SELECTION OF DRIVES AND CONTROL SCHEMES FOR MACHINE TOOLS Machine tools and drives Horse power requirement for driving the machine tools MOTOR REQUIREMENTS FOR MACHINE TOOLS. SELECTION OF MOTORS Speed control of Drill press Application of Motors to Planers, Shapers Reversible motor drive quick return mechanism GRINDING MACHINES VFD

1. SELECTION OF DRIVES AND CONTROL
SCHEMES FOR MACHINE TOOLS
BATCH MEMBERS –
NITHYAPRIYA- 15E134
PRASHANNA R – 15E136
PRAVEENKUMAR S – 15E137
PREETHI A – 15E138
PRIYAA M – 15E139
RAJESH T – 15E141
R RAKSHIT RAJAN -15E142
RANJITH KUMAR – 15E143

2. Machine tools and drives
 Machine tools – devices for cutting , imparting a material to their required shape
 They draw power from a single source such as an electric motor or engine
 Will act as a load at first and there will be a marginal decrease in the speed , but
considered to be constant
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3.  When a machine tool is driven , its maximum torque will be dependent on the
motor power rating (HP/ KW) , and rotary speed (RPM)
 Connection – couplings(quick engaging) , disengage-able clutches .
 Allows the transmission of rotatory power from one shaft to another
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4. Example
 Motor shaft being coupled with a reduction gearing input shaft by coupling , once
mounted , it can be removed only for maintenance purpose or any replacement
 Clutches , on other hand use to disengage the driver and the shaft being driven to
cease the power transmission ( done based on the requirement of optimal power
output )
 This is the general mechanism of a machine tool drive
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5.  A feed drive will position the machine tool to a desired location ( carrying of its
components )
 Improvement in positioning accuracy and better speed control with enhancing of
the quality and the productivity of such machine tools
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6. Horse power requirement for driving the
machine tools
 Should be accurate
 How large or small a motor must be ? , accurate data
 Ex: A piece worker requiring a motor of large capacity for his tool to provide the
cuts at relatively higher speeds with continuous running of motor or with some
intermittent breaks .
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7.  Group drives are preferred over individual drives , group drive is a motor that
drives a short length of line shafting
 Expensive installation was required for individual drives in large plants for the
builders
 The use of open or enclosed motors for the machine tools depends on its working
condition , but the open one is mostly preferred
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8.  Best arrangement for group drives - A machine shop divided
into small units and each department will have a separate
motor
 Requirements in a short length – proper mounting and
placement at accessible positions
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9. MOTOR REQUIREMENTS FOR
MACHINE TOOLS.
 Reliable and low cost.
 They must be capable of speed control.
 Acceleration should be fast.
 Braking should also be effective.
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10.  Variable speed operation with constant torque.
 Machine design depends on duty cycle.
 Requirements of drive motor:
 Fast Response
 Wide range of speed control
 Low vibrations
 Better thermal capacity
 Low maintenance
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11. TYPES OF MOTOR
SERIES WOUND MOTOR:
 Speed is inversely proportional to the flux.
 High starting torque.
SHUNT WOUND MOTOR:
 Constant speed from no load to full load.
COMPOUND MOTOR:
 Drop in speed from no load to full load is considerably more than Shunt Motor.
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12. SELECTION OF MOTORS
 SHUNT MOTOR:
Lathes, boring mills , milling machines.
 COMPOUND MOTOR:
Shapers, planers , slotter.
 SERIES MOTOR:
Cranes , Hoists.
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13. REQUIREMENTS MOTOR
Constant speed, no load to full
load
Shunt Motor
Varying speed, varying with Series Motor
Semi constant speed , no load
to full load
Compound Motor
Adjustable speed ,remaining
constant for one adjustment,
load to full load.
Shunt Motor with
adjustable field resistance
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14. Speed control of Drill press
-UNIVERSAL MOTOR

