Full exam for Advanced Manufacturing Processes in the Mechanical Engineering degree programme at Politecnico di Milano. The document covers: Exercise n. 2 – technological problem Your workshop has recently received a big order of keychains made of stainless steel AISI 304 of thickness 4mm. Properties of AISI 304 are reported in Table 1. In your facility there are two laser cutting machines with different laser
Full exam for Advanced Manufacturing Processes in the Mechanical Engineering degree programme at Politecnico di Milano. The document covers: Exercise n. 2 – technological problem Your workshop has recently received a big order of keychains made of stainless steel AISI 304 of thickness 4mm. Properties of AISI 304 are reported in Table 1. In your facility there are two laser cutting machines with different laser
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Exercise n. 2 – technological problem Your workshop has recently received a big order of keychains made of stainless steel AISI 304 of thickness 4mm. Properties of AISI 304 are reported in Table 1. In your facility there are two laser cutting machines with different laser sources and optical properties. Your goal is to maximize productivity processing all parts with only one machine. Base your decision on the theoretical feed rate you can obtain with the two machines. The properties of the two machines are in Table 2. Table 1: Physical properties of AISI 304 𝝆 𝑪𝒑 𝑻𝒎 𝑻𝟎 𝑳𝒇 𝑳𝒗 [kg/m3] [J/(kg°C)] [°C] [°C] [kJ/kg] [kJ/kg] 8000 500 1455 20 270 5955 Table 2: Available laser cutting machines. Machine Source Power A BPP Collimated diam. Fiber core diam. Collimation lens Focal lens [-] [-] [kW] [-] [mm·mrad] [mm] [µm] [mm] [mm] 1 Co2 4,5 0,15 3,5 12,5 - - 150 2 Fiber 3,0 0,20 1,0 - 50 100 200 Figure 1: Keychains of the order. You are asked to: 1. Compute the waist diameter, 𝑑+, and the intensity at the waist, 𝐼+. 𝑑+,./0 = _________ µm 𝐼+,./0 = _________ kW*cm-2 𝑑+,12345 = _________ µm 𝐼+,12345 = _________ kW*cm-2 2. Compute the maximum beam diameter (interacting with the material), 𝑑∗, and the corresponding beam intensity, 𝐼∗. Consider that the focal position is set for both machines at 3,5mm below the upper surface of the sheet to avoid burr formation. 𝑑./0∗ = _________ µm 𝐼./0∗ = _________ kW*cm-2 𝑑12345∗ = _________ µm 𝐼12345∗ = _________ kW*cm-2 3. Can you perform the manufacture with both machines? Machine 1 (CO2) yes ☐ no ☐ Machine 2 (Fiber) yes ☐ no ☐ 4. Compute the theoretical cutting speed for all the machines that allows to perform the manufacture. Choose the machine that gives you higher productivity. Approximate the kerf width with the waist diameter and consider a…
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