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

• 1) Rolling – between two rollers, presses• 2) Splitting – scissors, sawmill, flame-cutting• 3) Clamping – centering by axis-hole• 4) 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 shaft

Plain 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 rotor have nearly supersonic velocity!