Speeding Up Blade Milling. - Free Online Library

Speeding up blade milling

Parker Hannifin's Air & Space Div, City of Industry, CA,

supplies their assembly plant in Irving, CA, with precision bladed

stator and rotor components for turbine-engine starter motors. With

conventional machining, production was not fast enough - only four

parts/shift - and reject rate was 20 percent, so they needed to improve

both speed and quality.

A major bottleneck was a four-spindle tracer mill. After checking

the alternatives, they bought a multi-spiwndle, four-axis, precision CNC milling machine from Rigid Machine Tool Inc, enhanced with four

high-speed (24,000 rpm) spindles from IBAG North America, Milford, CT.

Since installation, the components are being produced four times faster,

with a reject rate of less than 1 percent. This solved both their

quality and quantity problems.

One part is a 416 stainless stator, 0.375" wide by 4.5"

dia. A stationary part, it directs air flow into the rotor of the

turbine engine's starter motor. There are a dozen different stator

and rotor configurations.

Each of this stator's 41 contoured, thin-wall blades is

generated with a 3.970" pitch diameter. Total depth of cut is

0.600". Four work-pieces are each mounted on horizontal rotary

tables and milled simutaneously by the four IBAG spindles. The machining

cycle requires ten roughing passes and two finishing passes. All four

spindles use 0.110" dia end mills for both operations. Feed rate is

9.4 ipm for roughing and 4.5 ipm during finishing. Four parts are

produced in two hours, in batch runs of 75 to 100 parts to meet

just-in-time (JIT) requirements.

"The improvement is much more than simply a time factor,"

points out Joseph Dowling, manufacturing manager. "The new

high-speed, milling process has had a positive effect on subsequent

operations, mainly because of better part quality. For example, before,

it was never certain how much time part-balancing would require. Now,

the balancing time is held to a minimum because the machine and

high-speed spindles combine to produce components with virtually

absolute concentricity. Spin tests at up to 80,000 rpm are now more of a

quality verification than a check to determine what corrections are

necessary. Part repeatability is within 50 millionths."

Using small diamet.er cutters at very high speeds results in

extremely clean cuts - a 32 rms surface finish. "Higher speeds also

help keep costs down," adds Dowling. "Longer tool life is a

product of high rpm's. If the cutter is running too slowly,

excessive heat is generated, which adversely affects tools and parts. In

a high-speed application, chips are evacuated quickly and carry the heat

out with them." Roughing cutters for the 4.5"-dia stators last

two cycles and finishing cutters last eight cycles. Changing tools takes

15 sec.

For more information, IBAG North America, unit of Siber Hegner

North America Inc, 84 Research Dr, Milford, CT 06460 or circle 380.

PHOTO : Stator blank before and after high-speed milling

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Is This Bad Starter Motor?
Sounds more like a connection problem or bad battery. Even if the starter was bad and the connections and battery were in good shape the voltage would not drop below 8 volts. Check for poor connection at the battery (both the positive and negative cables) The battery when charged up should show a static charge of 12.7 volts Hope this helps1. how does an induction motor work?The simplest of all electric motors is the squirrel-cage type of induction motor used with a three-phase supply. The armature of the squirrel-cage motor consists of three fixed coils similar to the armature of the synchronous motor. The rotating member consists of a core in which are imbedded a series of heavy conductors arranged in a circle around the shaft and parallel to it. With the core removed, the rotor conductors resemble in form the cylindrical cages once used to exercise pet squirrels. The three-phase current flowing in the stationary armature windings generates a rotating magnetic field, and this field induces a current in the conductors of the cage. The magnetic reaction between the rotating field and the current-carrying conductors of the rotor makes the rotor turn. If the rotor is revolving at exactly the same speed as the magnetic field, no currents will be induced in it, and hence the rotor should not turn at a synchronous speed. In operation the speeds of rotation of the rotor and the field differ by about 2 to 5 percent. This speed difference is known as slip. Motors with squirrel-cage rotors can be used on single-phase alternating current by means of various arrangements of inductance and capacitance that alter the characteristics of the single-phase voltage and make it resemble a two-phase voltage. Such motors are called split-phase motors or condenser motors (or capacitor motors), depending on the arrangement used. Single-phase squirrel-cage motors do not have a large starting torque, and for applications where such torque is required, repulsion-induction motors are used. A repulsion-induction motor may be of the split-phase or condenser type, but has a manual or automatic switch that allows current to flow between brushes on the commutator when the motor is starting, and short-circuits all commutator segments after the motor reaches a critical speed. Repulsion-induction motors are so named because their starting torque depends on the repulsion between the rotor and the stator, and their torque while running depends on induction. Series-wound motors with commutators, which will operate on direct or alternating current, are called universal motors. They are usually made only in small sizes and are commonly used in household appliances.2. is it bad to have a car with a lot of miles but new motor?well you got the tranny. that can go at any time. but if it is good then you will only have the odds and ends3. How does an AC motor work?Basically, an AC motor is a type of motor that is operated by an alternating current. It has two basic parts. First is a stationary stator and another is rotor.The above diagram shows the configuration of stator winding. I am giving an example for 3 phase motor. Hence, in above diagram A, B and C are the three phases. When the current is supplied to the windings, all the three windings become electromagnets. When the current reverses polarity of the winding also reverses.The stator windings are 120 degrees apart. Now, when the supply is given to the windings, only 2 phases of the supply are active and the remaining one phase is non-active or has no current flowing through it. Hence, the one phase which has no current flowing through it will have no magnetic field.Let us assume that at the start phase A has no current and no magnetic field produced. Phase B has current in negative direction and phase C has current in positive direction. Now, at some time 1, phase A has current in positive direction and phase B has in negative direction. While phase C has no current and no magnetic field. The resultant magnetic field vector has rotated 60 in the clockwise direction. Now at some time 2, phase A has current in positive direction and phase C has in negative direction while phase B has no current and magnetic field. The resultant magnetic field vector has rotated another 60.Now, after the end of 6 such cycles, the resultant magnetic filed vector would have rotated 360 or one full rotation. This is known as the Rotating Magnetic Field.Now, According to Faraday's law of induction,An emf induced in any circuit is due to the rate of change of magnetic flux linkage through the circuit.As the rotor winding in an induction motor or AC motor are either closed through an external resistance or directly shorted by end ring, and cut the stator rotating magnetic field, an emf is induced in the rotor copper bar and due to this emf a current flows through the rotor conductor. Here the relative speed between the rotating flux and static rotor conductor is the cause of current generation.As per Lenz's law,The rotor will rotate in the same direction to reduce the cause i.e. the relative velocity.The rotor speed should not reach the synchronous speed produced by the stator. If the speeds equals, there would be no such relative speed, so no emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated. Consequently the rotor can not reach the synchronous speed. The difference between the stator (synchronous speed) and rotor speeds is called the slip. The rotation of the magnetic field in an induction motor has the advantage that no electrical connections need to be made to the rotor.where Ns is the Synchronous speed and Nr is the Rotor speed.THANK YOU FOR READING.Ashutosh Sharma ( )How does an AC motor work?.
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