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How to Install a CNC Spindle & VFD

by Matthew Cole

Installing a CNC spindle and VFD can seem complicated the first time because there are several separate parts to deal with: mounting the spindle, wiring the motor, grounding and shielding the cable, setting up cooling, configuring the VFD and finally connecting the CNC controller.

This guide walks through the installation in the order we would approach it, using a 1.5kW water-cooled spindle, H100 Mini VFD and DDCS V4.1 controller as the worked example.

Important: A VFD is connected to mains voltage and can retain dangerous voltage internally after power has been switched off. Mains wiring and protective-earth connections should be completed or checked by a suitably qualified person. Always isolate the machine and allow the VFD to discharge before touching any wiring.

What You Need

For a typical installation you will need:

  • A correctly matched spindle and VFD kit
  • A spindle bracket if using a round spindle
  • Shielded spindle cable of the correct core size and conductor size
  • An EMI filter
  • Suitable mains wiring and electrical protection
  • Low-voltage control cable if connecting a CNC controller
  • A pump, pipe and coolant reservoir if using a water-cooled spindle

The current CNC Online 1.5kW water-cooled kit includes the spindle, VFD, spindle clamp, 75W water pump, 5m water pipe and seven ER11 collets.

1.5kW water-cooled CNC spindle used in a spindle and VFD installation

1.5kW Water-Cooled Spindle

H100 Mini VFD used to control CNC spindle speed and operation

H100 Mini VFD

Step 1 – Mount the Spindle

Start by physically mounting the spindle to the Z-axis.

How to Do It

  1. Mount the spindle bracket securely to the Z-axis plate.
  2. Loosen the spindle clamp enough for the spindle body to slide into position.
  3. Insert the spindle and position it so the electrical connector and cooling ports remain accessible.
  4. Set the spindle height so there is enough travel for the cutters you normally use.
  5. Tighten the clamp evenly. Do not excessively tighten the clamp and distort the spindle body.
  6. Move the Z-axis through its full travel by hand or jog it carefully and check that no cables or cooling pipes can snag.
Check before moving on: The spindle must be secure, straight and able to move through the full Z-axis travel without pulling on cables or pipes.

Step 2 – Run the Spindle Cable

The spindle is powered from the VFD using three motor phases. The cable between the VFD and spindle should be shielded to help contain electrical noise.

Route the spindle cable before terminating it so you know exactly how much cable is required. Leave enough extra length for full machine movement, but avoid large unnecessary coils of cable inside the control cabinet.

How to Route It

  1. Run the shielded cable from the VFD position to the spindle.
  2. Route it through the drag chain or normal machine cable path.
  3. Move the X, Y and Z axes through their complete travel.
  4. Make sure the cable never becomes tight at the limits of travel.
  5. Keep the spindle cable away from limit-switch, probe and 0–10V control wiring wherever practical.
POWER SIDE
VFD Output
↓
Shielded Spindle Cable
↓
Spindle
SIGNAL SIDE
DDCS Controller
Limit Switches
Probe Wiring
0–10V Speed Signal

Step 3 – Prepare the Shielded Cable

The braided shield around the spindle cable helps contain electrical noise generated by the VFD. The outer insulation needs to be removed carefully so the shield can be terminated correctly.

1. Strip Back the Outer Insulation

Carefully remove enough of the grey outer jacket to expose the braided metal shield underneath. Do not cut through the insulation on the individual conductors.

2. Prepare the Braided Shield

Pull the braid together so it can be terminated cleanly. The photo below shows the pigtail method used in the original CNC Online spindle installation.

If a pigtail connection is used, keep it as short as practical. Where the installation allows it, a proper shield clamp or EMC cable gland that contacts the braid around the cable provides a better high-frequency connection.

Important: The braided shield does not replace the protective-earth conductor. Follow the grounding requirements of the specific spindle, connector and VFD being installed.

View Shielded Spindle Cable →

Step 4 – Connect the Spindle Cable to the VFD

With all power disconnected, the three spindle phase conductors connect to the motor-output terminals of the VFD.

VFD

U     V     W
↓    ↓    ↓
3 Motor Conductors
↓
SPINDLE
Protective earth is connected separately according to the spindle and connector arrangement.

