Toshiba EC 8502 Alarm: Injection Pressure Limit Exceeded — Troubleshooting
Published: 2026-06-02
Toshiba EC 8502 triggers when the injection pressure measured at the nozzle tip transducer exceeds the set limit value for more than 0.5 seconds. This is a protective alarm — the machine stops the cycle to prevent mold damage from excessive...
Toshiba EC 8502 triggers when the injection pressure measured at the nozzle tip transducer exceeds the set limit value for more than 0.5 seconds. This is a protective alarm — the machine stops the cycle to prevent mold damage from excessive injection pressure. Common causes: frozen gate (material solidified in gate before filling completed), blocked nozzle tip (contamination or degraded material), excessive injection speed setting relative to material viscosity, or a faulty pressure transducer providing incorrect readings.
Troubleshooting protocol: 1. Check actual pressure curve on the injection monitoring screen — compare peak pressure to the alarm threshold. 2. Verify nozzle temperature — if nozzle is 10-15°C below setpoint, material viscosity increases sharply, driving injection pressure up. 3. Purge the barrel through the nozzle into free air — if purge pressure is normal, the restriction is in the mold (blocked gate, insufficient venting). If purge pressure is high, the nozzle or check ring is the restriction point. 4. Verify the pressure transducer zero offset — transducer drift can cause false pressure readings.
Alarm Details
| Alarm Code | 8502 |
|---|---|
| Brand / Machine | Toshiba |
| Severity | High (Cycle Stop) |
| Component | Injection Unit / Pressure Transducer |
| Affected Systems | Injection Pressure Control |
Troubleshooting Protocol
Identify which zone/component triggered the alarm. Record the error code, timestamp, and any measured deviation values shown on the diagnostic screen.
Power down the machine and follow Lock-Out Tag-Out procedures. Visually inspect the affected component for physical damage, loose connections, polymer leakage, or carbonized material.
Using a multimeter, check resistance/continuity on the affected circuit. Verify SSR functionality and fuse integrity. Compare readings to OEM specifications.
Replace the failed component with an OEM-approved part. Do not substitute with generic equivalents unless validated for the specific machine model and operating conditions.
Restart the machine, verify the alarm is cleared, run a test cycle, and document the root cause, repair performed, and parts replaced in the machine maintenance log.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Engel 405 Injection Pressure Limit |
Frequently Asked Questions
What causes intermittent 8502 alarms?
Intermittent 8502 alarms typically result from inconsistent material viscosity — check drying consistency (moisture analyzer), barrel temperature PID tuning, and regrind percentage variation. A worn check ring that seals inconsistently can also cause intermittent pressure spikes.
Related Diagnostics & Materials
Netstal Alarm 102: Heating Zone Temperature Out of Range...
Netstal Alarm 102 occurs when the actual temperature of a specific heating band in the injection barrel deviates...
Arburg Error 320: Barrel Heating Control Failure -...
Arburg Error 320 is a critical interlock alarm triggered when the Selogica controller detects no current flow to one...
Engel Alarm 405: Screw Recovery Time Exceeded - Diagnostics & Fix
Engel Alarm 405 is generated by the CC300 controller when the screw recovery (plastication) time exceeds the maximum...
Netstal Alarm 301: Mold Protection Force Exceeded -...
Netstal Alarm 301 is one of the most critical safety alarms in injection molding—it triggers when the clamping unit...
Sumitomo Demag Alarm 220: Clamp Force Not Reached -...
Sumitomo Demag Alarm 220 triggers when the NC5 (or NC5 plus) controller detects that the actual clamping force...
KraussMaffei Alarm MC45: Injection Pressure Limit...
KraussMaffei Alarm MC45 is generated by the MC6 controller (KM's latest-generation control platform) when the...
Wittmann Battenfeld Alarm B6: Ejector Position Fault -...
Wittmann Battenfeld Alarm B6 triggers on the Unilog B8 (or B6/B6P) controller when the ejector system fails to reach...
Arburg Error 290: Screw Rotation Speed Deviation -...
Arburg Error 290 is triggered by the Selogica controller when the actual screw rotation speed (measured by the screw...
References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org