In this lesson we will find a program previously saved in NC memory and make it ready to run. At this stage we will not yet press CYCLE START; we will only call the program and check that it is the correct one.
1. What is NC memory?
NC memory is the Mitsubishi M70 control unit’s own internal memory. Programs saved here can be found from the program list, edited, selected, run in AUTO/MEMORY mode, backed up to another device and deleted when needed. For example the O1000 program we created in the previous lesson is in NC memory.
2. What does calling a program mean?
Calling a program means making a program in memory the active program. For example if memory contains O1000, O1001, O1200, O2000, selecting O1200 opens its content on screen. But seeing a program on screen and running it are not the same operation. The correct order: find the program → select it → check its content → reset it to the start → switch to the run mode → give CYCLE START.
3. First select the correct mode
To only view or edit a program, EDIT mode is generally used; to prepare it to run, MEMORY or AUTO mode is used. By builder you may see MEMORY, AUTO, MEM or AUTOMATIC on the panel; their basic logic is the same. The Mitsubishi M700 handbook states that the automatic operation modes include MEMORY, TAPE and MDI; if the automatic mode is not selected, the program cannot be started.
4. Opening the program list
General sequence: enter the EDIT or MONITOR section on the control screen → find the PROGRAM (or FILE / LIST) soft key at the bottom → open the program list. The programs in NC memory appear (e.g. O1000, O1001, O1200, O2000). On some M70 panels the file size, date, program description, memory used and the device the file is on may also appear next to the program number.
5. Check the device the programs are on
When you open the list, first look at which device is selected. If the device section shows MEM / MEMORY / NC MEMORY, the control unit’s internal memory is selected. If USB / IC CARD / CF CARD is shown, an external device may be selected. Since in this lesson we will call the program from NC memory, the device must be set to MEMORY.
6. Selecting the program from the list
If there are few programs, arrow keys can be used. For example to open O1000: open the list → use the up-down arrow keys to reach O1000 → check that the line is selected → press the appropriate select key. This key may be INPUT, SELECT, OPEN or FILE SET depending on the machine. When the program is selected, its content appears on screen:
O1000
N10 G21;
N20 G17 G90;
N30 G40 G49 G80;
N40 M30;7. Searching by typing the program number
If there are many programs in memory, searching with arrow keys takes time; in that case searching by program number is used. For example to find O1200: open the PROGRAM/EDIT screen → find the search field or SEARCH key → type O1200 → INPUT → the control finds O1200 and brings it to the screen. On some panels typing only 1200 is enough; but using the letter O when searching is clearer.
8. What does TOP SEARCH mean?
A frequently seen expression on M70 screens, TOP SEARCH is used to find the start section of the program or to search from the beginning of the program. It is used especially when you are stuck in the middle of a program, when the cursor is on a lower line, when you want to run the program from the start and during Program Restart Type 2. The Program Restart source explains that in Type 2 the program is selected with Top Search and then the program name is transferred to the relevant field using File Set.
9. How do we know the program is selected?
After the program is called: Program number — the correct O number must appear at the top of the screen or on the first line (e.g. O1200). Program content — the lines of the selected program must appear on screen. Active program field — the active program number can be seen on the MONITOR screen. Cursor position — a cursor appears at the start of the program or on the line you selected. Just moving onto the O1200 line in the list does not activate the program on every panel; the selection operation (INPUT, SELECT, OPEN or FILE SET) must be completed.
10. Resetting the program to the start before running
If a program has been run or edited before, the cursor may have been left in the middle. For example below the cursor may be at N50 — in that case CYCLE START must not be given directly; the program must be reset to the start.
O1000
N10 G21;
N20 G17 G90;
N30 T1 M6;
N40 S1500 M3;
N50 G0 X0 Y0; <-- Cursor may be here
N60 M30;General method: call the correct program → press TOP SEARCH → wait for the return to the program start → check that the cursor is on the first line → re-verify the program number. When the program is reset to the start, the cursor is usually on O1000 or the program’s first executable line.
