📷 IMAGE AREA — After a tool breakage: noting the stopped line/tool on the panel and resuming with Program Restart
Recommended size: 1200×630 px (16:9, hero) · WebP/JPG · <150 KB · filename: mitsubishi-m70-tool-breakage-restart.webp · alt: Mitsubishi M70 resuming the program after a tool breakage with Program Restart
After a tool breakage, the operation is not just fitting a new tool. From the panel, the operator must check where the program stopped, which tool is active, the new tool’s offset values, and whether the program will continue from the start or with a restart. The M70 Program Restart document states that the restart function can be used to resume an interrupted program in cases like tool wear and tool breakage.
1. The first action when a tool breaks
When a tool breaks: the operator may notice it and press FEED HOLD, the machine may raise a load/tool-check alarm, the tool may jam inside the part, the program may be stopped with RESET, or in an emergency Emergency Stop may be used. In a normal, controllable situation FEED HOLD is used first; if there is still danger to the tool/part, EMERGENCY STOP can be used. After the machine stops, the active program line and tool info must be noted before giving RESET.
2. Information to record on the panel
Before changing the tool, note: the active program number, the stopped N line, the active tool number, the H number used, the D number used, the spindle speed, the G54–G59 coordinate system, the G41/G42 state, the G43 tool length compensation and, if any, the active canned-cycle type. Example: Program O1200, stopped line N450, Tool T6, length offset H6, radius offset D6, workpiece zero G54. This information ensures the correct tool and offset are used during the restart.
3. If the broken tool is inside the part
When a tool breaks, a broken tip may be left inside the part; in that case the program is not continued. First stop the spindle, check the machine has fully stopped, move the tool away from the part safely, check whether a broken tip is left in the part, inspect the tool holder and the pull stud, and check that the part/clamping has not moved. Pulling the tool straight up at rapid is not always safe; if the broken tool is jammed in the part, expert intervention is needed.
4. Replacing the broken tool
After the machine is brought to a safe state, the tool can be changed. General sequence: (1) Move the tool to a safe Z position. (2) Switch to MDI mode. (3) Remove the broken tool from the magazine or replace it with a new tool. (4) Check that the new tool is registered to the correct tool number. (5) Verify the active tool and magazine info. If the magazine was left mid-change, the ATC recovery procedure must be applied.
5. Checking the new tool’s length offset (H)
Even if the new tool is the same type and same nominal length, its real length may differ. So for the new tool, check the Length Geometry, Length Wear and H offset number. For example T6 → H6; after the new tool is measured, the H6 Geometry value is updated, and the Wear value left from the old tool is checked separately.
6. What to do with the old Wear value?
The broken/worn tool may have had a Wear correction (e.g. H6 Length Wear −0.080, D6 Radius Wear +0.020). When a new tool is fitted, these values must not be assumed automatically correct. General approach: note the old Wear value, measure the new tool’s Geometry, zero the Wear field or edit it per the production procedure, and make a small correction after the first measurement. If the old wear compensation is left on the new tool, the new tool may cut too much or too little.
7. If the tool diameter or radius changed (D)
The new tool’s real diameter may differ from the old one (e.g. old 10.000 mm, new 9.960 mm) — in that case the D offset value must be checked. If the program uses G41/G42, a wrong D value affects the pocket dimension, the outer contour dimension and the slot width. When a new tool is fitted, not only H but also the D compensation used must be checked.
8. Should the program be run from the start?
Running from the start is more suitable when: the program is short, starting from the beginning is safe, the machined surface can be recut, it is not clear where the program stopped, the part/zeros changed, or the restart point is not safe. Program Restart can be used when: the program is very long, it is a mold/heavy CAM program, most of the program is complete, the part and coordinates have not changed, and the new tool and offsets are verified. The M70 Program Restart function is designed to resume the program from where it stopped, especially after a tool breakage, power failure or operator intervention.
9. Resuming with Type 1
If the program was reset but the program and file were not changed, Type 1 can be preferred. General sequence: MONITOR → RESEARCH → TYPE 1 → INPUT; then the “Restart search is completed” message is waited for. The control finds where the program stopped automatically.
10. MSTB History check
After the restart point is found, the MSTB HISTORY screen is opened; it shows the previously used M commands, S speeds, T tools and B auxiliary functions. After the new tool is fitted, the operator must check the correct tool, spindle speed, M3/M4 direction and M8 coolant command. The document states that seeing more than one tool or speed is normal and that only the values needed for the restart point should be selected.
11. The INPUT warning on MSTB History
When a command is selected on the MSTB History screen and INPUT is given, the command can run immediately: M3 → the spindle may start turning, M8 → the coolant may turn on, S2500 → the spindle speed may be prepared. So before giving INPUT, check that the door is closed, the tool is in a safe position, the correct tool is in the spindle, and the correct speed/direction is selected.
