Hi all recently bought a 4x8ft Chinese 1325 single cylinder overhead gantry type milling machine. Having recently sold my other CNC machine which was running ncstudio.
Mach3 is taking some getting used to due to the sheer number of menus and being new to the layout.

I've managed some things such as offsetting my start point from the machines home Co ordinates.
I ran a code today to follow the outline of the 8x4 sheet of my  bed, the start point was bang on and running along the x left to right was fine until it came to what the software recognised as 1220mm but the cylinder stopped 10mm short of, then as it run up the y axis is stopped short of the top by 20mm from the top of my 8x4 sheet. Going back left of the x axis was spot on to stopping and running back down the Y axis to the x stop point was also spot on. Can anyone shed some light on this? I thought maybe I had to alter the limits on my config screen? But that didn't seem to make a difference.

The machine Co ordinates of my X axis where it meets the 1220mm end of the sheet is reading 1230mm
And the y axis upper machine Co ordinates where it meets the top of the sheet at 2440mm reads 2514mm

Any help would be much appreciated guys thanks in advance

Sounds like your steps per unit settings are slightly wrong in the motor tuning config menu.

Thanks for the reply, how could I check or alter this? As I say new to mach 3 I've no idea, slightly off topic could I run the machine using ncstudio instead of mach 3?

Do you have the Mach 3 Mill manual?  It describes exactly how to set this parameter, either by calculation (for which you need to know your leadscrew pitch, any gear or pulley ratio between the stepper (or servo) motor), and the microstep setting of the driver; or by measurement.  You can download the manual from
https://www.machsupport.com/help-learning/product-manuals/

That's great thank you I didn't have the manual that will be a lot of help cheers

hi thanks after reading through the manual im still no wiser as to how to get my maximum x axis and Y axis limits defined, if anyone could show me a video or tutorial relating to setup would be much appreciated thanks

"The machine Co ordinates of my X axis where it meets the 1220mm end of the sheet is reading 1230mm
And the y axis upper machine Co ordinates where it meets the top of the sheet at 2440mm reads 2514mm"

So it thinks X has moved 1230 mm but has actually moved 1220 mm, and Y has moved 2440 but reads 2514.  Since it goes back to zero correctly it hasn't hit the end stops.  Mach 3 works in steps per unit, so many steps per mm in your case.  So if you asked X to move 1.23 mm it would actually move 1.22mm.  Therefore you needs to increase the number of steps/mm it's set to by 1.23/1.22 = 1.0082.  Similarly the Y number by 2.514/2.44 = 1.03033

To do this you need to open Mach3 and click on the "Config" menu, then select "Motor Tuning" from the list that drops down.  You will get a window with a blue graph on a black background with various things you can change.  At the top it will say X AXIS MOTOR MOVEMENT PROFILE, and at the bottom left is a white box with "Steps per" above it.  Look at the number in it, with a calculator multiply it by 1.0082, then type the result back into the box and press return.  When you do this the SAVE AXIS SETTINGS button text will go black - press the button which saves your change and greys out the text again. 

Now click the Y AXIS button near the top right, and repeat with the Y axis factor.  Save again.  The Z axis probably needs correcting too, just repeat the same process clicking Z Axis.  Then clock OK at bottom right to exit the menu.  It's probably wise to close and restart Mach 3.

I think my arithmetic is right, but you may have to divide by those factors rather than multiply.

Also ideally you would accurately measure the actual movement of the cutter relative to the table over a shorter distance, say 50 or 100mm, to get the factors.  This is covered in the manual in section 5.5.1, and there is also an automatic procedure described in 5.5.2.3 - though you still have to measure the distance moved.

Does your machine have leadscrews to move the axes, or toothed belt, or what?  Axes with leadscrews are probably best set up by calculation as long as you know the screw pitch.