Assignment - sand casting, metal forming and cross sections PDF

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University of Sunderland, UK B (HONS) ELECTRONIC & ELECTRICAL ENGINEERING EAT227 Manufacturing Process ASSIGNMENT 1 Answer 3 Questions Name: UOS ID : SCM ID: Lecturer: Submission Form Hardcopy: Yes/ No Softcopy: Yes/No Declaration : I declare that this material, which I now submi...

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University of Sunderland, UK B.ENG (HONS) ELECTRONIC & ELECTRICAL ENGINEERING EAT227 Manufacturing Process

ASSIGNMENT 1 Answer 3 Questions

Name: UOS ID :

SCM ID: Lecturer:

Submission Form

Hardcopy: Yes/ No

Softcopy: Yes/No

Declaration : I declare that this material, which I now submit for assessment, is entirely my own work and has not been taken from the work of others, save and to the extent that such work has been cited and acknowledged within the text of my work. I understand that plagiarism, collusion, and copying are serious in the university and accept the penalties that would be imposed should I engage in plagiarism, collusion or copying.

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Q1) If you were to incorporate lettering or numbers on a sand-cast part, would you make them to protrude from the surface or recess them into the surface? What if the part were to be made by investment casting? Explain your answer. The answer depends on the casting process used. letters and numbers are commonly machined, and it is easier to machine recessed characters than protrude ones. -Applied marking is applied to the finished product and used mostly to identify castings with information that changes part-to-part such as serial numbers or part data for example made by laser, vibration engraving or ink stamping. -Integral marking is embedded into a pattern mold so that the identical marking appears on each part cast. It is permanently cut into the pattern mold, and difficult to alter without adding more cost to the casting. It can be either protrude (raised) or recessed (depressed) on the casting surface, casting metal factories tend to prefer that marking be protruding (raised). The reason for this is that the work on surface of a part is the inverse in the pattern mold. So a recessed letter marking will be raised on the surface of the mold so will be very susceptible to damage from handling of the mold. In sand casting a pattern will be machined then the recessed pattern letters will produce sand molds of protruding letters. The parts will then have recessed letters vice versa of mold. it is easier to produce letters and numbers by machining them into the surface of a pattern so the pattern will have recessed letters. The sand mold will then have protruding letters, as long as the pattern is faithfully reproduced. The final part will then have recessed letters. In investment casting, (also called Lost-wax casting, or precision casting), the mold will be machined directly and the parts will have protruding letters. the patterns are produced through injection molding and is easier to include recessed lettering in the injection molding die (instead of machining protruding letters). As a result, the mold will have recessed letters and the pattern will have protruding letters. Since the pattern is a replica of the final part, the part will also have protruding letters.

In general, it is easier to produce recessed letters in sand castings and protruding letters in investment casting. investment casting is more expensive than sand casting but closer and smaller dimensional tolerances with better surface finish is better achieved with investment casting. Therefore, for certain parts such as barrels for handguns, investment casting is preferable.

Q2) Sheet metal forming is widely used in the automobile industry, examine the part of a car and discuss the process or combination of processes by which you think they were made. Sheet Metal is a thin sliced metal sheet with a thickness between 0.4mm to 6mm. any thickness above that is known as plate and thickness below the range is known as a leaf. Sheet metal is one of the main materials used in metal working due to its ability to be cut and formed, and mostly considered to be high strength, good dimensional accuracy, and good surface finish and relatively low cost. Parts created from Sheet metal forming is used in almost every sector of industrial production: -Automotive industry (e.g. doors, hoods, fenders)

-Aircraft industry (e.g. wings, fuselage)

