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A&C Notes (Sem VIII) Kaustubh V. Kokane

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A&C Notes (Sem VIII)

Kaustubh V. KokaneB. E. Production, KGCE

CONTENTS

1. Semi/Fully Automated Machine Tools .................................................. 2

2. Material Transfer Devices ..................................................................... 4

3. Advantages and Limitations of Pneumatic Power Systems ................... 9

4. Compressor......................................................................................... 11

5. Advantages of Hydraulic Fluid Power Automation .............................. 16

6. Linear and Rotary Actuators ............................................................... 16

7. Principles of Digital Hydraulics ............................................................ 18

8. Servo v/s Proportional hydraulics ....................................................... 20

9. Types of Transducers + Selection ........................................................ 21

10. Types of Sensors ................................................................................. 24

11. Industrial Application of Electrical Control Circuits ............................. 25

12. Pump Unloading Circuit ...................................................................... 26

13. Microprocessor Based Control Systems .............................................. 26

14. Servo Motor v/s Stepper Motor .......................................................... 27

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1. SEMI/FULLY AUTOMATED MACHINE TOOLS

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The conventional general purpose automated lathes can be classified as,

(a) Semiautomatic :

capstan lathe (ram type turret lathe)

turret lathe

multiple spindle turret lathe

copying (hydraulic) lathe

(b) Automatic :

Automatic cutting off lathe Single spindle automatic lathe

Swiss type automatic lathe

multiple spindle automatic lathes

Semi-automatic turret lathes

Sometimes machines similar to those above, but with power feeds and automatic turret-indexing at the

end of the return stroke, are called "semi-automatic turret lathes". This nomenclature distinction is

blurry and not consistently observed. The term "turret lathe" encompasses them all. During the 1860s,when semi-automatic turret lathes were developed, they were sometimes called "automatic". What we

today would call "automatics", that is, fully automatic machines, had not been developed yet. During

that era both manual and semi-automatic turret lathes were sometimes called "screw machines",

although we today reserve that term for fully automatic machines.

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Automatic turret lathes

During the 1870s through 1890s, the mechanically automated "automatic" turret lathe was

developed and disseminated. These machines can execute many part-cutting cycles without

human intervention. Thus the duties of the operator, which were already greatly reduced by

the manual turret lathe, were even further reduced, and productivity increased. These

machines use cams to automate the sliding and indexing of the turret and the opening and

closing of the chuck. Thus, they execute the part-cutting cycle somewhat analogously to the

way in which an elaborate cuckoo clock performs an automated theater show. Small- to

medium-sized automatic turret lathes are usually called "screw machines" or "automatic screw

machines", while larger ones are usually called "automatic chucking lathes", "automatic

chuckers", or "chuckers".

2. MATERIAL TRANSFER DEVICES

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INLINE TRANSFER MACHINE

ROTARY TRANSFER MACHINE

For further reading, tinyurl.com/82voulz (Full chapter on Material Transfer Devices- MUST

READ) and bp5azr6

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For further reading,tinyurl.com/cds5va3

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3. ADVANTAGES AND LIMITATIONS OF PNEUMATIC POWER SYSTEMS:

As a power medium, compressed air has numerous distinct advantages such as:

easy to transport and store;

unlimited conductive geometry;

offers little risk of explosion or fire;

Is a very fast working medium and enables high working speed to be obtained;

provides flexibility in the control of machines;

provides an efficient method of multiplying force;

no return lines necessary;

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efficient and dependable.

The main disadvantages of compressed air are:

safety precautions are necessary in handling;

expensive compared to some mechanical, electrical or hydraulic means for a

given application;

generally suitable for relatively Iow power requirements;

pressure limits;

leakages must be controlled to maintain usable pressures;

dirt and humidity must not be present.

Advantages of pneumatics

Simplicity of Design And Control

Machines are easily designed using standard cylinders & other components. Machines operate

by simple ON - OFF type control.

Reliability

Pneumatic systems tend to have long operating lives and require very little maintenance.

Because gas is compressible, the equipment is less likely to be damaged by shock. The gas in

pneumatics absorbs excessive force, whereas the fluid of hydraulics directly transfers force.

Storage

Compressed gas can be stored, allowing the use of machines when electrical power is lost.

Safety Very low chance of fire (compared to hydraulic oil).

Machines can be designed to be overload safe.

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4. COMPRESSOR:

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Reciprocating, rotary screw and rotary centrifugal air compressors

The three basic types of air compressors are

reciprocating rotary screw rotary centrifugal

These types are further specified by:

the number of compression stages cooling method (air, water, oil) drive method (motor, engine, steam, other) lubrication (oil, Oil-Free where Oil Free means no lubricating oil contacts the compressed air) packaged or custom-built

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Reciprocating Air Compressors

Reciprocating air compressors are positive displacement machines, meaning that they increasethe pressure of the air by reducing its volume. This means they are taking in successive volumes ofair which is confined within a closed space and elevating this air to a higher pressure. Thereciprocating air compressor accomplishes this by a piston within a cylinder as the compressing and

displacing element.

