📷 IMAGE AREA — Measuring X–Y squareness on an M70 vertical machining center with a square master and dial indicator
Recommended size: 1200×630 px (16:9, hero) · WebP/JPG · <150 KB · filename: mitsubishi-m70-squareness-measurement.webp · alt: Mitsubishi M70 CNC squareness measurement with square master and dial indicator
On CNC vertical machining centers, the X and Y axes moving exactly perpendicular to each other is important for the dimensional and geometric accuracy of machined parts. When the squareness between the axes is off, square pockets, perpendicular faces and hole centers can deviate from the programmed position. The Pitch Error Compensation feature on the Mitsubishi M70 control lets measured and consistently repeating axis errors be compensated at set intervals. But this does not replace mechanical repair: the machine’s mechanical condition must be checked first, and then only the repeatable and measurable residual errors should be corrected with parameters.
When is squareness compensation done?
Squareness adjustment may generally be needed: during the machine’s build and precision-setup phase; after replacing a linear rail or linear carriage; after a serious crash/impact; when a regular and repeatable squareness error is seen between the X and Y axes; when a constant same-direction dimensional deviation occurs in square, pocket and hole positions; when a small but stable error remains after mechanical adjustments. Errors that change randomly, behave differently at different points, or give a different result on each measurement must not be corrected directly with a parameter. In such a case the rails, ball screws, bearings, couplings, measuring system and mechanical connections must be checked.
Required measuring equipment
For a sound squareness check, precise measuring equipment must be used: a precision square master or square plate; a dial indicator with about 1–2 micron resolution; a solid magnetic stand; a cleaned machine table; a table to record the measurement results. If the square master’s own squareness error is unknown, the measurement may not be reliable; the accuracy of the measuring equipment directly affects the adjustment result you can achieve.
What to do before starting
- The machine’s current parameter and system backups must be taken.
- Tools, the vise and any parts that could obstruct measurement must be removed from the table.
- The contact surfaces of the table and square master must be cleaned.
- The machine must be brought to operating temperature.
- The X and Y axes must be sent to the reference position.
- The emergency stop and axis-motion controls must be verified to work.
- The current parameter values must be recorded separately before any change.
How is the squareness between X and Y measured?
On vertical machining centers the first check is usually between the X and Y axes. 1) Placing the square master: the square master is placed on the cleaned table; one of its faces is aligned as parallel as possible to the X-axis motion. This first parallelism setup is very important — if the master is not parallel to X, the value seen on Y may not show the real squareness error. 2) Zeroing the X direction: the dial indicator is mounted in the spindle or a suitable fixed fixture and touched to the master’s X-direction face; moving along X, the face is set as close to zero as possible, and after the master is fixed its position is not changed. 3) Measuring the Y axis: the indicator is moved to the master’s Y-direction face, the Y axis is moved at set intervals (e.g. every 20 mm) and the value at each position is recorded.
| Measurement point | Y-axis position | Indicator value |
|---|---|---|
| 1 | Start point | Measured value |
| 2 | 20 mm | Measured value |
| 3 | 40 mm | Measured value |
| 4 | 60 mm | Measured value |
| … | … | … |
How many mm after the machine reference point the measurement started must also be recorded. 4) Evaluating the error: if the error increases regularly as the Y axis advances, there may be an angular squareness deviation between the X and Y axes. If a value near zero at the start increases regularly along Y, the error may be stable and repeatable; but the same measurement must be repeated several times and the results verified to be similar.
Which axis should be compensated?
The reference axis in the measurement and the axis where the motion error is seen must be distinguished. Example: motion is along the Y axis, and a progressively increasing deviation is measured in the X direction; small corrections are applied to the X axis depending on the Y-axis motion. The aim is not to physically fix the mechanically faulty axis with a parameter; the control applies small position corrections to the other axis against the measured deviation. If which axis is taken as reference and which axis is compensated are chosen wrong, the existing error can grow; the decision must be made only from precise, repeated measurements.
Entering the M70 squareness compensation screen
General sequence to reach the parameter screen: on the control, enter the MAINTE screen → select MAINTE again from the submenu → select PSSWD INPUT → enter the authorized maintenance password and confirm with INPUT → select PARAM from the submenu → go to the Er Comp. Param screen where the error compensation parameters are → reach the parameter group around #4000. The appearance of the screen menus and the password authorities can differ by the machine’s builder settings.