12. When is Type 2 needed?
If Type 1 is not suitable or the operator wants to return to the start of a specific operation, Type 2 can be used: the program is selected, the line/block is set, the restart search is done relative to that point. But after a tool breakage, starting from the exact breakage line is not always correct. For example if the breakage was on N450 G1 Z-20. F150, instead of starting directly from N450, an earlier safe line containing the tool change and preparation commands is preferred:
N400 T6 M6
N410 G54 G90
N420 S2500 M3
N430 G0 X... Y...
N440 G43 H6 Z50.
N445 M8
N450 G1 Z-20. F150This way the tool, speed, zero and offset commands are re-applied in the correct order.
13. Re-machining the same hole or operation
If the breakage occurred in a drilling cycle, the state of the half-finished hole must be checked. For example if the tool broke during G83 Z-40. R2. Q5. F120.: the real depth of the hole may be unknown, the broken tip may be inside, and the new tool may be damaged approaching the old hole at rapid. In that case, instead of just restarting the G83 line, the hole state, the broken tip, the Q peck amount and the R level must be checked; if needed, the operation is re-run from a safe start point.
14. Care on contours using G41 and G42
If the breakage occurred while cutter radius compensation was on, do not start directly from the middle of the contour. In the example, if the tool broke on N120, starting directly from N120 can prevent the compensation vector from forming correctly; a safer start is N100 or the line with the safe lead-in move of compensation.
N100 G41 D6 X0. Y0.
N110 G1 X100.
N120 Y50.
N130 G40 X110.The Mitsubishi programming manual states that cutter radius compensation is started with G41/G42 and the D command and cancelled with G40.
15. Checking the G43 tool length compensation
After the new tool is fitted, make sure the correct H number is used in the program. Correct: T6 M6 → G43 H6 Z50.. Wrong: T6 M6 → G43 H5 Z50. — using the wrong H value while T6 is loaded can cause a serious Z-axis error. G43, G44 and G43.1 are in the same compensation group; G49 cancels these tool length compensations.
16. If the compensation was changed while the program was running
After the new tool is fitted, the H or D compensation may have been changed during the program stop. The Mitsubishi programming manual states that if the compensation amount is changed during continuous operation, a Single Block stop or Feed Hold, the new value may take effect in the next block. So: check from which block the compensation change takes effect, select a safe earlier block instead of restarting the block where the breakage occurred, and do not make large corrections.
17. If tool life management is used
If tool life management is active on the machine, the state of the broken tool must be updated on the tool management screen. Depending on the machine, you can: take the tool out of use, select a spare tool, reset the usage counter, update the tool group, enter the new tool’s H and D info. The Mitsubishi programming manual explains that the tool group, tool number, tool life and offset info can be managed by the control.
18. Final check before resuming the program
- Is the correct tool in the spindle, is the active tool number correct?
- Are the H and D compensations correct, were the Wear values checked?
- Is G54–G59 correct, are the spindle speed and direction correct, is the coolant on?
- Is a broken tool left inside the part, is the start line safe?
If any of these checks is uncertain, the program must not be continued.
19. Short application: resuming with Type 1
(1) Stop the program when the tool breaks. (2) Note the program, line, tool, H and D info. (3) Check the broken tool and part. (4) Fit the new tool. (5) Set the new tool’s Geometry and Wear values. (6) Open MONITOR. (7) Select RESEARCH. (8) Select TYPE 1. (9) Start the search with INPUT. (10) Wait for the “Restart search is completed” message. (11) Open MSTB HISTORY. (12) Check the correct tool, speed, M3/M4 and M8. (13) Move the tool to a safe position. (14) Start the restart move with low override.
20. Short application: returning to a safe operation start (Type 2)
(1) Check the new tool’s H and D values. (2) Find the operation start of the broken tool in the program. (3) Determine the tool-call line. (4) Check the G54, G90, G43 and spindle commands. (5) If G41/G42 exists, start from the compensation lead-in line. (6) Select a safe start line with Type 2. (7) Complete the restart search. (8) Watch the first moves with low override.
In short: when a tool breaks, record the stopped line/tool/H/D info on the panel; check the new tool’s H and D offsets (and the old Wear); decide whether to continue from the start or with a restart; select Type 1/Type 2; verify the correct tool/speed/direction/coolant with MSTB History; and with G41/G42 and G43 active, start from a safe preparation line instead of the exact breakage line.
📷 IMAGE AREA — Selecting the correct T/S/M on the MSTB History screen and starting from a safe preparation block instead of the exact breakage line
Recommended size: 1200×675 px (16:9) · WebP/JPG · <150 KB · filename: mitsubishi-m70-mstb-history-restart-line.webp · alt: Mitsubishi M70 MSTB history tool selection and safe restart line