Am completely new to CNC machine. I have my new zenbot CNC machine with G540 controller and mach3 software.

Am using an online CAD for designing and online cad itself converts my design to G-code an trasfers to MAch3. My problem is in tool height changes. Whenever the tool height is changed, the Z axis tool travel length is changes i.e increased or decreased. so the milling goes wrong. i.e, the tool cuts my work table. is the tool height is associated with motor tuning (i.e, steps/unit). . . Can any one plz help me in this regard?

also I have an external ESTOP button which is connected to the PC through USB. This button is just an NO switch connected to a board and it'l be activated when pressing and triggers the space key in my computer so that the ESTOP will be activated in the controller through MACH3. What I need in this setup is, I want to stop the spindle when the ESTOP is activated. I tried the settings in mach3 general config. But no use.

And my milling works properly when I setup the motor inputs under ports&pins option as Active high (direction input). I connected three limit switches for three axis but i works correctly when the direction input are setted as Active low. If direction input are stated as active high, then the machine moves reversely while homing (ref all home) I cant link these two conflicts and resolve. I want my machine and limit switches to work with active high config.



Can anyone suggest me the settings in this regard? Thank you

My problem is in tool height changes. Whenever the tool height is changed, the Z axis tool travel length is changes i.e increased or decreased. so the milling goes wrong. i.e, the tool cuts my work table. is the tool height is associated with motor tuning (i.e, steps/unit). . . Can any one plz help me in this regard?

Not sure what you are meaning here. Are you using more than one tool and the new tool cuts off on depth? If yes then you either need to set all your tools up in the tool table if they are preset in holders or you need to rezero the new tool when you place it in the collet.

also I have an external ESTOP button which is connected to the PC through USB. This button is just an NO switch connected to a board and it'l be activated when pressing and triggers the space key in my computer so that the ESTOP will be activated in the controller through MACH3. What I need in this setup is, I want to stop the spindle when the ESTOP is activated. I tried the settings in mach3 general config. But no use.

First thing to say is USB is not the safest way to connect an E-Stop but thats up to you.
If Mach is in E-Stop the spindle should stop, assuming of course the spindle is being controlled from Mach, so not sure where your problem lies. Maybe I am just not understanding what you are meaning.

And my milling works properly when I setup the motor inputs under ports&pins option as Active high (direction input). I connected three limit switches for three axis but i works correctly when the direction input are setted as Active low. If direction input are stated as active high, then the machine moves reversely while homing (ref all home) I cant link these two conflicts and resolve. I want my machine and limit switches to work with active high config.

Config menu then Homing and Limits, you can tell Mach which way to home (Negative or positive) from there.
Hood

Thank you. I'l checkout everything again

I have more question. Please suggest in this regard

Can I home all axes when g540 profile is loaded in mach3? ie., I want to home all axes automatically without clicking ref all home buttom when mach3 is opened? Is it possible? please suggest. Thank you

You need to press Reset before you can do anything, that is a safety measure and really shouldnt be interfered with. It could be possible to get the RefAll to work automatically after the reset is pressed but again it has safety implications as it may not be expected that that will happen. I really dont see why you would want to have it that way as clicking a button is in my mind not a huge problem but you may have your reasons. It could be accomplished in several ways but all would have their drawbacks  and likely the best one would be to alter the Reset button so that it becomes a VB button and after it does the Reset it will then reference the machine from that button code.
Hood

Mr.Hood, your replies sounds better for me to learn about CNC. Thank You.
I have one more question which is, How to set make the machine to move to origin position automatically? am using three limit switches to home the axes. But my home position and origin position are different. Home position and origin position are diagonal. I want to move the axes to origin position fro home position. Is it possible to set offsets to function automatically? Please suggest. Thank you

If I understand what you are wanting you would need to alter the VB script in the RefAll button so that after it moves home on all axes it will then move to the position you wish.
Hood