The presentation often consists of 3 main parts: introduction, body, and conclusion. Before the presentation, it is essential to prepare a lot of things. You should search for the information for the topic in advance, divide the tasks among team members and practice speaking. In the introduction, you should greet the audience and give the overall objective and structure of your speech, so it is easy for the audience to follow. During the presentation, focus on the main points and try to give examples or pictures to illustrate your ideas. Making eye contact or interacting with the audience is also advisable so they will be involved in the content. Do not read from the slide or look up the ceiling because it may show your confidence. After the presentation, you should allow the audience to ask questions and check their understanding by asking them questions. Remember to give references and thank the audience for listening.

There are seven main types of plastics, each identified by a number from 1 to 7, with different properties and applications. the first is PET. it have the properties is oxygen prevention widely recycled and the PET is mostly used for food and drink packaging. the second is HDPE. it is an incredible resistant resin used for not only grocery bags, milk jugs, recycling bins, agricultural pipe... the properties of HDPE are hard, resistant to impact, subjected to high temperatures, recyclable. the third is PVC. it is the world third-most widely produced synthetic plastic polymer. PVC is versatile, hardly recyclable. it is used for rigid form: building and construction industry to produce door and window profiles and pipes. flexible from: plumbing, writing and electrical cable insulation and flooring. Polyethylene (LDPE, code 4) is soft, flexible, and moisture-resistant, used for plastic bags and food wraps. Polypropylene (PP, code 5) is strong yet flexible, heat-resistant, making it suitable for food containers and bottle caps. Polystyrene (PS, code 6) is lightweight and easy to mold, often used in protective packaging and disposable cups. Other plastics (code 7) include specialized materials used in high-tech applications. These are all the most popular plastics available today.

In this paragraph, I would like to describe the following plastic moulding process. As you can see in the figure, the name of the process is extrusion moulding. There are six steps in this process. Firstly, we move the polymer pellets from the hopper to the cylinder. Second, an electric motor turns the screw in the extrusion moulder. Third, the cord polymer pellets move along the cylinder. In the next step, heaters warm the polymer pellets and tum them into a liquid. Then, the warm, soft molten polymer moves along the cylinder. Finally, the machine pushes the molten polymer out into the mould. They’re some information about the plastic moulding process by extrusion moulding. I hope they are useful for you.

In this paragraph, I would like to write about typical problems of plastic injection moulding. Plastic injection moulding has three typical problems: short shot, void and sink wark. The first problem is the short shot, the cause is there is not enough plastic in the shot and the plastic pressure loss in the mould is too high, the solution is to check the shots continuously and use plastic with high melting capability. The second problem is void, which is caused by plastic shrinkage ( a hole suddenly develops in a thick section during cooling), the solution is to increase the injection pressure to force more materials into the mould and reduce shrinkage. And the final problem is sink wark, the cause is the internal stress is too high and the part has low surface rigidity, the solution is to increase holding pressure and holding time. They’re some information about typical problems of plastic injection moulding. I hope they are useful for you.