How to Do It

  1. Confirm that the VFD is isolated from mains power and has discharged.
  2. Remove the VFD terminal cover.
  3. Identify the terminals marked U, V and W.
  4. Connect one spindle phase conductor to U.
  5. Connect the second phase conductor to V.
  6. Connect the third phase conductor to W.
  7. Connect protective earth according to the VFD and spindle wiring arrangement.
  8. Terminate the other end of the cable at the spindle connector using the confirmed spindle pinout.
  9. Use strain relief so movement of the machine cannot pull directly on the electrical terminals.
  10. Before applying power, check that no loose strands can contact another terminal.
Do not guess the spindle connector pinout. The three phase pins and protective-earth connection must be confirmed for the exact spindle being installed.
Check before moving on: With power still disconnected, check the cable terminations are tight, there are no exposed conductor strands and the spindle cable cannot pull out of either end.

Step 5 – Install the EMI Filter

The EMI filter helps reduce electrical noise entering or leaving the VFD through the AC supply. It sits on the incoming supply side of the VFD.

AC Supply → EMI Filter → VFD

The current CNC Online EMI filter is rated at 20A and 220V AC.

Mains-voltage section: The AC supply, EMI filter, VFD input and protective-earth wiring should be connected according to the markings on the equipment and local electrical requirements by a suitably qualified person.

View the 20A EMI Filter →

Step 6 – Connect the Water Cooling

If you are installing an air-cooled spindle, skip this step.

A water-cooled spindle must have coolant flowing before the spindle is run.

Reservoir → Pump → Spindle → Return to Reservoir

How to Do It

  1. Place the water pump inside a suitable clean coolant reservoir.
  2. Connect one length of pipe to the pump outlet.
  3. Connect the other end of that pipe to one of the spindle's water ports.
  4. Connect a second pipe to the other spindle water port.
  5. Route that pipe back into the reservoir.
  6. Secure the pipe so movement of the Z-axis cannot pull it off the spindle fittings.
  7. Fill the reservoir sufficiently for the pump to remain submerged.
  8. Switch the pump on.
  9. Watch the return pipe and confirm that coolant is flowing continuously back into the reservoir.
  10. Check both spindle fittings and all pipe joints for leaks.
Check before moving on: You should see a steady coolant return and no leaks around the spindle or pump. Do not run a water-cooled spindle if coolant is not circulating.

Read our Water-Cooled Spindle Guide →

Step 7 – Set Up the H100 Mini for the Spindle

Before connecting the DDCS controller, first get the spindle running correctly from the VFD itself. This makes fault-finding much easier because you know the spindle and VFD work before adding controller wiring.

Our worked example uses the CNC Online 1.5kW water-cooled spindle:

  • Power: 1.5kW
  • Voltage: 220V
  • Rated Current: 6A
  • Rated Frequency: 400Hz
  • Maximum Speed: 24,000 RPM

Enter the Main H100 Settings

Parameter Value What It Does
F001 0 Run/stop from the VFD keypad for the first test
F002 3 Use the potentiometer on the VFD panel for local speed control
F004 400Hz Spindle reference frequency
F005 400Hz Maximum output frequency
F008 220V Maximum motor voltage
F140 1.5kW Motor rated power
F141 220V Motor rated voltage
F142 6.0A Motor rated current

Parameters such as motor pole count and rated motor speed should only be changed when the correct values are confirmed from the spindle documentation or nameplate.

View the H100 Mini Manual →

Step 8 – Test the Spindle From the VFD

You can now perform the first spindle test before connecting the CNC controller.

How to Test It

  1. Remove the cutting tool for the initial test where practical.
  2. Switch on the water pump if using a water-cooled spindle.
  3. Check again that there are no coolant leaks.
  4. Power the VFD.
  5. Use the VFD speed control to select a suitable test speed within the spindle's operating range.
  6. Press RUN on the VFD.
  7. Watch the spindle as it accelerates.
  8. Listen for unusual noise and watch for excessive vibration.
  9. Check that the VFD is not displaying a fault code.
  10. Press STOP and allow the spindle to come to a complete stop.

Check the Rotation Direction

If the spindle is turning in the wrong direction, switch the complete system off, isolate the VFD and allow it to discharge.

Swapping any two of the three U/V/W motor conductors will reverse the rotation direction.

