MET221 Manufacturing Processes Week 3 Review Assignment Chapter 23 Problem 1. (Rule Surface Roughness) A turning operation is performed on C1008 steel (a ductile steel) using a tool with a nose radius = 1.3 mm. Cutting speed = 61 m/min and feed = 0.27 mm/rev. Compute an estimate of the surface roughness in this operation. (Hint: the ratio of actual to ideal roughness can be read on the figure below) Actual Ratio Theoretical 2.4 2.2 2.0- 1.8 1.6- 1.4- 1.2 Ductile metals Cast irons Free machining alloys 1.0 0 100 30.5 200 Cutting speed-ft/min 61 Cutting speed- m/min 300 400 T 91.5 122 Problem 2. (Determining Cutting Speeds in Machining Economics) A turning operation is performed with HSS tooling on mild steel, with Taylor tool life parameters n = 0.12, C = 60 m/min. Work part length = 450 mm and diameter = 80 mm. Feed = 0.20 mm/rev. Handling time per piece = 4.0 min, and tool change time = 1.5 min. Cost of machine and operator = $27/hr, and tooling cost $2 per cutting edge. Find the a. cutting speed for maximum production rate and b. cutting speed for minimum cost Problem 3. (Production Rate and Cost in Machining Economics) For the two cutting speeds computed in problem 2, determine: a. the hourly production rate and b. the cost per piece. Chapter 24 Problem 4. (Grinding) 1 (SI units) Wheel diameter = 160 mm, and infeed = 0.03 mm in a surface grinding operation. Wheel speed = 1500 m/min, work speed = 0.25 m/s, and crossfeed = 4 mm. The number of active grits per area of wheel surface = 35 grits/cm. When the wheel is engaged in the work, determine: a. average length per chip, b. metal removal rate, and C. number of chips formed per unit time for the portion of the operation Problem 5. (Grinding Operations and Grinding Machines) (USCS units) In a centerless grinding operation, the grinding wheel diameter = 8 in, and the regulating wheel diameter = 5.0 in. The grinding wheel rotates at 1500 rev/min, and the regulating wheel rotates at 180 rev/min. The inclination angle of the regulating wheel = 2.3. Determine the production rate of cylindrical work parts whose diameter = 0.5 in and length = 5.0 in. MET221 Manufacturing Processes Week 4 Review Assignment Chapter 25 Problem 1. (Electrochemical Machining) An ECM operation is used to cut a hole into a plate of stainless steel that is 10 mm thick. The hole has a rectangular cross section, 15 mm by 25 mm. The operation is accomplished at a current = 1300 amps. Efficiency is 97%. Determine the feed rate and time to cut through the plate. The specific removal rate C for stainless steel = 2.46 102 mm/A-s. Problem 2. (Electric Discharge Machining) Iron is to be machined in an EDM operation. If discharge current = 30 amps, what is the expected metal- removal rate? The melting point of iron is known to be 1539C, and the metal removal rate constant of proportionality K = 664 in SI units (5.08 in U.S. customary units) Chapter 27 Problem 3. (Electroplating) A steel part with surface area A = 130 cm is to be tin-plated. What average plating thickness will result if 15 amps are applied for 10 min in an acid sulfate electrolyte bath? The cathode efficiency for tin is E = 90% and the plating constant C = 4.21 x 102 mm/amp-s. Chapter 32 Problem 4. (Build Cycle Time in Stereolithography) The square cup-shaped part shown is fabricated using stereolithography. The base of the cup is 35 mm on each side and 4 mm thick. The walls are 3 mm thick, and the total height of the cup = 50 mm. The SL machine used for the job uses a spot diameter = 0.25 mm, and the beam is moved at a speed = 1000 mm/sec. Layer thickness = 0.10 mm. Repositioning and recoating time for each layer = 20 sec. Compute an estimate of the cycle time to build the part if the setup time = 15 min. Figure for Problem 4. 1 50 Problem 5. (Cost per Piece in Additive Manufacturing) The cost of the stereolithography machine is $60,000 installed. It operates 5 days per week, 8 hours per day, 50 weeks per year, and is expected to last 5 years. Material cost for the photopolymer = $150/L. Assume that all of the photopolymer in the container that is not used for the part can be reused. Labor rate = $25.00/hr, but labor will be used for only 30% of the build cycle, mostly for setup. The post- processing time = 5.0 min/part. Using the cycle time of 3.27849 hr, determine the cost a part of volume 22564 mm