Programming of CNC Machines. Ken Evans
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Figure 2-1 FANUC 30i Machine Tool Controller Courtesy FANUC FA America
1. Become familiar with common CNC machine operator panel functions.
2. Become familiar with common machine control panel functions.
3. Learn common operations performed at the machine control.
4. Learn how to use the controls to input setup data including tool and work offsets.
5. Learn how to use the control to edit programs.
6. Examine some common cases of problem situations and learn how to solve them.
Every CNC Machine Tool has an operation panel and a control panel that provide the interface for the operators and programmers with the machine tool, sometimes referred to as the Human Interface (HMI). By using the operator panel, we physically manipulate the working components of the machine to do what we need; 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 an example of an operation panel.
The following descriptions for the model shown in Figure 2-2 represent the configuration for a common operator panel. Some differences exist for each manufacturer’s operator panel, but they generally contain the same features. Figure 2-2 shows a panel for a three-axis mill. The panel used for a lathe would be essentially identical except for the axes keys for X and Z only. You should consult the applicable manufacturer manual for detailed descriptions that match your needs. Please note that the Handle (Manual Pulse Generator) is not shown, although it is described in the text. Another common item not shown here are those lathe-specific switches used to change the chucking direction from external to internal. The following sections describe the buttons in order from top-left to right for the three columns of buttons in Figure 2-2.
Figure 2-2 Common Operator Panel Courtesy FANUC FA America
FEEDRATE OVERRIDE
The Feedrate Override dial allows the operator to control the feedrate by adjusting the position of the dial (Figure 2-3). During auto-cycle, when the dial is at the 100 position, the feed will occur at 100% of the programmed value. The control of the work feed is defined by the F-word in the program. You can increase the percentage of the value entered in the program to 120% or decrease it to 0%. This feature provides you the control needed to fine tune feeds. You can also use this feature to control feedrates while using the manual jog mode function. The same is true for the Spindle Override feature, which enables you to override the programmed control spindle speed between 50 and 120%.
Figure 2-3 Feed and Spindle Override Courtesy FANUC FA America
EMERGENCY STOP
The EMERGENCY STOP is the large, red, mushroom-shaped button used to stop machine function when an emergency situation occurs. Examples of such situations are
• overloading of the machine
• the machined part has come loose
• incorrect data in the program or work/tool offsets have caused a collision (crash) between the tool and the workpiece
When this button is pressed, all program-commanded feed rates and spindle revolutions are halted immediately. To recover from an “E-Stop” condition, you must reset the program controller and Home 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; 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 2-4 EMERGENCY STOP Courtesy FANUC FA America
PROGRAM PROTECT
When the Program Protect key switch is in the ON condition (vertical), it prohibits any program changes to be made (Figure 2-5). 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 AS9100 require that CNC program integrity be insured by locking out access to editing.
Figure 2-5 Program Protect Key Switch Courtesy FANUC FA America
OPERATION PANEL KEY DESCRIPTIONS
This section introduces the function of each individual key/button (Figure 2-6).
PROGRAM SOURCE
On some operation panels, a rotary switch referred to as Mode Select is used instead of the buttons shown in Figure 2-6. 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 example, operator panel buttons are used to specify the control or operational mode.
Note: When the buttons are pressed, they are active and remain so until another mode button is pressed that overrides it. In some conditions, multiple Light Emitting Diodes (LEDs) may be lit simultaneously. The LED above the button is lit when the mode is ON and active.
Auto
Pressing this button enables the CNC programs 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
Pressing this button selects the program edit mode. The EDIT mode enables you to enter the part program to control memory via keypad and soft-keys, enter any changes to the program, transfer program data via one of several communication interfaces (RS232, USB, Memory Card, or Ethernet) to or from an offline storage device, or check the program file memory, file locations, and storage capacity.
MDI-Manual Data Input
Pressing the MDI button selects the MANUAL DATA INPUT mode. 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 when machining 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.