VMC - Hydraulic Counterbalance - Pressure Switch - Replacement

Applies to machines built from: 
May, 1995 to May, 2012
AD0331 Rev B

VMC - Hydraulic Counterbalance - Pressure Switch - Replacement - Introduction

This procedure tells you how to do these tasks:
  • Release the nitrogen gas from the tank.
  • Replace the pressure switch on the tank for a hydraulic counterbalance.
  • Fill the tank with nitrogen gas to the correct pressure.
Safety Notes
Caution: When you do maintenance or repair on CNC machines and their components, you must always follow basic safety precautions. This decreases the risk of injury and mechanical damage.

Do these steps before you do work in the machine or in the control cabinet:
  • Set the main circuit breaker to the OFF position.
  • Use an approved lock with an approved safety tag. Always follow lock-out procedures in accordance to local government rules.
  • After turning off the machine, wait at least 5 minutes before working in the control cabinet, to allow power to dissipate. Wait for the voltage indicator LED on the vector drive to go off completely.
  • Always turn off the main air supply when you work on any part of the pneumatic system.
  • Make sure to rest the spindle head on a block of wood when work is done on a vertical axis. This will prevent any unintended movement that could result in the axis falling.
  • Never alter any safety circuits on the machine.
You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes. Serious damage to the machine components can result in costly repairs. The service technicians at your Haas Factory Outlet (HFO) have the training and experience, and are certified to do these tasks safely and correctly. The repair and service work performed by your HFO is protected with a limited warranty.
danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not fully understand. If you have any doubts about doing a procedure contact your Haas Factory Outlet (HFO) and schedule a service visit.

Prerequisites

This procedure applies to many parts. You need only (1) of the switches listed under Parts Included to complete this procedure.

Machine Compatibility

Do this procedure on VF-series machines that have a hydraulic counterbalance system.

Parts Included

[A]
32-0022B
QTY: 1
SWITCH, PRESSURE 900 PSI
[A]
32-1006B
QTY: 1
SWITCH, PRESSURE 750 PSI
[A]
32-3004B
QTY: 1
SWITCH, PRESSURE 600 PSI
[A]
32-3006B
QTY: 1
SWITCH, PRESSURE 1000 PSI
[A]
32-3008B
QTY: 1
SWITCH, PRESSURE 450 PSI
[A]
32-3009B
QTY: 1
SWITCH, PRESSURE 1400 PSI
[A]
53-0015
QTY: 1
SWITCH, PRESSURE 1000 PSI (S0LID STATE)

Tools Required

Charge/Discharge Kit, (P/N 35-4050A)
Regulated dry nitrogen tank, 250 cu ft (7079 liters). The gas supply must have a right-hand thread, CGA 580 (.965-14 NGO-RH-INT) fitting. Welding grade gas is acceptable.

VMC - Hydraulic Counterbalance - Pressure Switch Replacement

Step 1

Jog the spindle head to 14.5" (36.8 cm) above the table.

Put a wood block on the table. Lower the spindle-head casting onto it.

caution: Do not let the spindle touch the block. This causes damage to the spindle.
Push POWER OFF.

Set the main circuit breaker to the OFF position. Lock the main circuit breaker. Use an approved lock with an approved safety tag.

Step 2

Disconnect the two-pin end of the pressure switch cable [1] from the pressure switch.

Warning: Before you do this step, put on eye protection. Do not disconnect the hose [2] to the hydraulic cylinder.

Remove the tank from the machine. Do not twist the hose [2] for the hydraulic cylinder. Put the tank vertically on the ground.

Remove the cap [3] from the Schrader filler valve.

note: If your system has a two-end tank system, a second Schrader valve is at the bottom of the tank. Remove the cap from the top valve.

Turn the T-handle fully counterlockwise on the gas chuck [4] attached to the "Charge/Discharge-Kit" (P/N 35-4050A).

With your fingers, tighten the nut on the gas chuck onto the Schrader valve.

Put the other end of the hose into a bucket.

Slowly turn the T-handle clockwise until the system starts to release the nitrogen gas. The time for this to complete is 10 minutes or less. Make sure the pressure gauge shows 0 psi.

Turn the T-handle fully counterclockwise and remove the gas chuck [4] from the Schrader valve.

Step 3

Remove the used pressure switch.

Install the PRESSURE SWITCH ASSY 1400PS [A]. Use a wrench to tighten the switch.

Warning: Before you do this step, put on eye protection.

With your fingers, tighten the nut on the gas chuck [1] attached to the Schrader valve.

note: Make sure you turn the T-handle of the gas chuck fully counterclockwise.
note: If your system has a double-ended tank system, a second Schrader valve is at the bottom of the tank. Use the top valve.

Attach the other end of the hose to the source pressure [2]. Slowly open the valve on the source pressure while you monitor the pressure gauge. Open the valve slowly at the start to protect the seals in the Schrader valve.

Step 4

Pressurize the system to the correct psi (bar). For the correct value, refer to the chart at the end of this procedure.

Install the tank into the machine.

Push ZERO RETURN. Push Z.

Examine the tank and hoses for leaks or unusual noises. Make sure the tank pressure is correct at the top of travel. Add nitrogen if necessary. Remove the "Charge/Discharge-Kit" (P/N 35-4050A). Replace the valve cap.

 

 

 

 

 

 

 

 

 

 

 

 

Counterbalance Pressure Chart

This chart shows the correct pressures for the counterbalance tank. Measure the pressure at the top of Z-Axis travel for VMCs and at the top of Y-Axis travel for HMCs. Pressure that is 50 psi (3 bar) higher than the value in the chart is permitted. But pressure that is lower than the value in the chart is not permitted.

 

Model Made After Pressure Made After Pressure Made 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 - - - - - -

 

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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