Mitsubishi M70/M700 Training Lesson 1: Introduction to Program Management

📷 IMAGE AREA — Mitsubishi M70 operator panel and program list screen
Suggested alt text: Mitsubishi M70 CNC control operator panel and program management screen

In this first lesson we will not yet open or run a program. First we learn what a CNC program is on the Mitsubishi M70 control, where it is stored, and which basic concepts we will meet on screen. The aim is to keep the operations in the following lessons from getting confused.

1. What is a CNC program?

A CNC program is the full set of commands that tell the machine which operations to perform and in what order. A program generally contains motion commands, tool-call commands, spindle speed commands, feed values, coolant commands, workpiece-zero selection and program stop/end commands. The Mitsubishi M70 control executes programs by reading them line by line.

O1000
G21 G17 G90
G54
T1 M6
S1500 M3
G0 X0 Y0
G0 Z5.
G1 Z-2. F100
M30

Each line here makes the machine perform a separate operation.

2. The difference between program, line (block) and command

The three concepts beginners confuse most: Program is the full set of operations the machine will perform (e.g. O1000, the program number). Line (block) is each operation line in the program (e.g. G0 X100. Y50. is a single block). Command is the G, X, Y, Z, F, S, M, T expressions inside a line. For example in G1 X50. F200, G1 is cutting feed, X50. is the target position on X, F200 is the feed rate. According to the Mitsubishi programming manual, a program consists of multiple lines and the end of each line is separated by an EOB (end-of-block) mark.

3. The program number (O number)

Each program has a program number so it can be distinguished from the others, and it usually starts with O: O1000, O2000, O3500. The first character is a capital letter O; it must not be confused with the digit zero. For example O1250 is program number 1250. The Mitsubishi 700/70 programming manual states that the program number must be given at the start of the program on an independent line.

4. The N number (line/sequence number)

Some lines in the program can be given an N number (e.g. N10 G0 X0 Y0, N20 G1 Z-5. F100, N30 G0 Z100.). N numbers are not always mandatory for the program to run; but they are useful for finding a wanted line, seeing where the program stopped, restarting from a specific block, easily locating a faulty line and doing a Program Restart. In Program Restart Type 2 the user can manually specify the program number, line number or block number; so orderly N-number use makes restart operations easier.

5. Where are programs stored on the M70?

A CNC program does not always have to be in the same place. On the M70 control a program can generally be in one of four areas.

5.1 NC memory

NC memory is the control unit’s own internal memory (like a computer’s internal disk). Programs here can be selected directly, edited, deleted, copied and run in MEMORY/AUTO mode. Most daily-used programs are kept here. Advantage: no USB, card or computer connection is needed while the program runs. Caution: its capacity is limited; very large mold programs may not fit.

5.2 CF card / IC card

Some M70 panels have a CF or IC card slot. These cards are used to back up a program, transfer a program to the machine, copy an NC-memory program to the card, store large programs externally and (if the machine supports it) run the program from the card. Before using the card, make sure the control sees it; do not remove the card during file reading or program execution.

5.3 USB memory

Some M70 panels have a direct USB port; on others it may have been added later by the machine builder. USB is generally used to load a program, back it up, move it to another machine and transfer a PC-prepared program to the CNC. But there is an important distinction: not every M70 machine runs the program on the USB directly. On some machines USB is only for file transfer; in that case the program is first copied to NC memory and then run from memory. This depends on the builder’s panel and PLC setup.

5.4 Computer connection (RS-232 / Ethernet / DNC)

Programs can also be sent from a computer (RS-232 serial, Ethernet, host connection, DNC software). Method 1 – transfer to NC memory: the program is sent from the PC to the CNC, then selected from memory, AUTO/MEMORY is opened and it runs with CYCLE START; the PC connection is not needed while running. Method 2 – run in DNC/TAPE mode: the program is sent line by line from the PC without being fully loaded into memory; used for very large programs, mold machining and programs that do not fit in memory. The PC connection must not be broken while DNC runs.

