Filed under: Mass Production
Clock Casing
The casing for my clock if put into mass production would be injection molded. This involves forming the mold which could be done by electrical discharge machining (EDM). This process allows prehardened molds to be shaped so that no heat treatment is required. The process uses a shaped electrode normally made from graphite or copper. This is lowered into the mold surface which is immersed in paraffin oil. A voltage is added which sends electrodes between the mould and the tool which causes erosion of the mold surface in the inverse shape of the electrode. Once the molds are formed these are closed and heated plastic can then be forced into them using the pressure of the injection screw. The plastic then takes the shape of the mold.
A lot of consideration and thought needs to be put into the design of the molded parts of the clock. This ensures that the parts will not be trapped in the mold and that the molds can be completely filled before the molten resin solidifies. This compensates for material shrinkage and minimises imperfections in the parts.
For this design the casing would be made in two parts, these two parts are called the core and the cavity. To ensure the mold does not get stuck, the direction from which the core and cavity are removed from each other need to be angled. Due to the bucket like shape of the casing, after the molding process the casing is likley to shrink in its mold. Pins would be the popular method of withdrawing the mold from the core. Other methods for withdrawing the mold are but air ejections, and stripper plates.
A mold can produce several copies of the clock cassing part at the same time, the number of coppies is known as cavitation. For the production of this clock casing a multi -cavity tool would be used.