Single-stage and two-stage reciprocating compressors are commercially available.

Single-stage compressors are generally used for pressures in the range of 70 psig to 100psig.

Two-stage compressors are generally used for higher pressures in the range of 100 psig to 250 psig.

Note that

1 HP ~ 4 CFM at 100 psi

and that 1 to 50 HPare typically for reciprocating units. Compressors 100 hpand above are typicallyRotary Screw or Centrifugal Compressors.

The reciprocating air compressor is single acting when the compressing is accomplished using onlyone side of the piston. A compressor using both sides of the piston is considered double acting.

Load reduction is achieved by unloading individual cylinders. Typically this is accomplished bythrottling the suction pressure to the cylinder or bypassing air either within or outside thecompressor. Capacity control is achieved by varying speed in engine-driven units through fuel flowcontrol.

Reciprocating air compressors are available either as air-cooled or water-cooled in lubricated andnon-lubricated configurations and provide a wide range of pressure and capacity selections.

Rotary Screw Compressors

Rotary air compressors are positive displacement compressors. The most common rotary aircompressor is the single stage helical or spiral lobe oil flooded screw air compressor. Thesecompressors consist of two rotors within a casing where the rotors compress the air internally. Thereare no valves. These units are basically oil cooled (with air cooled or water cooled oil coolers) wherethe oil seals the internal clearances.

Since the cooling takes place right inside the compressor, the working parts never experience

extreme operating temperatures. The rotary compressor, therefore, is a continuous duty, air cooledor water cooled compressor package.

Rotary screw air compressors are easy to maintain and operate. Capacity control for thesecompressors is accomplished by variable speed and variable compressor displacement. For thelatter control technique, a slide valve is positioned in the casing. As the compressor capacity isreduced, the slide valve opens, bypassing a portion of the compressed air back to the suction.Advantages of the rotary screw compressor include smooth, pulse-free air output in a compact sizewith high output volume over a long life.

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The oil free rotary screw air compressor utilizes specially designed air ends to compress air withoutoil in the compression chamber yielding true oil free air. Oil free rotary screw air compressors areavailable air cooled and water cooled and provide the same flexibility as oil flooded rotaries when oilfree air is required.

Centrifugal Compressors

The centrifugal air compressor is a dynamic compressor which depends on transfer of energy froma rotating impeller to the air.

Centrifugal compressors produce high-pressure discharge by converting angular momentumimparted by the rotating impeller (dynamic displacement). In order to do this efficiently, centrifugalcompressors rotate at higher speeds than the other types of compressors. These types ofcompressors are also designed for higher capacity because flow through the compressor iscontinuous.

Adjusting the inlet guide vanes is the most common method to control capacity of a centrifugalcompressor. By closing the guide vanes, volumetric flows and capacity are reduced.

The centrifugal air compressor is an oil free compressor by design. The oil lubricated running gear isseparated from the air by shaft seals and atmospheric vents.

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STEPS TO COMPRESSOR SELECTION & SIZING:

I Understand the Application

What is the compressor supposed to do?

II Find Out the Details

Gas, pressures, temperatures, capacities, etc.?

III Scope of Supply

Who is to supply the motor, switchgear, piping, etc.?

IV Size the Compressor

V Select Accessories

When all of the above has been done, this information can be combined

with what is known about the customer's 'needs/desires' to generate a

successful quotation.

For details refer tinyurl.com/7dpewwb

For pneumatic components refer tinyurl.com/bo9scg2

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For a full chapter on compressor selection and types,tinyurl.com/85lvvnfand cugpmq3

5. ADVANTAGES OF HYDRAULIC FLUID POWER AUTOMATION:

Advantages of hydraulics:

Fluid does not absorb any of the supplied energy.

Capable of moving much higher loads and providing much higher forces due to the

incompressibility.

The hydraulic working fluid is basically incompressible, leading to a minimum of spring

action. When hydraulic fluid flow is stopped, the slightest motion of the load releases the

pressure on the load; there is no need to bleed off pressurized air to release the pressure

on the load.

6. LINEAR AND ROTARY ACTUATORS

Linear and Rotary Actuators

Motors offer excellent controllability and are therefore used as the drive sources of various automated equipment. In manycases a motor is combines with various mechanical components such as a ball screw, belt and pulley, and rack and pinionto convert the motor rotation to a different type of motion needed to drive the equipment. Oriental Motor has various linearand rotary actuators consisting of a motor assembled with the necessary mechanical components to meet the variousneeds of automated equipment.

