Plastic injection is a manufacturing technique based on pouring liquid plastic into a mold with a desired form. This process is not knew and it is at the heart of almost all products you see in your daily life: from cars to spaceships passing through dishes and medical devices, for example.
For instance, the plastic bumper of a car is made by plastic injection. The same is true for the caps of some bottles.
This industrial process requires different machines and different resines or polymers and although it seems a simple process a number of problems arise during operation. Some examples of plastics are,
- polypropilene (PP),
- high density polyethylene (HDPE),
- acrylonitrile butadiene styrene (ABS),
- polycarbonate (PC),
- among others.
Fig. 01 Here is a photo of the pellets in the form of small cylinders, ready to be used in a plastic injection machine.
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| Fig. 02 Here is a photo of the bag in which polymer pellets are sold. This is for high density polyethylene (HDPE). |
Three important actors
The mold, the machine and the polymer are the most recognizeble actors in this process. Molds are specially designed and manufactured to hold high pressures of the order of thousands of psi. These are very expensive parts of the process. On the other hand, the machine comes in a variety of pressure capacities and automation features. Also, no any mold can work along any plastic injection machine. Finally, the polymer is key because the mold is designed with a given polymer in mind and this has to meet certain physical properties if good quality products are to be manufactured.
Any question? Write in the comments and I shall try to help.
Other stuff of interest
- Understanding the law of Boyle
- Measuring atmospheric pressure
- Some examples of temperature instruments
- Minor losses - Formulas
- What is a process variable?
- What are the most important process variables?
- Time dependence of process variables
- A list of process variables
- Composition variables for mixtures
Ildebrando.
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