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### Author Topic: need help step per unit  (Read 8441 times)

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#### elgammmmal

• 9
##### need help step per unit
« on: May 05, 2009, 12:53:01 PM »
I've read tuning motor chapter,and make my calculation as below
pitch=1/5 =0.2                effective pitch =0.2x2=0.4
screw revs per unit =1/0.4 =2.5
motor revs per unit= 2.5xNs/Nm=2.5x1 =2.5    (1:1 drive ratio because my gear has no teeth)
mach3 steps per motor revs =200x32 = 6400
mach3 step per unit = 6400x2.5 =16000
would you please check this calculation if it right and if drive ratio 1:1 is right or not.

#### Jeff_Birt

• 1,107
##### Re: need help step per unit
« Reply #1 on: May 05, 2009, 01:04:26 PM »
Quote
mach3 steps per motor revs =200x32 = 6400

You have a 32 microstep drive?

You also have a very low drive ratio which will give you very little torque. You are essentially direct driving a low pitch lead screw.
Happy machining , Jeff Birt

#### Tweakie.CNC

• 8,022
• Super Kitty
##### Re: need help step per unit
« Reply #2 on: May 08, 2009, 12:01:20 PM »
Hi elgammmmal,

Are you working in mm or inches here.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

#### elgammmmal

• 9
##### Re: need help step per unit
« Reply #3 on: May 08, 2009, 12:16:52 PM »
hi Tweakie
thank you for your interest  and my machine  set up  in mm .

#### sixmile

• 44
##### Re: need help step per unit
« Reply #4 on: May 08, 2009, 12:54:25 PM »
screw revs per unit =1/0.4 =2.5

You are working in mm and it takes 2.5 revolutions of your screw to go 1mm?   Is that correct?

• 4,895
##### Re: need help step per unit
« Reply #5 on: May 08, 2009, 01:21:53 PM »

pitch=1/5 =0.2                effective pitch =0.2x2=0.4
My guess is a 5 TPI double cut thread. 0.2" pitch, 0.4" lead.

screw revs per unit =1/0.4 =2.5
2.5 turns per inch

motor revs per unit= 2.5xNs/Nm=2.5x1 =2.5    (1:1 drive ratio because my gear has no teeth)
Assuming 1:1..........Don't understand "Toothless Gear".

mach3 steps per motor revs =200x32 = 6400
32 microstep
mach3 step per unit = 6400x2.5 =16000
Looks right to me but the units look to be INCHES

RC
« Last Edit: May 08, 2009, 01:23:57 PM by Overloaded »

#### M250cnc

• 591
##### Re: need help step per unit
« Reply #6 on: May 08, 2009, 03:58:28 PM »
pitch=1/5 =0.2                effective pitch =0.2x2=0.4
My guess is a 5 TPI double cut thread. 0.2" pitch, 0.4" lead.

My guess is 5mm = .2" approx twinstart = 8mm .4" approx

mach3 steps per motor revs =200x32 = 6400
32 microstep

6400/8 = 800 steps

Phil
The Good Thing About Mach3, Is It's very Configurable

#### elgammmmal

• 9
##### Re: need help step per unit
« Reply #7 on: May 08, 2009, 05:53:35 PM »
motor revs per unit= 2.5xNs/Nm=2.5x1 =2.5    (1:1 drive ratio because my gear has no teeth)
Assuming 1:1..........Don't understand "Toothless Gear".
.in mach 3 guide says (if the motor has a gear ,chain or belt drive to the screw with Nm teeth on the motor gear and Ns teeth on the screw gear then motor revs per unit = screw revs per unit xNs/Nm).my motor has gear with belt drive to the screw the gear is flat with no teeth so how can I calculate Nm and Ns.shall I ignore Nm and Ns in my calculation or there is anther way to calculated.

• 4,895
##### Re: need help step per unit
« Reply #8 on: May 08, 2009, 06:02:31 PM »
Are you meaning you have pulleys and a belt but they are smooth with no cogs ?
That would be odd for an axis drive train.
If so...  measure the OD of each pulley. Then divide the driven pulley dia by the drive pulley dia. That will be the ratio.
If they are the same OD it will be 1:1.