Need Stepper formula for $100

Projects General Guidance
1

Hello once again , this time i have trouble calculating the value for $100 (X) (Y) & (Z) I've look all over the web to find how to calculate the steps and each place I find has a different method that comes out wrong .Im using a lead screw with 1/4 steps on the driver , Arduino CNC Shield , the machine is home built and I think I got most of the bugs ,but wont be sure until I configure X,Y,Z and run a bunch more test.The driver is a A4988 ,CNC Shield V3 GRBL1.1 lead screw 1.8 degree .Any suggestion would be appreciated .

Thank you

2

What does 100 dollars have to do with stepper motors?

3 
lead screw 1.8 degree

I have never seen a lead screw specified that way. Usually they are specified by diameter and pitch. A, common, stepper is 200 steps per revolution or 1.8 degrees per step.

This is a 3D printer calculator that I use. It includes a lead screw calculator to use once you figure out what lead screw you have.

4

I thought he was offering $100 for anyone that could tell him the formula.

5

RogerM:
Hello once again , this time i have trouble calculating the value for $100

If you just want to pay someone to write a program for you please ask in the Gigs and Collaborations section of the Forum

...R

6

$100 is the variable used for steps/mm on the x axis when using GRBL. There are similar values for the y and x axes ($101 and $102)

See GRBL Settings

7

UKHeliBob:
$100 is the variable used for steps/mm on the x axis when using GRBL.

It is a shame that it was necessary for you to explain that when the OP could so easily have done so himself.

...R

PS, perhaps someone should tell the GRBL folks about the concept of meaningful variable names :slight_smile:

8

So I guess no one knows the formula for calculating step per mm , such as :

steps per rotation/mm per rotation /microstep fraction .

so Ex :- 200 / 10 /.25 = 80

so I told the machine to move 10 but it moved 2.4 so 1/2.4 = .4166

so .4166 X 80 = 33.33 steps but this value is to low to enter the setting in X,Y or Z GRBL

so my question is whats the actual formula for ($100=X ), ($101=Y) ($102=Z)

or what am I missing?

9

If you are driving a lead screw then you are interested in mm travel per step - so you need to factor in the pitch of the thread .
Can you not just write a simple sketch , send it say 100 steps and measure the screw movement , then work out steps per mm of lead screw and use that ?

10

Alright so the pitch of my lead screw is 1.8 how do i factor that in ?

11

1.8 what?

12

the pitch of my lead screw is 1.8 degree & 8mm thread so how do figure out what I need to calculate

steps/mm?

13

Are you saying the lead screw diameter is 8mm or that the lead screw pitch is 8mm?

What does 1.8 relate to?

14

the lead screw pitch is 1.8 degree the rod is 8mm

15

Pitch of a screw is normally specified in turns per unit length.
This has already been mentioned.

16

Alright , so the place I get my hardware don't say much about details , there more of a supplier than technical people so I guess the pitch would be 8mm , so how do I add this to a formula or is there a better formula from the one I posted above ? or perhaps free software to provide the answer because 33.33 steps for X,Y are really low values or just completely wrong .

17

RogerM:
so I guess the pitch would be 8mm ,

This is just crazy.

The pitch of a screw is the distance from the top of one thread to the top of the next Thread. That distance will not be 8mm. It is much more likely to be 1mm or 1.5mm if it is a metric thread.

The simple way to determine the pitch is to rotate the screw by exactly 10 turns and measure how far the carriage moves. Divide the movement by 10 and you have the pitch.

...R

18

so rotate the screw 10 full revolutions and divide by 10 revolutions the distance traveled .Ok , let me ask you this

if the lead screw is 1.8 degree and for 1 revolution is 360 degree so then the formula is 360/1.8 = 200 steps
which is already in UGS .Now for X,Y, Z I have to compensate for the A4988 driver set a 1/4(.25) microsteps , so that value in UGS comes to 250 steps ,so when i tell it to move say 20 mm and it moves 7.4mm what am i missing ?

19

what am i missing ?

if the lead screw is 1.8 degree and for 1 revolution is 360 degree so then the formula is 360/1.8 = 200 steps

No.

You need to know the threads pitch, not the angle and also the effective diameter.

Have a read of this:- Bolt Science - Basic Terminology related to Screw Threads

I find the idea of a thread's angle being 1.8 degree is a bit fine for a lead screw.

20

Alright Mike thanks alot Ill look into it and once I find the pitch how do I calculate the steps needed for X,Y,Z ?