The basic structure of a presentation includes 3 main parts: introduction, body and conclusion. Before the presentation, First of all, you need to know your audiences, create an outline, then prepare and practice fluently, the last you should choose comfortable presentation style. During the presentation, firstly, you don’t just look at paper or slide and read, let use gesture, body languages and look the audiences. You can make some example from personal stories or your experiences in your life to help the presentation not boring. At the end of presentation, you can emphasize the main ideas one more time. You should not take questions during your presentation, If you don't want to lose your inspiration and forgot the scription. After the presentation, you can ask what people want to know about the presentation, then answer those questions. Finally,  you should say “thanks” and “goodbye” to the audiences.

That all .

-introduce myself :

+name,age,address

+my university

+hobby

-Skills

Writing

Hello everyone. I’m here today to introduce myself.

- This talk is divided into three main parts:

+ Firstly, I'd like to talk about name age, work

+ Then, I'll be talking about my hobbies

+ Finally, I'll be looking at my skills.

My name is An , i’m 21 years old .Currently ,I am a mechanical engineering student in haui.My hometown is Bac Ninh. My hobby are listen to music, playing game, learn foreign language.

I develop skills from my hobbies such as communication skills, foreign language skills and teamwork. That is overview about myself. Thanks you for listen.

Secondly, straight roller bearings use cylindrical rollers to support radial motion. Next, tapered roller bearings use conical rollers to support radial forces and thrust forces. Finally, thrust roller bearings use barrel-shaped rollers to support thrust motion.

Firstly, spur gears are the most common and simplest types of gears with teeth projecting towards or away from the centre. They are used in low-speed applications but they can’t control noise at high speed.

Secondly, helical gears are similar to spur gears except that their teeth are cut in spiral shape. Helical gears are used in high-speed applications, large power transmission, or control noise.

Thirdly, bevel gears are types of gears that have a conical form and they can be used to transmit rotational power through shafts at an angle, normally 90 degrees to each other.

Next, rack and pinion comprises a circular gear(the pinion) engaging a linear gear(the rack), which operate to convert rotational motion into linear motion.

Finally, these are worm and worm gear. A worm has just one continuous tooth and pairs with a worm gear, which helps reduce speed.

Belt drive is one type of mechanical drive where motion and power are transferred from one shaft to another by means of friction between belt and pulleys. In contrast, chain drive is one type of power transmission system that transmit motion and power by means of successive chain with sprocket special toothed wheels.

Besides, they have many other differences. Firstly, belt drive is made of polymers, while chain is made of alloys. Secondly, chain drive can operate in high temperature and moist conditions but belt drive cannot. Thirdly, belt drive mustn’t lubricate, whereas the chain drive needs to be lubricated regularly. Moreover, chain drive can operate under high loads, whereas belt drive can operate under high speed conditions. Finally, when operating belt drive is silent but chain drive is noisy.

Application of belt drive are flour mills, coolant pump, lubricant pump, belt conveyor… Whereas, chain drive is used in bicycle, motorbike and material handling equipment.

CAD enables the designer to quickly layout a preliminary design and change it as often as necessary. Unlike CAD, manual drafting requires designers draft every single detail by hand with pencil or ink on a media such as paper or polyester film using drafting instruments and equipment. Designers using CAD need to have just minimum skills for operation but analytical skills are more required. In contrast, manual drafting requires users must have desgining skills and explanation skills.

CAD is different from manual drafting in term of accuracy. While CAD provides high accuracy in representation and less error in interpretation, drawings made by manual drafting can be easily misread because of ambiguity and drawing errors. Moreover, CAD provides ease of use and tremendous flexibility to designers to make the required changes or modifications. But CAD is quite expensive and it is required professional training before using it, while manual drafting costs quite little and does not have to professional training.

The CAD software has a lot of functions. Firstly, it’s used to sketch out the ideas. Besides, it helps designers to experiment with features and dimensions. Moreover, the engineers can use it to produce models and detailed drawings.

CAD has some advantages. The first is easy and intuitive to use from the beginning. The secondly, it is very easy to use for 3D modelling. Finally, CAD is quick and easy to create parts, add them to assemblies and create drawings. However, CAD also has some disadvantages. If people want to use it, they must cost big amoun of money. Besides, it contains some unnecessary features for common user.

