Z axis incorrect

[maddog 62]

hello everyone
iv dusted off my old machine and am going to have another go at trying to get to know it better
with a few trial runs iv found that i am loosing depth of cut to what i have programmed. ie programmed to cut to a depth of 6mm but actual final cut was only 4.24mm
after a call to Russell (Epineh) he suggested that i first check the Z movement in mach to the actual movement of the spindle

i set the base of the spindle 55mm from the bed zeroed the Z axis and then lifted the spindle 45mm on the z counter on mach
that should have ment that the spindle should be a total 100mm from the bed, wasnt it was 89mm off the bed. a loss of 11mm.
the machine is a 6040 chinese cnc
according to the specs sheet the ball screws are dia 16mm with a pitch of 5 mm
the motors are 387 oz motors from Homann supplies (with a lot of outside help i changed the moter rewired and fitter G540 stepper controlers to it)
the info/help i am after is what should the correct configeration be for the new setup, and were in mach do i change the settings
thankyou in advance for any feed back that maybe provided.
cheers Tony

[SawDustSniffer]

I believe your CNC is a 6545 the same as mine

1st check the " scale " setting next to the z axis read out , it might not be set too 1:1 (1.0000 )

if not that try
Config , motor tuning , zaxis setting , " steps per " box should read 400
dont forget to save your axis settings before you leave

[maddog 62]

SawDustSniffer
thanks heaps will check it out in the morning
cheers Tony

update
yep setting was wrong had it at 300 instead of 400 changed and now working as required
again thanks heaps
one headache solved
cheers tony