SMC Bathroom Base Mold

The SMC bathroom base mold is a thermosetting composite compression mold that uses high temperature and pressure to form waterproof shower tray bases from SMC fiberglass sheets in one step. It is widely used in integrated bathrooms and home shower enclosures, offering advantages such as waterproofing, high strength, dimensional stability, and easy cleaning.

 

I. Composition of the Mold Foundation Structure

 

1. Upper mold (cavity surface) - The surface where the product is formed. It undergoes mirror finish / anti-slip texture polishing to determine the flatness of the chassis surface, anti-slip patterns, water outlet, and the accuracy of the water diversion slope. The cavity roughness is Ra ≤ 0.4 μm. Regular chrome plating is applied, with a thickness of 5 to 10 μm for anti-sticking mold, wear resistance, and corrosion resistance.

 

2. Lower mold (back mold): Forms the back ribs and mounting flanges, combined with a multi-point ejection mechanism to ensure smooth demolding of large flat products without deformation.

 

3. Heating temperature control system with built-in electric heating rods and thermal oil pipelines ensures stable mold temperature between 135°C and 155°C, with a temperature difference of 5–10°C between upper and lower molds, guaranteeing uniform curing of SMC resin and a temperature control accuracy of ±3–5°C.

 

4. Venting system: A 0.03–0.05 mm deep vent groove should be provided at parting lines, sprue gates, and corners of ribs to exhaust air from the mold cavity, preventing defects such as bubbles, short shots, and localized whitening in the product.

 

5. Guided Clamping and Ejection Mechanism: Large four-column precision guide with clamping plate, combined with multi-point ejector pins or stripper plate ejection system, featuring mold release angles of 1° to 3°, suitable for production on hydraulic presses ranging from 500T to 1200T.

 

 

II. Selection of Common Mold Steels

 

production lot size	die steel	Heat treatment hardness	service life	applicable scene
Small and medium-sized batch sizes (within 100,000 units)	P20 Hardened Steel	HRC28~32	80,000 to 120,000 mold cycles	Regular model chassis for domestic sales
Mass production	H13 (4Cr5MoSiV1) heat-treated steel	HRC48~52	200,000 to 350,000 mold cycles	Foreign trade, year-round mass production model
Ultra-high frequency mass production	ASP60 Powdered High-Speed Steel	HRC58~62	More than 500,000 moldings	Multi-shift automated production line

 

 

III. Key Points of Core Design

 

1. Product functional structure design

Drainage slope：The mold cavity is designed with a 1.5° to 3° unidirectional drainage slope, and an accurate water drainage channel is formed precisely, eliminating water accumulation;

· The drain port insert: It adopts a detachable insert design, allowing for quick replacement of different diameter drain structures, and one mold can be adapted to multiple drain accessories;

· Anti-slip texture: The mold surface can be made into dot, grid, or stripe anti-slip relief patterns, with a depth of 0.3 to 0.8mm, balancing anti-slip and easy demolding;

· Back reinforcement layout: Grid-shaped ribs are evenly arranged to enhance the chassis load-bearing capacity and prevent deformation and warping during long-term use.

 

2. Process Parameter Matching (Mass Production Standard)

· Mold Pressing Force: 60 - 100 MPa, conventional press machine tonnage 800T, 1000T;

· Molding Temperature: Upper mold 145 - 155℃, Lower mold 140 - 150℃;

· Curing Cycle: 4 - 7 minutes / mold, adjusted according to the thickness of the chassis (conventional 4 - 8mm);

· SMC Sheet Material Loading Quantity: 10% - 15% more than the theoretical weight of the product, to ensure complete filling of the cavity without material shortage.

 

3. Key Points of Defect Prevention Design

1. The parting surface is designed at the side flange position of the chassis, avoiding the appearance surface, thereby reducing the workload of edge trimming;

2. The cutting edges of the flanges are precisely matched to control the thickness of the overflow material, significantly reducing the post-processing burrs;

3. The large flat cavity is optimized for stress, avoiding warping and deformation of the product after demolding;

4. The exhaust grooves are densely arranged at the lower water inlet and corner dead zones to solve the common problems of bubbles and pinholes.

 

 

IV. Main Product Specifications and Mold Types

Square chassis：800×800mm,900×900mm,1000×1000mm(Right-angle shower enclosure)

Rectangular base plate：1200×800,1400×900mm(One-piece shower enclosure)

Fan-shaped / Diamond-shaped chassis：900×900,1000×1000mm(Corner Shower Room)

Customized special-shaped model： Integrated with a water-blocking strip, equipped with a built-in washing machine chassis, and a non-obstructive recessed chassis mold.

 

V. SMC Molding Production Process Flow

SMC sheet cutting and weighing → Mold cleaning and application of release agent → Evenly spreading of sheet → Mold closing and high-pressure hot pressing for curing → Opening of mold and multi-point ejection for demolding → Product trimming and fine processing of water inlet → Inspection and packaging.

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