📷 IMAGE AREA — M70 tool magazine, ATC change arm and the active/standby tool screen
Recommended size: 1200×630 px (16:9, hero) · WebP/JPG · <150 KB · filename: mitsubishi-m70-tool-magazine-atc.webp · alt: Mitsubishi M70 tool magazine ATC change arm active standby tool
In this guide we cover tool calling, tool change with M6, active and standby tool information, tool magazine mix-ups and interrupted tool changes on the Mitsubishi M70 control. There is an important distinction: the M70 control manages the T command and the basic NC functions of a tool change; the magazine’s arm, pot, sensor, door and clamp sequence is mostly managed by the machine builder’s PLC program. So on two different machines using the same M70 control, the tool-change screen and recovery method may not be the same; the Mitsubishi programming manual also states that the tool builder’s instructions are the basis for machine-specific operations.
1. What is a tool magazine?
The tool magazine is the system where the cutting tools to be used on the machine are stored. Common types: umbrella type, chain type, drum type, arm-changer ATC (Automatic Tool Changer) and systems that take the tool directly with the spindle. In a tool change, generally: the wanted tool is prepared → the axes go to the tool-change position → the spindle stops and is oriented → the magazine/arm is positioned → the current tool is removed → the new tool is placed → the clamp signal is verified → automatic operation continues. The details of this sequence depend on the builder’s PLC design.
2. What is the T command for?
T is the tool-select command (e.g. T5 → selects tool number 5). But T5 does not immediately load the tool into the spindle on every machine; on most vertical machining centers T5 M6 is used (T5 selects, M6 starts the change). In the Mitsubishi programming manual T is defined as a separate tool function; the machine-side magazine and change operation of the tool number works together with the builder’s PLC scheme.
3. Are T and M6 written on the same line?
The common use is T5 M6. On some machines, for a faster cycle, the next tool can be prepared in advance: T5 M6 ... T8 — here T5 is loaded into the spindle, T8 can be prepared as the standby tool in the magazine, and it is changed on the next M6. On another machine, when T8 is written the magazine may not move immediately; the behavior depends on the PLC program. The presence of separate data fields for “active tool” and “standby tool” in the M700 Handbook shows that the control can track the active and the standby tool separately.
4. Active tool and standby tool
The active tool is the one currently in the spindle (e.g. ACTIVE TOOL: T5). The standby tool is the one prepared for the next change (e.g. STANDBY TOOL: T8). The tool screen may show Active Tool, Standby Tool, Next Tool, Spindle Tool, Magazine Tool, Tool Pot, Tool Number; the screen names vary by builder.
5. Is the tool number the same as the magazine pot?
Not always. Fixed-pot system: tool 5 is always kept in pot 5 of the magazine (T5 → Pot 5). Random-pot system: the control tracks in memory which pot a tool is in (e.g. T5 → Pot 18, T8 → Pot 4, T12 → Pot 27). In this system the operator must not confuse the tool number with the pot number; if a tool is physically moved to another pot and the control table is not updated, the system can call the wrong tool.
6. Tool-change position (G30.1–G30.6)
When changing a tool, the axes may need to go to a safe position. The M70/M700 programming manual has commands to return to a special tool-change position from G30.1 to G30.6 (e.g. G30.1; or G30.2;). These positions and the axis-move order can be set from settings related to #8206 TOOL CHG. But not every machine program uses G30.1; on some machines M6 positions the axes automatically, on some the programmer first goes to a safe Z with G53, on some a builder-special M code is used or the PLC does all the positioning. So a tool-change line taken from another machine must not be copied directly.
7. Changing a tool with MDI
A tool change can be done manually from the MDI screen: (1) Check the machine is not running. (2) Verify the axes are safe. (3) Switch to MDI mode. (4) Type T5 M6. (5) Complete the line with INPUT/EOB. (6) Give CYCLE START. (7) Watch the tool change. (8) Check the active tool info. On some machines tool preparation is needed first, then M6 (T5; then M6;). The machine’s previously used standard sequence must be taken as the basis.
8. What to check before a tool change
Before giving M6: the spindle must be stopped, the tool-change area clear, the Z axis at a safe position, the magazine cover closed, the tool arm at its home position, the tool clamp signal normal, the air pressure sufficient, Emergency Stop not active, no alarm present and the correct tool number written. If the machine does not detect one of these conditions, it may not start the tool change.
