Water-Assisted Injection Molding (WAIM) utilizes high-pressure water injection to hollow out thick-walled thermoplastic components during the molding cycle. This process eliminates sink marks, reduces part weight by up to 30%, shortens cycle times for thick sections, and creates smooth internal fluid channels. Designed for structural parts requiring high rigidity and complex hollow geometries.
Technical Specifications
|
Parameter |
Specification Range |
|
Max Shot Weight |
Up to 5,000 g |
|
Clamping Force |
160T – 1,200T injection molding machines (Equipped with high-precision servo water-assist controllers) |
|
Water Pressure Range |
10 MPa – 30 MPa (Precision servo-controlled) |
|
Dimensional Tolerance |
Standard ISO 20455-getClass 1 (±0.05 mm to ±0.15 mm) |
|
Wall Thickness |
Nominal: 2.5 mm – 8.0 mm; Core Hollow Ratio: 40% – 70% |
|
Max Part Length |
Up to 1,500 mm (depending on flow path geometry) |
Key Features
Sink-Mark Elimination: Internal water pressure pushes molten polymer against the mold cavity walls, completely removing exterior sink marks on thick ribs and bosses.
Hollow Internal Channels: Produces clean internal passages suitable for fluid transfer, wire routing, or structural reinforcement.
Weight Reduction: Decreases component mass by 20% to 30% compared to solid thick-walled injection molding without sacrificing flexural rigidity.
Reduced Warping: Uniform cooling from both external mold walls and internal water core minimizes internal residual stress and thermal distortion.
Materials & Options
|
Polymer Grade |
Typical Application |
Compatible International Brands |
|
PA6 / PA66 (GF30%) |
Automotive under-hood tubes, structural handles |
DuPont Zytel, Lanxess Durethan, BASF Ultramid |
|
PP (Talc / GF filled) |
Automotive interior trim, appliance housings |
LyondellBasell Moplen, Borealis |
|
ABS / PC+ABS |
Consumer electronics, ergonomic housings |
SABIC Lexan, Covestro Makrolon, Ineos Styrolution |
|
PBT / PBT-GF |
Electrical connectors, fluid housings |
Celanese Celanex, DSM Arnite |
Color Options: Custom color-matching via masterbatch or pre-colored resin.
Secondary Operations: Ultrasonic welding, CNC trimming, laser marking, and leak testing for hollow channels.
Manufacturing Process
DFM & Mold Flow Analysis:
Mandatory pre-production engineering review. Simulate water penetration path, core breakthrough risks, and solidification behavior using CAE software before tooling fabrication.
Tooling Fabrication:
Precision CNC machining and gun-drilling. Build hardened steel molds (P20, H13, or 2344) integrated with high-pressure water injectors and sealing shut-off nozzles.
Polymer Injection & Water Core Formation:
Synchronized injection sequence. Inject molten thermoplastic into the closed mold cavity to partially fill the section, immediately followed by high-pressure water injection to hollow the core.
Water Drainage & Decompression:
Cycle completion. Evacuate pressurized water through dedicated recovery valves, purge residual moisture with compressed air, and open the mold to eject the hollow part.
Quality Control & Manufacturing Facility
Quality Management System: Manufacturing operations strictly managed under IATF 16949 and ISO 9001 certifications, ensuring full traceability from raw resin lot to finished molded parts.
CMM Inspection: 3D coordinate measuring machines verify critical dimensions, hole locations, and geometric tolerances against CAD models.
Pressure Decay Testing: Pneumatic or hydraulic pressure decay leak testing conducted on 100% of parts requiring internal fluid channels.
Density & Section Analysis: Regular destructive cut-section sampling to verify uniform internal wall thickness and core hollow ratio.
Process Monitoring: Closed-loop injection molding machines record real-time pressure, velocity, and water injection curves for lot control.
Customization
Tooling Transfer: Accept existing production molds or build new multi-cavity tooling tailored to your press tonnage requirements.
Insert Molding: Overmold metal threaded inserts, brackets, or pins during the WAIM cycle.
Custom Packaging: ESD-safe trays, protective foam inserts, or bulk returnable containers configured to logistics specifications.
Applications
Door grab handles, roof rails, instrument panel structural beams, radiator coolant pipes, and seat frame components.
Refrigerator door handles, washing machine structural brackets, and ergonomic power tool housings.
Lightweight machine frames, fluid distribution manifolds, and tubular protective guards.
Packaging & Delivery
Packaging Configuration: Individual polyethylene bagging, layered corrugated cartons, and ISPM 15 compliant heat-treated wooden pallets.
Lead Time: Tooling fabrication: 4 to 6 weeks; Pilot samples: 1 week post-tooling trial; Mass production: 3 to 4 weeks per shipment.
Shipping Terms: FOB, CIF, or DDP via sea freight, air cargo, or express courier.
FAQ
Q: What is the primary advantage of Water-Assisted Injection Molding over gas-assisted molding?
A: Water has a much higher thermal capacity and is incompressible compared to nitrogen gas, resulting in faster internal cooling, thinner and more uniform internal walls, and smoother internal channel surfaces.
Q: How do you prevent water from remaining inside the hollow part after molding?
A: The injection sequence includes an automated compressed-air purge phase immediately following water evacuation, ensuring internal cavities are completely dry before part ejection.
Q: What file formats are required for quotation and DFM analysis?
A: We accept 3D CAD files in STEP, IGES, or Parasolid format, along with 2D drawings specifying critical tolerances, material grades, and annual volume projections.
Q: Can threaded metal inserts be molded into water-assisted parts?
A: Yes. Brass or steel threaded inserts can be loaded into the mold manually or via robotics prior to polymer and water injection.
Q: What is the minimum wall thickness achievable with WAIM?
A: Nominal external wall thickness typically ranges from 2.5 mm to 8.0 mm, with internal residual wall thickness controlled between 1.5 mm and 3.0 mm depending on material viscosity.
Q: What is the expected lifespan of the injection molds?
A: Tooling lifetimes typically range from 300,000 to over 1,000,000 production shots, depending on the mold steel grade (e.g., P20 vs. H13) and the reinforced polymer abrasive characteristics.
Q: How do you handle quality disputes or non-conforming shipments?
A: All shipments are accompanied by an Inspection Report (COA/CPK). Any non-conforming parts identified upon inspection are subject to immediate replacement or credit following our standard RMA procedure under IATF 16949 guidelines.
Request a Quote
Submit your project requirements, 3D CAD models, and estimated annual quantities to receive a formal DFM feedback report and commercial quotation within 24 hours.
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