1. Hey guys,

Ive just bought another machine and have had to strip the board out of it in order for it to work. Ive now stuck my spare EDINGCNC CP5 board in, however, doing this as you know i have to set the steppers etc up again.

The machine come with the following:

90 tooth pulley on the pinion
18 tooth on on the motor side
HTD500 5M Belts

Stepping leadshine drivers are set to 1600 steps per revolution @ 8 microsteps via dipswitches

Maybe its just a brain fart, but im struggling to work this out more so the ratio of the belt and pulley so if someone can give me the easy way that would be great

2. To get pinion to rotate 1 revolution the motor needs to turn 5 revolutions (90/18)
1600 pulses rotates motor 1 revolution.
So need 1600 x 5 = 8000 pulses for pinion to turn 1 rev.

Can't work out distance (D) travelled for 1 rev of pinion without more info.(Num teeth on pinion & rack mod if it's r&p)

Once you know distance travelled for 1 rev of pinion= D, then distance per pulse = D/8000

**Edit, seems you need pulses per mm so its 8000/D

Cheers
Last edited by Greeny; 18-03-2017 at 01:23 AM.

3. Nice one Greeny! Its helical rack and pinion pal, I can get the pinion teeth count but not what mod it is

Any ideas it's not wrote on or anything.

Sent from my iPhone using Tapatalk Pro

4. Sorry don't know much about helical r&p.( or any r&p if truth be known )
I suppose you could move axis by hand & measure how far you need to move it to rotate pinion 1 revolution.
This would give you a very rough but sensible number which you could then refine by trial & error.

Hopefully someone else will have a much better answer!
Last edited by Greeny; 17-03-2017 at 05:49 PM.

5. ## The Following User Says Thank You to Greeny For This Useful Post:

6. Mark it and rotate one ful revolution and measure distance moved.. . . Simplizzzzz

7. ## The Following User Says Thank You to JAZZCNC For This Useful Post:

8. I will give that a go cheers lads

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9. how many teeth on pinion and whats it's diameter

10. Originally Posted by JAZZCNC
how many teeth on pinion and whats it's diameter
23 teeth and 32mm dia mate

11. OK so im getting round about 96.16mm for one revolution of the pinion.

96.16 divided by 8000 = 0.01202 steps per revolution ???
Last edited by D-man; 17-03-2017 at 09:13 PM.

12. Originally Posted by D-man
23 teeth and 32mm dia mate
1.25MOD is 32.69mm OD.
24DP is 1.09" (27.68mm), and 20DP is 1.308" (33.22mm), and 22DP does not appear to be a common size.

So assuming 1.25MOD and me reading the correct number from the chart, gives a pitch of 3.926mm per tooth, or 90.289mm for one rotation of the gear.

Or to assume 20DP, it would be 91.7194mm per rotation.

Are you sure it's a 23 tooth gear?
As even working backwards from 96.16mm, it doesn't fall on any common tooth size.
That's assuming I'm not making a complete hash of the calculations.

Off course, easier option would be just to measure the distance over as many teeth as possible and calculate the tooth pitch that way.

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