6. Why does the program’s location matter?

Because calling and running the program changes according to where it is.

For example, when a program in NC memory is selected, no USB connection is needed; but in a program running via DNC, if the computer or communication is lost the program may not be able to continue.

7. Basic operating modes

Key and mode names may vary by machine, but generally you meet these modes. EDIT mode: for creating or changing a program (opening a new program, writing/changing a line, deleting a program, changing the program number). MEMORY / AUTO mode: runs the program in NC memory automatically; the logic is the same — the program is selected, brought to the start, CYCLE START is given, and it runs automatically. MDI mode: the area where short commands are typed by hand and run once (e.g. S1000 M3 to rotate the spindle); not used to run a long part program. TAPE / DNC mode: for running the program from an external device or computer (RS-232, DNC software, external file transfer); may not be active on every machine. The Mitsubishi handbook notes that the automatic operation modes include MEMORY, TAPE and MDI; if the wrong mode is selected or more than one mode is active at once, automatic start cannot be performed.

8. Screen sections you will meet often

Screen names may vary by builder, but generally: MONITOR — for watching the running program (active program, running block, axis positions, spindle speed, feed, active tool, M/S/T commands). EDIT — the program writing and editing screen (we will cover creating a new program from this section in the next lesson). PROGRAM / FILE — the program list and files (program number, file name, size, device, date). SETUP — machine settings and some I/O settings; in this training used only when program transfer is needed. The Program Restart source shows that to re-search an interrupted program, MONITOR is used first and then the RESEARCH menu.

9. RESET and FEED HOLD are not the same

This distinction is very important for later lessons. FEED HOLD pauses the program temporarily: the program stops, the active program is not lost, and it resumes when CYCLE START is given. RESET can cancel program execution: the program may return to the start, active commands may change, direct continuation from where it stopped may not be possible and a Program Restart may be needed. The Mitsubishi handbook states that when a reset signal is given, the program execution position returns to the start of the program and automatic operation must be run from the beginning. In short: FEED HOLD to pause, RESET to cancel. But behavior can differ according to the builder’s PLC implementation.

10. The basic keys that start and stop the program

CYCLE START starts the selected program or resumes a temporarily stopped program. FEED HOLD temporarily stops program motion. RESET cancels the program or resets the control. EMERGENCY STOP stops the machine in a real danger and is not a normal program-stop method. The Program Restart source explains that programs stopped by a power failure, Emergency Stop, an accidental Reset or user intervention can be restarted with the Restart function.

11. The basic running sequence for beginners

The general logic of running a program: find the program → select the correct program → check the program content → bring the program to the start → select the correct operating mode → lower the feed and rapid override → give CYCLE START → watch the program on screen. If the program is on USB, the USB device is selected first; if it is in NC memory, it is selected directly from the memory program list; if it will come from a PC via DNC, TAPE or DNC mode is used.

12. Lesson summary

In this lesson we learned: a CNC program is the machine’s operating instruction; programs are defined by an O number; N numbers indicate the lines in the program; a program can be in NC memory, on a CF card, on USB or on a computer; the calling and running method changes by location; EDIT mode is for writing a program, MEMORY/AUTO mode runs the program in memory, TAPE/DNC mode runs an external program; FEED HOLD pauses temporarily, RESET can cancel, and CYCLE START starts or resumes.

Next lesson — Lesson 2: Creating a new program on the Mitsubishi M70 and starting to write a program (switching to EDIT mode, typing a new program number, creating a program, entering a line, using EOB, saving the program and the “program already exists” warning).

📷 IMAGE AREA — M70 operating modes (EDIT / MEMORY / MDI / DNC) and the CYCLE START, FEED HOLD, RESET keys
Suggested alt text: Mitsubishi M70 operating modes and cycle start feed hold reset keys