Editorial Technical Reference

Injection Unit

This page explains how Injection Unit is classified within Machinery and Equipment Manufacturing. Technical values and manufacturer relationships are research references; confirm the current specification and supplier evidence for each order.

Technical Definition & Core Assembly

The component of a silicone molding machine responsible for melting and injecting silicone material into the mold cavity.

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Product Specifications

Technical details and manufacturing context for Injection Unit

Definition
The injection unit is a critical subsystem within a silicone molding machine that performs the material preparation and injection functions. It receives raw silicone material (typically in pellet or liquid form), heats it to the appropriate processing temperature, mixes it thoroughly to ensure homogeneity, and then injects it under controlled pressure into the mold cavity to form the desired silicone product. This unit is designed for precision and reliability, with key parameters including an injection volume of 50–500 cm³, injection pressure of 120–180 MPa, screw diameter of 30–60 mm, injection rate of 50–200 cm³/s, screw speed of 20–120 rpm, temperature control accuracy of ±1 °C, heating power of 5–15 kW, operating temperature range of 20–40 °C, operating humidity of 30–80% RH, ingress protection rating of IP54–IP65 (per IEC 60529), material grade S136 (DIN 1.2083), and weight of 500–1500 kg. The unit is constructed with hardened alloy steel for the barrel and screw, tool steel for the non-return valve and nozzle tip, and heat-resistant seals. These specifications are reference ranges that must be verified for the specific model and application. The injection unit operates by feeding silicone material into a heated barrel via a hopper or feed system. A reciprocating screw or plunger within the barrel rotates and/or moves forward, conveying the material through heated zones. This action generates shear heat and combines it with external barrel heating to melt and plasticize the silicone. Once a precise shot volume is accumulated in front of the screw/plunger, the entire assembly acts as a ram, moving forward rapidly to inject the molten silicone through a nozzle and into the closed mold under high pressure. For proper selection, consider the required shot size, material viscosity, and mold geometry. Interfaces include the hopper feed, barrel heating zones, screw drive, and nozzle. Verification questions should address actual performance data, material compatibility, and compliance with relevant standards. Maintenance signals include inconsistent shot weight, pressure fluctuations, or temperature deviations. Failure boundaries include excessive wear on the screw or barrel, seal degradation, and nozzle blockage. Always confirm model-specific values and standards with the legal manufacturer or supplier.
Working Principle
The injection unit operates by feeding silicone material into a heated barrel via a hopper or feed system. A reciprocating screw or plunger within the barrel rotates and/or moves forward, conveying the material through heated zones. This action generates shear heat and combines it with external barrel heating to melt and plasticize the silicone. Once a precise shot volume is accumulated in front of the screw/plunger, the entire screw/plunger assembly acts as a ram, moving forward rapidly to inject the molten silicone through a nozzle and into the closed mold under high pressure.
Common Materials
Hardened alloy steel (barrel, screw), Tool steel (non-return valve, nozzle tip), Heat-resistant seals
Technical Parameters
ParameterTypical rangeNotes & selection driver
Injection Volume50–500 cm³Determines maximum part size per shot.
Injection Pressure120–180 MPaHigher pressure for high-viscosity silicone.
Screw Diameter30–60 mmAffects plasticizing capacity and shear.
Injection Rate50–200 cm³/sCritical for filling thin-wall cavities.
Screw Speed20–120 rpmHigher speed reduces residence time.
Temperature Control Accuracy±1 °CEnsures consistent melt viscosity.
Heating Power5–15 kWSufficient for rapid heat-up.
Operating Temperature Range20–40 °CAmbient condition for stable operation.
Operating Humidity30–80 % RHNon-condensing to prevent material contamination.
Ingress Protection RatingIP54–IP65Protects against dust and water jets.IEC 60529
Material GradeS136Corrosion-resistant steel for silicone.DIN 1.2083
Weight500–1500 kgAffects installation and handling.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM
  • Barrel
    A heated cylindrical housing that contains the screw and provides thermal energy to melt the silicone material.
    Material: Hardened alloy steel with bimetallic liners
  • Reciprocating Screw Part
    Rotates to convey, shear, mix, and melt the material, then acts as a ram to inject it into the mold.
    Material: Hardened alloy steel (nitrided or bimetallic)
  • Heater Bands
    Electric heating elements wrapped around the barrel to provide precise temperature control along its length.
    Material: Ceramic or mica-insulated metal sheaths
  • Hopper
    Holds and feeds the raw silicone material (pellets, granules, or liquid) into the barrel.
    Material: Stainless steel or aluminum
  • Nozzle Part
    The tip that seals against the mold sprue bushing and directs the molten silicone into the mold.
    Material: Tool steel

