Tool Release Piston - How it Works and Troubleshooting Guide

How it Works

The Tool Release Piston (TRP) assembly is an essential part of all mill spindle configurations.

When activated the TRP pushes on the spindle drawbar to force it open and release the tool. When deactivated the TRP retracts and breaks contact with the spindle drawbar. The spindle drawbar then provides clamping force on the tool holder. This activity is monitored by either one or two sensors on the TRP, depending on the type of TRP.

  • [1] 40-taper
  • [2] 50-taper
  • [3] 40-taper inline drive

The purpose of the TRP is to release the tool from the spindle. This can be done automatically during a tool change or manually using the tool release button. This is used to remove and install tools into the spindle.

The TRP is a pneumatic assembly that is controlled by solenoids. The solenoids are activated by commands from the processor to the I/O PCB, which then sends 120 VAC out to the TRP pre-charge and tool release solenoids. When a tool release is commanded:

  • The pre-charge solenoid is energized to send low pressure air output, controlled through a regulator, to the TRP. The TRP gently engages with the spindle drawbar.
  • A fraction of a second later the tool unclamp is commanded and the main TRP solenoid is activated. Full air pressure is supplied to the TRP.
  • The TRP pushes the spindle drawbar out to release the tool.
  • The unclamp sensor confirms the tool unclamp status.
  • When the tool change is complete, or the tool release button is released, the TRP solenoid is closed and air is exhausted from the TRP.
  • The TRP return spring retracts the TRP piston.
  • The TRP breaks contact with the spindle drawbar. Drawbar force is applied to the tool in the spindle.
  • The TRP sensor registers the tool clamp status in diagnostics and confirms the TRP cycle is complete.

Symptom Possible Cause Corrective Action Section
Alarm 134 TOOL CLAMP FAULT, or the TRP does not activate when commanded. The solenoid is inoperable. Test the solenoid. 1
The air volume is low. Check the air system. 2
Parameter 71 is incorrect (CHC). Check the value of Parameter 71 3

The TRP hits the drawbar and makes a loud banging noise.

The precharge regulator is not adjusted properly. Properly adjust the precharge regulator. 4
Precharge pressure incorrect on a fixed regulator. Replace the fixed regulator.
The TRP does not push out enough to release the tool. There is an air leak. Check air system and low air delay Parameter 76. 2
The drawbar is damaged. Inspect the drawbar. 5
The TRP pushout is not properly adjusted. Verify and adjust the drawbar height. 7
The piston o-ring has no lubrication, or the piston/bore or o-ring is damaged. Replace the TRP. 9
The TRP retracts slowly. The return spring is broken. Replace the return spring. 6
The exhaust muffler is clogged. Test the exhaust muffler. 8
The piston o-ring has no lubrication, or the piston/bore or o-ring is damaged. Inspect the piston o-ring. 9

Section 1

Symptom: Alarm 134 TOOL CLAMP FAULT, or the TRP does not activate when commanded.

Possible Cause: The solenoid is inoperable.

Corrective Action:

Clean the solenoid valve.

Press and hold the tool release. Check the voltage to the solenoid. It should have 120 VAC. If there is no power, make sure it has a good connection to the I/O PCB.

If the connection to the I/O PCB is good, refer to Solenoid - How it Works and Troubleshooting Guide to troubleshoot the solenoid.

Section 2

Symptom: Alarm 134 TOOL CLAMP FAULT, or the TRP does not activate when commanded. The TRP does not push out enough to release the tool.

Possible Cause: The air volume is low. There is an air leak.

Corrective Action:

Check the air pressure supply.

Check the air volume supplied to machine. Refer to the Air Requirement section in the New Machine Setup / Pre-Installation for required hose size and other instructions.

Check for air leaks in supply hose / solenoid exhaust / TRP.

Verify Parameter 76 Low Air Delay is set to 1500.

Section 3

Symptom: Alarm 134 TOOL CLAMP FAULT, or the TRP does not activate when commanded.

Possible Cause: Parameter 71 is incorrect (CHC).

Corrective Action:

Check the value of Parameter 71, DRAW BAR OFFSET.

Model P71 Value Model P71 Value Model P71 Value
DM/DT 0 Mini Mill 111000 VF1-VF4 83300
EC 0 S Mini Mill 66600 VF2SS-VF4SS 555000
EC1600 40000 Office Mill 12000 VF5/40-VF12/40 66600
ES 0 OM1A, OM2A 112000 VF3/50-VF12/50 40000
GR 66600 SR 0 VM 111000
GR408 0 Toolroom 111000 VR 0
MDC 0 UMC 66600 VS 0

Section 4

Symptom: The TRP hits the drawbar and makes a loud banging noise.

Possible Cause: The precharge regulator is not adjusted properly.

Corrective Action:

Adjust or replace the precharge regulator:

  • Adjustable regulator [1] - Properly adjust the precharge regulator. If the precharge regulator is damaged and is unable to adjust, replace it.
  • Fixed nonadjustable regulator [2] - Verify the pressure, replace the precharge regulator if pressure is incorrect.

Section 5

Symptom: The TRP does not push out enough to release the tool.

Possible Cause: The drawbar is damaged.

Corrective Action:

Remove and inspect spindle drawbar for broken spring washers or any other damage.

Inspect spindle drawbar for damaged o-ring seals (TSC machines only). Go to Spindle - Drawbar - How it Works and Troubleshooting Guide to troubleshoot the drawbar.

Section 6

Symptom: The TRP retracts slowly.

Possible Cause: The return spring is broken.

Corrective Action:

If the return spring is broken, replace the TRP base assembly.

Section 7

Symptom: The TRP does not push out enough to release the tool.

Possible Cause: The spindle TRP tip height is not properly adjusted.

Corrective Action:

40T TSC Belt Drive Only - Inspect the TRP tool release bolt, or carbide tip for excessive wear or damage.

Verify the spindle drawbar pushout and sensor adjustments.

Adjust the height by adding or removing shims. Go to diy.haascnc.com and reference TRP switch adjustment for more information.

Section 8

Symptom: The TRP retracts slowly.

Possible Cause: The exhaust muffler is clogged.

Corrective Action:

Remove the exhaust muffler from the solenoid and test TRP operation. Replace the exhaust muffler if necessary.

Section 9

Symptom: The TRP does not push out enough to release the tool. The TRP retracts slowly.

Possible Cause: The piston o-ring has no lubrication, or the piston/bore or o-ring is damaged.

Corrective Action:

40T Belt Drive Only - Remove the TRP and apply lubricant to the TRP housing.

Install the TRP on the machine and in the correct place. Cycle the machine. DO NOT ACTIVATE TRP WHEN THE TRP IS NOT IN PLACE, DAMAGE TO THE TRP MAY OCCUR.

The TRP base is not serviceable due to the high spring pressure. If damaged, the assembly must be replaced.

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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