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Computer-Aided Design (CAD) is a digital approach to technical drawing, utilizing specialized software to generate accurate, editable, and complex illustrations. In contrast, manual drafting involves drawing by hand with traditional instruments like pencils, compasses, and drafting tables. CAD offers multiple functions including precise scaling, layering, and 3D visualization, making it ideal for efficiency and error reduction. Manual drafting, though more tactile and expressive, is often limited by slower execution and difficulty in making revisions. While CAD promotes speed, consistency, and digital storage, manual drafting relies heavily on the drafter's craftsmanship and attention to detail. Despite CAD becoming standard in most industries, manual drafting still holds educational and artistic value, especially in early concept development or when technology isn’t available.

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Bearing Purchase Report

Dear Supervisor,

As instructed, I have purchased different types of bearings to replenish our stock. I bought them from ABC Industrial Supplies on July 13, 2025. The bearings include ball bearings, roller bearings, and thrust bearings.

Ball bearings consist of inner and outer rings, steel balls, and a cage. They reduce rotational friction and support radial and axial loads, commonly used in electric motors and fans. Roller bearings contain cylindrical rollers instead of balls and are ideal for heavy radial loads, used in gearboxes and conveyor belts. Thrust bearings are made up of bearing balls or rollers, raceways, and cages, and are designed to support axial loads in vertical shafts, typically found in automotive and aerospace systems.

These bearings are essential for ensuring smooth machine operation and reducing wear on rotating components.

Best regards,

Ngoc Liem

Apprentice Technician

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To give an effective presentation, it is important to follow a clear structure: introduction, body, and conclusion. Prepare thoroughly before your presentation by researching your topic, outlining, and practicing your speech. You should also know your audience and prepare any visual aids. During your presentation, speak clearly, maintain eye contact, and use body language to engage your audience. Avoid reading from slides or speaking in a monotone voice. After your presentation, invite questions and politely respond, even if the feedback is critical, and send the audience a summary. Thank the audience and provide contact information if necessary. To impress your audience, project confidence, use visuals effectively, and tell relevant stories or examples. Good delivery and preparation will leave a lasting impression and make your message memorable.

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Coupling Purchase Report

Dear Supervisor,

I have purchased three types of couplings: beam coupling, flexible coupling, and rigid coupling. They were bought on July 13, 2025, from VietTech Mechanical Supplies.

The beam coupling is made of a single piece of metal with helical cuts, allowing angular, axial, and radial misalignment. It is ideal for encoders and stepper motors. The flexible coupling consists of two metal hubs and an elastomeric element (spider) in between. It absorbs shock and vibration, commonly used in pumps and compressors. The rigid coupling includes two solid metal hubs and screws, designed for precisely aligned shafts. It is suitable for high-torque applications such as conveyors.

All these couplings are essential for transmitting torque between shafts, ensuring smooth mechanical power transfer in various systems.

Best regards,

Ngọc Liêm

Apprentice Technician

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A gear is a mechanical device with teeth that fit into the teeth of another gear to transmit motion and torque between rotating shafts. Gears play a crucial role in machines by changing the direction of motion, adjusting rotational speed, and increasing or decreasing torque. There are four main types of commonly used gears: spur gears, helical gears, bevel gears, and worm gears. Spur gears have straight teeth and are used in simple, low-speed systems due to their efficiency and ease of manufacturing. Helical gears, with their angled teeth, offer smoother and quieter operation, making them suitable for high-speed or heavy-load applications. Bevel gears have conical shapes and are used to change the direction of shafts, often found in automotive systems. Worm gears consist of a screw-like worm and a gear wheel, allowing for large speed reductions and non-reversible movement. Gears are essential in devices like cars, clocks, elevators, and industrial machines.

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Two common types of mechanical drives are belt drives and gear drives, each serving the purpose of transmitting power and motion between machine parts. Belt drives use flexible belts, typically made from rubber, leather, or synthetic materials, stretched between pulleys. They are suitable for long-distance power transmission and can absorb shock loads. Some slippage may occur in belt drives, which can protect machinery from damage but slightly reduces efficiency. Gear drives, on the other hand, use interlocking toothed wheels made of metal to transfer motion with high precision and no slippage. They offer greater efficiency and are ideal for applications requiring exact timing and high torque. However, gear drives are generally more expensive and need regular lubrication and maintenance. Belt drives are commonly used in fans, agricultural equipment, and washing machines, while gear drives are found in cars, industrial machines, and clocks.

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AutoCAD is one of the most popular and widely used CAD programs developed by Autodesk. It offers a range of features including 2D drafting, 3D modeling, annotation tools, and support for various file formats. AutoCAD allows users to create precise technical drawings for architecture, engineering, and product design. Its key functions include drawing lines and shapes, scaling objects, creating layers, and rendering 3D visualizations. One major advantage of AutoCAD is its accuracy and efficiency, especially when editing and modifying designs. It also integrates well with other Autodesk software. However, a significant drawback is its steep learning curve, which may be challenging for beginners. In addition, the software requires a paid license, which might not be accessible to everyone. Despite these limitations, AutoCAD remains a powerful tool for professionals in design industries.

