Injection Screw Head

As an experienced Chinese manufacturer of Injection Screw Head, HAPPY PLASTICS supplies durable replacement screw tips to restore stable plasticizing pressure. Fabricated from premium Cr12MoV tool steel and vacuum quenched to HRC 58–62, our components eliminate frequent check ring chipping and black speck contamination during fast color changeover procedures.

Technical Specifications

To withstand long-duration high-pressure injection cycles without premature erosion, HAPPY PLASTICS’s Injection Screw Head is manufactured against rigorous metallurgical benchmarks. We offer customized alloy material solutions matched to the abrasion level of your specific molding resin:

• SKD61 (H13) Base Tool Steel: Vacuum hardened to HRC 50–54. It features outstanding thermal shock resistance and structural toughness, suitable for non-filled general-purpose plastics including PP, PE and PS.

• Bimetallic Surface Overlay Welding: For abrasive materials such as 30% glass fiber reinforced PA66 or PBT, a 1.5 mm tungsten carbide alloy layer (HRC 60–65) is plasma arc welded onto the wear surface of the check ring.

• Gas Ion Nitriding Treatment: Surface hardness exceeds 950 HV with controlled nitriding depth ranging from 0.4 mm to 0.6 mm, providing reliable anti-corrosion performance against corrosive volatiles released by PVC, halogen-free flame retardants and POM.

• Dimensional Precision: All threads and critical sealing surfaces are precision cylindrical ground post heat treatment, with concentricity strictly controlled below 0.015 mm.

Solving Typical Production Bottlenecks & Molding Defects

Installing a properly customized Injection Screw Head eliminates localized abnormal wear that triggers structural flaws on finished plastic parts:

Eliminate Melt Backflow & Shot Weight Deviation

If the check ring fails to fully seal against the thrust washer during injection stroke, molten polymer flows backward along screw flights, leading to unstable cushion thickness and inconsistent part weight. Our precision ground 45° sealing bevel achieves complete mechanical sealing within 0.1 second of forward screw movement, restricting shot-to-shot weight fluctuation within ±0.2%.

Prevent Resin Degradation & Black Speck Formation

Standard or worn screw heads retain dead flow zones where heat-sensitive resins like PC, PMMA and ABS stagnate and carbonize under sustained heat. Our CFD-optimized streamlined flow geometry removes all material retention areas. Combined with high-gloss mirror finishing (Ra ≤ 0.2 μm), melt flows uniformly in a first-in, first-out pattern, accelerating color switching efficiency by up to 35%.

Reduce Tip Cracking & Cold Startup Damage

Operators often initiate injection cycles before the barrel reaches standard operating temperature. Unmelted pellets generate extreme torque that fractures screw head threads. Our design adopts rounded thread root fillets instead of sharp V-shaped grooves to evenly distribute mechanical stress, lowering thread breakage risk by 40%.

Target Industrial Application Scenarios

The installation of a robust Injection Screw Head is essential for high-yield manufacturing lines across several specialized sectors:

Precision Automotive Components

For thick-walled automotive connectors and engine bay housings molded with glass-filled polyamides, our bimetallic 3-piece valve assemblies maintain steady melt cushion under injection pressure over 180 MPa, effectively eliminating sink mark defects.

High-Speed Packaging & Thin-Wall Molding

High-speed production of bottle caps, closures and thin-wall food containers adopts high-MI PP resin, requiring instantaneous valve response under short cycles. Our lightweight low-inertia check rings reduce mechanical response lag and sustain stable melt pressure through millions of production cycles.

Core Advantages of Cooperating with HAPPY PLASTICS

• 36 Years of Accumulated Engineering Data: Founded in 1990, HAPPY PLASTICS maintains a comprehensive dimension database covering mainstream domestic and international injection molding machine brands. This allows us to manufacture an accurate Injection Screw Head matching your specific model and year.

• ISO9002 Certified Quality Management: Every component undergoes full inspection via coordinate measuring machines (CMM). Axial runout and thread tolerances are fully verified before shipment to guarantee interference-free installation.

• 90-Day Structural Quality Warranty: Our dedicated after-sales team tracks product operating performance. Free replacement is provided within 90 days for confirmed material cracking or premature abnormal wear under specified standard molding parameters.

Customization & Standard Manufacturing Workflow

To ensure your new Injection Screw Head aligns perfectly with your production setup, every order follows a structured manufacturing protocol: 

[Resin & Wear Performance Analysis] → [Machine Dimension Database Matching] → [5-Axis CNC Precision Milling] → [Vacuum Heat Treatment / Bimetallic Cladding] → [Mirror Polishing & CMM Final Inspection]

1. Resin Performance Analysis: We evaluate key properties of your molding material, including glass fiber loading ratio, processing temperature and corrosive flame retardant content, to select the optimal metallurgical solution.

2. Geometric Custom Calculation: If your barrel has been worn, honed and enlarged, our technical team calculates the exact oversized outer diameter to restore standard sealing clearance.

Product-Specific Technical FAQ

Q: Why does the check ring crack or chip prematurely when molding transparent polycarbonate (PC)?

A: PC features high melt viscosity and requires heavy injection pressure. Conventional nitrided steel delivers high surface hardness but insufficient overall toughness; repeated cyclic impact will cause micro-spalling of the nitrided layer. For optical-grade PC or PMMA molding, we recommend fully through-hardened tool steel such as DC53 or SKH51 with mirror polishing. This grade delivers superior impact resistance and removes stress concentration points.

Q: How to judge if the existing Injection Screw Head assembly is worn without removing the full screw?

A: The most obvious on-production signal is unstable or vanishing melt cushion at the end of injection stroke, accompanied by inconsistent dosing times. If injection pressure remains high yet the cushion keeps shrinking to zero during holding phase, grooves have formed on the sealing surface of the check ring or thrust washer, allowing melt backflow.

Q: Can your factory customize a 3-piece non-return valve set for re-bored or honed barrels?

A: Yes. After barrel honing and enlargement, standard-size components create excessive radial clearance and severe melt backflow. You only need to provide the actual inner diameter of the honed barrel and thread specifications of your screw end. Our engineers calculate and machine oversized check rings and thrust washers to restore the optimal 0.02 mm–0.04 mm radial sealing gap, cutting costs by avoiding full barrel replacement.