# Setting Spindle RPM (Mach4)

Problem: Not going the correct RPM?

Is the spindle encoder configured correctly?

- Option 1
- Test with a Tachometer and make sure it matches the RPM in Mach.

- Option 2
- Zero the HiCON encoder
- Rotate the spindle 360 degrees
- How many encoder counts did it move?
- Enter that value into the HiCON Config Window “RPM Counts / Rev” (access the Configure menu option, then plugins and select the HiCON plugin).

Is it linear?

- Set pulley max to 1000
- Command 1000
- Command 500 (1/2 of max)
- Command 100 (1/10 of max)
- Is the actual linear with the commanded?
- If it isn’t, then the VFD may be configured with 4-20mA control or the breakout board may have a problem.

Set Max Frequency

- Calculate the Max Hz like this: Max Hz = Base Frequency / Rated RPM * Desired Max RPM
- For example, 60 Hz / 1770 RPM * 4000 RPM = 135.59 Hz.
- The Base Frequency and Rated RPM should be on the motor name plate.
- Make sure Desired Max RPM is not faster than the Max Motor RPM.

If you cannot locate the motor’s frequency, the name plate should tell you how many poles there are on the motor.

Using the motor’s maximum RPM and its number of poles, you can calculate the frequency with the formula below.

Base Frequency = Max RPM * Number of Poles / 120

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