Arburg 350 Alarm: Ejector Forward Limit —… — Causes & Fixes
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-08-15
Arburg Error 350 is triggered when the ejector mechanism fails to reach the forward position within the programmed time limit, or when the ejector forward limit switch is not actuated within the expected stroke. The ejector system pushes the...
Arburg Error 350 is triggered when the ejector mechanism fails to reach the forward position within the programmed time limit, or when the ejector forward limit switch is not actuated within the expected stroke. The ejector system pushes the molded part off the core half of the mold after the mold opens. If the ejector does not move forward sufficiently, the part will not be ejected, and the next cycle will attempt to inject over the stuck part, potentially causing catastrophic mold damage.
Alarm Details
| Alarm Code | 350 |
|---|---|
| Brand / Machine | Arburg |
| Severity | High (Cycle Interruption) |
| Component | Ejector Mechanism / Hydraulic Cylinder |
| Affected Systems | Selogica Controller / Ejector |
Troubleshooting Protocol
Open the mold and inspect the core side for molded parts that were not ejected. If a part is stuck on the core, manually remove it using brass tools. Check the ejector pins for signs of wear or damage — bent pins, broken pins, or pins that are not flush with the mold surface.
The ejector stroke may be set too short to fully eject the part. Review the ejector stroke setting in the Selogica controller. The stroke should be sufficient to push the part completely off the core, plus an additional 2-3mm of clearance. Increase the stroke setting by 5mm increments and test.
The ejector hydraulic pressure may be insufficient to overcome the part release force. Check the ejector pressure setting in the controller. Increase the pressure by 10% increments and observe the ejector movement.
For spring-return ejector systems, broken or weakened return springs can prevent the ejector plate from returning fully. Inspect all return springs for cracks or permanent set. Replace any springs that show signs of fatigue. Verify that the ejector plate moves freely on the guide pins.
Common Root Causes
The following root causes are ranked by probability based on field experience with this alarm code:
Low oil level is the single most common cause of hydraulic pressure alarms. The pump draws air when the oil level drops below the pump intake, causing cavitation, pressure fluctuations, and eventual pump damage. Check the oil level with all cylinders retracted (clamp open, injection unit retracted). Use only the specified ISO grade (typically ISO VG 46 for most injection molding machines). Mixing different viscosity grades creates erratic pressure response.
Hydraulic oil contamination causes proportional valves, servo valves, and pump wear. Particle contamination (ISO 4406 > 20/18/15) causes valve spools to stick, leading to erratic pressure control and nuisance alarms. Water contamination (emulsified oil, milky appearance) reduces lubricity and causes pump cavitation. Take an oil sample for analysis — particle count and water content (Karl Fischer test) confirm contamination levels.
Piston pumps and vane pumps develop internal wear over time, allowing oil to bypass the pumping elements. This reduces flow rate and maximum pressure capacity. Measure the pump's case drain flow — a worn pump has significantly higher case drain flow than the OEM specification. A typical axial piston pump should have case drain flow below 5% of rated flow; above 10% indicates the pump needs replacement or overhaul.
A pressure relief valve stuck partially open bleeds hydraulic pressure back to the tank, preventing the system from reaching the commanded pressure. Listen for continuous flow noise at the tank return line when the pump is running but no axes are moving — this indicates the relief valve is passing oil. The proportional valve's solenoid coil should be tested for resistance (check against OEM specification) and the valve spool should be inspected for contamination.
Hydraulic accumulators (bladder or piston type) maintain system pressure during peak demand and absorb pressure shocks. A ruptured bladder results in zero accumulator function, causing pressure drops during simultaneous axis movements and pressure spikes when valves close. Check the nitrogen pre-charge pressure with a charging kit — the pre-charge should be approximately 60-70% of the maximum system pressure. A flat accumulator (zero pre-charge) indicates a ruptured bladder.
Preventive Maintenance
Follow these preventive maintenance measures to reduce the frequency of this alarm:
- Take hydraulic oil samples for analysis every 500 operating hours. Test for ISO 4406 cleanliness code, water content (Karl Fischer), and viscosity. Change the oil when the particle count exceeds 20/18/15 or water content exceeds 500 ppm.
- Replace hydraulic return-line filters every 500 operating hours (or per OEM schedule). Never exceed the filter's rated pressure drop — a clogged filter bypass valve opens and allows unfiltered oil to circulate, accelerating pump and valve wear.
- Test accumulator nitrogen pre-charge pressure monthly. Log the pre-charge pressure in the machine maintenance record. A gradual pressure loss indicates a leaking valve core; a sudden loss indicates a ruptured bladder requiring immediate replacement.
OEM Replacement Parts
| Part Name | OEM Part Number | Est. Price |
|---|---|---|
| Arburg Ejector Forward Limit Switch | AR-350-ELS | $80-180 |
| Arburg Ejector Cylinder Seal Kit | AR-350-ECS | $200-450 |
| Arburg Ejector Position Transducer | AR-350-EPT | $350-700 |
Prices are estimated US market ranges. Contact your OEM distributor for exact pricing. {zone} = zone-specific variant.
Same Alarm on Other Machine Brands
If you operate multiple injection molding machine brands, the same fault may appear under different alarm codes:
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Engel Ejector Alarm | |
| Netstal Ejector Fault |
Frequently Asked Questions
What is the difference between a forward limit switch alarm and a position alarm?
A forward limit switch alarm (Error 350) indicates that the ejector has not physically reached the forward limit switch position — this typically means the ejector is not moving far enough forward, or the switch is misaligned. A position alarm indicates that the actual ejector position does not match the programmed position — this could be a calibration issue, a position transducer failure, or a mechanical obstruction.
Can mold temperature affect ejector operation and trigger Error 350?
Yes. A mold that is too hot can cause the molded part to shrink tightly onto the core, increasing the force required to eject the part. A mold that is too cold can cause the part to shrink excessively, potentially falling off the core before the ejector stroke is complete. Both conditions can cause the ejector to fail to reach the forward position.
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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