Mold making and casting is a fascinating activity which can take varied forms. From clay modeling to making simple one-part molds or the more complicated approach of two-part molds. In fact, mold makers even make multi-part molds at times to capture all facets and other details of the model. The procedure of making molds also varies from pouring the mold making material to spraying it or even brushing it on the model.
Apart from the regular blanket, glove and even shell type, another making and casting technique is injection molding. It is actually a simple procedure in which the casting material is forced into this under pressure!
Injection molding can be done in single or multi-part molds. Since it is favored for capturing minute details, generally complicated two-part molds feature in injection molding. Tiny holes (called sprues) are bored into the mold all along its surface. This is where the casting material will be injected into this.
The casting material like polyurethane resin is filled in a syringe and the large hypodermic needle is inserted into the mold sprues. Pressure is applied to ensure all cavities are filled. The procedure continues until the casting material spews out of all the sprues. This shows that the casting material has displaced the air inside the mold and adequately filled all the nooks and crannies in the mold.
It is allowed to cure before being demolded carefully. You will find a thin-bodied cast that is an exact replica of the original model, down to every tiny nook and crevice. Other casting methods fail to achieve such a high level of precision. The demolded piece does not need to be cleaned or finished much either. However, models with large undercuts cannot be replicated with injection molding.
Injection molding is a commonly-used manufacturing process for producing thin-walled parts with great accuracy. It is generally used to make small plastic, metal and even glass items. Model parts for miniature cars, trains and complicated superhero figures are made with the injection molding process. It will yield accurate copies very quickly and in large numbers too.
The manufacturing process involves feeding the casting material into a machine which crushed it to a liquid state before injecting the same into the mold under high pressure. This mechanical process is repeated again and again to make multiple copies. The plastic in the mold is allowed to cool before being ejected from the mold.
While injection molding is a simple process that proves cost-effective, making the molds can turn out very expensive. It has to be made with steel or aluminum and precision machined to capture all the details properly. However, when artists use injection molding technique in their studios, they make use of clay modeling techniques and silicone rubber to make a precise block mold. This serves well for injection molding!