PE Mechanical Machine Design case studies
PE Mechanical Machine Design · Put your knowledge to work in context.
PE Mechanical: Machine Design and Materials is one of the three NCEES PE Mechanical examinations, and it is the one aimed at engineers whose work centers on mechanical components, assemblies, and the materials they are made from. Like every PE exam, it tests for a minimum level of competency in the discipline and is designed for engineers with at least four years of post-college work experience. The PE Mechanical Machine Design case studies are 5 cases and about 4,023 words.
1Axial End-Play Stack: Worst-Case Versus Statistical Tolerancing
A gearbox output shaft is located axially by a housing bore, one ball bearing, a spacer, and an end cover. The design requires assembled end play of 0.02 to 0.12 mm so the bearing is neither preloaded nor loose.
749 words, about 4 min2Shaft Fatigue at a Keyway Under Normal and Jam Loads
A 35 mm diameter shaft of 1045 cold-drawn steel (Sut = 630 MPa, Sy = 530 MPa) drives a gear through a parallel keyway. The keyway ends are milled with a standard end-mill radius and the shaft surface is turned.
785 words, about 4 min3Hardness and Distortion After Quench and Temper of a 4140 Shaft
A 4140 through-hardened drive shaft, 70.0 mm finished diameter by 900 mm long, is specified at 285-321 HB with a minimum 12 mm hardened depth. The current route is: rough turn to 72.0 mm, austenitize at 845 C, oil quench, temper at 600 C, then finish grind to size.
875 words, about 4 min4Bearing Life Below Target: Bad Batch or Wrong Design Point?
A 50 mm line shaft in a split pillow block runs at 1,200 rpm under a steady 6.0 kN radial load. The selected 6210 deep-groove ball bearing has a basic dynamic load rating C = 35 kN, and the design target is 20,000 hours at 90% reliability.
758 words, about 4 min5Capability, Gauge Error, and a 10 Micron Escape on a 25 Micron Bore
A 6061-T6 hydraulic manifold bore is specified at 40.000/40.025 mm. The supplier gauges 100% of production with an air-plug gauge mastered with a ring at 20 C, in a shop held at 28 C; parts are gauged within a few minutes of machining.
856 words, about 4 min