[greenjeens]

Im tuning my motors in Mach 3. Im at 1/8th step, 333oz Nema 23, direct drive 12t pinion. What should my steps per inch be in motor tuning. Im thinking 2400? Also when I get ready to cut a part made in sheetcam, Will that be my maximum machine speed to cut out a part?

[Torchhead]

You are missing an important number: The pitch of the gear rack OR the diameter of the pinion. The number of teeth have nothing to do with the ratios unless you know the number of teeth per inch (TPI) of the matching rack OR you know the diameter of the pinion. That is because the distance it moves per rev is a function of the circumference of that gear. The TPI of the rack and the number of teeth on the circumference lets you do the same math.

The formula for calculating the number of steps per inch with R & P are covered in the BladeRunner AIO User Manuel (3 parts) on the CandCNC website on the manuals page . Find the section on Table Physics to get an illustrated tutorial on that and motor tuning.

[greenjeens]

looks like I have a 24 pitch gear rack.

[Torchhead]

that would indicate the pinion moves 1/2" per rev. and that works out to pinion gear diameter of .158 (???) Pitch is actually the distance between teeth so a .24 pitch means there is a little less than 5 (4.`16666) TPI. That gives a diameter of 1.3263 (probably closer to reality) That would also mean that it moves the load 4.1666 inches per rev.

If it takes 200 X 8 (1600) steps to move it 4.1666 inches or 384 steps to move 1" All of this is dependent on the numbers you provided. The TRUE resolution does not use the microstepping number so the TRUE resolution on that would be .021 inches You will get somewhat better than that at lower speeds but you cannot count on it for overall accuracy. Then you have to add up all of your inaccuracies on top of the resolution to get actual accuracy. It's best to have about 5 to 10 times the resolution than you want in final accuracy. You can NEVER get more accuracy than your resolution (defined at the distance you move the cutter with one step)

384 steps per inch is pretty course.....good news though....you will have rally awesome rapids! unfortunately rather poor acceleration.

[Mzones]

1019.108 is the number you are looking for, if you have a 24 pitch pinion.

Divide number of teeth on gear by the gear pitch, (12 /24 =.5000 ) Multiply pi. (.5000 X 3,14 = 1.57 )
Divide your steps per rev by previous answer (1600 / 1.57 =1019.108 )
This is assuming Motor is 200 step per rev. 8 micro steps , 12 tooth, 24 pitch.

[Mzones]

Understand what the pitch of a gear means .
Pitch is actually the number of teeth in 1" pitch diameter.

A 16 tooth, 16 pitch gear, has a 1" pitch diameter.
A 24 tooth, 24 pitch gear, has a 1" pitch diameter.
A 32 tooth, 32 pitch gear, has a 1" pitch diameter.
A 16 tooth, 8 pitch gear, has a 2" pitch diameter.

Simple, isn't it ?

I cant quite figure out Torchhead's math.

[BTA PLASMA]

The bladerunner manual is wrong when it comes to steps per.

Steps per is a simple number. Lets say you have 2-1 ratio with a 1" pitch diameter. That's (pi) 3.14 * pitch diameter divided by ratio then divide that number by 2000 gives resolution (1/10 microstep or like previously mentioned 1600 1/8). Then take 1 divided by resolution and you have your steps per.

So for a 1"pd with 2-1 reduction it would be 3.14*1 = 3.14 then divide it by 2 you get 1.57 then divide by 2000 you get .000785. For steps per take 1 divided by .000785 your steps per are 1273.88

12 tooth 24 pitch gear has a pitch diameter of .5"

This means You have a steps per of 1273.88 same as the example above but with no reduction and a smaller gear with a 1/10 microstep or .0009815 resolution or 1018.84 steps per with a 1/8 microstep.


This is per CandCNC manual

Calculating the beginning Steps per UNit on an AXIS
Use the following formala to get a ballpark steps per unit number in MACH
Psr = Pinion Speed increase ratio = Pitch Dia [in inches] * PI (3.1416)/1
Target Steps per Unit = (Psr X 2000)/Belt Reduction ratio
This will give you the required number of steps it takes to move 1”

From the manual you would get this result. .5*pi = 1.57/.5 = bad result. Should read pinion resolution = pitch dia*pi/ratio (if applicable)/2000. Resolution = 1/pinion resolution.

[BTA PLASMA]

Your actual steps per number can fluctuate a half step depending on which value you use for pi. If you go 4 decimal places deep you will get a different number than 2 decimal places. You may never see the actual difference in cutting but it is there. Two examples are what the previous poster got for steps per using course math for steps per vs a few decimal places in the figures I posted.

