Setting up the DeskCNC controller.

Transcription

1 1) Determine the steps to linear motion ratios for each axis. 2 2) Determine Maximum velocity (speed). 3 3) Setting up the software Machine Tab 4 4) Setting up the software DeskCNC Setup Tab 5 5) Setting up the software Axis Setup Tab 6 6) Setting up the software Machine Velocities Tab 7 Throughout this manual, each page is written to be a standalone operation. If the setup steps are followed in sequence, the machine setup dialog can be opened once and the changes all saved at one time, rather than after modifying each tab of the machine setup dialogs. Copyright IMService 2005 Page 1 9/16/2005

2 1) Determine the steps to linear motion ratios for each axis. The Axis ratios are used in the DeskCNC machine setup. In the case of the IMService servo drivers with Globe motors, the belt reduction is setup so that one revolution of the output shaft is about 2.8 revolutions of the motor shaft. The motor has a 500 line encoder. With quadrature, the motor produces 2000 counts per revolution. The 2.8:1 ratio calculates to around 2.8 * 2000 = 5600 counts per rev of the output shaft. If the motor is mounted on a 10 pitch lead screw, then the linear motion ratio is 10 * 5600 or 56,000 steps per inch. A 20 pitch lead screw would be 20 * 5600 or 112,000. The precise ratio is and calculates to steps per rev. Common lead screw ratio calculations: Inch Steps Per Lead Screw Inch Metric Steps Per Lead Screw mm Stepper motors are usually 200 steps per rev, and sometimes 400. Steppers can also be driven at different step ratios. The following table shows common stepper ratios: Inch 200 Steps per Rev 400 Steps per Rev Screw Full Half ¼ 1/8 1/10 Full Half ¼ 1/8 1/ Metric Screw Copyright IMService 2005 Page 2 9/16/2005

3 2) Determine Maximum velocity (speed). The maximum velocity is used to limit individual axis speed, and is also an input to the acceleration curve. Use the axis ratio from 1) above, and calculate the expected maximum velocity or speed at which the axis will travel. In the case of a Sherline mill with DeskCNC servos and Globe motors with 2.8:1 belt reduction the axis ratio is The maximum servo motor speed is 2800 rpm. This is 2800 * 2000 or steps per minute. Divide the maximum steps per minute by the steps per inch to calculate the maximum velocity: / = 49.6 inches per minute Discount this value by about 10% for a safe margin = 45 inches per minute Calculate the maximum velocity in Steps per second by (Max speed in ipm * Steps per inch) /60 sec per minute 45ipm * = steps per minute /60 = steps per second For a metric screw with 1mm pitch and steps per mm: The maximum steps per minute is the same as for an inch screw. Use the ratio of steps per mm to calculate the max velocity / = 992 mm per minute Discount this value by about 10% for a safe margin = 890 mm per minute Calculate the maximum velocity in Steps per second by (Max speed in mm/min * Steps per mm) /60 sec per minute 890mm/min * 5647 = steps per minute /60 = steps per second Note that the inch and metric values are nearly the same, the differences are caused by rounding. Max velocity is not required to 15 decimals as it is usually programmed using 0-2 decimals. For other servo and stepper motors, the max velocity will be controlled by the motor performance curve, driven voltage, mass and condition of the machine slides. It may be necessary to calculate a number of max velocities to achieve a satisfactory balance between the desired speed and the laws of physics that will control the actual machine motion. Copyright IMService 2005 Page 3 9/16/2005

4 3) Setting up the software Machine Tab Click the navigation buttons at the top of the dialog to find the Machine Tab: Check 3 or 4 axes for a CNC mill or CNC router, or 2(ZX) for a CNC lathe Leave Rotary checked unless you are setting up a 4 axis foam cutter. Check a slaved axis if you are setting up a router with 2 motors on a single axis. Check 2 nd Generation Controller. For a lathe only: Check rear turret if the tool is mounted behind the center of rotation, i.e.: the part is between the operator and the cutting tool. Enter the steps per revolution of the encoder mounted to the spindle (for threading). Copyright IMService 2005 Page 4 9/16/2005

5 4) Setting up the software DeskCNC Setup Tab Click the navigation buttons at the top of the dialog to find the DeskCNC Setup Tab: Check the units for your machine, MM or inches. The grid size under Display is indicated, the defaults are 1.0 inch (G20) and 5.0 mm. Adjust these values to change the graduation of the light gray machine grid that appears on all DeskCNC screens. Under Machine size, enter the minimum and maximum values or the X, Y, and Z-axes. This will change the overall size and location of the Grid in X and Y, and the location in Z If you are using a keyboard that uses a different character for the decimal point, enter that character in the Decimal Separator box. The Jog Distances can be customized on this screen using the add and delete buttons. Some of the defaults are listed here: Copyright IMService 2005 Page 5 9/16/2005

6 5) Setting up the software Axis Setup Tab Click the navigation buttons at the top of the dialog to find the Axis Setup Tab: Enter the Steps per inch or steps per mm for each axis Enter the Max Velocity in Steps per seconds. Reverse the direction of each axis by placing a minus sign in front of the steps per inch (or steps per mm) values. Note: Tool motion determines the correct axis direction on a CNC machine. If text is engraved upside down, reverse the Y-axis direction. If text is engraved backwards, reverse the X-axis direction. Copyright IMService 2005 Page 6 9/16/2005

7 6) Setting up the software Machine Velocities Tab Click the navigation buttons at the top of the dialog to find the Machine Velocities Tab: 1-Enter an Acceleration Scale of 10 2-Enter your Max Velocity 3-Enter a Start Velocity of 10% of the Max Velocity After these 3 values are entered, change the acceleration by adding zeros and adjusting the value until the graph shows a line that ends in the upper right corner. Make sure that there is no vertical component at the right side of the time-velocity graph. After the acceleration is adjusted, the acceleration scale can be modified to control the total acceleration time. For a small machine like a Sherline, start a about.100 seconds and increase as needed up to.300 seconds or more for larger machines that will require more time to get up to speed. You can change the Fast, Med, and Slow jog velocities on this page if they are not scaled to your machine speeds and units. Copyright IMService 2005 Page 7 9/16/2005