PLC545 is a 4-channel LPT-port CNC step motor driver in box. Each channel (step motor driver) supports microstep 2/4/8/16 devison, 45V/5A power rating, up to 200kHz STEP pulse frequency, mid-band resonance compensation and step motor phase-currents morphing. Each step motor driver has build in Оver-voltage, Back EMF, Over-current, Short-circuit, Reversed-polarity protection and automatic Idle-current reduction, activated on STEP pulse absence. PLC545 has 3 power relays, 5 opto-inputs (to connect limit switches, E-STOP button, etc.) cooling pump timer and PWM>Voltage converter to control spindle Frequency Converter (FC). Device is compatible with MACH3/TurboCNC/LinuxCNC and similiar CNC software. All input signals from PC LPT-port are buffered and optoisolated. PLC545 is optimized to control bipolar and unipolar step motors NEMA 17, 23 size and other similar with 4, 6 and 8 wires.
Critical speed is the first resonant frequency (speed) of the rotating shaft. Resonance in a rotating shaft can be catastrophic and even break the shaft. However, not all ball screws will necessarily exhibit such behavior since the nut represents another support of the shaft, permanently changing the unsupported length of the shaft and its resonant frequency.
It is necessary to confirm if the ballscrew rotational speed is within 80% of the critical speed of the ballscrew.
Figure 3.17 shows a diagram which summarizes the allowable rotational speed of the ballscrew shaft.
The allowable rotational speed is regulated also by dm - n value (dm: Diameter of central circlof steelball, n: Revolution speed-RPM) Which expressesthe peripheral speed.
For precision (Accuracy grade C7-C0) dm - n is lower that and equal to 70,000.
To make this calculation we have provided a handy calculators to measure the critical speed of a ballscrew.
The output form this calculator will show the approximate point at which the ballscrew will start to resonate (Whip) and you should consider to set the maximum RPM to 80% of this speed.