Programming of CNC Machines. Ken Evans

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Programming of CNC Machines - Ken Evans

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stops the operation, the second starts automatic operation, and the last key merely indicates when a program stop is encountered. Their specific functions are described below:

       Cycle Stop (Feed Hold)

      Pressing the CYCLE STOP button during automatic operation will halt all feed movements of the machine. It will not stop the spindle r/min or affect the execution of tool changes on some machines. When the CYCLE STOP button is pressed, the LED located on the button goes on, and the LED located on the CYCLE START button goes off. This button is used when minor problems are encountered, such as coolant flow direction or when checking DISTANCE-TO-GO during setup. When the problem is remedied, press CYCLE START again to resume automatic cycle operation. It is not recommended using this button to interrupt a cut because the spindle does not stop; therefore, damage to the tool or part may occur. When pressed during the execution of the tapping or threading cycle, CYCLE STOP will take effect after the thread pass or the tap is withdrawn. If the tap breaks during the tapping cycle, the only way to stop the machine is by pressing the RESET button on the controller or the EMERGENCY STOP button.

       Cycle Start

      The CYCLE START button is used to start automatic operation. Use this button in order to begin the execution of a program from memory. When the CYCLE START button is pressed, the LED located above this button goes on and the active program will be executed to the end.

       PRG STOP (Program Stop)

      When a Program Stop is commanded in the program by the program word M00, automatic operation is stopped and the LED on this button is turned on. This button does not have an ON/OFF function that affects the program stop condition. It is merely an LED indicator lamp to indicate when a program stop condition is active.

       OPERATION

      The keys in the Operation section (middle column) are used for manual operation of the machine during setup and initial startup. Their specific functions are described below:

       REF (Reference)

      Press the REF button to activate it. Then, pressing the X or Z buttons in the positive direction (X, Y or Z for machining centers) causes the machine to return to the Machine Zero position for each axis in relation to the machine coordinate system at the rapid traverse rate (maximum feedrate). The button must be held until the axis indicator LED is lit.

       Jog

      Pressing the JOG button activates a manual feed mode that allows the selection of manual feed movements along single axes X or Z (X, Y, or Z for machining centers). With the button activated, use the Axis/Direction (+ or –) buttons and the Feed Override dial to move the desired axis at the chosen feed rate. On some controls, Speed/Multiply is a rotary type switch that activates this function.

       INC (Incremental)

      Press the INC (Incremental JOG) button to activate the JOG mode in incremental steps. When the INC option is selected from the Operation Mode buttons, the incremental step selected by the Speed/Multiply buttons determines the magnitude of the displacement along the chosen axis in the selected direction. When one of the axes directional buttons is pressed and released, the movement will be as follows:

      X1 = a movement of .0001 inch or .0025 millimeters (mm)

      X10 = a movement of .001 inch or .0254 mm

      X100 = a movement of .010 inch or .254 mm

      X1000 = a movement of .100 inch or 2.54 mm

      The buttons used to select the axis and the direction of movement (+, RAPID, and –) are located in the third column on the fourth row of the Operator Panel, as shown in Figure 2-6 for this controller.

      For example, to displace the tool along the X-axis in a positive direction by the value of .010 inch, follow these steps.

      • Press the INC button.

      • Press the X100 button.

      • Press the X button to activate the axis.

      • Press the + button once.

      Each time the button is pressed, a displacement of the selected value results.

      If the JOG mode is selected when one of these buttons is activated, and the selected axis button is pressed and held in, the movement will occur at feed as indicated by the % Traverse Feed override dial.

       Handle

      Pressing the HANDLE button activates the manual handle feed mode for the selected axis. This handle is known as the Manual Pulse Generator (MPG). Pressing this button places the machine in the HANDLE mode, which enables manual control of axis movements [for X, Y, or Z; or for rotational axes 4 (A), 5 (B), or 6 (C)] by use of the handle after activating their respective axis buttons (Figure 2-7). For instance, press HANDLE, then press X, and then use the Handle to move to the desired position along the X-axis. By turning the handle clockwise, you can move the tool in a positive direction with respect to the position of the coordinate system. By turning the handle counterclockwise, the tool is moved in a negative direction with respect to the position of the coordinate system. The handle contains 100 notches, each of which corresponds to an increment (distance to be moved). Turning the handle, you can feel the displacement from one notch to the next.

      To set the magnitude for the distance to be moved, press one of the Speed/Multiply buttons as described in the INC section above.

       Caution: If the handle is rotated quickly while the magnitude is set at X100 or X1000, the tool will move at a rapid feed rate and a crash could occur!

      When the HANDLE mode is selected, the incremental step selected by the Speed/ Multiply buttons determines the magnitude of the movement along the chosen axis in the selected direction. Each button setting corresponds with the scale of the hand-wheel. One full revolution of the hand-wheel (360°) corresponds to 100 units on the scale. On the button X1, the X means “times” the minimum increment. In manual control, you must use the + or – buttons to identify axis direction as well as to determine the axis of displacement.

      Usually, X1 is used when you are precisely dialing-in the zero of the workpiece and when you are determining the tool length offset. For example, if you need to move the machine table with respect to the tool by 1.00” along the X-axis in a positive direction, follow these steps:

      • Press HANDLE mode button.

      • Press the axis directional button +X.

      • Press the SPEED/MULTIPLY button X10.

      • Turn the handle one full revolution (100 units) and then check the value of the displacement on the screen. It should indicate a movement of 1.00 inch.

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       X, Y, Z

      The X, Y, and Z buttons correspond with each of the linear axes. When one is pressed, that

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