UV for Z axis issue

[maginter]

I am starting to get into some prety detailed stuff and really want to dial my set up in. One issue I have is with the Z axis, it is off from the programmed value. I have read the threads about changing the UV to get it corrected. I have a 2002 vintage PRT with the G4 upgrade. I have a 20 tooth gear that drives the Z. My current setting for the Unit Value of the Z is 2291.831. With that value it is off. I have entered 2350 for the UV, but an not sure this is totally correct. I have read about calculating the UV for the Z, but I am obviously not entering somthing correctly.

Can someone help and point me in the right direction?

TIA,

Mark

[ken_rychlik]

Your 2291.8310 is the same as my prt was. That should work unless you have different motors.

What part number are your motors?

Kenneth

[maginter]

Hi Kenneth -

Sorry for the delay, but I was tied up.

The Motor is a Vexta and is Model # A6497-9412KTG and is driven by a Botrods controller.

Thanks,

Mark

[ken_rychlik]

My motors are the same. The botrod controller is the only difference we have. That is a home brew thing, and Dirk is the only one that could help you with that part.

Kenneth

[maginter]

Thanks......

I'll check with Dirk...

[maginter]

Well, I checked with Dirk and he said that it is pass thru and the values should be the same...... So that being said, any other ideas?

[ken_rychlik]

When you say it is off, how are you setting your zero and where are you measuring to know that it's off?

Kenneth

[jerry_stanek]

How much is it off by? Could it be your zeroing plate

[ken_rychlik]

or the bit slipping in the router,

or the z motor loosing steps,

or the set screws on the gear loose,

???

[maginter]

My zero plate it entered correctly. It is a .121

Here is an example. I zero the top of the material with the Zplate. When I enter zero into the Z adjustment table, the yellow pop up window, it is dead nuts on the top of the material. Lets say that the material is 1 1/4". Then I want to make a cut that is 7/8" deep. Instead of the cut being .875 inches it is .815 inches deep. No adjustments too place in between. This is at all test locations on the table. So no unevenness of the table or location specific issues. The dimension that it is off seems to be proportional to the cut depth. That that proportion is I have not figured out yet.

[maginter]

No bit slip, motor loose or moving or set screw. gear is tight without backlash.

[ken_rychlik]

so if you move the z up to 4 inches, how far up does it go?

[maginter]

I will do that experiment tomorrow......

[ken_rychlik]

I had a bad collet once and the bit would not stay put in the router. It would slip into the collet deeper when cutting.

After the file I would move the z to zero and it would not be there anymore.

I know you said the bit is correct after you zero the z, but how about after running the file check that again.

[maginter]

Ok, here is the results on my experiment. I set up the router with a 1/4" rod in a 1/4" collet for a predictable measuring surface. The shift is very consistant. I atrubute the differeence between the 1.5" and .5" to measuring error. I was using expanding calipars and that distance was tight to measure off the material.

You thought????

[ken_rychlik]

everything is off about the same as your zero being off.

I think your UV is correct and something is wrong with your zero plate and or routine.

If your vaules were off say ten thousandths at one inch, then it should be off 40 thousandths at 4 inches. That ain't happening.

You have to get your base zero equal to zero and the rest should be pretty close then.

Kenneth

[maginter]

So you think that it is the zeroing routine is off.... That makes sense and is the only thing I haven't checked. I will let you know what I find....

[ken_rychlik]

Well, before you said that after the zero routine, it was dead "on" for zero, but your measurements just told other wise.

Start there.

[maginter]

If I measure the zplate I get .121. When I run the set up routine, I have .121 entered for the plate thickness. Is ther another location that this is entered to set the zero plane for the z axis? I would have thought the only other location would e the zero routine.

[ken_rychlik]

c:\sbparts

Is where the file is located. It is called z zero routine.

You can look in there and change values if need be, or if you want another copy of it, email me and I will send you the one I am using.

Pay close attention to the decimal point. Those things are tricky.

Kenneth

[maginter]

If you could send me a copy, I could try that. My email is mark.a.ginter@gmail.com

I found it in my C drive and everything looks correct. I f get a copy from you I can do a compare.....

Thanks!

[maginter]

OK.... I just ran the file you sent me and it was dead nuts on..... So that being said, there is something wrong in the OEM file that causes it to be off. I will go through the code and the varibles and see what it is doing. at least I know I am not going mad!

Thanks for ALL your help on this Kenneth...... I really appreciate it!

[ken_rychlik]

Your Welcome.

I am just paying back all the kindness others have shared with me.

Kenneth

[jerry_stanek]

you said you zeroed it to the top of the material is your material exactly whe you say it is or is it thinner. After you cut have you checked to see if the bit is still zeroed on top of the material.