Everything you always wanted to know about plastic coating.

 

Plastisol dip coating is a thermal process. Metal parts are preheated, dipped, and then post heated. During the dip, heat in the parts gels the surrounding material. The hotter the parts and the longer the dip, the thicker the gelled coating. During the "cure", the plastisol fuses. Naturally, temperatures and dipping profiles are critical in determining the amount of plastisol buildup on the part. Prior to plastic coating the object to be coated can be "primed". The primer will make the coating adhere to the part.

 

Although the coatings can be quite thick, .250" or even more on some parts, the outside dimensions of the parts are surprisingly controllable. 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 developed machinery that is possibly the most accurate in the world. Our equipment is both high precision and efficient. Our 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 also compounds its own plastisols. Therefore we are very responsive to special requirements of properties and colors.

A Fluidized bed is an amazing thing to see. Plastic powder Is fluidized by gently blowing air into the bottom of the tank. Before the powder is fluidized its about as penetrable as fine beach sand. Once the air goes on, the bed rises about 30%, and looks like its boiling at the surface. If you put your hand into the bed, (scary), it goes in with no resistance at all.

 

The part to be coated is preheated in an oven, then dipped into the fluidized bed. As powder particles come in contact with the hot parts, they melt on. The coating builds up quickly and uniformly. After the part is withdrawn, here may be enough heat left to completely fuse the coating and even melt the surface smooth. If there is enough, were done, just cool, inspect and pack. Otherwise the part is returned to the oven for a very short time.

 

Fluid bed coatings usually are in the thickness range of .007" - .020", although we have achieved .070" under some conditions. Thicker coatings require us to use multiple dips or plastisol coating.

 

Since there is no sharply defined surface to a fluid bed, parts cannot be dipped to a line. If a partial coating is required we have to resort to trimming or masking.