Plastic refrigerator parts moulding

In addition, our company has established cooperative relationships with plastic raw material suppliers, printing manufacturers, etc. to ensure the supply of raw materials and printing quality. Through our rich experience and perfect supply chain, our company can provide customers with high-quality customized plastic refrigerator parts moulding products to meet their specific needs. At the same time, we have 10 years of professional foreign trade service experience, understand the foreign trade process, and better serve our customers. For plastic refrigerator parts moulding products, we can make corresponding plastic parts, which is mainly done through injection molds.

Refrigerator plastic components fall into five categories: decorative exterior parts, structural load-bearing parts, cooling air duct components, storage/organizing parts, and flame-retardant electrical components. Examples include door shells, inner liners, drawers and crisper bins, shelf supports, air duct covers, ice trays, door seal brackets, compressor shrouds, and interior partitions. These products operate in environments cycling between -20°C and room temperature and come into contact with moisture and food oils. Specific requirements include flame retardancy, low-temperature impact resistance, and dimensional stability (resistance to deformation). Mainstream materials include HIPS, modified PP, ABS, GPPS, and flame-retardant ABS. Key molding parameters focus on low-temperature toughness, low shrinkage, odorlessness, low internal stress, and hydrolysis resistance. The following sections outline the molding essentials, covering raw material pretreatment, mold design, the injection molding process, post-processing, and defect prevention.

I. Raw Material Selection and Pretreatment

Material Selection and Matching

Modified PP is primarily used for inner liners, storage drawers, and crisper bins due to its low-temperature resistance, grease resistance, low water absorption, and moderate cost. ABS is selected for door panels and decorative trim because of its high gloss, which facilitates film lamination and painting. High-impact HIPS is used for cabinet insulation liners and air duct plates, offering low molding shrinkage and stable rigidity. GPPS is used for transparent freshness boxes and storage shelves. Flame-retardant ABS is used for compressor shrouds and electrical boxes to meet appliance fire safety standards.

Strict Control of Material Recycling: The inclusion ratio of regrind (sprues/runners) for aesthetic parts must not exceed 10%. Mixing recycled scrap into inner liners or load-bearing shelves is prohibited; repeated recycling significantly reduces low-temperature toughness, making parts prone to cracking when storing frozen food. When mixing materials, only food-grade, low-migration mold release agents and odorless masterbatches are permitted; the use of pungent additives is strictly forbidden to prevent residual odors inside the refrigerator. Flame-retardant materials must be mixed and processed separately from standard plastics to avoid compromising flame-retardant properties.

Mixing Control Requirements

Use a vertical mixer to blend materials at low speed (under 300 rpm) for 6 to 10 minutes. Filled/modified PP should not be subjected to high-speed mixing to avoid powder agglomeration, which causes surface pitting. ABS and HIPS are relatively brittle; friction-induced heat buildup must be minimized to prevent premature degradation and yellowing of the pellets. After mixing, materials should be stored in sealed containers to prevent contamination by dust or oil.

Drying and Dehumidification Specifications

ABS and HIPS are highly hygroscopic; molding with high moisture content leads to silver streaks and bubbles, making parts prone to fracture at bubble sites under low-temperature stress. Drying standards: ABS at a constant 80°C for 3–4 hours; HIPS at 75°C for 3 hours; moisture content controlled below 0.04%. PP and GPPS have extremely low water absorption and generally do not require drying for standard production; however, in high-humidity environments (such as the "Plum Rain" season in southern regions), drying at 60°C for 1 hour to remove surface moisture is sufficient. After drying, materials should be conveyed via sealed hoppers to prevent re-absorption of atmospheric moisture.

II. Key Points for Mold Design and Machine Setup

Refrigerator plastic parts are typically large-area, thin-walled shells. Liners and drawers feature large dimensions with wall thicknesses of 1.6–2.2 mm; uneven thickness makes them prone to sink marks and warpage. Mold design focuses on optimizing cooling, venting, and balanced ejection systems.

Mold Steel Selection

For ABS exterior door shells, 718H pre-hardened mirror-finish steel is used for the cavity to ensure a uniform, glossy surface free of scratches or pits after polishing. P20 pre-hardened steel is selected for PP and HIPS liner molds to ensure stable mass production. Cavities for molds using filled/modified or flame-retardant materials undergo nitriding treatment to resist erosion from powders and flame-retardant additives, thereby extending mold service life. All internal corners feature radius (R) fillets to eliminate stress concentrations and prevent cracking during low-temperature thermal cycling.

Balanced Cooling System (Key to Preventing Warpage)

Liners and long drawers have high length-to-width ratios; molds utilize symmetrical, conformal cooling channels wrapping around both sides. Spiral cooling cores are installed within thick-walled mounting bosses and reinforcing ribs to minimize temperature differentials between thick and thin sections. Strict zoned mold temperature control: 50–60°C for ABS cosmetic parts; 30–40°C for PP liners; 40–50°C for HIPS air duct components. Excessive PP mold temperatures exacerbate crystallization shrinkage, leading to undersized drawers and sticking during operation; conversely, excessively low temperatures result in high residual internal stress, causing warping or deformation during low-temperature use.

Venting and balanced ejection design

For large-area liners with long melt flow paths, air entrapment and burning are prone to occur at distant weld lines; continuous, fine venting slots (0.012 mm deep) are machined along the long sides of the parting surface. Dense ribbing at the bottom utilizes a symmetrical multi-point layout of ejector pins and flat ejectors to ensure uniform ejection force and prevent the drawer from tilting or lifting on one side. Auxiliary ejector blocks are added for the thin-walled air duct cover plate to prevent punch-through or stress whitening.

