Hello all, thanks in advance for your help.  I am a new CNC Hobbyist, I have built a 4 x 4 CNC from some plans I bought. It is a Joe 4x4 Hybrid CNC if anyone has built one. Now to my problem, I am running Mach 3 Version R2.63, I have everything calibrated fine, I jog the machine with MDI commands on X, Y, Z and if I ask it to move G00 Z 1.0 it moves a inch, all great. 

Well when I output a file from VCarve Pro using the post processor of Mach 2/3 Arcs (inch) (*.txt) all is fine, EXCEPT on the first pass, it always cuts about 1/16th too deep. Always, I do not have any tool offsets loaded, I jog the bit to the top of the work surface, zero everything and run the file...1st pass is always too deep. If I make a file with say a 4" circle, pocketed 1/2" deep with a 2" circle pocketed 1/2" deep inside, the circles are spot on, 4" and 2" no prob, the depth of the 1st pocket is always 1/16th too deep, but the 2nd pocket, cut deeper as intended, is spot on depth wise.... 

SO what would be causing the extra depth on my Z Axis? I hate to bother you all but am at my wits end. 
 
I will post whatever files or screenshots that would be helpful, I just really need to tackle this issue so I can make this thing work right. 

Thanks again for your time. 

Respectfully,

Michael Fuller

Is the axis moving further than the code is telling it to go? Does the DRO show that it is moving further than the code is telling it to go?

Hood

When I jog it on any axis it moves as intended, I can check any axis with a caliper that measures in thousandths and all seems fine, people have looked at the G Code and said it looks fine, but it cuts too deep on the Z axis 1st pass every time, if for instance the file has multiple depths to it, or layers, the 2nd, 3rd pass etc it does not add any " mystery " depth, but if I make a file where the Z depth is 0.00...it will still cut into the material almost a even 1/16th of an inch every time.  I have no tool offsets set at all that I can see or find, a friend who works with CNC's came over and helped me check all 3 axis with his calipers, we jog it any direction with MDI commands it does fine, when I cut a file, ask it to cut say a word, .0100 deep into a piece of wood, it adds a 1/16 to it..I am stuck lol...

Please attach your code, I am not the best with G-Code but I may see something there or hopefully Graham or others will if I dont. Also please attach your xml, you will need to rename it before you attach it or the forum wont accept it, copy it to your desktop then rename it to Mjolnir07.xml as that helps us keep track of whos xml it is.

Hood

The Mach3mill.xml file?
Gcode for last project attempt.
Renamed Mach3mill.xml file

Much Thanks for your help.

Respectfully,

Michael

Got to nip out for a while but from a quick look I see you have a tool height offset in the code, line N50 has a G43.

Hood

Hi, Michael

Post your G-code file, If the second  cir. Z depth is correct, Is the Z depth in the first one correct in your G-code.

Double check your VCarve drawing depth settings, If it was a Mach/Z axis error the second one should have the same error.

Thanks, Chip

( V-Carve 1 )
( Mach2/3 Postprocessor )
N20G00G20G17G20G90G40G49G80
N30G70
N40T1M06
N50G00G43Z0.7874H1
N60S16000M03
N70G94

Thats the safe travel heighth I think isnt it...?

Respectfully,

Michael Fuller

My apologies, when I read earlier and you said you have no offsets I thought you mean in your code but you are meaning in the tooltable.
 Can you attach your tools3.dat please, you will find it in your Mach3Mill folder in the macros folder.
Hood

Here ya go sir. And thanks again for the effort from all of you.

Respectfully,

Michael

P.S. Hey Hood, the web says the town you live in is a famous place for Golf....are there cries all day of " Four......." followed by a thwack and a wizz as the ball flies by? 
P.S.S. Wouldn't let me do a dat file so I zipped it....