In conclusion, I think it is still a powerful support tool for users, due to its functions and advantages.

Plastics have interior mechanical properties such as stiffness, strength, and temperature resistance to the materials they have replaced.

In the past, because the technology was not completely developed, plastics were not widely used and humans have not seen the seriousness of plastic waste. But now, plastics are one of the most popular ingredients in the world, they are the raw materials present in many objects. Therefore, the pollution of plastic waste is currently extremely serious. In the future, the world will find another material that can replace plastic so as not to affect people and the environment.

Plastics have many advantages but they also have some disadvantages.Firstly, they are light in weight and chemically stable. Secondly, they are easily moulded into different shapes and sizes. Beside, plastics are good insulation and low thermal conductivity. Thirdly, they have a good impact resistance and do not be rusted. Next, good transparency and wear resistance are two of their advantages. Finally, Plastics have low processing cost and can be easily deformed but not good dimensional stability.

Firstly, Code 1 plastics is polyethylene terephthalate (PET), this is one of the most commonly used plastics. It’s lightweight, strong, transparent and often used to produce food and drink packaging as Water bottles and Food containers.

Secondly, Code 2 plastics is high-density polyethylene (HDPE). It ‘s much stronger and thicker than PET.  HDPE is the most commonly recycled plastics in the world because it will not break under exposure to extreme heat or cold.

Applications of HDPE: Milk cartons, toys, and grocery bags…

Thirdly, Code 3 plastics is polyvinyl chloride(PVC). It’s lightness and durability. This plastic is resistant to chemicals and weather, make it ideal for building and construction applications; Besides it doesn’t conduct electricity so it is used for making wires and cable.

However, we must note that PVC is the most dangerous plastic to human health so    it has been called the “poison plastic”.

Fourth, It is low-density polyethylene(LDPE). A softer, clearer, and more flexible version of HDPE. It’s often used as a liner inside beverage cartons, and in corrosion-resistant work surfaces and other products.

For Examples: Plastic/cling wrap, garbage bags, grocery bags and beverage cups…

Fifth, It is polypropylene (PP). This is one of the most durable types of plastic. It is more heat resistant than some others, which makes it ideal for such things as food packaging and food storage that’s made to hold hot items or be heated itself. It’s flexible enough to allow for mild bending, but it retains its shape and strength for a long time.

For Examples: Straws, bottle caps, prescription bottles, hot food containers, packaging tape…

Sixth, that is polystyrene(PS). Better known as Styrofoam, this rigid plastic is low-cost and insulates very well, which has made it a staple in the food, packaging and construction industries. Like PVC, polystyrene is considered to be a dangerous plastic.

For Examples: Cups, takeout food containers, shipping and product packaging…

Finally, This category is a catch-all for other types of plastic that don’t belong in any of the other six categories or are combinations of multiple types. It is classified in the #7 recycling code.

For Examples: Eyeglasses, baby and sports bottles, electronics, CD/DVDs…

First, that is short shots. It is a phenomenon when the air is trapped in the cavity to create bubbles in the part. To solve this problem, you should check the shots continuously and use plastic with high melting capability. Besides, you need to increase gate size and runner.

Second, that is void. It is a phenomenon when pocket of air is trapped withiin or close to the surface of an injection moulded prototype and causing some voids in the part. To deal with this problem, you need reducing wall thickness and slow down colling rate. Moreover, you had better increase gate size and locate it at the thick part of the moulding.

Third, that is sink mark. It is a phenomenon in which the mold cavity cannot be completely filled by molten plastic, resulting in a portion where there is no plastic. To solve this problem, you should reduce mould temperature, have enough shot size and reduce wall thickness for faster cooling.

Firstly, you must check water line pressure gauges and air pressure everyday to avoid interruptions. Secondly, coolant levels and oil levels are need to be checked everyweek to make sure that the engine operates efficiency. Finally, you had better inspect spindle bearing and drive belt semi-annually to help lathe machine can operate more smoothly, besides, you need changing oil regularly about twice a year.

In order to help the lathe machine can operate durable, we need to comply and fulfill the requirements of it.