# Machsupport Forum

## Mach Discussion => General Mach Discussion => Topic started by: elgammmmal on May 05, 2009, 12:53:01 PM

Title: need help step per unit
Post by: elgammmmal 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.
Title: Re: need help step per unit
Post by: Jeff_Birt 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.
Title: Re: need help step per unit
Post by: Tweakie.CNC on May 08, 2009, 12:01:20 PM
Hi elgammmmal,

Are you working in mm or inches here.

Tweakie.
Title: Re: need help step per unit
Post by: elgammmmal on May 08, 2009, 12:16:52 PM
hi Tweakie
thank you for your interest  and my machine  set up  in mm .
Title: Re: need help step per unit
Post by: sixmile 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?
Title: Re: need help step per unit
Post by: Overloaded 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
Title: Re: need help step per unit
Post by: M250cnc 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
Title: Re: need help step per unit
Post by: elgammmmal 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.
Title: Re: need help step per unit
Post by: Overloaded 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.
Title: Re: need help step per unit
Post by: Overloaded on May 08, 2009, 06:10:05 PM
If they are timing pulleys, just count the teeth on each pulley. Then divide.

Is this the type you have ?
Title: Re: need help step per unit
Post by: elgammmmal on May 08, 2009, 06:18:44 PM
I've attach a picture of the pulley I'm using hope that can be help
thank you
Title: Re: need help step per unit
Post by: Overloaded on May 08, 2009, 06:29:16 PM
Well all you need to do is measure the OD of the 2 pulleys then divide but that probably will not work well for accurate motion control.

What exactly are you building ?
Title: Re: need help step per unit
Post by: elgammmmal on May 08, 2009, 06:39:04 PM
I'm building cnc router for woodworking and I did try to use timing pulley but it is not available in my town I'm form Egypt so if it important I may make an order  by any on line store. sorry for my poor writing
Title: Re: need help step per unit
Post by: Overloaded on May 08, 2009, 07:21:43 PM
Your writing is really quite good.
I'm sure you would have been dissapointed if you had used the smooth pulleys.
Good luck to you and post some pictures of your machine when you get it together.
Regards,
RC