When we intend to change the machining process to PM, we need to consider 4 questions: 1.     The quantity is big enough to ensure the investment of mould is reasonable, because the machining maybe doesn't need to make mould;2.     Evaluate the structure and tolerance, to prove the feasibility, then offer necessary changes;3.     Evaluate the required physical properties, it should be in the limitation of PM process;4.     Calculate and see if the PM process is really cost-efficient than other technologies. Gennerally speaking, there are few parts which are totally meet all above 4 points, but anyhow, the successful decision of PM is the result of positive compromise and deeply technical conversation. The main classifications of gear:1.     Pinion gear2.     Ring gear3.     Duplicate gear4.     Sprocket5.     Pulley6.     Worm gear7.     Spline hub They are widely used in motor, enginee, gearbox, oil pump, water pump and other structure of transmission. Advantages of PM gear:Few waste of the material, formed directly by only one or two times of pressingHigh efficiency, stable quality levelLow material and production cost Weakness of PM gear in comparison with machining gear:Yield strength, breaking stength of the toothDensity 7.2 g/cm³Profile precision H6~H8Macrohardness 25-40 HRCMicrohardness 60 HRC Max The application of PM partsAutomobile:Enginee parts, crankshaft timing belt pulley, water pump pulley, oil pump pulley, driving and driven gear, driving and driven sprocket, cam, bearing cap, rocker arm, bushing, thrust plate, valve guide, inlet and exhaust valve seat.Transmission parts, gear hub and parts of various high and low speed synchronizer, clutch gear, cam and camshaft (*), sliding block, shift lever, axle sleeve, guide block, synchronous ring. Motorcycle:Driven gear and parts, sprocket, starter pawl, ratchet, star gear, duplicate gear, pinion gear, gear ring, variable gear, pushrod cam, shaft sleeve, sliding bearing, centring sleeve, driven disc, inlet and exhaust valve seat. Oil pump parts:Oil pum gear, gear hub, various rotors, inner rotor and outer rotor, gerotor, cam ring.