9. How do you tell a tool change was interrupted?
Signs: the tool-change arm is left in the middle; the magazine looks half-indexed; the tool does not seat fully in the spindle; the pot is left down/up; the spindle does not complete the clamp; the program waits on the M6 line; a PLC/user alarm appears; the active tool info is not updated; Cycle Start is not accepted. In this case M6, RESET or CYCLE START must not be given repeatedly.
10. First actions if the tool change is interrupted
Stop automatic execution with FEED HOLD or RESET if needed → check that all motion has stopped → note the alarm message and code → look at the physical position of the arm/magazine/pot → check whether there is a tool in the spindle → note the active and standby tool numbers → check the air pressure → check the door/magazine sensor messages → use the builder’s ATC Recovery screen or manual recovery procedure → call technical service if the procedure is unknown. The tool arm, pot or spindle must not be touched by hand.
11. Does RESET fix the tool change?
Not always. RESET can cancel the M6 command, stop the program and clear the alarm message; but the mechanical system can be left with the arm in the middle, the pot down, the tool half-clamped and the magazine half-indexed. So giving M6 again right after RESET can cause a collision or a jam of the arm mechanism. The real mechanical position of the tool changer must be determined first.
12. Why don’t tool-change alarms fully appear in the Mitsubishi list?
Most tool magazine alarms are not standard Mitsubishi alarms but the machine builder’s PLC alarms; they usually appear as a U group or a builder-special message. Example messages: ATC ARM NOT HOME, TOOL POT NOT UP, TOOL POT NOT DOWN, SPINDLE ORIENTATION INCOMPLETE, TOOL CLAMP ERROR, TOOL UNCLAMP ERROR, MAGAZINE POSITION ERROR, AIR PRESSURE LOW, TOOL NUMBER MISMATCH. The exact solution for these is in the machine builder’s alarm book. The M700 Handbook classifies user PLC alarms as a separate group.
13. Common tool-change problems
A. Spindle orientation not complete: the spindle must stop at a specific angle for the change; a spindle orientation alarm, waiting on M6, the arm not moving. Check whether the spindle has fully stopped, whether there is a spindle alarm, whether the orientation sensor reads (encoder/drive/parameter work is a technical-service job). B. Tool clamp not complete: the new tool entered but the clamp signal did not come — dirty taper, holder not fully seated, low air pressure, unsuitable pull stud, clamp sensor not signaling. The operator only does basic checks like visible dirt, wrong holder and air pressure. C. Tool unclamp not complete: the old tool did not come out — no unclamp signal, low air, tool jammed in the taper, damaged pull stud. Trying to knock the tool out with a hammer is not correct. D. Magazine cannot find the right pot: magazine position error, pot number mismatch — magazine sensor, loss of the reference pot, table confusion, wrong pot number, mechanical jam. The pot number must not be changed manually. E. Pot does not go up/down: pot sensor, air, solenoid valve, mechanical jam, door/interlock. F. ATC arm not at HOME: if a new M6 is given, the arm can move in the wrong direction; the builder’s ATC Recovery screen may have commands like ARM CW/CCW/HOME, POT UP/DOWN, TOOL CLAMP/UNCLAMP, MAGAZINE CW/CCW — these are not the same on every machine and can cause a collision if used in the wrong order.
14. How does a tool number mix-up occur?
A tool may have been removed from the magazine by hand, fitted to a different pot, the random magazine table not updated, the tool change interrupted, the spindle tool changed by hand, the control turned off or data lost during an alarm, or the pot number confused with the tool number. Sign: the screen shows T5, but T8 is actually in the spindle. In this case the program must not be run.
15. Verifying the active tool info
After a tool change, three pieces of information must be compared: the tool the program wants, the active tool shown on screen and the real tool in the spindle. Example: Program T5 M6, Screen Active Tool T5, Spindle physically T5 — if all three are the same, the tool info is consistent. If one differs: AUTO operation is stopped, the tool table is examined, the builder’s recovery procedure is applied, and service is called if needed.
16. If the spindle tool is removed by hand
On some machines a tool may be removed by hand for maintenance/fault; in that case the control may still think the old tool is in the spindle (Control: Spindle Tool T5, Reality: spindle empty). On a new M6, the control may not search for T5 in the magazine or may make a wrong pot move. If the spindle tool was removed by hand: the tool management screen must be updated, the Spindle Tool info corrected, the pot-tool matches checked and the builder’s procedure used. This operation must not be done by guessing.