Features of Linear and Rotary Actuators

Equipped with a motor offering excellent controllability, our linear and rotary actuators offer the following advantages over

hydraulic and pneumatic actuators:

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The actuator is very stable when operated, even at low speeds. It also offers smooth acceleration and decelerationoperation.

Motions can be programmed with multiple stopping points. With a linear and rotary actuator using a stepping motor, adjustment of position and speed can be performed easily

using data. Setup change is also simple, as you need to do is change the data.

Advantages of Using Linear and Rotary Actuators:

When automated equipment is designed, various factors must be taken into consideration including the production linelayout, installation environment, ease of maintenance, configuration of electrical wiring and control system, and so on. Thismeans many man-hours are needed to select the motor and other mechanical components and create a parts list,

drawings, operating manuals and the like. Use of linear and rotary actuators can reduce this time and offers additionalbenefits.

Higher Design EfficiencyThe primary feature of automated equipment is its ability to implement a series of basic operations such as "transfer","push" and "rotate." In other words, you can design automated equipment by selecting and combining linear and rotaryactuators capable of performing these basic operations. Since all you need is to select an actuator, you can save the timeand effort.

Shorter Production Time and Higher QualityWhen building equipment in-house by assembling a motor and mechanical components (see illustration), the quality ofassembly affects the traveling resistance and position accuracy, therefore ultimately adjustments will be needed to achievethe expected operating performance. On the other hand, our linear and rotary actuators are complete products guaranteedto provide the specified operating performance, so use of linear and rotary actuators reduces adjustment work and ensuresuniform quality.

For further reading,tinyurl.com/7guw6hq

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7. PRINCIPLES OF DIGICAL HYDRAULICS

Digital Hydraulic Transformer

The third embodiment, the subject of this proposal, is a device designed to be coupled with a fixed displacementhydraulic actuator (i.e. conventional hydraulic cylinder) in order to achieve variable displacement functionally. Thisdevice, the Digital Hydraulic Transformer (DHT), converts hydraulic energy by way of a proprietary new component,the Transtatic Bridge. An input flow at a certain given pressure is transformed to an output flow at another pressurelevel almost without loss. Except for small internal energy losses due to sliding friction and seal leakage, theconversion is also reversible, as the product of input pressure and flow is equal to the product of output pressure andflow.

Current designs allow for the transformation factor between input and output to be from .0667 to 15. For example,1000 psi fluid could be transformed into fluid at a pressure between 66 and 15,000 psi. The DHT principle couldeasily be compared to an electric transformer where the product of voltage and amperage remains constant. Of thethree primary embodiments of digital hydraulic technology, the DHT represents both the most advanced and the mostimmediately marketable form due to its compatibility with existing designs.

While current systems dissipate hydraulic energy by throttling flow, the DHT transforms hydraulic energy. Inprinciple, throttling can yield efficiencies down to 0%. Conversely, transformation is a reversible process with,theoretically, 100% efficiency. In the case of throttling, input flow equals output flow. With transformation, input energyequals output energy. The transformation can even move in the opposite direction. That is, a low load pressure maybe transformed back to a higher working level. At that point, this fluid is once again of use to the hydraulic system.This is energy redistribution, a necessary component of four-quadrant operation.

A proof of concept prototype, shown in Fig. 13, based around the preexisting VDLA prototype, was built in 2007 todemonstrate the DHTs attainable energy savings as final control element of a hydraulic servo drive. DHTfunctionality was achieved through the use of the VDLA, an attached load cylinder, and appropriate directional valves.The prototype was powered by and performance quantified by a test rig, and was connected to the lift cylinder of aforklift. The lift cylinder served as end actuator, as shown in Fig. 14. By quantifying pressures and flows during thelifting and lowering of varying loads, it was proven that the DHT can be effectively implemented as final controlelement in energy saving four-quadrant hydraulic servo drives. The DHT-enabled forklift required over 70% lessprime mover energy to complete standard work cycles.

For further reading,tinyurl.com/cnzaydp

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8. SERVO V/S PROPORTIONAL HYDRAULICS

ACC. TO APPLICATIONS (IMP):

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9. TYPES OF TRANSDUCERS

For detailed description of transducers and sensors (MUST READ)tinyurl.com/d7k2ga2

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10. TYPES OF SENSORS

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11. INDUSTRIAL APPLICATION OF ELECTRICAL CONTROL CIRCUITS

tinyurl.com/6tllplb

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14. SERVO MOTOR V/S STEPPER MOTOR

tinyurl.com/6vpmdgl (Suspected ans for servo hydraulics v/s digital hydraulics)

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