Plastisol for Dip Moulding

Dip moulding refers to the process of dipping a solid male mould, or mandrel, gelling a plastisol layer, fusing the gelled plastisol and then stripping the hollow parts.

Applications :-

• Electroplating Jigs
• Hand Tools
• Footwear
• Textiles Screen Printing
• Dip moulding products

Method:

Preheating:-

Tools or parts must reside in the preheat oven long enough to absorb adequate heat for the dip process. This is largely determined by trail and error and is effected by plastisol thickness requirements, tool material (alloy), oven heating characteristics, and number of preheat stations. On very heavy tools or parts, this part of the process can easily be the most time demanding of the entire process and would ultimately control overall cycle time. This is overcome by adding more preheat sections to the machine design when it is known that large, heavy parts will be processed

Dipping

At this stage Pre Heated mould is dipped in liquid plastisol .Time of dipping depends upon the thickness required

Curing (fusing)

Dipped tools or parts must reside in the cure oven long enough to properly cure the plastisol. Time and temperature requirements are sometimes determined by trial and error and are effected by plastisol thickness, tool material (alloy), oven heating characteristics, and number of cure stations. On very large tools or parts with heavy coatings, this part of the process can be the most time demanding of the entire process and would ultimately control overall cycle time. Most plastisols require a 180 degree to cure or fuse. This varies with different formulations Over curing parts can also cause the plastisol to become too liquid and drip. Proper curing is usually verified by visual inspection and tear testing
 
Cooling

There are basically 3 ways to cool parts that have been dip molded or coated; forced air, ambient air, and water quench

Water cooling is the most efficient means, but is restricted in most medical applications. Forced air cooling is usually accomplished by fans operating on a timed circuit. The operator programs the fan on time to turn the fans off before cooling the parts too much. Too much cooling can make a mandrel dipped part difficult to remove from the mould. Under cooling can cause the part to distort when being stripped and can be a safety hazard if the parts are to be handled immediately after being striped (ejected).

The cooling process can be the “bottleneck” of the operation when processing heavy parts, thick coatings, or double dipped parts. The plastisol coating actually insulated the tool or mandrel and holds the heat in the metal longer. Thicker parts or double dipped parts (especially when using foams) increase the insulation properties making it more difficult to cool the tooling. In this case, more than one cooling station can be incorporated in the machine design when it is known that this type process is needed