15. Universal motor
 A universal motor is a series wound electric motor that can operate on both AC and DC
power.
 These are a lot comparative to those of DC series motors but the series motor develops
less torque when working from an AC supply than when working from an equivalent DC
supply.
 The working of a universal motor is similar to a series dc motor, they are also used for
numerous different purposes where speed control and high qualities of speed are
necessary.
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16. Speed control
 Speed control of Universal Motors can be possible
by following ways
 Phase angle Control
 PWM Chopper control
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17. Phase angle control
 In phase angle control method Speed control is achieved by varying the firing angle for
the TRIAC.
 Phase angle control is very cost effective solution but not very efficient.
 The AC universal motor drive controls the rotation speed by means of phase-angle
partialization.
 This method consists of changing the RMS voltage applied to the motor, where voltage is
a function of the firing angle of the Triac.
 Continuous speed control of a universal motor running on DC is very easily accomplished
using a thyristor circuit.
 A thyristor supplies the motor during the positive mains half cycle. Both the thyristor and
its control are connected in such a way that the motor back-EMF compensates the motor
load variations to adjust the speed.
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18. PWM chopper control
 In PWM method rectified AC line voltage is switched at a high frequency by a Power MOFSET or
IGBT device to generate time varying voltage for the motor.
 In this method to control the motors by providing stable speed control, preventing large currents
and drawing minimum harmonic current from ac mains supply are required.
 To meet these requirements using AC chopper with current and speed feedback is preferred.
 The pulse width modulation (PWM) technique , also known as chopper drive is used to adjust the
voltage applied to the motor.
 With the variation of the PWM duty cycle, the effective voltage seen by the motor can be changed.
 The advantage of PWM modulation with respect to phase-angle partialization is higher efficiency,
less acoustic noise and better , but it can have an impact on brush life duration.
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19. Drill press
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20. Application of Motors to
Planers, Shapers

