12 teeth and rack is a 20 pitch and they are direct drive.

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29 Jul 2019 10:34 - 29 Jul 2019 10:39 #140872 by pl7i92
hi
the tb6560 is best on halfstepping
and on plasma it is well good to go for
the rack pinion is it a metric one T modell

seams your pitch of 20inch i guess is very high

it woudt help enourmous on module knowing
maedler.de/product/1643/1618/zahnstangen...ckig-gerade-verzahnt

Attachments:
Last edit: 29 Jul 2019 10:39 by pl7i92. Reason: image

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29 Jul 2019 12:30 #140882 by Carrball05carrball05@
This is the one I got it’s from
McMaster Carr

www.mcmaster.com/5174t21

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29 Jul 2019 14:32 #140888 by Todd Zuercher
Those are almost certainly Diametral Pitch (usually abbreviated DP). You can be sure by counting and measuring the distance for 20 teeth on your rack. If the disance for 20 teeth is about 1" then it truely is pitch. But I suspect it will be about 3.14" meaning it is DP.
For DP and if you use 1/8 micro-stepping, the steps/per inch should be.
8*200/12*pi/20=848.82636steps/inch.

Just remember when using micro-stepping your true resolvable accuracy will probably not be any better than if the drives were only set to 4x micro-stepping no matter how high you set the micro-stepping. But it should still help to smooth your motion (What micro-stepping is truly for.)

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29 Jul 2019 17:09 #140897 by Carrball05carrball05@
I counted the teeth on a 1 inch margin and it’s 7 teeth. I entered the number on the configuration the measurement on the 2 lines I made and it equal out to 1.86” so I entered that and when I ran a command to move x axis 5 inches it was going way too far. So I kept tuning the number and I got it to be almost accurate with a value of .54 not sure how that is or if there is another configuration I need to make?

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29 Jul 2019 17:12 #140899 by tommylight
No other configuration.
That is the best way, change it a bit and measure, repeat till you get accurately what you command from Linuxcnc, save and make chips ! :)

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