Mold installation and setup specifications

Large molds for refrigerator liners and door shells are paired with 500T–1000T injection molding machines; clamping plates must be tightened evenly to prevent extensive flash caused by high-pressure injection. Flow detectors are installed on cooling circuits to ensure unobstructed flow; low-pressure mold-closing protection is calibrated to prevent cavity damage from residual sprue material; and comprehensive leak testing is performed on cooling circuit connections to eliminate moisture ingress into the melt, which could cause bubbles.

III. Key points of injection molding process control

Core process strategy: Low shear, staged holding pressure, and adequate cooling to minimize internal molding stress and enhance low-temperature impact resistance. Barrel Temperature Zoning

ABS door shell: Feed zone 160°C, middle zone 180–190°C, nozzle 195–205°C; temperature must not exceed 210°C, as high heat reduces material toughness, making it prone to cracking upon impact in cold environments.

Modified PP inner liner/drawer: 190–220°C, nozzle 210°C; excessive heat causes additive migration, resulting in white spots and odors on inner walls.

HIPS air duct panel: 180–205°C; flame-retardant ABS electrical components: maximum temperature 230°C to prevent decomposition and failure of the flame-retardant system.

Staged Injection Filling

Long inner liners and drawers utilize three-stage variable-speed filling: low-speed buffering at the gate, medium-to-high speed filling for the cavity mid-section, and reduced speed at the distal weld line area to minimize internal stress caused by molecular shear. Injection pressure: 80–110 bar; insufficient pressure results in weak weld lines prone to breakage after cooling, while excessive pressure causes increased flash and internal stress accumulation.

Two-Stage Holding Pressure

PP exhibits significant crystallization shrinkage; therefore, two-stage holding pressure is required for compensation. The first stage fills the cavity, while the second stage compensates for cooling shrinkage, eliminating sink marks on the inner liner's sidewalls and bottom. Holding time: 6–10s for thin-walled air duct panels, 12–18s for thick-walled storage drawers; material plasticization for the next cycle occurs simultaneously during the holding phase to shorten the overall molding cycle.

Cooling and Part Removal Specifications

Cooling time is calculated at 3–4s per 1mm of wall thickness; a standard 2mm inner liner requires 8–12s of cooling. Parts with insufficient cooling may appear flat upon demolding but can undergo permanent deformation during prolonged low-temperature storage. Mold opening and ejection must be performed at low, steady speeds; an automated robot removes the parts, which are then laid flat on a level fixture—stacking or compressing hot plastic parts is strictly prohibited.

We are a plastic refrigerator parts moulding manufacturer, providing high-quality plastic refrigerator parts moulding manufacturing. As long as you want to customize/develop plastic refrigerator parts moulding products, you can find us. We have professional injection mold design and mature manufacturing technology, providing you with one-stop service, from product design-mold making-product production-product packaging-product transportation, we can help you in every link. As long as you come to us, we will provide you with the ultimate service and satisfy you in terms of product quality, production time, information dialogue, etc.

Plastic Injection Mould making

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Factory

We are Custom Plastic Mold factory. Our factory is plastic injection mold maker. we has 17 years of experience in professional custom plastic mold and 10 years of foreign trade experience. We are custom Plastic Mold supplier. We can provide custom Plastic Mold service. Our factory can make the Injection molded plastic parts, and the quality of the products will satisfy you.

We have more than 50 high-end machines and hundreds of engineers and designers. We can provide one-stop service, from product design - mold making - product production - product packaging - transportation. We have a complete production chain. We can meet all your requirements.

Services we provide:

Professional custom mold service, Plastic mold design and manufacturing .plastic product production, product design, mold design, blow mold customization, rotational mold customization, die-casting mold customization. 3D printing services, CNC manufacturing services, product packaging, customized packaging, shipping services.

We always adhere to the principles of quality first and time first. While providing customers with the highest quality products, try to maximize the production efficiency and shorten production time. We are proud to tell every customer that our company has not lost any customer since its establishment.If there is a problem with the product, we will seek a solution actively and take responsibility to the end.

FAQ

Q1: Are you trading company or manufacturer ?

A: We are manufacturers.

Q2. When can I get the quotation?

A: We usually quote within 2 days after we get your inquiry.

If you are very urgent, please call us or tell us in your email so that we can quote for you first.

Q3. How long is the lead-time for mold?

A: It all depends on the products' size and complexity. Normally, the lead time is 25 days.

Q4. I have no 3D drawing, how should I start the new project?

A: You can supply us a molding sample, we will help you finish the 3D drawing design.

Q5. Before shipment, how to make sure the products quality?

A: If you don't come to our factory and also don't have the third party for inspection, we will be as your inspection worker.

We will supply you a video for production process detail include process report, products size structure and surface detail, packing detail and so on.

Q6. What is your payment terms?

A: Mold Payment: 40% deposit by T/T in advance, 30% second mold payment before sending out the first trial samples, 30% mold balance after you agree the final samples.

B:Production Payment: 50% deposit in advance, 50% before sending out the final goods.

Q7: How do you make our business long-term and good relationship?

A:1. We keep good quality and competitive price to ensure our customers benefit for best quality products.

2. We respect every customer as our friend and we sincerely do business and make friends with them, no matter where they come from.