The required shape is achieved through plastic deformation, without undergoing any machining like milling. In most cases elastic deformation leads to spring-back which occurs after forming is complete. Spring-back is the geometric change made to a part at the end of the forming process when the part has been released from the forces of the forming tool affecting the dimensional accuracy of a finished part. General metal working processes are sand casting, die casting, extrusion and etc. In automotive metal forming, the blank sheet metal called “the blank”, is stamped, cut or bent into a shape needed for an automobile's body part. i.e. Doors, from a solid block of metal in a cubical or lens-like shape. In bending, force is applied to a sheet metal work piece to produce a curvature of the surface. Bending is generally used to produce simple curved surfaces rather than complex ones. A mechanically operated press drives a punch against sheet metal, forcing it into a simple die with enough pressure to produce a permanent change in the metal's shape. If not enough pressure is used, the metal can spring back into its original shape. If too much is applied, it can break. In drawing, the sheet metal is forced against a die that has been cut into the three-dimensional shape of car door, often a curved shape. As a result, the die is used as a mold for the metal. This technique can produce relatively complex shapes. Once again, pressure is applied to the work piece using a hydraulically or mechanically operated punch. Lubricant is used to make the metal slide more smoothly against the die, avoiding the possibility of wrinkling. If any then the wrinkled edges are trimmed from the metal which how the fuel tank is made. An automated device using robotic hands moves the work piece, door in this case from stage to the next stage. a device called a stamping press is used with a series of dies to cut and form the door shape. Extrusion is used to produce long metal objects, such as rods and tubes. The metal work piece is forced into a die with a hole in the opposite end. The metal is extruded through the hole to form

the shape. It is used to manufacture important parts of a car's drive train or the anchors that hold seatbelts in place. The forging process uses a press that hammers the metal against a block with a hard surface (anvil). It can be hammered repeatedly to form complex shapes. This can be used as an alternative to the drawing process. The above processes are generally used with cold metal. Hot metal can also be used, sometimes at high enough temperatures that the molten metal can be poured into a die. This requires very expensive dies that can withstand the heat and must be done quickly, to minimize the exposure of the die to the molten metal. Doors built up in separate assembly lines are placed on a conveyor belt to be mounted onto the rest of the body. Doors are lifted by a specially designed lift to lift them and locate them accurately to the car body. Bolts are torqued, and verified, to a specific value to mount the doors, also deck-lids and car hoods undergo same procedure. a number of robots will weld the readymade metal sheets of car parts and doors into location. the roof panel is placed on top of the sheet metal layer cake that is created and welded into place. The ditch molding is a simple method where a panel is placed on top of the vehicle and has an offset surface that allows resistance spot welding (RSW). The more complex methods have either brazing or laser welding to produce a continuous flat surface over the entirety of your roof. At this point the body without wheels, a chassis, a motor, or an interior but the right shape, then moved to body finishing, to sand and smooth the body panels and find and fix any problems or defects that show up before painted. A computer is used to guide metal forming operations through complex sequences for example, the action of the hammer can be programmed in advance to produce complex and artistic shapes. computers also control the flow of the work piece between multiple stages in the operation to produce the finished shape. Even with the arrival of carbon fiber, Sheet metal forming is still of great importance to the automotive industry. Most high volume production cars are made from sheet metal. Metals are still the main materials used in the automotive industry. This is due to Metals being able to undergo plastic deformation. This means the metals can be made into most shapes.

Q3) Design a few set of rolls to produce cross sections other than those shown in figure1 ( H section part). Sectional rolling: The roll forming process works by passing sheet metal through a series of rollers, with each of these rollers adding shape to the metal as it passes through. The rolls work together to form the desired cross section. Since the process is consistent and easy to repeat, roll forming is used to produce high volumes of metal components. For the manufacturing of bars and standard structural sections, section rolling is applied by using grooved rolls. The process starts with hot rolling in the cogging mill, to break down the ingot structure and to reach the bloom size. A further reduction by hot rolling leads to square billets. Blooms and billets represent the starting material for section rolling operations. The finished shape is reached through a number of passes that deform the material uniformly, avoiding excessive secondary tensile stresses which may lead to crack formation. This can be achieved by rotating the material sidewise, especially in the early passes. the alternate sidewise rotation of the material from oval to diamond-shaped grooves is to achieve uniform flow. Fins bulging through the rill grooves during deformation should be avoided. Roll pass design for the production of complicated shapes such as standard structural sections are based on experience and differs from one manufacturer to another. There are many cross section roll designs such as I-beam, Rail, Channel and Angle part.

References: 1- Discovery and Science Channel's How It's Made Car Doors episode.( www.sciencechannel.com). 2- Manufacturing Technology: Materials, Processes, and Equipment, By Helmi A. Youssef, Hassan A. El-Hofy, Mahmoud H. Ahmed, CRC Press; 1 edition (March 31, 2017). 3- Manufacturing Processes for Design Professionals, Rob Thompson, Thames & Hudson, 2007....