Previous poster 1019.108
My # 1018.84

And of course the number will change if you round up like taking 1600/1.57

To get the closest numbers you should use the pi function and the same math I have shown. We can get repeatability within .0003 this way with very little to no mechanical backlash.

[Torchhead]

Understand what the pitch of a gear means .
Pitch is actually the number of teeth in 1" pitch diameter.

A 16 tooth, 16 pitch gear, has a 1" pitch diameter.
A 24 tooth, 24 pitch gear, has a 1" pitch diameter.
A 32 tooth, 32 pitch gear, has a 1" pitch diameter.
A 16 tooth, 8 pitch gear, has a 2" pitch diameter.

Simple, isn't it ?

I cant quite figure out Torchhead's math.

The user stated he had a 12 tooth gear and 24 TPI rack. I took that to mean the gear actually had 12 teeth total around the outside.
Obviously gears are described differently because to me PITCH is the distance from the center of one tooth to the next.

But if you take all of the teeth out of the equation and use the diameter (pitch diameter) and roll it along a flat plane it will travel PI times the diameter each full rev.

So I assume from the list that you posted, a 12 tooth 24 pitch gear is .5 in diameter and moves 1.57 inches per rev. A 12 tooth gear (total teeth) to get the same tooth pitch as the rack would have to have a circumference of 12 X .04166 or very close to 1/2" The diameter would be that divided by PI.

So I assume the gear circular pitch has to match the linear pitch of the rack at 24 TPI. that was a number I did not have or did not assume.

I prefer to deal with the actual pitch diameter and that is simply a wheel of diameter D rolling along a plane X. Assuming no slippage it moves the load PI times the diameter of the wheel and that expressed in inches lets you define the steps per inch if you know the steps per rev. It can also take into account any gearing or belt reduction in between using just the ratios

Thanks for the lesson on how spur gears are described.

I make mistakes but seldom twice.

[Mzones]

What I was trying to show was the relationship of the pitch to diameter.
If you d1vide the number of teeth by the pitch, this gives you the pitch diameter.
It does not matter what the pitch is.

[Mzones]

The shortest distance between two points is a straight line.

If you are using a 24 pitch pinion, you use a 24 pitch rack,
no calculations needed.

If 1 rev = 2000 steps, and 1 rev = 1.57".

2000 / 1.57 =1273.88530

Also there is no need to multiply any number by 1.


Gear racks are not defined as TPI.

Gear racks do not have a circumference .

[BTA PLASMA]

*1 is a reference to the reduction ratio only.

[victorofga]

if it is 1/8 microstep, and counting on motor 200 step then one turn is 1600 step..
if ,,, I say if one turn move your pinion 1/2 inch then need two turn for one inch

twice 1600 equal 3200 step per inch..

to calibrating use the available length of movement..

send the unit as long as you can.. like 12 inch, 24 or 30... and compare the actual movement with you expected.. at this ratio you cant rely on a small measured unit, like one inch..

in explanation, with tapemeasure you can measuring 1/32 or a little better..
if 24 inches you measure as 1/32 precision, then one inch will be 24 times more precise virtually. so the different on 24 inch divided back to inches resulting so small error than you can measure only with micrometer..

[Mzones]

It's been a long time since I was in grade school math.
Maybe I could get a little help here telling me what I am
doing wrong.
Ok we have a 12 tooth 24 pitch pinion. a stepper motor @ 200 steps per rev,
8 micro steps, direct drive

200 X 8 = 1600 (steps per rev)
12 / 24 =0.5 ( pitch diameter )
0.5 X 3.14 = 1.57 (circumference)
1600 / 1.57 = 1019.108 ( steps per inch)

How can I be so far off ?
What's so hard about it?
I guess I just don't get it!

[victorofga]

I gave an example..
and said IF one turn moves half inches the pinion..

I tried to give a simple example.. theres the if word..

I didn't checked your calculations.. probably ok. you also try to involving the distance as pinion going for within one turn..

[mactec54]

Mzones

200 X 8 = 1600 (steps per rev)
12 / 24 =0.5 ( pitch diameter )
0.5 X 3.14 = 1.57 (circumference)
1600 / 1.57 = 1019.108 ( steps per inch)


If this is the Pitch Diameter, then you have to Divide Diameter x 2 to find the circumference .5 / 2=.250 x 3.14=.785398

1600 / .785398=2037.183695, if your numbers are correct the steps/per then is 2037.183695

If you are using Mach3 then you should be doing the axes set up steps/per by using the control, it is most times more accurate, Just select the Settings Button & you will find it just above the Reset Button, there are videos on you tube as well how to do this