17. Tool table / magazine screen
| Field | Function |
|---|---|
| Tool No. | Tool number |
| Pot No. | Magazine pot |
| Spindle Tool | Tool in the spindle |
| Standby Tool | Standby tool |
| Next Tool | Next tool |
| Length Offset | Length offset number/value |
| Radius Offset | Radius offset number/value |
| Tool Life | Tool life |
| Usage Count | Usage count |
| Remaining Life | Remaining life |
The M700 Handbook has separate PLC fields for usage time, life, usage count, length offset and wear data for the active and standby tool. This information can be shown to the operator if the screen is prepared by the machine builder.
18. Tool life management
On the Mitsubishi control, tool life can be tracked by usage time, tool-clamp count and use count. Tool groups and life data can also be defined from within the program with G10/G11 commands; the manual describes separate input formats for tool group, number, life, length and radius offset data. But this feature may not be active on every machine. What matters for the operator: heed the tool-life-expired warning, check that the spare tool is defined correctly, reset the life counter per the builder’s procedure when a new tool is fitted, and check the old wear value.
19. Checking H and D after a tool change
Even if the tool changed correctly, a collision can occur if the wrong compensation is used. For example T5 M6 → G43 H3 Z50. — T5 is called but H3 is used; it is technically programmable, but if the program scheme expects T5 to use H5, it can be an error. After a tool change, the T number, H number, D number, Geometry and Wear values must be checked.
20. Should the tool-changer parameters be changed? (#1327)
The M700 Handbook has the #1327 3D ATC type parameter for tool change and 3D drawing (0: one standby tool, 1: two standby tools, 2: no standby tool). But this is not a normal operator parameter for setting the physical ATC mechanism; it concerns how the tool change is shown in the 3D drawing. The following tool-changer values must not be changed by the operator: the tool-change position, the pot count, the arm rotation direction, the sensor inputs, the spindle orientation angle, the clamp/unclamp timings, the PLC constants and the magazine reference info. A wrong parameter can make the physical changer and the control screen work inconsistently.
21. Safe decision table when a tool change is interrupted
| Situation | Operator’s approach |
|---|---|
| M6 did not start | Check alarm, air, door and safety conditions |
| Magazine turns but does not stop | Stop the operation, call service |
| Arm left in the middle | Do not give a new M6, use the recovery procedure |
| Tool entered the spindle halfway | Do not command motion, have the clamp state checked |
| Screen and real tool differ | Do not run the program, correct the tool table |
| Pot left down | Do not move the axis, use the builder procedure |
| Spindle orientation alarm | Check the spindle alarm and orientation state |
| Low air pressure | Fix the air pressure, then reset in the builder order |
| Repeating ATC alarm | Call technical service |
22. Why can’t ATC recovery be fully described from the source?
The Mitsubishi sources explain the T command, the tool functions, the tool-change positions, the active/standby tool data and the PLC/alarm structure; but the manual recovery order of the physical changer belongs to the machine builder. For example on one machine the correct order may be POT DOWN → ARM 60° → UNCLAMP → ARM HOME, while on another it can be completely different. So it is not correct to give step-by-step arm-rotation or sensor-forcing instructions without the builder’s specific ATC Recovery manual.
23. Short application: normal tool-change check
(1) Stop the machine. (2) Switch to MDI mode. (3) Check the axes are safe. (4) Type T5 M6. (5) Confirm the command. (6) Give CYCLE START. (7) Watch the magazine and arm movement. (8) Check the active tool is T5. (9) Verify the real tool in the spindle is T5. (10) Check the H5 and D5 values.
24. Short application: the tool change was interrupted
(1) Do not give a new command. (2) Check the machine has fully stopped. (3) Note the alarm code. (4) Determine the tool in the spindle. (5) Record the active and standby tool info. (6) Look at the arm, pot and magazine position. (7) Check the air pressure. (8) Open the builder’s ATC Recovery screen. (9) Recover only in the builder’s order. (10) Compare the tool table with the real state. (11) Test the system with a dry tool change. (12) Report to service if the problem recurs.
In summary, in this guide we learned the difference between the T command and M6, the active/standby tool logic, that the tool number can differ from the magazine pot, the G30.1–G30.6 positions, changing a tool with MDI, recognizing an interrupted change, why ATC alarms mostly belong to the builder, comparing the tool table with reality, and why M6/RESET must not be given at random in an interrupted change.
📷 IMAGE AREA — The builder’s ATC Recovery screen (ARM CW/CCW, POT UP/DOWN, CLAMP/UNCLAMP) and the tool table
Recommended size: 1200×675 px (16:9) · WebP/JPG · <150 KB · filename: mitsubishi-m70-atc-recovery-screen.webp · alt: Mitsubishi M70 ATC recovery screen arm pot clamp unclamp and tool table