Jet 830 Vertical Milling Machine CNC Conversion
By Matt Dralle
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Jet 830 Mill CNC Conversion
The conversion consisted of a standard Jet 830 manual vertical milling machine. Mounts for the X, Y, and Z axis stepper motors were fabricated out of 6061 T6 aluminum bar stock. Holes were tapped into the mill's chassis as necessary to support the mounts. 650 oz Steppers motor are used and provide plenty of power for most operations. Mitutoyo Liner Scales were fitted to the three main axis and a Starrette scale was fitted to the knee for remote readout on a Mitutoyo readout box. See the link below for details on the special protocol converter that was developed for the application.
Ahha Design Group's excellent CNC package was used to control the milling machine running on a 333 Mhz Pentium II computer system. The performance of this computer system over the previous system, a 100 Mhz Pentium I, was very noticeable and made operations much smoother.
A quick change spindle accessory was added to the mill and has been found to be invaluable in the creation of production part quantities.
Below are some photos of the conversion. Note both the CNC conversions as well as the Linear Scale installations.
- Jet 830 Complete CNC Conversion
- Milling Table with FuelChec Fixture and Sample Parts
- X Axis Stepper Motor and Mount
- Y Axis Stepper Motor and Mount
- Z Axis Stepper Motor and Mount
- Z Axis Scale Detail
- AhHa CNC Gear
- Starrette Linear Knee Scale
- Mitutoyo 3 Axis Linear Scale, Mitutoyo Knee Scale Readout
- Quick Change Accessories
- Mobile Base
Spindle Motor Upgrade
The Jet 830's 115v, single phase spindle motor was upgraded with a 240v, three phase motor. A special inverter was installed to convert from the neighborhood's 240v single phase. The inverter also includes the ability to adjust the speed and direction of the motor. Using digital outputs from the Ahha CNC gear, a special relay board was constructed that allow speed and direction control of the spindle motor under CNC control. The photos below detail the installation including a schematic diagram of the relay board. The Ahha CNC gear has an 8-bit DAC that is used to drive the inverter's voltage output control. This is a very, very slick setup. Highly recommended.
- 240v Single Phase to Three Phase Converter
- Three Phase Converter and Three Phase Motor
- Inverter Wiring with Relay Board - A
- Inverter Wiring with Relay Board - B
- Inverter Wiring with Relay Board - C
- Relay Board - Bottom
- Relay Board - Top
- Relay Schematic
- Motor Dampening Resistors
Sample FuelChec Parts
Using a CNC CAD program called "XCAD Pro", the part is first laid out in a wire-frame format. All dimensions are entered including the depth of pockets, holes, and champhers. Next, the part can be rendered in shaded 3D and rotated in any direction to verify visually that the part is correctly designed. Once the part has been satisfactorily designed, a special CNC plug-in to the XCAD program is used to apply tool-paths for all of the cutting motions necessary to cut the part on the machine. Again, the cutting can be modeled in 3D to be sure the developer's plan matches the program. From here, the newly generated CNC code is moved onto the CNC computer connected to the Milling Machine and the actual part is cut.
In the case of the FuelChec part shown below, both a Front side and a Back side must be cut. A special fixture is used to hold the raw material during the cutting process. The fixture also allows the material to be removed and flipped over to allow for the necessary front and back CNC operations. The fixture must be able to hold the part in perfect alignment in both orientations.
Below are some bitmaps and photos of the FuelChec Faceplate part that was developed using the CNC system.
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