KraussMaffei Alarm MC48: Injection Pressure Transducer Failure — Troubleshooting
Published: 2026-06-04
KraussMaffei Alarm MC48 triggers when the MC6 controller detects an implausible signal from the injection pressure transducer — either a frozen (unchanging) reading, a reading outside the sensor's calibrated range, or a sudden spike/drop...
KraussMaffei Alarm MC48 triggers when the MC6 controller detects an implausible signal from the injection pressure transducer — either a frozen (unchanging) reading, a reading outside the sensor's calibrated range, or a sudden spike/drop inconsistent with the injection cycle phase. Unlike overpressure alarms (MC45), MC48 indicates a sensor hardware fault, not a process condition. The machine cannot safely inject without accurate pressure feedback.
Root cause: (1) Melt ingress into the transducer diaphragm — polymer melt has penetrated past the transducer tip seal, solidifying on the sensing element and mechanically locking it. (2) Damaged transducer cable — the cable from the transducer to the MC6 I/O module is flexed with each injection cycle and eventually fatigues internally. (3) Transducer drift from thermal cycling — repeated exposure to 350-400°C melt followed by cooling to mold temperature causes the sensing element to drift over time, eventually exceeding the controller's acceptable deviation threshold. (4) Electrical noise — VFD or servo drive harmonics inducing false signals on the transducer's mV output.
Alarm Details
| Alarm Code | MC48 |
|---|---|
| Brand / Machine | KraussMaffei |
| Severity | High (Process Stop) |
| Component | Injection Pressure Transducer / Melt Pressure Sensor |
| Affected Systems | MC6 Controller / Injection Unit |
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 Pressure Sensor Alarm | |
| Arburg Pressure Transducer Fault |
Frequently Asked Questions
How can I verify a pressure transducer is faulty before replacing it?
(1) Check the transducer zero reading with the injection unit depressurized (screw retracted, no back pressure). It should read 0 ±0.5% of full scale. (2) Apply a known pressure using a dead-weight tester and verify the reading matches within ±1%. (3) Compare the transducer reading during injection to a portable pressure gauge installed in the nozzle adapter — a difference >5% indicates transducer drift or damage. (4) Wiggle the transducer cable while watching the pressure display — intermittent fluctuation indicates cable damage. Transducer replacement cost: $400-800. Labor: 30 minutes with the barrel hot (care required to avoid burns).
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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