Overview of Plastisol Dip Molding - more information
Dip molding is defined as a process where a dipping mandrel is dipped into a liquid polymer, typically plastisol, to eventually create a solid form on the external surface of the mandrel. The cost of molding by dipping is always low. Most molds are very simple and inexpensive. Dip molding, if automated is competitive with most other molding process.
Dip molding has its origin in candle making. After the second world war, vinyl plastisol came on the market for non-military use. Plastisol dippings immediately became the standard for tool handles, and it still is.
Piper was founded in 1958 as a chemical company, supplying a range of coating materials to the rapidly growing plastic coating industry. Piper completed its first dip molding job in 1959.
Plastisol is a vinyl compound that is liquid at room temperature and will keep for years. When heated it fuses into ordinary vinyl never to liquefy again. Plastisols can be compounded to produce vinyls in almost any durometer (hardness), clarity and color; and with resistance to electricity, chemicals and weathering. Surface appearance can range from shiny to matte. Plastisol can also be compounded to meet many standards, including for FDA food contact, Non-Toxic, USP Class VI , UL, MIL-P-20689 and A-A-59464A.
Plastisol dip molding is a thermal process. Metal mandrels, (or other materials that can withstand the process temperatures,) are preheated, dipped, and then post heated. During dipping, heat in the mold transfers to the plastisol and gels the surrounding material. The hotter the mold and the longer the dip, the thicker the gelled coating. During the post heat (or "cure",) the plastisol fuses. Naturally, temperatures and dipping profiles are critical in determining the amount of plastisol buildup on the part. It's amazing to see the shapes of parts that can be made by dipping. Since they are elastic, complex parts can easily be stripped off the dipping molds.
The parts made by dip molding are precise. Plastisol follows the details of the mandrel exactly. The inside of the dipped part is an exact negative of the mold. It even has the same surface texture, (shiny or matte,) that the mold has. The outside dimensions of the parts are surprisingly controllable. Wall thickness can be held to very close tolerances. Using precisely controlled ovens, dip speeds, dip times, and withdraw speeds; a range of wall thickness configurations of is achievable.
Piper Plastics has designed, developed and built custom dipping machinery that is computer controlled, precise and efficient. Our proprietary oven technology utilizes high velocity forced air and PID control accurate to ±1°F at 450 degrees. Our dipping profiles are infinitely adjustable with resolution and accuracy of .005” and 0.1”/minute in position and velocity respectively. Piper’s technology results in lower costs because of low reject rates, fast setup time, and fast cycle times associated with computer-controlled equipment.
Currently Piper operates 19 centrally networked dipping systems in both industrial and clean room environments. We operate our systems 24 hours per day, and are adding capacity on a constant basis.
Piper can also formulate its own plastisols. Therefore we are very responsive to special requirements of properties and colors.