The Molding Process Of Melamine Resin And Its Application in Washbasins

Melamine resin (melamine formaldehyde resin, MF), as a thermosetting material,It has the characteristics of being stain-resistant, scratch-resistant, not easily deformed, non-toxic and odorless, making it very suitable for making household washbasins (especially for small-sized apartments and simple washroom scenarios). Its main forming processes include compression molding, transfer molding, injection molding, laminating, and casting. Among them, compression molding is the most mainstream and mature method and is also the main forming way for melamine washbasins.

 

I. Compression molding (Compression molding / Hot press molding)

The most commonly used process, which is also the core molding method for melamine washbasins, Suitable for household ordinary washbasins, simple washbasins, wall-mounted small washbasins, etc., balancing practicality and economy.

Principle: Put the melamine molded plastic (powder/plate, which can be added with color powder and antibacterial agents, suitable for the appearance and hygiene requirements of the washbasin) into the customized washbasin mold (corresponding to single basin, double basin, with storage slot, etc. styles), close the mold and apply pressure. The resin melts and flows to fill the mold cavity. After high-temperature cross-linking and curing, it becomes the washbasin blank.

 

Typical parameters (suitable for washbasins)

Mould temperature: 155–175°C (The upper mould is slightly higher by 5°C to ensure the smooth surface of the basin and reduce defects)

Forming pressure: 18–22 MPa (for the thickness of the basin wall of the washbasin, to avoid air holes and depressions)

Cycle: 60–150 seconds (depending on the size of the basin, a small wall-mounted basin takes 60–90 seconds, and a large single basin takes 90–150 seconds)

Post-curing: 80–100°C oven for 40–60 minutes (improves the water resistance and toughness of the basin, preventing cracking from prolonged exposure to water)

 

Process (for washbasin only)

1. Mix the materials (add melamine powder, color powder and antibacterial agent according to the formula to ensure uniform color and no odor of the washbasin) → 2. Preheat (heat the plastic mold to 40–50°C to facilitate flow and filling into the mold) → 3. Add the material (pour the preheated material into the washbasin mold cavity and spread it evenly) → 4. Initial pressure and exhaust (close the mold under low pressure and remove the air from the cavity to avoid bubbles and pinholes in the basin body) → 5. Hold and cure (apply high pressure and constant temperature to allow the resin to fully cross-link and form the shape of the washbasin) → 6. Demolding (cool down to below 80°C to demold, avoiding deformation of the basin body) → 7. Edge trimming/Post-curing (trim the basin edge and rough edges, and then undergo post-curing in an oven to enhance durability)

 

Exclusive craftsmanship for washbasins: Two-color/textured process. It can produce melamine washbasins with marble-like or ceramic-like textures. The process is as follows: apply base color material → initial pressing → exhaust air → maintain pressure → demolding → lay texture material / apply imitation stone film → secondary maintaining pressure → finished product. It is suitable for different home decoration styles.

 

 

II. Transfer Molding Process

Applicable: Compact melamine washbasins with complex structures, such as integrated washbasins with built-in storage compartments, overflow outlets, and reserved channels for drainage, as well as artistic washbasins with irregular shapes (such as oval or irregular-shaped basins).

 

Features: The materials are heated and melted in the feeding chamber, then pushed into the closed basin mold cavity through the flow channel for solidification. The pressure is uniform, the burrs are few, and the dimensional accuracy is high. It can precisely form the overflow ports, storage slots and other details of the basin, avoiding post-processing and improving the yield rate.

 

Compression molding: The equipment/molds are more expensive, but it is suitable for complex structure washbasins and solves the problem that the compression molding process is difficult to form irregular and multi-detail washbasins. It is often used in the production of mid-to-high-end melamine washbasins.

 

 

III. Injection Molding

Applicable: Large-scale production, high dimensional accuracy melamine washbasins, such as standardized small washbasins, children's special washbasins (uniform size, simple shape).

Features: Melamine is a thermosetting material. Injection molding requires precise temperature control: the barrel operates at a low temperature (60–80°C, to prevent premature curing and clogging), and the mold operates at a high temperature (160–180°C, for rapid cross-linking and curing); the automation level is high, the molding cycle is short, and it can achieve batch production of washbasins, with smooth surface of the basin body and good dimensional consistency.

Process (for washbasin only): Molding plastic → Preheating of the mold barrel (at low temperature) → High-speed injection into the hot mold (washbasin cavity) → Holding pressure for curing (to ensure uniform thickness of the basin wall and no shrinkage marks) → Demolding (automatically demolded after cooling, reducing the need for manual intervention)

Challenges: Likely to cause clogging and flow marks (affecting the appearance of the washbasin), bubbles (affecting durability); requires a dedicated thermosetting injection molding machine, which is costly. Therefore, it is only used for the mass production of standardized melamine washbasins and is not suitable for small-batch or irregular-shaped basins.

 

 

IV. Laminating

Applicable to: Integrated products for the panels and countertops of melamine washbasins, such as melamine washbasin and washroom set (with the countertop being laminated melamine board and the basin and countertop being formed as one piece), or decorative panels for washbasins (to enhance the surface texture).

 

Process (for washbasin only):

Paper or fabric impregnated with melamine resin (optional wood-grain or stone-texture patterns, suitable for bathroom sink style) → Dry (semi-cured B stage) → 2. Multi-layer stacking (stack the decorative layer, structural layer and sink cavity mold together) → 3. Hot press machine (150–160°C, 5–10 MPa) pressurized curing → 4. Cutting, trimming, forming an integrated melamine sink with a countertop.

Product features: The countertop and the basin are integrally formed, without any joint gaps. It is resistant to stains and scratches, easy to clean, suitable for minimalist home decoration scenarios for washing and rinsing, and weighs less than ceramic washbasins, making installation more convenient.

 

V. Casting Process

Applicable to: Transparent/semi-transparent melamine washbasins (such as simple acrylic-textured washbasins), artistic display-style washbasins (with unique shapes, no need for high strength), and surface coatings for washbasins (to enhance glossiness and water resistance).

Features: Liquid melamine resin + curing agent. Pour into the washbasin mold under normal pressure/low pressure. Heat (80–100°C) for curing. The equipment is simple, the mold cost is low, and it can produce complex shapes. However, the molding cycle is long (2–4 hours), the basin body strength is relatively low, and it is only suitable for small,non-load-bearing decorative washbasins and not suitable for frequent daily use scenarios.

 

VI. Process Comparison

technology	merit	drawback	Typical washbasin product
mould pressing	The equipment is simple, low in cost, has good luster, strong water resistance, and is suitable for most household scenarios.	Low efficiency, high labor intensity, and difficult to form complex structures	Ordinary household washbasins, wall-mounted small basins, simple washroom basins
transfer moulding	Complex components with high precision, capable of forming details such as overflow ports and storage slots, with few burrs.	The molds are expensive, there is material loss in the channels, and the cost is relatively high.	With storage compartments, unique-shaped artistic washbasin, mid-to-high-end integrated basin
injection molding	High degree of automation, short production cycle, and good consistency, suitable for mass production.	The equipment is expensive and the process control is strict, which makes it prone to flow marks and bubbles.	Standardized small washbasins, children's special washbasins
Laminating	The countertop and the basin body are integrally formed, with no gaps. It is resistant to scratches and stains, and has a good appearance texture.	Only plate-like / integrated structure, with limited design options	Mica washbasin (body and countertop integrated), decorative panel washbasin
casting	The equipment is simple and the mold cost is low. It can produce transparent/unique-shaped products.	Long duration, low intensity, and average water resistance	Decorative washbasin, small artistic style basin