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Yesterday, I bought some couplings because our stock was empty. I ordered them from a supplier in China through the Internet. I purchased two kinds: rigid couplings and flexible couplings

Rigid couplings have two solid hubs and bolts. They connect two shafts firmly and are used in pumps and compressors. Flexible couplings include two hubs and an elastic part. They allow small misalignment, reduce vibration, and are applied in conveyors and fans.

These couplings are necessary to keep our machines running smoothly.

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An effective presentation should have three parts: introduction, body, and conclusion. Before the presentation, you need to prepare your content, make simple slides, and practice speaking. During the presentation, you should speak slowly, clearly, and look at the audience. You should not just read the slides or talk too fast. After the presentation, you can answer questions politely and thank the audience. . To make the audience impressed, you can use pictures, real examples, or short stories. You should also stand confidently and use a clear voice. If you prepare well, speak with confidence, and connect with the audience, your presentation will be more effective and easier to understand.

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A gear is a rotating machine element with teeth that mesh with another toothed part to transmit torque and motion. Its main functions are to change speed, direction, and torque in mechanical systems. There are several common types of gears, such as spur gears, helical gears, bevel gears, and worm gears. Spur gears have straight teeth and are used for simple, parallel shafts. Helical gears have angled teeth, run more smoothly, and are suitable for high-speed applications. Bevel gears are cone-shaped and transfer motion between intersecting shafts. Worm gears consist of a screw meshing with a gear, allowing large speed reduction and compact design. Each type of gear has unique features, making them useful in applications like clocks, automobiles, machines, and industrial equipment. They play an essential role in power transmission systems.

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There are two common types of mechanical drives: chain drives and belt drives. A chain drive uses a metal chain and sprockets to transmit motion, while a belt drive uses a flexible belt and pulleys. The function of both systems is to transfer power between shafts, but their features are different. Belt drives are quieter, less expensive, and allow some slip, which can protect machines from overload. However, they are less efficient and require more maintenance due to wear and stretching. Chain drives, on the other hand, provide higher efficiency, no slippage, and can transmit more power over longer distances, but they are noisier and require regular lubrication. Belt drives are widely used in fans, washing machines, and conveyors, while chain drives are common in bicycles, motorcycles, and heavy machinery.

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CAD (Computer-Aided Design) and manual drafting are two ways to create technical drawings. CAD uses a computer and software to draw and edit designs, while manual drafting is done by hand with tools like rulers and pencils. Both are used to show ideas clearly in engineering and design. CAD is faster, more accurate, and easier to edit. It also allows 3D modeling and saves time. Manual drafting, on the other hand, takes more time and effort because every change must be redrawn. However, it helps students understand drawing skills and basic geometry better. Today, CAD is more common in industries, but manual drafting is still useful for learning the basics of technical drawing.

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AutoCAD is one of the most popular CAD programs used by engineers, architects, and designers. It is developed by Autodesk and offers many useful features such as 2D drafting, 3D modeling, and precise measurement tools. The main function of AutoCAD is to help users create and edit technical drawings easily and accurately. It also allows users to store and share designs in digital format, which saves time and improves collaboration. The advantages of AutoCAD are high accuracy, quick editing, and the ability to work with complex designs. However, it can be expensive and requires time to learn for beginners. Overall, AutoCAD is a powerful and essential tool for modern design and engineering work.

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The manufacturing process is called aluminum casting and machining. The product is made of aluminum and it has five main steps. First, molten aluminum is poured into a mold to form the shape of the wheel. When the metal cools, the wheel is removed from the mold. Next, the wheel is turned on a machine to shape the center. After that, the bolt holes are drilled. Then, the surface is milled and finished to make the wheel smooth and accurate. Before the process ends, a worker checks the quality carefully. Finally, the aluminum wheel is completed and ready for use.

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Plastic is a common material made from petroleum. It is light, strong, cheap, and easy to shape, so it is used in many products such as packaging, household items, car parts, and medical devices. Plastics also have good corrosion resistance and electrical insulation. Thanks to these properties, they are very useful in industry and daily life. However, plastics also cause problems. Most plastics cannot decompose, and plastic waste can pollute the environment, especially the oceans. In the future, I think bioplastics and better recycling technologies will reduce pollution. As a mechanical engineering student, understanding plastic helps me choose the right materials and design better products.

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There are seven common types of plastics, and each type has a different code number. They are PET (1), HDPE (2), PVC (3), LDPE (4), PP (5), PS (6), and other plastics (7). PET is strong, transparent, and used for bottles and food containers. HDPE is tough and chemical-resistant, so it is used for pipes and fuel tanks. PVC is durable and used in cables and window frames. LDPE is flexible and used for plastic bags. PP has high heat resistance and is used for car parts and medical equipment. PS is lightweight and used for cups and packaging. Type 7 includes special plastics for engineering applications. Understanding these materials helps us choose the right plastic for each product.

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The process in the picture is called injection moulding of plastic. It has four main steps: feeding, melting, injecting, and cooling. First, plastic pellets are put into the hopper. Then, the screw turns and pushes the plastic forward. The plastic melts because of the heat in the cylinder. Next, the melted plastic is injected through the nozzle into the mould. Inside the mould, the plastic cools and becomes hard. Finally, the mould opens and the solid plastic product is ejected. This process is used to make many plastic parts quickly and with good quality.

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There are several common problems in plastic injection moulding. The main ones are short shots, flash, sink marks, and warping. A short shot happens when the mould is not completely filled, usually because of low temperature or pressure. To fix this, we can increase the injection pressure or temperature. Flash occurs when melted plastic escapes from the mould; this is caused by a poor mould fit, and it can be solved by tightening or repairing the mould. Sink marks appear when the plastic cools unevenly, so improving cooling time helps. Warping happens when the part bends after cooling, often due to different cooling rates. To prevent warping, we can adjust the cooling system and temperature balance in the mould.

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To keep the milling machine in good condition, customers should do five kinds of maintenance work. Clean the guideways every day to avoid interruptions and control fluid motion. Check the oil level daily to make sure the engine runs well and doesn’t overheat. Renew the oil every six months for smooth operation. Clean the machine every week to remove dust and dirt. Check the bearing slackness once a year to prevent slippage. Doing these maintenance tasks regularly helps the milling machine work efficiently and last longer.

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Last week, I bought some bearings because our stock was empty. I ordered them from a supplier in Korea through the Internet. I purchased two kinds: ball bearings, roller bearings. Ball bearings include an inner ring, outer ring, balls, and a cage. They reduce friction and support both radial and axial loads, often used in motors and fans. Roller bearings have cylindrical rollers between two rings. They can carry heavy radial loads and are applied in conveyors and gearboxes. These bearings will help us continue production without delay.