11. Resetting the program with RESET
On some M70 applications the RESET key can return the program’s execution position to the start. The M700 Handbook states that when a reset signal is entered, the program execution position returns to the program start and the operation must be run from the beginning. But relying only on RESET is not correct; after RESET check: is the correct program still active, is the cursor at the program start, is there an alarm on screen, is the operating mode correct, are the tool and spindle stopped? The safest method is to reselect the program and do TOP SEARCH after RESET.
12. The first line and the first motion line are not the same
The first line of the program is usually the program number (O1000); but the first line that starts machine motion may be lower down. In the example O1000 is the program number, N10–N50 are preparation commands, and N60 is the first axis move. Resetting the program to the start does not mean just going to the first motion line; the preparation commands at the start (unit, plane, coordinate system, tool, speed) must also be read. So in normal running the program must be started from the beginning.
O1000
N10 G21 G17 G90;
N20 G40 G49 G80;
N30 G54;
N40 T1 M6;
N50 S1500 M3;
N60 G0 X0 Y0;13. Checking that the program is correct
After calling the program, do not run it immediately; first check: program number (is O1000 correct), program start (is the cursor at the start), program end (is there M30 or a suitable end command), tool call (does T1 M6 call the correct tool), workpiece zero (does G54 select the correct coordinate system), spindle speed (is S1500 M3 suitable). If there is a subprogram call such as M98 P2000 in the program, is the called subprogram present in memory? The Mitsubishi programming manual states that if the searched subprogram number is not found, a program error occurs.
14. The difference between the active program and the program shown on screen
In some cases the operator may have opened a program on the EDIT screen, but another program may still be active in automatic operation. So check two places: the program number shown on the EDIT screen and the program number shown active on the MONITOR screen. They must be the same. For example if the EDIT screen shows O1200 and the MONITOR screen shows O1000, O1200 may not yet be selected active for automatic operation; reselect the program and apply the INPUT/SELECT/FILE SET operation.
15. Preparing the program to be run
Once the program is found and checked, the preparation sequence: (1) Select the correct O program. (2) Check its content. (3) Reset to the start with TOP SEARCH. (4) Switch to the MONITOR screen. (5) Check the active program number. (6) Select MEMORY/AUTO mode. (7) Lower the feed override. (8) Lower Rapid Override. (9) Turn on Single Block if needed. (10) Do not give CYCLE START yet. Running the program is covered in the next lesson.
16. What to do if the program cannot be found
- Wrong device may be selected: USB/CF card may be selected instead of NC memory; set the device to MEMORY.
- The letter O may be entered wrong:
01000may have been typed instead of O1000; make sure the first character is the letter O. - The program may have been deleted: if it is not in the list, it may have been deleted earlier.
- It may be saved under another number: check similar numbers (O1000, O1001, O1010).
- It may be protected/hidden: some O8000/O9000 programs may be hidden by a parameter.
- Another part system may be selected: in multi-part systems the program may be saved in a different part system.
17. Conditions that block automatic start
Even if the program is selected correctly, CYCLE START may not work. According to the M700 Handbook, the following can block automatic start: the automatic operation mode is not selected, the RESET signal is still active, Feed Hold is active, an axis is moving, the NC is not ready, a program/file write is in progress, a file delete is in progress, the program search is not complete, more than one automatic mode is selected at once, or host-computer communication is ongoing. In these cases, instead of forcing START, the warning on screen should be read.
18. Application example and lesson summary
General sequence to call O1000 in NC memory: open the EDIT/PROGRAM screen → check the device is MEMORY → open the list → find O1000 → move onto the line → INPUT/SELECT/OPEN → check the content opened → TOP SEARCH → check the cursor is at the start → switch to MONITOR → verify the active program is O1000 → select MEMORY/AUTO → check the program before giving CYCLE START. In this lesson we learned to open the NC memory program list, select the correct device, search with arrow keys and by O number, activate the program, reset to the start with TOP SEARCH, compare the EDIT/MONITOR program number, and the checks to do when a program cannot be found.
Next lesson — Lesson 4: Running a program in NC memory safely (switching to AUTO/MEMORY mode, giving CYCLE START, using Single Block, stopping with Feed Hold and resuming, the effect of RESET, what to do at program end).