Troubleshooting Boy 25Ton Ejector Retraction Faults

On a Boy 25Ton machine, the panel commands Y60, the ejector extends normally, then retracts only about halfway and the cycle hangs before the next mold movement. Start with ISH7: interference between its cam-follower roller and the safety cover can hold the hydraulic valve partly shifted and restrict motion in either direction. Do not begin by replacing cylinder seals or the Y60 return spring.

Read the symptoms before opening the circuit

Separate the original ejector fault from faults introduced during repair. One observation can eliminate an entire branch of troubleshooting.

Symptom or test result	Most useful interpretation
Y60 extends the ejector normally, but the cylinder rebounds or retracts halfway	The energized path works. Check the spring-return path, ISH7, mechanical binding, and hydraulic pressure during retraction.
Pressing or moving the ISH7 roller stops ejector travel in either direction	ISH7 controls a hydraulic path used by both extension and retraction. Partial actuation can meter or block flow.
Cycling the safety cover temporarily restores ejector operation	Look for marginal cam engagement, roller interference, or cover misalignment before dismantling the cylinder.
Removing the mold does not change the fault	Resin flash, a broken mold ejector retainer, and binding inside the mold become less likely.
Replacing the ejector-cylinder seals produces no change	The piston seal was not the cause. Return to the external valve and interlock path.
Pressure rises close to the system relief setting while the ejector stalls	The circuit is probably deadheaded by a bind, blocked passage, or valve that has not shifted fully.
Pressure remains very low during the commanded movement	Flow is bypassing through a relief or open path, or the selected circuit is not being pressurized.
The ejector works after service, but the mold cannot open or close and an inductive sensor remains dark	Check the full-retract sensing hardware. A coupling block installed backward can prevent the controller from receiving the retracted permissive.

Trace the spring-return hydraulic path

Y60 is a single-solenoid directional valve with spring return. Successful extension proves that the output command, coil, and energized valve path can produce motion. It does not prove that the spring-return position, downstream passages, mechanical interlocks, or retract confirmation are correct.

An intact return spring and an undamaged spool narrow the fault, but they do not clear the rest of the circuit. A second valve held between positions can throttle the return path even when the Y60 spool returns completely.

ISH7 is the decisive component in this installation. Its cam-follower wheel sits at the safety cover. When the wheel catches the side of the cover, the valve does not release cleanly. A partially shifted hydraulic valve creates a restricted opening, so the cylinder can start moving and then slow or stop as load and pressure change.

Retraction also has less theoretical force than extension on a single-rod cylinder. Extension force is Fextend = P × Apiston; retraction force is Fretract = P × (Apiston − Arod). That force difference can expose a bind, but it does not explain why moving the ISH7 roller can interrupt both directions. That test points to valve actuation, not merely cylinder geometry.

Check ISH7 first

Start here. Finding ISH7 physically is more useful than repeatedly tracing lines around Y60.

1. Run a controlled ejector cycle and confirm whether the failure occurs only on retraction or can affect extension as well.
2. Cycle the large safety cover through its normal travel. If ejector behavior changes immediately afterward, inspect the cover-operated hydraulic device.
3. Identify the three switches monitoring the cover. In this installation, two had electrical cables; the heavier third device had no cable and carried the hydraulic symbol shown on the schematic. That device was ISH7.
4. Isolate machine energy before placing hands near the roller, cover, or ejector. Check whether the cam-follower wheel moves freely and releases completely through the cover's full travel.
5. Inspect the side clearance between the wheel and the safety cover. Look for contact marks, a roller riding on the cover edge, loose mounting, or a cover shifted laterally.
6. Use an approved controlled test to correlate valve actuation with ejector motion. In the failed setup, roller actuation could stop the ejector during either extension or retraction.

That last result is the functional proof. A roller that controls both directions is upstream of the symptom; replacing parts inside the ejector cylinder will not correct its partial actuation.

Measure pressure before dismantling the cylinder

Use pressure to distinguish a blocked circuit from a circuit that never develops force. The gauge at M5 can show the general system response, but a gauge connected at the cylinder gives the clearest comparison between the commanded movement and the pressure actually reaching the actuator.

