Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. They are common equipments in liquid conveying system. Manufacturing process of check valve is the matter needing attention. There are 6 main steps in making check valve. The check valve is made of iron but the shape of it is pretty complexity. So in the first step, iron will be melted into liquid shaped and then casted in a mold. Next, the workpiece is grinded to remove redundant details. After that, it will be drilled to make holes. These holes are for assembling check valve to tubes. After drilling, the worker will paint the valve. Painting helps the valves can have corrosion resistance and it looked prettier too. The fifth step is assembling. The bolts will be tightened to connect all the parts of a valve. Finally, The inspector will check if the product is qualified or not. Nowaday, there are more and more ways to create a check valve but the cast manufacturing is still the most common way because of it’s high economic. 

Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Nowadays, plastic is used in all fields and we can easily see it in our daily life. It can be material for mechanical industry, medical industry, electronics,… Plastic is versatile. Because of that, plastic can be shaped easily into a wide range of form to make a variety of products. Plastic has a lightweight and it is also durable. It does not react with air or water, is unaffected by various chemicals. And almost types of plastic have a cheap price. In spite of its advantages, there are some bad points of plastic. The worst problem is pollution. From past to present, plastic pollution is still a big problem of mankind. In the past, humans can not recycle plastic. But now, we have many solutions. Many new types of plastic are invented and they are recyclable and can biodegrade. The scientists are trying to create a new type of plastic that can biodegrade and still has all the good properties of nowadays plastics. Almost everyone wants plastic can be used widely without worries about plastic pollution in the future. 

Plastic is a very common material nowaday and it is applied in many fields. Because of that, manufacturing plastic products also develop vigorously. One of the most modern way to create plastic products is injection moulding. There are 6 steps in plastic injection moulding: Feeding, Plasticization, Pushing, Injection, Cooling and Ejection. In the first step, pellets of plastic are fed from the hopper to a cylinder. Next, they are pushed through the cylinder by a rotating screw. When they come near to the output of cylinder, plastic will be heated by heating system. After that, every plastic pellets become moulten plastic. In the third step, the scew stops rotate then a ram in front of the srew moves straight forward. This ram pushes the soft warm plastic toward a nozzle. By the force of the ram, soft plastic is injectedd though the nozzle to a shaped cavity in the two halves of a mould. When the plastic fills full of the mould, it is cooled and then become hard in the cavity. In the last step, the mould opens and cold, hard, solid plastic shape is ejected. After these steps, plastic product just need to be grinded to become the final product.

A bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. Most bearings have three main parts: inner race, outer race and rollers. There are several types of bearings that I have known: ball bearings, rolling contact bearings, journal bearings, straight roller bearings, tapered roller bearings and thrust roller bearings. Ball bearings use spherical rollers to support radial and axial motions. Straight roller bearings use cylindrical rollers to suppport radial load. Tapered roller bearings have the same function with SRB but their rolling parts are conical rollers. The last are thrust roller bearings with barrel-shaped rollers to support thrust motion.To sum up, there are three common functions of bearings: minimize friction during operation, hold - orient the rotating shaft or rotating parts, hearing forces and bearing loads acting on the rotating shafts or rotating parts. Because of these usefulness, bearings have a wide range of applications. Due to that, bearings can easily be found in any industrial machine such as: motor-bikes, cars, machine tools, conveyor systems,… We can not look directly at bearings in daily life but they are parts of many things among us.

There are two common types of drives nowaday: belt drives and chain drives. They have the same function is to transmit motion and power from shaft to another. But actually they have many differences. Firstly, It is about their mechanism of action. Belt drives work by means of friction between belt and pulleys when Chain drives do it by successive chain with sprocket special toothed wheels. Next to that, They also have the difference in their material. Belt drives are made of rubber, plastic, urthane. Chain drives are made of metal with number of links. Unlike Belt drives, Chain drive cause noise and vibration. Belt dives are different from chain drives because of their slippage. Slippage is the reason why there is frictional loss in belt drives and low-efficiency. The efficiency in chain drive is very hight (usually above 95%). The slippage in belt drives also can protect motor when it is overload. So we can say that slippage is both a strength and a weakness of belt drives. Both belt drives and chain drives are need the maintenance. Belt drives need to be re-tension when chain drives need lubrication frequently. Lastly, their application. Because of the differences, they are used in different applications. Belt drives are used in flour mills, pumps, CAM shaft, lathe machines… And Chain drives are used in bicycle, motorcycles, material handling equipment.

Plastic injection moulding is one of the most moderm ways to create plastic product. But it still have some problems that make defective product. These problem are: short shot, void, sink mark, flash, jetting and brittleness. Two most commonly problems are short shot and void. Firstly, short shot is that there is not enough plastic in the shot. Lossing pressure in the mould is also cause short shot. This problem can be solved easily by 3 ways. First solution is checking the shots continuously and use plastic with high melting capability. The second solution is to increase fill speed, plastic and mould temperature. The last way is to increase gate size and runner. The second problem is void. It is caused by plastic shrinkage ( a hole suddenly develops in a thick section during cooling ). Plastic volume changes when plastic is heated or cooled. There are 4 solutions for the void problem. First: increase the injection pressure to force more material into the mold and reduce shrikage. Second way is to reduce wall thickness. One more solution is to slow down cooling rate. The last solution is to increase gate size and locate it at the thick part of the moulding. 

A lathe is a machine tool that rotates a workpiece about an axis of rotation to perform various operations such as cutting, sanding, drilling, deformation, facing, and turning, with tools that are applied to the workpiece to create an object with symmetry about that axis. Lathe is usually used to cut cylindrical workpiece. Lathe is the combination of many mechanical systems. These systems are: belt drives, gear sets, bearings, coolant system, machine body and cutter. They are assembled and work correctly together. Lathe has so many parts. Because of that, it also has lots of problems for each machine system. There are 3 types of time-based maintenance: Daily maintenance, Weekly maintenance and Semi-annually maintenance. Each type has its own object. First type is daily maintenance: check line pressure gauges and air pressure, warming up , cleaning chip filter. The second is weekly maintenance: Inspeting all filters, cheking coolant levels, inspecting oil/gease. The last, semi-annually maintenance: inspecting spindle bearing and belt drive, changing oil. These maintenance works have so many benefits for the lathe machine. With the drive system, re-tensioning help drive work more work more efficiently and also avoid slippage. After that is the gear set. Changing oil for gearset is important if we want to reduce noise and vibration. Next, checking water line pressure gauges and air pressure is to reduce occlusion inside the coolant system. Inspect spindle bearings help us to detect the fault in time and then replace new bearings. This work will reduce noise, vibration. It also help avoid shaft broken and worn out of gear sets. Overall, maintenance help machine work smoothly, enduring and improve product quality. So having maintenance schedule is very important for any types of machine.