Programming of CNC Machines. Ken Evans
(HMI). The Operator Panel is the method with which we physically manipulate the working components of the machine to do what we need and the Control Panel is where the program data are entered and stored. A thorough understanding of each is necessary for successful CNC Machine use. First, we will study and example of an Operation Panel.
Figure 2 Operation Panel Courtesy GE FANUC
The following descriptions for the above diagram represent the configuration for a common Operators Panel. Some differences do exist for each manufacturer Operation Panel, but they generally contain the same features. The illustration shows a panel for a two-axis lathe. The panel used for a mill would be essentially identical, except for the added keys for the additional axes. The user should consult the applicable manufacturer manual for detailed descriptions that match their needs. Please also note that the Handle (Pulse Generator) and the Rapid Traverse Override buttons are not shown in this view of the controller, although it is described in the text. Another common item not shown here are the switches used to change the chucking direction from external to internal and are specifically for lathes.
OPERATOR PANEL FEATURES FEEDRATE OVERRIDE
The Feedrate override dial allows control of the feedrate when the operator adjusts the position. At the 12:00 o’clock position the feed, during auto-cycle, will occur at 100% of the programmed value. This allows the control of the work feeds defined by the F-word in the program. The percentage of the value entered in the program can be increased or decreased. This feature offers the operator the control needed to fine tune feeds. It can also be used to control feedrates while using the manual jog mode function.
Figure 3 Feed Override
EMERGENCY STOP
The EMERGENCY STOP is the large, red, mushroom-shaped button used to stop machine function when an emergency situation occurs. Some example situations are: overloading of the machine, a clamping of the machined part has come loose, or incorrect data in the program or work or tool offsets have caused a collision (crash) between the tool and the workpiece. When this button is pressed, all program commanded feedrates and spindle revolutions are halted immediately. Recovery from an “E-Stop” condition requires resetting the program controller and Homing of the machine axes. To reset the EMERGENCY STOP button, turn it clockwise. It should “pop-out” of the depressed condition. Check the monitor for any alarm signals and take note of the Alarm # and description, and then eliminate the cause that forced the use of the EMERGENCY STOP button. Press the Reset button to clear all pending commands and Home the machine axes when no interference conditions are present.
Figure 4 Emergency Stop
PROGRAM PROTECT
When this key-switch is in the ON condition (vertical), it prohibits any program changes to be made. The condition does not affect work or tool offset adjustments. Some shops set this condition to ON, remove this key and allow only the programmer or set-up person access to the key. This is especially true in larger shops with multiple shifts and many workers. Some Quality programs like ISO9000 require that CNC program integrity is insured.
Figure 5 Program Protect Keyswithch
PROGRAM SOURCE
On some operator panels, a rotary switch referred to as Mode Select is used instead of buttons that are shown here. This switch includes both automatic (AUTO) and manual operation functions. The position of this switch determines whether the machine utilizes the automatic or the manual control. This switch can also be positioned to allow the entry of data into the control manually (Manual Data Input or MDI) or to make changes to the program through the EDIT mode. For this purpose, operator panel buttons are used to specify the control or operational mode.
Figure 6 Program Source
Note: When the buttons are pressed, they are active and remain so until another mode button is pressed. In some conditions, multiple Light Emitting Diodes (LED’s) may be lit simultaneously. The LED in the upper left corner of the button is lit when the mode is ON and active.
Auto
By pressing this button, the control mode enables the CNC commands stored in the memory to be executed for automatic operation. When the Cycle Start button is pressed, and this mode is active, automatic operation will occur.
Edit
By pressing this button, the program edit mode is selected. The EDIT mode enables the user to enter the part program to control memory, enter any changes to the program and transfer data from the program via RS232 interface to an offline storage device or check the program file memory and storage capacity.
Note: The RS232 interface is a 25-pin serial cable connector (in Figure 7) is located behind the flip-up door just below the Program Protect key switch. This connection is also used for DNC (Direct Numerical Control) program operations when the program is too large for the controller memory and is executed directly from a remote Personal Computer (PC).
Figure 7 RS232 Communications Interface Port
MDI-Manual Data Input
By pressing this button, the MANUAL DATA INPUT mode is selected. The MDI mode enables the automatic control of the machine, using information entered in the form of program blocks without interfering with the basic part program. This mode is often used during the machining of workpiece holding equipment such as soft-jaws and during setup. It corresponds to single moves (milling surfaces, drilling holes), descriptions of which need not be entered to memory storage. MDI mode can also be used during the execution of the program. For example, suppose the program is missing the command M03 S350; needed to turn on the spindle, clockwise, at 350 r/min and the End-Of-Block character (;). In order to correct this omission, press the SINGLE BLOCK button and then the MDI button. Using MDI, the user can enter functions M03 and S350 from the control panel keypad followed by the EOB character. Then, enter this command by pressing INPUT on the control panel. Press AUTO to reenter the program auto-cycle mode and then press CYCLE START to continue execution of the program from memory.
OPERATION SELECT
The following buttons are related to the automatic operation of the machine. Activating one of these buttons has an effect on the operation and is described on the next page:
Single Block
The execution of a SINGLE BLOCK (SINGL BLOCK) of information is initiated by pressing this button to turn it ON. Each time the CYCLE START button is pressed, only one block of information will be executed. This switch can also be used if you intend to check the initial performance of a new program on the machine or when the momentary interruption of a machine’s work is necessary.
Figure 8 Operation Selection Buttons
Block Delete
BLOCK DELETE (BLOCK DELET) is sometimes called Block Skip. When this button is pressed and is active simultaneously with the auto-cycle mode, the controller skips execution of the program blocks that are preceded by the slash (/) symbol and that end with the end of block (;) character. For instance, if a section of the part program or a particular block of the program is not presently