Squareness compensation parameters
| Parameter | Function |
|---|---|
| #4000 | Selection of the compensation method |
| #4001 | Axis whose motion or position will be corrected |
| #4002 | Reference axis |
| #4003 | Number where the compensation data will start |
| #4004 | Start point of the compensation application |
| #4005 | End point of the compensation application |
| #4006 | Measurement or compensation factor |
| #4007 | Distance between measurement points |
The compensation values are usually entered into the data fields from #4101 onward. The last data number used varies depending on the measurement distance and the selected interval.
How the parameters work
When the measurement interval is set to 20 mm, the control uses the relevant compensation data for each 20 mm motion zone of the selected axis: the first data represents the correction in the start zone, the second the correction at the next measurement point, and the following data the corrections continuing along the axis. The values to be entered must not be copied from another machine — each machine’s geometric error is different; the compensation table must be prepared only from measurements made on that machine.
Entering the compensation values
After the measurement results are collected: the start/end points of the measurement are set → the measurement interval is entered into the parameter → the axis to be corrected is selected → the reference axis is selected → the compensation data start number is set → the correction amount for each measurement point is entered into the data fields in order → the same measurement is repeated after each change → the values are corrected in small steps according to the indicator results → the squareness result is re-checked along the whole travel. The sign of the values is extremely important — positive/negative values entered in the wrong direction can increase the error rather than reduce it; very small corrections must be made first and the axis behavior measured.
Using a measurement program
The axis can be moved at fixed intervals with a short program (e.g. advancing the Y axis in 20 mm steps and recording the indicator value at each point). But before using a program: the travel limits must be checked, the contact between master and indicator must be safe, the feed must be kept low, Single Block must be used, and the first moves must be watched with low override. Instead of a program, the axis can also be moved manually at the set intervals.
📷 IMAGE AREA — M70 Er Comp. Param (#4000) screen and Drive Monitor → Mach err comp val line
Recommended size: 1200×675 px (16:9) · WebP/JPG · <150 KB · filename: mitsubishi-m70-er-comp-param-screen.webp · alt: Mitsubishi M70 error compensation parameter screen 4000
How is the applied compensation checked?
After the parameter entry, whether the control applies the correction can be checked from the drive monitor screen. General menu sequence: DIAGNOS → DRIVE MONITOR → SERVO UNIT. Using the page keys, the screen with the Mach err comp val line is opened; this line shows the machine error compensation amount the control applies as the axis moves. If the value keeps showing 0, there may be no active compensation on that axis; if the value changes as the axis moves, the control may be using the defined table. The value changing on screen alone does not mean the setup is correct — the result must be re-measured with the indicator.
Checks to do after the adjustment
When the Pitch Error Compensation values are changed, the machine’s real position in certain regions can also change. So the following must be re-checked: the tool change position, the tool magazine approach position, the pallet change position, the second and auxiliary reference points, the tool length values, the workpiece zeros, the touch probe calibration, the tool measuring sensor position, the soft limits, and the fixture/attachment approach distances. After the checks are complete, a trial must be done with low feed and low rapid moves.
Common mistakes
- Using another machine’s values: each machine’s geometric deviation is different; example values must not be entered directly into another machine.
- Hiding a mechanical fault with a parameter: backlash, a loose rail, a damaged bearing, a ball-screw problem or a non-repeating position error must not be fixed with compensation.
- Not aligning the master parallel correctly: if the square master’s first face is not parallel to X, the Y-direction measurement comes out wrong.
- Deciding from a single measurement: the measurement must be repeated at least a few times and the error must recur in the same regions.
- Entering large values at once: the values must be changed in small steps and the measurement repeated after each change.
- Not checking reference points after the adjustment: a parameter change can affect critical positions like tool change, probe or workpiece zero.
Conclusion
Mitsubishi M70 squareness compensation helps reduce measurable and repeatable geometric deviations between the X and Y axes. A successful result requires precise measuring equipment, correct axis selection, a suitable measurement interval and controlled parameter editing. This operation is not just about entering values; measuring, evaluating, making small corrections and re-measuring must be carried out together. On a machine with a mechanical problem, the mechanical issue must be fixed first, and parameter compensation applied as the final fine adjustment.