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Math regarding „counts per unit“ in Mach4

Forums Software Math regarding „counts per unit“ in Mach4

This topic contains 3 replies, has 2 voices, and was last updated by  Janne 1 month, 1 week ago.

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  • #3535

    Martin Flemig
    Participant

    Hi

    If we use the RAW as racks version, should the math respectively the result for calculating the „counts per unit“ in Mach3/4 for each machine the same, as long as we use racks and pinions with the same specs (Mod, Straight toothed, 20° engagement angle, etc.)?

    What are your recommended inputs for this field? Or should it be calculated individually?

    #3537

    Janne
    Keymaster

    Hi, yes if the racks are MOD1 and the gears 16teeth then the specs would be the same no matter what version of Mach you use. I have noticed that different software’s asks for different calculations and i have lost track of it all but here is a guide that a wrote a few months ago:

    GRBL (Estlcam settings below this article but read this as well to understand what we are looking for)
    A typical stepper motor has 200 steps PER revolution. These are known as FULL steps or 1.8° per step.

    A Raw machine has a HDT3 or HTD5 timing belt which means that they have a pitch of 3mm or 5mm. Pitch is the distance between two tops or bottoms of the timing belt/racks or the distance between threads, if you use leadscrew as we do for the Z-axis.

    If you want to calculate a leadscrew then the math is simple just add the pitch of the leadscrew 3mm and divide it with 200 (stepr per revolution) and the number we will put as a value in GRBL (The settings in GRBL call for a PER mm number) for example is:

    200/3 = 66,66666666666667 steps to make something travel 1mm
    For timing belt we need to calculate how many teeth the pulley has and multiply it with 3 or 5 depending on the pitch, so for a 5mm pitch and 15 teeth (5×15) , then it will travel 75mm/rev

    So the math is :
    200/75= 2,666666666666667 steps to make something travel 1mm

    Micro stepping (Estlcam for exampl
    CNC shield with the A4988 Drivers uses 1/16 micro stepping when all jumpers are activated , which means each step is divided into 16 microsteps.

    A typical stepper motor has 200 steps PER revolution.
    200 steps x16 micro steps = 3200 total steps/rev So the value “steps per revolution” in Estlcam is 3200. If you use other drivers that has 32 micro steps that value would be: 200 steps x32 = 6400.

    “Distance per revolution” is what your machine will travel per revolution so for a HTD5 belt (5mm pitch) with a pulley that has 15 teeth that distance would be 15×5=75mm
    -HTD3 with a pitch of 3mm would be 15×3=45mm
    -Lead screw with a pitch of 3mm will travel 3mm per rev and that would be 3mm

    Mach 3
    The same math applies for Mach 3 but we need to extend it some more
    Mach3 or other software’s asks for how many steppes it takes for something to move 1mm, so let’s do the math with the lead screw that has a pitch of 3mm (it travels 3mm per rev) We use 16 micro steps setting on the drivers for the z-axis so the math is basically,

    1600/3 = 533,3333333333333 steps to make something move 1mm (again, if your thread is different, then the divider number will be different)

    533,3333333333333 is the number I put into Mach.

    • This reply was modified 1 month, 1 week ago by  Janne.
    #3539

    Martin Flemig
    Participant

    Thank you. I read this article already but i found no information regarding calculating it for a rack. I found only the information regarding belt an screw. I used the motedis mod1 rack an the 15teeth pinion from your list. May i ask whitch value you use for y and x motors?

    #3540

    Janne
    Keymaster

    I dont have the settings right now but if you download this file you can just replace the file in your Mach3 folder and the machine will work right away: http://cncmaskiner.org/Mach%203%20settings%20file.zip
    but its only for mach 3. If you use mach 4 then download a demo of mach3 and add the file then just copy the settings to Mach 4 manually.

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