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All tools must be maintained on a schedule, so does the CNC machine. A CNC machine is used to create nuts, bolts and many other parts using a rotating shaft  and a computer. There is a lot of work that goes into maintaining it. This schedule is usually divided into 4 levels: daily, weekly, every three months and every six months. First, on the daily schedule we need to check lubrication operating levels, and add oil if necessary, to make sure the cooling unit is operating correctly. Second, on the weekly schedule we must take the filter of the control cabinet and clean it to allow air to flow through for cooling. Third, we should check and clean the coolant filters, grease chains every three months. Final of schedule is every six months. We must clean the coolant tank and the radiator, drain and clean the hydraulic tank, and clean the lubrication unit. The above schedule helps the machine always operate stably with safety for users.

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All tools must be maintained on a schedule, so does the lathe machine tool. Lathes are used to create shafts, holes and round surfaces with a rotating shaft and a knife. There is a lot of work that goes into maintaining it. This schedule is usually divided into 3 levels: daily, weekly and semi- annually. First, on a daily schedule we need to check the water line pressure gauges, check air pressure, and clean chip filters. Second, on a weekly schedule we should inspect all filters, check coolant levels and inspect oil. And the final schedule is semi-annually, we had better inspect the spindle bearing, inspect the drive belt, and change oil. The above schedule helps the machine always operate stably with safety for users.

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In one injection moulding of plastic process always has some problems. Here are some typical problems and explain causes and solutions to these problems. The first is void( the air is trapped). Near the surface of the injection mould prototype the plastic shrinkage holes suddenly develop thick. Beside, the plastic volume changes when heated or cooled. And to solve the void problem, we can reduce wall thickness, slow down cooling rate or increase injection pressure. The second is the sink mark (the surface of plastic has holes in thicker areas). This problem is caused by two main reasons: the internal stress is too high and the surface rigidity is too low. So, we have three solutions for this problem: enough shot size, reduce wall thickness or reduce plastic.

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This picture is describe  the blow moulding process of plastic. And blow moulding process has seven steps. First, pellets of plastics are fed from the hopper into the cylinder and heated. Second, pellets are pushed along the cylinder by a rotating screw. Third, the screw stops rotating then a ram moves straight and the molten polymer is pushed toward a nozzle. Four, the molten polymer in the mould is inflated and expanded by compress air. Five, the plastic is cooled and become hard. Six, the screw continuous rotating and the process repeats. Final step, the mould opens and the shape is ejected.

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U6. Speaking (basic information of plastic)

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U6. Speaking (basic information of plastic)

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Plastic is synthetic materials that use polymers as a main ingredient. There are seven main types of plastic. First, Polyethylene terephthalate (PET/PETE) is a type very popular. PET can be used to produce food and drink containers. It is the most widely recycled plastic. Second, the High density polyethylene (HDPE) stronger and thicker than PET, incredibly resistant, be subjected to temperature. This plastic is used for grocery bags, milk jugs, shampoo bottle,... And as PET, HDPE is one of the most recycled plastic. Third, Polyvinyl Chloride (PVC) is synthetic plastic polymers. PVC have two basic forms: rigid and flexible. In rigid form, It is used to produce window, door, pipe,... and in flexible form, it use for plumbing, wiring,... PVC is hardly recycled, but it should be reused. Four, Low density polyethylene (LDPE) is type very flexible, transparent, the simplest structure, so it is easy and cheap to produce. It can be used to produce plastic bags, containers, and dispensing bottles. This plastic is not often recycled. Next, unlike LDPE, Polypropylene (PP) is hard and sturdy, and can withstand temperature. It use to produce car parts, yogurt containers. PP can be reused, but can not be recycled. And the six types of plastic is Polystyrene (PS). PS is inexpensive, easy to produce, but this plastic is highly inflammable and very dangerous when heated. PS can be used for insulation, egg carton. PS can not recycled. Final is some other plastic, the best known PC is types strong and hard. It is use to produce lenses for sunglasses, safety googles,.. PC never recycled.

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U6. Writing (base infomaiton of plastic)

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U6. Writing (base infomaiton of plastic)

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Plastic is synthetic materials that use polymers as a main ingredient. Plastic have some important properties: versatile, lightweight, chemically unreactive and very cheap. That is very convenient and gives a lot of applications: plastic bags, plastic bottles,....and they can reused. But, plastic have some disadvantages: hurt the environment because it cannot be recycled. In the past, we weren’t able to mould plastic into complex shapes. However, 100 years ago, manufacturers were able to produce modern synthetic plastic. And nowadays, plastic is widely used because we could mould plastic into complex shapes. In addition, plastic can be used in manufacturing to help designers reduce weight in aircraft. In near future, we will be able to make plastic from any kind of plant materials. In that way, we will save money by using smart plastic coatings on manufacturing components.

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U4. Speaking( compare CAD  and manual design)

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U4. Speaking( compare CAD  and manual design)

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Inventor, a CAD program developed from Autodesk, is a software used for creating detailed 2D and 3D designs, drafts, and models. Inventor has a lot of features including a vast library, design tool and modeling functions. Users can customize their workspace and work faster with keyboard shortcuts. Before manufacturing a product, you can be used Inventor to design 2D drawing, 3D drawing and simulation. Its advantages are extensive documentation and extensive community, making it friendly with users and applications in many industries. However, Inventor need a modern computer to operate and the cost to buy this software is very high.

