Need Help!- X and Y axis differ in motor tuning???

[tskguy]

Hi all,

I am a newbie DIY CNC'er and have been lurking here from a month or so. I just finished building an MDF desktop router. I used acme 16tpi lead screws with delrin nuts. The issue I'm having has to do with motor tuning. I did the math to calculate the steps per unit in Mach 3 and came up with 2015.74 steps per unit.
Here is how I did it. I have 1.8 degree steppers so 200 steps per rev. I have 16th micro stepping board so I get 3200 steps per rev. A 16 turn per inch converted to mm is 16 divided by 25.4 is .6299 revs per unit. Then I multiplied 3200 X .6299 to reach 2015.748.

Is that right??? So here is what I see on the machine. I did some test and noticed things are a little off. So I dug out the dial indicator and used mach3's calibration tool. First off according to the calibration the X axis was closer to 1951 steps per unit. The Z was the same number. But the Y axis is set to closer to 2200 in order to get an accurate 1mm. Part of me is wondering if the cheap screws I bought off ebay are to blame. Or maybe the cheap controller board I bought off ebay is to blame! Or should I just leave well enough alone?

Thanks for reading!!

[jalessi]

Tskguy,

Mach3 has a built in calibration utility.

Watch the video provided by Hoss.

YouTube- Improved Mach 3 Axis Calibration
Have a most awesome day,

Jeff...

[tskguy]

Thanks for the video....I actually used his quick and dirty method to come up with what I'm using now. I guess my ultimate question is why my x and y axis are so different? I am using the same screws for both axis. I suppose I shouldn't worry to much as long as its accurate. I plan on testing tonight by drilling a grid of 1mm spaced holes to verify that they are traveling the same distance.

Do think my math is good?

Eric

[ger21]

I guess my ultimate question is why my x and y axis are so different?

The screws must be a different pitch. Maybe your Y is 18 tpi?

[tskguy]

Maybe your right? I shouldn't worry as long as its calibrated in mach3 correctly thats all that really matters.

Thanks for the help guys! I will post a video of my little machine soon!

Eric

[lunchtrayrider]

measure over a variety of distances? maybe backlash or machine flexing?