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The manufacturing process shown in the image is called casting, specifically casting an aluminum wheel frame. The product is made of aluminum, a lightweight and durable metal commonly used in the automotive industry. There are five main steps in this process. First, molten aluminum is poured into a mold to create the basic shape of the wheel. Once the metal cools and solidifies, the mold is removed in the second step and the axle for the wheel is machined. In the third step, holes are drilled into the surface of the wheel to accommodate screws. In the fourth step, the wheel undergoes a finishing process, where any imperfections are smoothed out and details are added. Finally, in the fifth step, the product is inspected for quality and accuracy before being approved for use. Each step must be carefully performed to ensure that the aluminum wheel is strong, safe, and well-designed.

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Plastic is a synthetic material made from polymers, known for its versatility, lightweight nature, and ability to be molded into various shapes. It exhibits properties such as corrosion resistance, low electrical conductivity, and high strength-to-weight ratio, making it ideal for applications in packaging, automotive parts, electronics, and medical devices. The advantages of plastic include its durability, cost-effectiveness, and ease of mass production. However, its major disadvantage lies in environmental impact—most plastics are non-biodegradable, contributing to long-term pollution and harming ecosystems. With growing concerns about sustainability, the future of plastic is likely to shift toward biodegradable alternatives, improved recycling technologies, and bio-based polymers. As a mechanical engineering student, understanding the evolving landscape of plastic materials is essential for creating innovative, eco-friendly solutions across industries.

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There are seven common types of plastic, each labeled with a resin identification code from 1 to 7, and each has unique properties and applications. Type 1 is PET (Polyethylene Terephthalate), strong and commonly used in beverage bottles, medicine jars, and carpet fibers. Type 2 is HDPE (High-Density Polyethylene), known for its chemical resistance and safety for food containers like milk jugs and detergent bottles. Type 3 is PVC (Polyvinyl Chloride), flexible but not food-safe, often used in pipes and wiring insulation. Type 4 is LDPE (Low-Density Polyethylene), durable and flexible, used for plastic bags and films. Type 5 is PP (Polypropylene), heat-resistant and strong, ideal for food containers. Type 6 is PS (Polystyrene), lightweight and brittle, used in disposable cups and foam packaging. Type 7 includes other plastics like ABS, known for its toughness and use in electronics and medical devices. Understanding these types helps mechanical engineers select appropriate materials for each application.

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The process shown in the figure is called injection moulding of plastic, a common method for producing plastic components. This process consists of four main steps. First, plastic pellets are loaded into the hopper, which feeds the raw material into the heated cylinder. In the second step, the motor-driven screw rotates and moves the pellets forward, where they are gradually melted by external heaters and the frictional heat. In the third step, once the plastic is fully molten, a ram mechanism forces it through the nozzle into the mould cavity. The mould is a precise shape of the final product. Finally, in the fourth step, the plastic cools and solidifies inside the mould. After cooling, the mould opens and the finished part is ejected. This method is ideal for producing large volumes of identical plastic parts with high accuracy, used in industries such as automotive, electronics, and packaging.

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In plastic injection molding, several typical problems can affect product quality. One common issue is warping, where parts become twisted or bent due to uneven cooling or non-uniform wall thickness. To address this, it is important to ensure balanced mold design, proper cooling systems, and controlled cooling rates. Another frequent problem is short shots, which happen when the mold cavity is not completely filled. This may be caused by low injection pressure, blocked vents, or insufficient material flow. Solutions include increasing injection pressure, improving venting, and ensuring proper melt temperature. Sink marks are depressions on thick areas of molded parts, typically caused by shrinkage during cooling. To avoid this, manufacturers should use uniform wall thickness and optimize cooling time. Flash, which is excess plastic on the edges of parts, is often due to overpacking, worn molds, or high pressure. It can be prevented by adjusting injection parameters and performing regular mold maintenance. Regular monitoring helps maintain product quality.

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The machine tool is a milling machine. There are five kinds of maintenance work required: cleaning guideways, inspecting oil level, renewing oil, cleaning the machine thoroughly, and inspecting bearing slackness. These tasks are scheduled daily, weekly, semi-annually, and annually. Cleaning the guideways and inspecting the oil level must be done daily to avoid interruptions, control fluid motion, ensure engine efficiency, and prevent overheating. Cleaning the machine thoroughly is a weekly task to remove dust and dirt, keeping the machine in good condition. Renewing the oil is done semi-annually to ensure smooth and efficient operation. Inspecting bearing slackness should be performed annually to prevent slippage and maintain machine precision. Following this maintenance schedule helps extend the machine’s lifespan, reduce downtime, and ensure safe, consistent performance.