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U4. Writing( compare CAD and manual drafting)

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U4. Writing( compare CAD and manual drafting)

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If you are a mechanical engineer you must know two ways to draft drawings. There are CAD and manual drafting. First, CAD is a computer aided design program, while manual drafting means you design on paper. Second, CAD is used to create exploded views and manifold models quickly. Unlike CAD, manual drafting has the capability to draft every single detail with pencil on paper. In adition, CAD has higher accuracy than manual drafting. Next, CAD needs operation skills while manual drafting needs designing skills. With flexibility, if you have an error, you can make changes easily in CAD, but you should make changes from the beginning in manual drafting. Finally, for use the CAD program you need to pay a lot of money, while manual drafting very cheaper.

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There are two main types of drives: Belt drive and Chain drive. The function of belt drive is to transmit motion and power from one shaft to another by means of friction between the belt and pulleys. The chain drive is used for transmitting motion and power between successive chains with sprocket special toothed wheels. Unlike a belt drive which is made of rubber, plastic, urethane, or other substances but chain drive is made from metal with a number of links. In operating time, the belt drive can reduce noise and vibration but the chain drive causes noise and vibration. In addition, belt drives can slip easily. The chain drive never can do it. However, the efficiency of the belt drive is low due to frictional loss, the chain drive so high ( usually above 95%). Because the efficiency of the chain drive is high, it is regular maintenance including frequent lubrication. Both belt drive and chain drive are applications in life. Belt drives can be used in flour mills, coolant pumps, lubricant pumps, AC, CAM shaft, and lathe machine, …. And chain drives are used for bicycle, motorcycles, and material handing equipment.

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What is the gear? Gear is a rotating circular component of a machine with teeth. Nowadays, there are many types of gears: Spur gears, helical gears, worm and worm gears, rack and pinion gears, and bevel gears… First, spur gears are the most common to use. Spur gears have teeth projecting towards or away from the center. It's used in low-speed applications because spur gears can not control noise at high speed. Second, the helical gears have their teeth cut in a spiral shape. Unlike spur gears, helical gears are used in high high-speed applications and can control noise. Besides, helical gears are run more smoothly and quietly. Next, the worm has just one continuous tooth. It can pair with worm gear. They are used for reducing speed. In addition, rack and pinion gears consist of a circular gear engaging a linear gear. The purpose of rack and pinion gears is to convert rotational motion into linear motion. Finally, the bevel gears have a conical form. Bevel gears are used for transmitting rotational power through shafts at an angle, normally 90 degrees.

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In the world today, there are many types of bearings invented and applcation in mechanical engineering. Example: ball bearings, straight roller bearings, tapered roller bearings, thrust roller bearings and journal bearings… Their main parts are usually inter race, outer race and rollers, but journal bearing have no rolling parts. First, ball bearings are used for spherical roller, it can support radial and axial motion. Second, the function of straight roller bearings are transmit radial motion, it uses cylindrical roller. Third, tapered roller bearings with conical roller are used to radial thrust. Next, thrust roller bearings have barrel-shape roller are used for supporting thrust forces and radial forces. Moreover, bearings reduce friction, support rotating or sliding components, and enhance efficiency, making them essential in countless mechanical systems across industries ranging from automotive and aerospace to manufacturing and construction.

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In the world today, there are many types of couplings invented and applcation in mechanical engineering. First, a very common type is rigid coupling, which is used for reducing wear on the machine and keeping the shafts alignment. It consists of two hubs and a fastening mechanism. Second, beam coupling is used to transmit power from the driver shaft to driven shaft, accommodate several degrees of shaft offset. Beam coupling is consists of a single piece of material, it can made of alumium, titanium, stainless steel,.. Third, flexible coupling, designed to reduce noise and unwanted vibrations, transmits torque from shaft to another shaft. It typically consists of a flexible element. Finally, sleeve- style coupling, the purpose of sleeve- style coupling is to couple two components of the machine, reduce transmission shock loads. It consists is one empty tube. In short, each type of coupling is used for different purposes in each specific case.

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The check valve is a device that is used to prevent backflow in a piping system. it is often used for water, gasoline, compressed air and heat. The check valve is made of cast iron. Here are some steps to make a check valve:

First, the part is cast. This stage means that hot liquid material is poured into a container and cooled to make the correct shape.

The cast iron is then turned on a lathe machine to remove excessive materials.

Next, the holes are drilled with a drill.

After drilling process, the next step is painting. The material is covered with paint. When the paint is dry, the parts are bolted together using nuts and bolts.

The final step is inspection. The work is checked carefully to make sure it can operate well.

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Presentation is to present a problem in a methodical and systematic way in front of a group or many people in order to provide necessary information and knowledge to the audience. And an effective presentation comes from many elements: good preparation, content, slides, and yourself. A presentation is usually divided into three main parts: the introduction, development and conclusion. Before the presentation, you need to prepare well: learn about the subject, know your audience. Preparing well will give you more confidence before the presentation. After that, the most important thing is that you must make an outline of what you want to present. Next is during the presentation, you should make eye contact with your audience and use some gestures. Or you can walk around a radius of 1 meter. They can help you grasp audience attention. And shouldn’t forget to use your own experience as examples. Finally, after the presentation you should thank the audience and ask if they have any questions and answer them. You don’t have an answer? Don’t worry, you can tell them you will find answers and contact them later.