Mitsubishi CNC | M70-M80 Series | Axis Reference


CNC machines are machines that operate according to coordinate systems, and these settings are done by the manufacturer (with adjust of axis reference) before leaving the factory and the limits can be specified, etc.

However, in order to prevent damage during transportation of the machine, it is often necessary for the technical service personnel who perform machine installation to make Ref.Pos.

This process may not be necessary only in the initial installation, but may also have to be repeated in the case of removal of encoder, motor, bearing, encoder cable etc.

In this article, technical information will be given on how to do this.

Things to Know

  • This is a procedure that must be done with caution as it will set the limits of the machine, all preventive measures must be taken by authorized personnel.

  • Reference point identification is standard on Mitsubishi controls. However, the machine manufacturer can determine this by several different methods (dog type, dogless type, switch type, etc.). Only the manufacturer can know which method is used in your machine.

  • Reference points (motor zeroes) are usually defined at a distance of 2-3 mm from the limits. Therefore, the moving parts can hit the machine body without any warning because it cannot know the limits of a machine that is not set to reference. Therefore, when this is done, the current position of the machine axis must be continuously monitored.

  • The axis reset (reference point identification, motor zero reset) method described in this document is the standard procedure for Mitsubishi controlled machines. Manufacturers can develop and use their own methods without depending on this procedure. In such cases information on how to do this can be obtained from the manufacturer.

Once we have taken the above measures, we can start the axis zeroing process. In this article, it is explained how to “cancel” the current Ref.Pos to the machine and set it again. For a machine where Ref.Pos adjustment is not made, you will skip the “cancel” step and continue directly with the step of introducing zero position (B).

Set Axis Reference

Delete - Reset Axis Reference

This process is normally not used, but this document will explain for informational purposes. This procedure must also be known in order to readjust the axis zeros that are too close to the mechanical axis limit, because of miss-detected motor zeroes.
Clear axis reference:

  • Power On machine and NC.

  • Find parameter #2049 and write down its current value. What is important here is to note the axis value if you want to delete ref.pos. This value is usually 2, but the original value must be noted, as this value may vary from manufacturer to manufacturer.

Note: Here we enter “0” into the parameter for which axis you want to lose zero position. Make sure you select the correct axis you want to clear Ref.Pos before changing the parameter.

  • After the old value of #2049 is memorized, value 0 is entered and INPUT is executed.

  • The machine is switched off and on again, including the main switch. Machine may generate alarm.

  • #2049 is restored and the machine is switched off and on again incl. the main switch. Z70 alarm is generated when the machine is switched on. This is the alarm that says the axis is not set to Ref.Pos.

  • After this operation, the axis has forgotten the zero point and is now ready to redefine new reference point.

Define Axis Zero Position

Following steps is absolutely necessary in case of changing the encoder, motor or removing the motor from machine body.

Here’s how to do this step-by-step.

Mitsubishi CNC M70 and M80 series Axis Reference Set Page

Machine and NC is powered ON and MAINTE key is pressed.

1 – Here we see selected axis, make sure you select correct axis for your action.
2 – We see the current state of the selected axis. The text here may vary depending on current status of the machine and parameter #2049.
3 – This is the section where we will initialize our Ref.Pos setting.
4 – Here we activate our new Ref.Pos. This we do when we reached/moved to our dedicated position.
5 – With these buttons we select correct axis. Your selected axis is displayed at section (1).
6 – It´s also possible to select axis from here. Section (5) operation is more convenient.

Once we understand above section, we can start the process of zeroing.

  • First of all, axis is selected by buttons in section (5). If state section (2) for an axis appears with OK, it cannot be reset. ILLEGALITY indicates the use of the ABS Encoder and normally comes with Z70 alarm.
  • In window (3) – “1”is INPUT, and the axis is moved to the Ref.Pos in “Handle mode” with hand-wheel.

Note: The so-called zero point cannot be followed from the screen. Be sure you have documents or clearly marked positions identifying machine Ref.Pos.

Most machines are marked, and explained by the manufacturer in the machine’s Instruction Manual.

During this process, it´s needed to take precautions of safety.

  • After reaching the Ref.position required, put “1” In Window (4) and press INPUT. Now the process has been completed and the axis identified it´s zero-pos.
  • Now slowly move the axis in any direction by hand-wheel, axis will stop and section (2) will display “OK”. (Direction depends on MTB)
  • The operation is now completed and axis zero is defined and set.
  • In some cases, power off/on might be necessary one more time.

Important Note: Changing the axis zero-pos. cause’s machine geometry to change. Therefore, once you have made this setting, it is absolutely necessary to re-adjust settings such as tool changing position, pallet changing position, tool zeroes, measuring probe calibrations. Failure to do so may cause the machine to crash and cause injury. This process should be done by the authorized personnel.