Check before moving on: The spindle should start and stop correctly from the VFD, rotate in the correct direction, cool correctly and run without unusual noise, vibration or VFD faults.

Step 9 – Connect the DDCS V4.1 to the H100 Mini

Only after the spindle works correctly from the VFD should the CNC controller be connected.

The DDCS needs two main functions:

  • A 0–10V signal to tell the VFD what spindle speed to use.
  • An M3 output to tell the VFD when to start the spindle.
This wiring example is specifically for a DDCS V4.1 and H100 Mini. YL and HY VFDs use different terminal names and parameters.

Wire the Speed Signal

  1. Switch both the VFD and DDCS off.
  2. Run a low-voltage control cable between the DDCS and H100.
  3. Connect VSO on the DDCS to AI1 on the H100.
  4. Connect COM- on the DDCS to GND on the H100.
  5. Keep this control cable away from the U/V/W spindle power cable.

Wire the Start/Stop Signal

  1. Use OUT1 as the DDCS M3 spindle output.
  2. Connect OUT1 on the DDCS to X1 on the H100.
  3. The DDCS output is an open-collector output that switches toward COM-; it does not need mains voltage.
  4. Make sure the DDCS I/O supply is correctly powered or the OUT1 signal will not operate.
DDCS V4.1 Connect To H100 Mini Function
VSO → AI1 0–10V spindle-speed command
COM- → GND Control reference
OUT1 / M3 → X1 Spindle start command

Step 10 – Change the H100 to DDCS Control

The spindle has already been tested from the VFD. Now change the H100 so that the DDCS controls start/stop and speed.

H100 Parameter Value Purpose
F001 1 Run command comes from external terminals
F002 1 Speed command comes from AI1
F044 02 X1 operates as Forward / spindle start
F067 0 NPN input mode for this example
F070 00 AI1 uses 0–10V input

Step 11 – Set the DDCS V4.1 Spindle Parameters

On the DDCS V4.1, confirm the following spindle settings:

DDCS Parameter Value Purpose
#127 1 Assign M3 to OUT1
#188 0 – Analog Use 0–10V spindle-speed output
#190 0 – G-code Use the S value from the G-code
#192 24,000 RPM Maximum spindle speed

View the DDCS V4.1 Manual →

Step 12 – Test the Spindle From the DDCS

The final step is checking that the controller can start, stop and change the spindle speed.

Test Start and Stop

  1. Make sure the water pump is running if using a water-cooled spindle.
  2. Power the DDCS and VFD.
  3. Command M3.
  4. The DDCS OUT1 should activate and the H100 should start the spindle through X1.
  5. Command M5.
  6. The spindle should stop.

Test Spindle Speed

Enter several spindle-speed commands and confirm that the VFD frequency changes with the requested RPM.

  • S6000 M3
  • S12000 M3
  • S18000 M3
  • S24000 M3

With the 0–10V scaling working correctly, increasing the S value should increase the VFD output frequency and spindle speed proportionally.

Final check: M3 should start the spindle, M5 should stop it and changing the S value should change the spindle speed.

Quick Troubleshooting

Problem What to Check
Spindle does not run from the VFD Spindle wiring, VFD fault code, motor settings and cooling
Spindle works from VFD but not DDCS F001, OUT1 to X1 wiring, DDCS I/O power and #127
Spindle starts but speed does not change VSO to AI1, COM- to GND, F002, F070 and #188/#192
Spindle runs backwards Swap any two U/V/W motor phases after isolating and discharging the VFD
False limit-switch triggers Shield termination, grounding and cable separation
Water-cooled spindle gets hot Pump operation, coolant flow, reservoir level and blocked pipe
Using a YL or HY VFD?

The physical spindle installation, shielded cable, cooling and testing process remains similar, but the VFD terminal names and parameter numbers are different. Do not copy the H100 settings above into another VFD.

Still Choosing a Spindle?

Need Help Choosing?

Every CNC setup is different.

If you are unsure which spindle, VFD, controller, spindle cable or cooling components are correct for your machine, tell us about your CNC router, the spindle you are using or planning to use, your controller and what you are trying to achieve.

CNC Online South Africa can help you choose the spindle, VFD and supporting components that best suit your CNC setup.

Email: sales@cnconline.co.za
WhatsApp: 073 352 8930

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