21. Shaper
 A shaper is a machine tool that uses reciprocating straight line motion of the tool
and a perpendicular feed of the workpiece.
 By moving the work piece across the path of the moving tool a flat surface is
generated regardless of the shape of the tool.
 Metal is removed in the forward cutting stroke, while the return stroke goes idle
and no metal is removed during this period.
 Shaper can be used for shaping much smaller jobs.
 Shaper can employ light cuts and finer feed.
 The shaper is driven using quick return mechanism.
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22. Planner
 The planer is almost exactly similar to a shaper, and is primarily intended to
produce plane and flat surfaces by a single point cutting tool.
 The fundamental difference between a shaper and planer is that the table
reciprocates past the stationary cutting tool.
 Planer uses several tools to cut simultaneously and is meant for larger jobs.
 The drive on the planer table is either by gears or by hydraulic means or reversible
drives.
 Planer can employ heavier cuts and coarse feed.
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23. Shapper VS planer
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24. Mechanism of Shapper & planer
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25. Scotch yoke
 This is also known as slotted link mechanism.
 The slotted link mechanism is used for converting the linear motion of a slider
into rotational motion or vice-versa. This mechanism is generally found on
planer machines.
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26. Working
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27. Whitworth quick return motion
 This mechanism is used on shaping machine, which is quite large and on slotting
machine.
 The driving gear rotates at a constant speed. But the slotted link has a different
centre of rotation, its speed is not constant.
 The angle through which the driving gear and slotted link rotate on the forward
stroke is greater than the return stroke. This imparts the slow forward and quick
return motion.
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28. Working
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29. Selection of motor and drives
 In the case of planers, shapers, slotters, etc., the work is intermittent, being far
greater at some portions of the stroke than at others, and for this class of work the
compound DC motor is best suited.
 Drives used
 Hydraulic drive
 Variable speed reversible motor drive
 cross belt drive
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30. Cycle of operation
 The cutting stroke alternates with a non-cutting return stroke, as in the case of
planers and shapers .
 Successive operations of the tool occur in cycle as,
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31. Characteristics of motor
 In this class of work, a constant speed of the motor is not of as great importance
as with constant cutting tools, but it is, rather, desirable that the motor shall be
designed to take care of the over- loads that occur at the reversals, and for this
reason motors for use with tools of this class should be compound-wound.
 The result is that, as greater demand is made on the motor, the increase of current
that passes through it increases the torque of the motor.
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32. Contd..
 This also causes the motor to slow down, so that the speed for which the motor
should be adjusted is that desired when operating under cutting load. On the
return, when the load is light, the motor will consequently run faster than during
the cutting stroke.
 The average cutting speed of any of this class of tools will be between 25 and 50
feet per minute.
 Compound-wound motors are not used for such wide speed ranges as the shunt-
wound motors, since any considerable weakening of the shunt field so changes
the relation of the shunt to the series winding as to cause the motor to attain the
nature of a series motor, which is undesirable.
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33. Motor Equipment of a Planer
 The motor is mounted on the top of the
planer housings, and geared to a counter
shaft which carries the driving pulleys. The
use of the flywheel on the motor shaft is
most desirable, as it greatly relieves the
motor on the peak loads
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34. AVERAGE POWER REQUIREMENTS OF
PLANERS
Length of bed
(ft)
Horsepower
6 4 to5
8 6 to 7 ½
10 8 to 10
12 10 to 15
16 15 to 20
12 20 to 25
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35. AVERAGE POWER REQUIREMENTS OF
SHAPERS and SLOTTERS
STROKE
(in)
HORSEPOWER
16 2 to 4
18 2 to 3
24 3 to 5
30 5 to 8
STROKE
(in)
HORSEPOWER
10 4 to 5
12 5 to 6
24 10
30 10 to 15
The values are based on the use of two tool-heads and a
return speed having a ratio to the cutting speed of about
3 to 1
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36. Reversible motor drive quick return
mechanism
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37. Working
 All modern planers are equipped with variable speed electric motor which drives
the bull gear through a gear train. The most efficient method of an electrical drive
is based on Ward Leonard system
 This system was introduced by motor which is coupled with a DC generator, a DC
motor and a reversing switch runs, the DC motor will receive power from the DC
generator. At that time, the table moves in forward direction.
 At the end of this stroke, a trip dog actuates an electrical reversing switch. Due to
this action, it reverses the direction of current in DC generator with increased
current strength. Now, the motor rotates in reverse direction with higher speed
stroke with comparatively high speed
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38. Advantages of electrical drive
 Cutting speed, stroke length and stroke position can be adjusted without stopping
the machine.
 Large number of cutting speeds and return speeds are available.
 Quick and accurate control
 Return speed can be greatly increased reducing idle time.
 Another possible advantage when using a variable-speed motor and controlling
the speed of the motor at the end of the stroke is that much higher return speeds
can be obtained in connection with any desired cutting speed.
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39. GRINDING MACHINES

40. GRINDING MACHINES
 A type of machining using an abrasive wheel as the cutting tool
 Used to finish work pieces with high surface quality and high accuracy of shape
 A coolant will be used to prevent the overheat

41. TYPES OF GRINDING MACHINES
 Cylindrical grinder
 Surface grinder
 Bench grinder
 Belt grinder
 Gear grinder
 Jig grinder

42. SURFACE GRINDERS

43. SELECTION OF MOTOR
 Mostly, in normal mixer grinders, universal motors will be used
 DC shunt motor
 But for industrial applications, squirrel cage induction motor will be used
Speed control:
 Changing poles
 Changing frequency
 Changing supply voltage

44. VFD

45. ADVANTAGES OF VFD
 Energy saving
 Increased reliability
 Speed variations
 Soft starting
 Extended machine life and less maintenance

46. Reference
 Electric motor drives for machine tools
 www.mech4study.com
 www.mechanicalengineering.com
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47. THANK YOU!!