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Shafts for rotating machines
Sorting of rotating el. machines
• According power– Small < 10 kW– middle-class
up to 1 MW– big (not correctly
specified)
• Ac. principle– DC– asynchronous– synchronous– Alternative,
ECM etc.
• Ac. application - traction, - crane, slow/fast
rotating - compressors,
- explosion-proof, etc.)
Sorting of non-rotating machines
• Ac. power and voltage– low-power, up to
10 kW– middleclass, up to
1 MW– big
• Ac. design, assembly– air (transformers)– oil based– special (auto-
transformers, regulating tr., etc.)
• Acc. application– power plants– traction– ovens/furnaces– electrochemical– Etc.
(especially chokes, transformers, elmag. chucks)
Modern trend – increase of operating temperature (class „F“) very popular (190°C)
Characterization of production flow
Piece production– product = big machines or
technology element– layout designed according
technological requirements– special production
machines and templates are used
– exacting preparation of production and high requirements on the staff – qualifications!
Mass-production– product = small machines– layout according production
flow!– Often single-usage technology
equipment (machines)– just for one operation– using of „lines“ layout– more automation– lower requirements of staff -
qualification
Manufacturing of shaft
Initial material:• rolled- steel rod up to 150 mm• steel rod calibrated up to 70 mm
(for mass-production)• forged ingot, heated and hammered
Issue: strength, precision of mechanical turning, dimensions acc. standards
Note: Quality of material is checked, some off-takes are done and analyzed
Hammered shaft – production procedure
• casting (founding) – ingots with double mass
• hammering – at circa 700 °C
• pre-heating (possible)
• annealing - 700 - 800 °C (also „tempering), changing of
hardness and mechanical properties
• axis hole – off-taking of samples, analysis, also space for
winding or cooling
Tests of mechanical parameters.: visual, DC current,
ultrasonic, etc.
Mechanical turning of shafts• Rolling – between two rollers, presses• Splitting – scissors, sawmill, flame-cutting• Clamping – centering by axis-hole• Mechanical turning:
– Rough turning (big tolerance)– Finishing of surface (précising) – pads for bearings
Issues: using of more tools, troubles with clamping and accuracy. Today popular clamping with magnetic chucks or induction heating.
Cutting of grooves – sometimes by turning, more often by mill-tool.
Steps of mechanical turning
Finishing of surfaces (polishing)
• smooth (plain) shafts – small machines
• graded shafts (terrace) profile
• shaft with flange – just for rolling-bench
• special design – shaft made from segments
• special surface – grooving – for small machines
Sorting of shafts
Fixing rotor plates on shafts
Plain shaftPlain shaft with grooves (fixing)
Plain shaft with grooves and ruler
Shaft made from segments – fixing with „locks“
Complete process of mass production of shafts for small drivers
Balancing of shaft • vertical rotors – hydro („lens“ or lentils design)• horizontal rotors – AC generators, synchronous
rotors (rulers design)• principle:
– static balancing– dynamic balancing
• typical dimensions of rotors:– hydro generator: up to 6 meters height, diameter 6-10
meters,– synchronous generators: 10-12 meters length, diameter
up to 1 meter (limited with the solidity of used steel).
Note: some parts of the rotors have nearly the supersonic velocity!