Hi All,
I'm new to this so please bear with me.....I have tuned my motor using the steps per setting and am able to get consistant measurement for the value I used for tuning the motors, i.e. 4inches, but any other distance will be slightly off. whats going on, how do I find out if I'm losing steps, what is the screw mapping function and where is it explained in the manual, is screw mapping standard procedure for "tuning motors?
-Here is what i'm using to set up my mill;
circular "pocket" designed in software
ID 4.015
OD 4.287

after milling I get
 
ID 4.018+/-0.007
OD 4.330+/-0.007

these numbers are pretty consistant if I run multiple parts
I think the ID is set perfect but the OD is off, I guess my question is what other setting need to be made to get the correct distance value for any distance.
any help understanding what I need to do will be appreciated.
thx, eric
 

What kind of machine do you have? is it ball screws?
Have you used the step per unit button on the settings page to make sure your steps per unit are good?
Hood

If your machine is sound, I wouldn't think screw mapping would be necessary. How much backlash do you have on each axis?

Try Sherline mode under the ports and pins page. You will need to exit the software to have it take effect.

Thanks
Brian

thx for the fast reply guys.....

My unit is a ballscrew driven cnc router, I am using a xylotex board and Mach3 software.

As for setting the values I did that manually...basically I kept on adjusting the value untill the circle's ID matched (using calipers) what I drew in the software, i.e. ID 4.015". At that point I assumed that I was done calibrating/tuning the motor... the number came out to be ~6400 for both the x and y axis

I haven't used the auto steps per unit botton, I will try that tonight and see if my number and the number mach3 spits out are the same...i'll also try to put the unit in sherline mode and see what happens.....

As for backlash I'm not sure how I check the value of this.......I do notice some backlash thought I assume its about 4-7mils, 0.004-0.007", but I'm not sure....any good websites on how a non-pro can learn how to accurately figure out the backlash of an axis??

thxs a bunch guys, I'll work on it tonight and report my findings...
eric

Once you have the steps per unit pretty good you can then jog against a dial gauge, zero the axis you are moving then change to step mode and back off, when the needle just starts to move look at the DRO for the axis and the amount you see is more or less your backlash.
Hood

Hello:

I am using Mach2 with a bridgeport shopmaster unit to engrave, well trying to!!!

I tunned the stepper motors fine I think, and I am getting readable text, but somehow it looks like I am loosing steps, the letter "O" for instance, the cutting tool would have to finish right where it started right, well, it does't quite do so, I have been playing with different units/min different minimum pulse width, and still getting the same result, any ideas???

Have you checked your backlash?




Hey Hood, thats no fair. I just figured out why I can't get up early enough to get one on you. You are 5 hrs ahead of me. Guess I'm a Geographically challenged fool.

Sounds like backlash, do a check for backlash with a dial gauge.

Hood


Edit
too late in my reply Now what is puzzling me is the saying great minds think alike, cant be right especially in my case.
 Oh OK I got it, should be fools seldom differ

well I read your promt reviews, (i am surprised by the length of time that took you to answer). I went to my mill and found a little backlash. I tightened a screw and that almost eliminated the problem, my text almost looks perfect now, I probably have to look into the whole chain of elements to eliminate this completely....

question, shoouldn't there be a setting for backlash in the software itself, I mean, when you are doing things manually you always adjust for this yourself, just a thought.....maybe there is a setting and I don't know!!!!!

thanks guys, appreciate the promt response on the previous question!!!!!