Programming of CNC Machines. Ken Evans
the cursor moves one full line upward in the reverse direction each time.
Page-UP/DOWN Keys
Usually the length of the program exceeds what the height of the screen will display. The CURSOR move keys can be used to scroll through the program. When you press and hold the CURSOR button with the down or up arrow, the cursor will move through the program line-by-line. A more effective method to move a large amount is to use the two PAGE keys. Using these keys will advance in the direction selected by the number of lines the screen can display. The last block of a given page becomes the first block of the next page. Use the PAGE button with the arrow pointing up to change pages in the opposite direction.
Figure 30 Page Keys
Example:
O0001
N1G50X7.777 Z7.777 S1000
N2T0100M39
N3G96S600M03
In the above example, with the CURSOR resting below N then pressing the CURSOR button three times with the right-pointing arrow causes the cursor to be located below the letter (address) G.
By pressing the CURSOR button (with the arrow pointing up) repeatedly, the prompt will move to the first word of program O, which corresponds to the upper limit of cursor movement. Another fast way to return to the program head is to press the RESET key.
By pressing the CURSOR button once, with the arrow pointing down, the cursor will move down one line. If the cursor must be moved over a few or many words, you need not press the button repeatedly. Just press and hold this button down; the cursor automatically jumps one word at a time in the given direction. The PAGE keys allow for scrolling through long programs more effectively.
OPERATIONS PERFORMED AT THE CNC CONTROL
The following explanations are for operations considered routine for operators of CNC machine tools and are given in their sequence of use.
Please note that the following procedures are specific to the type controller depicted here (Fanuc 16 or 18 series). The procedures for another type control may be similar. Be sure to consult the manufacturer manuals specific to your machine tool operation and control panel.
The Machine is Turned on and Homed (Machine Zero)
Turn on the main power switch, and then press the ON Power button on the controller. Most modern machine tools will automatically start-up in the HOME mode. This means that before any automatic or manual operation may begin, it will be required to Home the machine first.
If the Operation selection LED, HOME, is not lit, press it now.
Using the Axis/Direction keys, press the direction necessary to HOME the machine. Note that many machine tools will have LED’s for each axis that are lit to indicate when an axis is HOMED.
Figure 31 Actual Position (Absolute) Screen
At machine start-up, a common screen displayed is ACTUAL POSITION (ABSOLUTE). If it is not displayed, press the function key labled POS then the soft key ABS. The displayed coordinate values represent the relationship between the Workpiece Zero and the Machine Zero (HOME). When the machine is HOME, press the soft key OPRT, then press ORIGIN and then press ALLEXE to zero each of the coordinate axes.
By pressing the soft keys, other display screens can be activated. For instance, when we press the button ABS (which corresponds to position), the digital counter appears on the screen for the X and Z axes, which is the absolute coordinate system for a given workpiece (for milling machines X, Y, and Z will be displayed). The position (POS) function is assigned four display screens and can be found by pressing the soft keys labeled; ABS, REL, ALL and OPRT. The first screen corresponds to a position change in the ABSOLUTE (ABS) system for X, Z, as illustrated. The second screen RELATIVE (REL) corresponds to position changes in the incremental system, U and W (for milling machines X, Y, and Z). The third, ALL gives representation of all four of the displays simultaneously on one screen as shown in Figure 32.
The values listed in the readout for MACHINE represent the distance from Machine Home position.
The DISTANCE TO GO readout is the most significant part of the third display. The coordinates in this quarter of the display of the screen correspond to the path that will be followed by the tool in order to complete the execution of a given block of information while under automatic operation.
Example:
N20G00Z0.
N22G01Z-12.000F.015
Figure 32 Position, Actual Position, Screen
Figure 33 Program Library Screen
When block N22 is first read by the control, the value Z-12.000 will appear under DISTANCE TO GO readout in the lower right corner of the screen. After moving a distance of 1 inch, the value of coordinate Z changes to Z-11.000, and so on. The other displays, “ABSOLUTE” and “RELATIVE” correspond to the first two display screens, but this time they are smaller so that all four may fit on one screen. All of the displays may be changed to read in millimeters, with respect to Machine Zero, by changing a machine parameter or by using a G-Code in the program.
A Program is Loaded From Memory
The program may be in the program directory but not activated for automatic operation. Follow these steps to activate a program.
1. Press the EDIT button to enter the EDIT mode.
2. Press the PROG function key.
3. Either the program contents or program file directory will be displayed.
4. Press the OPRT soft key.
5. Press the rightmost (continuous-menu key) soft key.
6. Use the keypad to enter the desired program number preceded by the letter address O.
7. Press the FSRH (forward search) and the EXEC soft keys.
The program will now be in the active status and ready to use for automatic operation.
An NC Program is Loaded Into Memory
Follow the steps below to load a program into the controller from an NC tape. Be sure that the input device is ready for reading (tape entry to tape reader if used).
1. Press the EDIT button on the operator’s panel to enter the Edit mode.
2. Press the PROG function key.
3. Either the program contents or program file directory will be displayed.
4. Press the OPRT soft key.
5. Press the rightmost (continuous-menu key) soft key.
6. Use the keypad to enter the desired program number to load preceded by the letter address O.
7. Press the READ soft key and then the EXEC soft key.
The program will be loaded into the controller’s memory.
A Program is Saved to an Offline Location
For example; an NC Tape, Floppy disc, PCMIA card, or PC hard disk connected via RS232.
Follow the steps below to save a program to an NC tape.
Be sure that the output device is ready for output.