[Iamwoodnut]

I am having a problem fine tuning my Y axis.
I just change it to rack and pinion and, after a bit of head scratching figured out the steps per inch. I had it running underneath before with a lead screw but could not get enough mechanical play out of the movement. I could easily move one side or the other an 1/8" or more. Tried different ways to brace it, but it wasn't enough.
So I mounted the motor to the middle of the Y axis (the motor has duel shafts see attached pic) and connected a shaft to each end of the motor. The pinion gear is 26mm at the pitch circle, 26 tooth. I can move the Y axis any where from 2" to the full18" and back no problem. It goes back to the same spots each time.
The problem comes into play when trying to move the axis less then .5". That's when it starts to either over shoot or under shoot the distance. Sometimes it only .002 out other times it .01 or more out. Right now I cant get it to move at all under .006". It's frustrating as I was able to fine tune the X axis right down to .001" with in about 20 mins, but it uses a lead screw not rack and pinion.
I have gotten as much mechanical play out of it as I can. I can still move one side if I push hard enough but that's the shaft bending at that point. Will figure out a bracket for that later. That shouldn't affect the movement under no load.

The stepper motor is 1.8 degree/step 200 steps/rev. Micro steps is 10 pulse/steps 2000 pulse/rev.
The pinion gear is 26mm pitch circle 26 teeth.

If I figured it out right my steps per inch is 621.93
I used this to figure it out.

26mm = 1.02362"

1.02362 x 3.14159 = 3.2157943558
200 / 3.2157943558 = 62.19303160330524
62.19303160330524 x 10 = 621.9303160330524
The above seems to work as I can move the axis large distances accurately. Its just when I get down to under an inch things seem to jump around. I played with the backlash settings but they didn't really help.

Not sure what the next step is. I was thinking of changing the motor with one of the other ones to see if the motor was the problem.
Would really like to get this up and running as I have people interested in some pieces I want to make.

[jeffrey001]

I think you should have one motor per side, torsion in those shaft is well enough to cause trouble.

Also, I would use 1:3 reduction belt and pulley so you have some precision when moving the gantry.

Jeff

[mactec54]

Iamwoodnut

There is no way that will work with any accuracy, you will need bearings to support each end of the shaft, plus at the motor end as well, you will also need to gear it down,anywhere up to 5:1 will work, most spring load the pinon into the rack, to try & eliminate any backlash

[Iamwoodnut]

Thanks guys,
Looks like I will be ordering another motor and driver to solve the problem.
Any tricks to fine tuning a slaved axis?

[mactec54]

Iamwoodnut

What you have will work just fine with ( 1 ) motor, Just use a support Bearing the at each end of the shaft , & have ( 1 ) Bearing in the center to support the shaft, mount the motor up above the shaft with a gear ratio

Use a larger diameter shaft all the way through,( one piece ) like 1" diameter, 3/4 may do the job, depends how long it is, machine the ends to suit the pinion

[Iamwoodnut]

OK I am really scrachin my head big time on this.
I got my new motor and driver, all installed with no problems. Still a bit of fine tuning needed but it close for now.

My NEW problem is on the X axis now. The only thing I touched was the wires to the driver, I added to them to make them longer. Now look at the attached picture. When I tried this test file my 2 OO's over lap but the rest of the letter spacing is fine? I have ran this program before with no problems.
I double checked my wiring, checked the motor tuning, blacklash setting and rebooted the computer. I tried again. Same result. OO's over lap. Checked the G code in Mach3 and didn't see anything wrong. Now look at the pencil line off the first t. This is were I zeroed the X axis for the second run. Were the router is now sitting this is were the it now zeroed AFTER running the program. Its moved -0.75" ???
Even the Machine Zero has moved -0.75" if I home this X Axis now it will hit the Y axis rail.

Going to try a couple of other test files and see what happens. Very confused.

[Iamwoodnut]

Well so far its just seems to be this file that is acting up. Don't have a clue why.
Will try and redo the gcode for it and see what happens. Tried 3 other files tonight and all worked OK.

[Iamwoodnut]

Ok this is the second time this has happen.
This time right in the middle of cutting the "M" the x axis loses (don't know how else to describe it) 3/8" ??!!
The file was made in Artcam and save to the hard drive then opened in Mach3 and cut all with in 3 mins. The computer for the mill isn't even hooked up to the net.
This getting very frustrating

[jeffrey001]

Try lowering the fast feed by 30% and adjust the acceleration.

I'm sure It's loosing step.

Do you always cute the part at the same place on the table, try another location.

Jeff

[Iamwoodnut]

Try lowering the fast feed by 30% and adjust the acceleration.

I'm sure It's loosing step.

Do you always cute the part at the same place on the table, try another location.

Jeff

Thanks Jeff I will try this.
The feed rate by default was 10% and I raised it to 50%, will lower it back down and try again.
It funny how it loses steps in the same place every time.

[jeffrey001]

I was not talking about the feed rate but rather the G00 moves.

It' called velocity in the motor tuning menu.


don't forget to click on the save button when you adjust motor velocity and accel.

Jeff

[Iamwoodnut]

Ahh, newbie mistake.
Question, does the velocity and acceleration have to be the same for both x and y axis?
My current velocity is 150 in/min and acceleration is 22 in/sec for all axis.

[jeffrey001]

Try velocity at 75ipm.

Jeff

[Iamwoodnut]

Thanks that worked :banana:
velocity 105 and acceleration 11
Turned out prefect.

[jeffrey001]

Happy for you, have a nice day.

Jeff