Every molding machine requires a consistent supply of plastic material during the production process. These materials are moved from the material storage area to the machines so that it can be molded into the desired product. If the final product requires coloring (which is common), the material will have to be mixed with colorants before it is sent to the machines.
Certain material requires a pre-drying process before they are sent to the machines to be molded. Therefore, handling of the raw plastic material (usually in pellet form), can become time-consuming and labor-intensive.
As such, most mid-size to large scale manufacturers use certain form of mechanical processes to feed their machines than to rely on manual loading.
The choice of material handling equipment depends on the following factors:
- The type of material (pellets, powder, etc.).
- The amount of material required (size of production run).
- The vertical and horizontal distances covered.
- Special functions requirement (such as mixing color).
Manual loading is the most cost effective methods. An operator will manually pour the plastic materials directly into the machine’s hopper. However, this method has several disadvantages.
- Wastage – operator might spill while pouring the resin into the hopper.
- The molding machine may stop and run out of material if the operator forget to refill.
- Dangerous – a person may have to climb onto the molding machine to reach the hopper, while carrying a heavy bag of resin.
- Contamination – manual loading can often cause contamination. Foreign particles can stick to the bag and while loading these particles will often drop into the hopper.
The most common type of mechanical loader is the auger type loader. It operates with a long-pitch auger screw, rotating within the tube. During operation, the rotating auger screw picks up material from the container and carries it to the machine’s hopper. Timers and level sensor are often attached to the system, so that the loader knows when to refill the hopper. While this system is inexpensive, it is however, very difficult to clean and should be considered only when one specific type of material are used for an extended period of time.
The most popular form of loading system is the vacuum loader (also known as an Auto Loader). It consists of a vacuum pump that is mounted on top of the molding machine’s hopper. A feed tube is connected to the pump, while the other end is placed inside a large material bin which is placed next to the machine. During operation, the vacuum pump sucks the material from the material bin and transfer it to the top of the hopper. It then dumps the fresh material directly into the hopper. Level sensors and timers are used to gauge the amount of materials in the hopper, and the time between each refill.
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