2019 02 14

Page 1

Course of ADVANCED MANUFACTURING PROCESSES Proff. Michele Monno – Barbara Previtali – Matteo Strano SURNAME NAME PERSONAL ID Exam - February 14th, 2019 Exercise n. 1 – Scientific article comprehension Your company is interested in a new machine solution for the cut of different materials. At first, stainless steel is considered to investigate different machine configurations. For this material, a single type of abrasive, GMA Garnet mesh #80, is used. Mass flow rate and water pressure are provided in Table 1. Table 1: Process parameters Symbol Value Unit Stainless Steel (SS) Water pressure 𝑃௪ 350 MPa Abrasive mass flow rate 𝑚̇ ௔ 8 g/s Thickness ℎ௔௖௧௨௔௟ 20 mm To take into account time requirements related to delivery dates requested by customers, two alternatives (1 or 3 cutting heads) are evaluated to predict the maximum feed rate levels reachable (Table 2). The paper “Cost optimization for multiple-head AWJ cutting” by A.M. Hoogstrate, 2006, may be helpful to preliminary evaluate the most convenient solution. Table 2 Symbol Value Unit Configuration 1 Machine cost 𝐶௥௣௟ 225000 € Number of cutting heads 𝑛௙ 1 - Electrical efficiency 𝜂௘ 70 % 𝑥௦௛ 1 - Configuration 2 Machine cost 𝐶௥௣௟ 350000 € Number of cutting heads 𝑛௙ 3 - Electrical efficiency 𝜂௘ 65 % 𝑥௦௛ 1.5 - Cutting head parameters (both configurations) Primary orifice diameter 𝑑௢௥ 0.33 mm Initial nozzle diameter 𝑑௙଴ 1 mm Discharge coefficient 𝑐ௗ 0.7 - Focuser length 𝑙௙ 76 mm Focuser cost 𝐶௙,௣ 100 € Focuser expected tool life 𝐿௙,௛ 80 h Orifice cost 𝐶௢௥,௣ 30 € Orifice expected tool life 𝐿௢௥,௛ 80 h It is required to: 1. Calculate the electrical power and the water flow rate required by the intensifier in the two configurations. Configuration 1 Configuration 2 𝒎̇ 𝒘,𝑺𝑺 [kg/s] 𝑷𝒕𝒐𝒕,𝑺𝑺 [kW] 2. Calculate maximum cutting speed…