The method involves pouring paste plastic (plastisol) into a preheated mold (cavity mold) that has been heated to a specific temperature. The paste plastic near the inner wall of the cavity will gel due to the heat. Subsequently, the ungelled paste plastic is poured out. The gelled paste adhering to the mold cavity is then thermally cured (baked), and after cooling, a hollow product is obtained from the mold.
Precisely measured thermoplastic powder (typically PVC, TPE, etc.) is poured into the cavity of the mold.
The mold is closed and placed into a heating oven. The mold undergoes slow, complex rotation around two perpendicular axes (typically horizontal and vertical). Heating raises the mold temperature, causing the plastic powder in contact with the mold's inner wall to begin melting.
During rotation, the molten plastic adheres evenly to the hot surface of the mold's inner wall. By controlling the rotation speed, angle, and time, the thickness of the plastic adhering to different areas of the cavity can be precisely controlled.
Once the desired thickness of the molten layer is achieved, the mold is removed from the heating oven and moved to a cooling station (typically using water spray or cold air). While rotation continues, the molten plastic layer cools and solidifies.
After the mold cools, rotation stops. The mold is opened, and the formed, hollow plastic part (skin) is removed.
Typically made from metal with excellent thermal conductivity and high surface finish. The most common is electroformed nickel mold, as it perfectly replicates complex details and textures from a master model (usually a sculpted pattern) and provides uniform heat conduction. Copper alloys or aluminum alloys are sometimes also used.
: The surface of the mold cavity directly determines the final product's appearance, texture, and dimensional accuracy. Therefore, its surface treatment (such as polishing, sandblasting, etching textures) is critical.
The mold itself must be robust enough to withstand repeated heating/cooling cycles and rotational stresses. Its design must facilitate powder filling, uniform heating, effective cooling, and easy demolding of the final part.
Unlike injection molding, the slush process does not require high pressure. Plastic powder melts and adheres to the mold wall under gravity and centrifugal force. Consequently, the mold does not need to withstand extremely high clamping forces, allowing its structure to be somewhat simplified compared to injection molds (though sealing and precision must still be ensured).
Slush molds are particularly adept at forming hollow parts with complex shapes, deep draws, fine textures, or requiring uniform thin walls – especially components difficult to form in one piece via other processes (like injection molding) or requiring superior appearance and feel.
This is the primary application area for slush molding technology.
Dashboard Skins
Door Panel Skins
Passenger Side Instrument Panel (IP) Skins
Armrest, Pillar Trim Cover Skins
Steering Wheel Covers (some processes)
Toys (e.g., balls, dolls)
Medical Device Handles, Protective Sheaths
Tool Handle Overmolds
Footwear Materials
Household Goods
Slush mold is a metal mold (commonly electroformed nickel) used in the slush molding process. Its core function is to enable plastic powder to melt and adhere uniformly to its precisely crafted inner cavity surface under heat and complex rotational motion, forming hollow plastic parts (especially skins) with complex shapes, fine textures, and uniform wall thickness. It plays an irreplaceable role in manufacturing automotive interior skins, serving as the key tool for achieving high-quality appearance and tactile feel.
