Variable-Frequency-Drive Retrofit Kits for Older Mills
VFD and VFD Plus kits from Servo Products convert older step pulley mills and worn-out variable-speed mills to smooth, electronic speed control. Unlike early VFD kits, these provide full torque at the lowest RPM.
Posted: August 28, 2020
Variable-speed components on milling machines typically wear out in five to 10 years and must be rebuilt, requiring thousands of dollars for a stop-gap repair. Variable frequency drive (VFD) and VFD Plus kits from Servo Products Co. (Eastlake, OH) are an alternative solution that provide a reliable, long-term fix by completely eliminating the machine’s needless sliding variable-speed pulley components.
Easy to install and operate, the plug-and-play kits increase reliability, versatility, and productivity with smoother, electronic variable-speed control. Adaptable to most applications, they can run the motor on 220V single-phase incoming power instead of three-phase power that requires a phase converter. Providing the required torque in a convenient package, it can go up to 5,000 RPMs in high gear, 10% to 15% higher than the standard milling machine. Unlike early VFD kits, these provide full-torque at the lowest RPM.
Both kits feature a red E-Stop button that milling machines typically don’t have, and an E-Stop safety circuit to prevent accidental startups.
Standard specs and features include:
- Two RPM ranges (50 to 500 and 500 to 5,000)
- Full torque throughout entire RPM range
- Accurate in both gear ranges
- Can run a three-phase motor with single-phase input (up to 3 hp)
- Sensor-less vector control
- All mounting hardware
- Spindle rotation is always correct
- Bright blue LED display that’s accurate in both gear ranges
- 10-turn potentiometer for accurate speed control
- Integrated dynamic braking resistor for quick forward/reverse changes, such as tapping applications
- A window to view VFD status.
The VFD Plus has these features as well as:
Four preset spindle speeds. In addition to one main speed for fast speed selection, there are an additional four presets for a total of five. Operators change spindle speeds with the press of a button.
Semi-automated tapping. A proximity switch automatically reverses and backs the spindle out of the tap at the user-set depth. Once back to the top position, the spindle turns forward, ready for the next tapping cycle. Put the drill in and set the speeds; i.e., push button “1” at drilling speed, then push button “2” at a tapping speed. This allows the operator to run through a desired sequence at the correct RPMs.
Servo also can tailor CNC packages to fit machine requirements, whether it’s a new installation or a retrofit of an old control, including VFD speed control through the program. Solutions for almost any milling, turning, or grinding application are supported by Servo partner High Quality Tools (Eastlake, OH, and Largo, FL), a retail supplier of replacement parts, tools, and accessories for vertical knee-type milling machines.
