If you are saying that your machine does not move the correct distance - say 1 inch, when you tell it to move 1 inch, then this is down to the correct number of steps per inch in your motor tuning page.

**HOWEVER** - you are **NOT** tuning it.

Steps per inch is a finite number, there is no discussion, no alteration, no adjustment etc, - just a number. It is made up as follows - all numbers multiply the previous answer.

I assume you are using stepper motors. Check, but these are normally now 200 steps per revolution = 200

Your drives will have a microstep facility - e.g. Gheckos at 10, others 4 or 8 or 16 - Ghecko =10 = 200 x 10 =2000

If you have any gear reduction between the motor and leadscrew - I have a 3 to 1 belt reduction = 2000 x 3 = 6000

The pitch of your leadscrew or whatever - mine was 10 turns per inch 10 x 6000 = 60000

For your system - assuming steppers and microsteps - start at 200 for the motors, I will leave out the microsteps for the minute because you don't say what you are using.

If the gear ratio between the stepper and the drive wheel is 4.8 to 1 then 200 x 4.8 = 960

Irrespective of the number of teeth, and the pitch etc. How many turns does your final gear wheel have to make to move down the rack by 1 inch. I don't understand what you mean by 1.0 pitch - is this one mm,cm,inch - my catalogue shows so many variations, I dont see one which matches yours.

In any case - the thing you need to know is - how many turns does the wheel do on the rack to move one inch - multiply 960 by say 1 - if the rack pitch is 16 and the number of teeth on the wheel is 16 = 960

And finally the number of microsteps your drives use - say 8 or 10.= 7680 0r 9600 etc

The thing I must impress on you is that this number is not negotiable. You cannot now try it and measure the distance the rack moves and adjust the number of pulses, either you have it right, or you have it wrong. There are several reasons why your axis do not move the correct distance, but steps per unit is not one of them.

By all means try and measure to check you are reasonable accurate. - move the carriage to the right - set up your measuring equipment - I use digital calipers - move the carriage by an MD! move **again to the right** eg. G0 X1 - so x will move exactly an inch, and then measure. On my steel lathe, I expect to be to 1 thou - but I can't measure any more accurately than that. If you always move in the same directiom eg move right, measure, move right, measure you take out all the backlash from the system, i.e. the gears, belt etc have taken up all the spare movement in that direction.

If you make the final measurement to the right, then (again using the MDI) reverse the movement and measure the answer should be 0, but will not be, becasue the gear, belts etc all have to settle in to push the opposite way. This is called backlash. All systems have it (althoug on some it is so small you cannot measure it) and Mach 3 can compensate for it, but that is another story.

To make you testing more reliable, decrease the speed of your traverse on the motor tuning page - I don't know what you have it set at, and decrease the acceleration. This will reduce the chances of the motors missing steps. Once you are satisfied that the machine is accurate, you can up the speed again.

Sorry to be so pedantic - this is one of the Bees in my bonnet - see previous posts on the subject.