Industrial Ecosystem & Supply Chain Structure

Complementary Systems
Downstream Applications
Specialized Tooling

Application Fit & Sizing Matrix

Operational Limits
pressure: Up to 200 MPa (maximum injection pressure)
flow rate: 0.1-100 cm³/s (injection rate range)
temperature: 20-200°C (typical silicone processing range)
slurry concentration: Not applicable (handles solid silicone pellets, not slurries)
Media Compatibility
✓ Liquid Silicone Rubber (LSR) ✓ High-Consistency Rubber (HCR) ✓ Thermoplastic Silicone Elastomers
Unsuitable: Abrasive-filled materials (e.g., glass-filled compounds) due to barrel/screw wear
Sizing Data Required
  • Shot Volume (cm³)
  • Injection Speed Requirement (cm³/s)
  • Clamp Force of Associated Molding Machine (kN)

Reliability & Engineering Risk Analysis

Failure Mode & Root Cause
Hydraulic cylinder seal degradation
Cause: Thermal degradation from high operating temperatures exceeding seal material limits, compounded by contamination from particulate ingress in hydraulic fluid
Screw and barrel wear
Cause: Abrasive wear from glass-filled or mineral-filled polymers, accelerated by improper temperature control causing material degradation and increased friction
Maintenance Indicators
  • Audible knocking or grinding sounds during screw rotation indicating mechanical wear or contamination
  • Visible hydraulic fluid leaks around injection cylinder or abnormal injection pressure fluctuations on control display
Engineering Tips
  • Implement predictive maintenance through vibration analysis on screw drive systems and regular oil analysis for hydraulic systems to detect wear precursors
  • Optimize thermal profiles using infrared thermography to prevent material degradation and maintain proper barrel/screw clearances through scheduled dimensional inspections

Indicative industry ranges for design and RFQ preparation. Confirm the exact figures and applicable standard with the manufacturer before specifying.

Compliance & Manufacturing Standards

Applicable Standards
ASTM D638 - Standard Test Method for Tensile Properties of Plastics

Quoted from the published standard.

Manufacturing Precision
  • Bore diameter: +/-0.01mm
  • Parallelism of platens: 0.05mm/m
Quality Inspection
  • Dimensional verification with CMM (Coordinate Measuring Machine)
  • Pressure decay leak test

Manufacturers of Injection Unit

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Frequently Asked Questions

What is the typical injection volume range for this injection unit?

The injection volume range is 50–500 cm³, which determines the maximum part size per shot. However, this is a reference range; the exact value depends on the specific model and application. Always verify with the manufacturer.

What materials are used in the construction of the injection unit?

The barrel and screw are made of hardened alloy steel, the non-return valve and nozzle tip are made of tool steel, and heat-resistant seals are used. These materials are selected for durability and resistance to wear and heat.

What is the ingress protection rating of the injection unit?

The ingress protection rating is IP54–IP65 as per IEC 60529, which indicates protection against dust and water jets. This is a reference range; the actual rating for a specific model should be confirmed with the supplier.

How does the injection unit achieve precise temperature control?

The unit features temperature control accuracy of ±1 °C, which ensures consistent melt viscosity. This is achieved through controlled heating zones and feedback systems. However, actual performance may vary; verify with the manufacturer.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification
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