KraussMaffei Alarm MC45: Injection Pressure Limit Exceeded - Troubleshooting Guide
Published: 2026-05-28
KraussMaffei Alarm MC45 is generated by the MC6 controller (KM's latest-generation control platform) when the measured injection pressure exceeds the programmed maximum pressure limit during the injection or holding-pressure phases. Unlike simple...
KraussMaffei Alarm MC45 is generated by the MC6 controller (KM's latest-generation control platform) when the measured injection pressure exceeds the programmed maximum pressure limit during the injection or holding-pressure phases. Unlike simple overpressure alarms on older machines that only trigger at the hydraulic system relief valve setting, MC45 is a process-control alarm—it monitors the actual cavity pressure proxy (via hydraulic pressure transducer on the injection cylinder) against a user-programmable limit, allowing the limit to be set well below the machine's maximum capability to protect delicate molds or thin-wall parts from flash damage.
On KraussMaffei CX and GX series machines equipped with the MC6 controller, the alarm diagnostic screen will display: (1) the phase in which the limit was exceeded (injection velocity-controlled phase vs holding-pressure phase), (2) the peak pressure recorded, (3) the programmed limit, and (4) the screw position at which the overpressure event occurred. This data is essential for differential diagnosis—an overpressure during the velocity-controlled fill phase suggests a blocked gate or cold sprue, while overpressure during the holding-pressure phase suggests a process setting issue (holding pressure set too high) or a material viscosity change (degraded polymer with lower melt viscosity allowing faster pressure transmission).
Alarm Details
| Alarm Code | MC45 |
|---|---|
| Brand / Machine | KraussMaffei |
| Severity | High (Process Deviation / Cycle Stop) |
| Component | Injection Unit / Hydraulic System |
| Affected Systems | MC6 Controller / Injection Cylinder |
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 Alarm 405 | |
| Arburg Injection Pressure Alarm |
Frequently Asked Questions
How do I differentiate between a gate blockage and a process setting issue when MC45 triggers?
Use the MC6 diagnostic screen to identify the screw position at which the overpressure occurred. If the alarm triggers early in the injection stroke (screw position >70% of shot size remaining), the cavity has barely begun filling and the pressure spike indicates a physical obstruction—blocked gate, cold sprue, or incorrectly seated nozzle. Purge the barrel and inspect the nozzle orifice. If the alarm triggers late in the stroke (screw position <20% remaining) during the switchover to holding pressure, it's likely a process setting issue—reduce holding pressure in 5 bar increments and verify the part is still fully packed. KraussMaffei also recommends monitoring the injection work (integral of pressure × flow over the injection phase) as a trending parameter—a sudden increase in injection work at constant settings is an early indicator of gate blockage before MC45 triggers.
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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