Hydraulic Counterbalance - How it Works and Troubleshooting Guide

Applies to machines built from: 
January, 1995

How it Works

The hydraulic counterbalance system uses a hydraulic cylinder to support the weight of the spindle head, and reduce the load on the verticle axis servo motor.

The hydraulic tank [1] is mounted upside-down on the column casting. It contains hydraulic oil and is pressurized with nitrogen gas. The hydraulic cylinder [2] is mounted to the column casting. The cylinder rod end is attached to the spindle head casting.

The pressurized oil is cycled from the hydraulic tank to the cylinder when the spindle head moves up and down. When the spindle head is moved to the top of travel, the nitrogen pressure in the tank decreases as the tank volume is increased by the oil flow out to the cylinder. The tank size, quantity, and pressure are determined by the machine model.

When you troubleshoot symptoms, refer to VMC - Hydraulic Counterbalance - Replacement for instructions on how to replace the system or drain pressure from the tank. Click the link or go to diy.haascnc.com and search for the document.

  1. Hydraulic Tank: mounted upside-down on the column of the machine. It holds the hydraulic oil and pressurized nitrogen.
  2. Hydraulic Cylinder: relieves vertical force from the spindle head on the verticle axis servo motor.
  3. Pressure Gauge: shows the system pressure.
  4. Hose Outlet: connection point for the hydraulic hose. The other end connects to the 90° fitting [8] on the hydraulic cylinder.
  5. Pressure Manifold: connected to the hydraulic tank.
  6. Pressure Switch: tells the control when the pressure is low.
  7. Schrader Valve: allows you to add or remove pressure.
  8. 90° Fitting: connection point for the hydraulic hose. The other end connects to the hose outlet [4] on the tank.
  9. Threaded Rod End: connects to the spindle head bracket.

System Pressure

Model Built After Pressure Built After Pressure Built After Pressure
PSI BAR   PSI BAR   PSI BAR
EC-1600/2000/3000 3/15/2004 1000 70 9/13/2004 550 38 6/14/2005 800 55
EC-630 3/21/2006 800 55            
HS-1 10/30/1997 600 51            
HS-3/4/7 6/5/1998 1150 79 6/18/1999 1200 83 2/29/2000 1250 86
VB-1 6/5/1998 1550 107            
VF-3/4 (VCE 1000/1250) 4/28/1995 1150 79            
VF-5 XRT 10/8/2004 750 52            
VF-5, VM-3, VF-3YT (VCE 1300) 7/21/1998 950 66 10/14/1998 875 60      
VF-5/50, VF-3YT/50 (VCE 1300) 7/21/1998 1100 76            
VF-6/7/10/12 - 50 (VCE 1600, 2000, 3000) 10/30/1997 1150 79            
VF-6/7/10/12 (VCE 1600, 2000, 3000) 10/30/1997 750 52            
VF-8/9/11 - 50 (VCE 1600, 2000, 3000) 7/21/1998 1550 107            
VF-8/9/11 (VCE 1600W, 2000W, 3000W) 10/30/1997 750 52            
VF-O/OE/EXT/1/2 (VCE 475/500/550/700/750) 4/28/1995 750 52            
VR-8/9/11 10/30/1997 1800 124 7/21/1998 1100 76 10/14/1998 1025 71
VS-1/2/3 2/29/2000 1250 86            
VTC 5/4/2002 1150 79            
  All pressures should be at the top of travel (+50, -0 psi) (+3, -0 bar)

Symptom Possible Cause Corrective Action Section
Alarm 107 EMERGENCY STOP

or

Alarm 820 COUNTER BALANCE FAILURE

There is low nitrogen pressure in the conterbalance system. Check for leaks on the cylinder and recharge the tank with nitrogen. 1
The pressure switch circuit does not operate correctly. Troubleshoot the wiring and switches. 2
The spindle head drops with EMERGENCY STOP on. There is low nitrogen pressure in the conterbalance system. Check for leaks on top of the counterbalance cylinder. 1
There is low oil level in the counterbalance system. Check for an oil leak on the cylinder.
The cylinder leaks oil. There is contamination in the oil. Check for the cause of contamination. 3
The hydraulic cylinder is misaligned. Check for the cause of the leak.

Section 1

Symptom: Alarm 107 EMERGENCY STOP. Alarm 820 COUNTER BALANCE FAILURE. The spindle head drops with EMERGENCY STOP on.

Possible Cause: There is low nitrogen pressure in the conterbalance system. There is low oil level in the counterbalance system.

Corrective Action:

Check for leaks on the top of the cylinder.

If there is no leak, recharge the nitrogen: Remove the cap [1] from the Shrader valve. Connect the Charge / Discharge kit (P/N 35-4050A) [2] to the Shrader valve [3]. Use the "System Pressure" chart at the beginning of the document for the correct pressure.

If the cylinder leaks oil: Go to Section 3.

Section 2

Symptom: Alarm 107 EMERGENCY STOP or Alarm 820 COUNTER BALANCE FAILURE

Possible Cause: The pressure switch circuit does not operate correctly.

Corrective Action:

Disconnect the pressure switch cable [1] from the pressure switch [2]. Make sure that there is no contamination on the connectors. Use a jumper to connect the pins on the cable. If the alarm resets, the pressure switch is at fault. If the alarm does not reset, go to diy.haascnc.com to troubleshoot the pressure switch cable [1].

Section 3

Symptom: The cylinder leaks oil.

Possible Cause: There is contamination in the oil. The hydraulic cylinder is misaligned.

Corrective Action:

Any leak in the hydraulic counterbalance system means the system is damaged [1], and must be replaced. Both the hydraulic cylinder and the hydraulic tank must be replaced together to avoid oil contamination.

For replacement instructions, refer to the document VMC - Hydraulic Counterbalance - Replacement on diy.haascnc.com. The replacement instructions include information on how to correctly align the cylinders. The new cylinder(s) must be correctly aligned to avoid damaging the new system and cause another leak.

Be aware: Many service and repair procedures should be done only by authorized personnel. The service technicians at your Haas Factory Outlet (HFO) have the training, experience, and are certified to do these tasks safely and correctly. You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes.

Danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not completely understand. Contact your Haas Factory Outlet (HFO) and schedule a service technician visit if you have any doubts about doing a procedure.

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