1. Record pressure during normal ejector extension.
2. Record pressure while retraction slows or stops.
3. Compare the stalled value with the machine's documented relief setting. Read that setting from the machine documentation or relief-valve data; do not substitute a guessed value.
4. If pressure approaches the relief setting, inspect for mechanical binding, a blocked passage, or incomplete valve shift.
5. If pressure remains low, trace the open return, relief, or bypass path that prevents pressure from building.
6. If M5 shows normal pressure but the cylinder port does not, isolate the restriction between the gauge point and the actuator.

The reservoir being about 3/4 inch below the filler cap does not prove correct pump delivery. The pump is submerged in this machine's tank, so absence of a visible external pump is normal for this installation. Confirm level against the machine's specified mark, then use pressure and flow behavior to judge delivery.

For schematic orientation, the P and T markings at Y60 indicate that B1 appears to be the pressure line and A1 the tank line. Verify the connection by tracing the actual manifold passages before disconnecting a hose or installing a gauge.

Correct the cover alignment and restore the permissive

The successful correction was mechanical alignment at ISH7, not replacement of the ram seals.

1. Isolate electrical and hydraulic energy, relieve stored pressure, and secure the safety cover.
2. Remove the cover mounting hardware needed for adjustment. The installed non-tamper fasteners were replaced with standard cap screws during this repair.
3. Move the safety cover laterally by 1/8 inch so its side cannot interfere with the ISH7 cam-follower wheel.
4. Tighten the mounting hardware and check roller clearance throughout the complete cover stroke. Preserve the guard's mechanical strength and interlock function.
5. Cycle the ejector and confirm full extension and full hydraulic retraction.

A second fault appeared after the ejector-seal work: the mold could no longer open or close, and the adjacent inductive sensor did not light. Comparison with another machine showed that a coupling block had been installed backward. Reorienting that block restored the full-retract indication required for mold movement.

Treat this as a separate feedback fault. Hydraulic retraction can be physically complete while the controller still blocks the mold because the retracted sensor never changes state.

Verify the complete machine sequence

Do not stop when the ejector moves once. Verify the hydraulic action, position feedback, guarding, and downstream mold permissives together.

1. Command several complete shot cycles and watch Y60 during ejector extension.
2. Confirm that the ejector extends to its working position and returns fully to the mechanical stop without pausing halfway.
3. Watch the full-retract inductive sensor. It must change state when the ejector reaches its retracted position.
4. Confirm that mold opening and closing become available only after the required ejector-retracted condition is present.
5. Move the safety cover through its full travel and verify that the ISH7 roller neither rubs the cover edge nor remains partly depressed.
6. Test the safety-cover interlock functions according to the machine's operating documentation. Do not bypass ISH7 or the electrical switches to obtain production motion.
7. Recheck pressure during extension and retraction. Investigate any repeatable rise toward relief pressure or failure to build pressure before returning the machine to service.

Avoid the fixes that waste time

• Replacing cylinder seals first: Seal replacement produced no change because the restriction was at the cover-operated hydraulic valve.
• Blaming the Y60 coil: Normal extension shows that the coil can energize and shift the valve for that direction. Concentrate on the spring-return circuit and series valve conditions.
• Stopping after inspecting the spring: A pristine spring and spool clear only the internals inspected. They do not clear ISH7 or another restricted manifold path.
• Assuming the mold is binding: Removing the mold without changing the symptom is a valid isolation test. Continue tracing the machine-side hydraulic circuit.
• Using reservoir appearance as a pump test: A nearly full tank says nothing about pressure under load.
• Cleaning every restriction immediately: A 1.5 mm throttle may be located below the P port when Y60 is removed. Inspect and clean it only after pressure testing points to a restricted supply passage, and maintain contamination control during reassembly.
• Ignoring repair-induced faults: When a new no-mold-motion symptom appears after cylinder service, inspect disturbed coupling and sensor hardware before reopening the original diagnosis.

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