Ejector Pump - PowerPoint PPT Presentation

Loading...

PPT – Ejector Pump PowerPoint presentation | free to download - id: 6f6e63-YmQwZ



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Ejector Pump

Description:

Ejector Pump The ejector pump is a type of vacuum pump. Gas is removed from a container by passing steam or water at a high velocity through a chamber that is ... – PowerPoint PPT presentation

Number of Views:82
Avg rating:3.0/5.0
Slides: 92
Provided by: RAMACHANDRAN
Learn more at: http://www.dss.nitc.ac.in
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Ejector Pump


1
Ejector Pump The ejector pump is a type of
vacuum pump. Gas is removed from a container by
passing steam or water at a high velocity through
a chamber that is connected to the container. The
mixing chamber contains both the gas from the
container and the steam or water. At the inlet
port, the ejector pump is connected to the
container that is being evacuated.
NITC
2
  • Melting

NITC
3
  • For both ferrous and non ferrous
    castings.(melting temperature upto 16500C)
  • Very accurate details obtained in intricate
    shapes
  • Excellent surface finish, machining and cleaning
    costs minimum.
  • Accuracy of 0.002 mm per mm obtained.
  • But, casting process costly.
  • Casting cost high.

NITC
4
  • PRODUCTION OF ALLOY WHEELS
  • METHOD OF PRODUCTION COUNTER PRESSURE DIE
    CASTING
  •  
  • The manufacturing process commences with the
    smelting of pure aluminium ingots in a 5-ton
    basin type furnace.

NITC
5
NITC
6
  • The furnace is a dry sole type furnace whose
    function is to smelt the primary raw material,
    and reprocess alloy scraps consisting of- wheels
    used in destructive testing by the quality
    control department, and the risers and gates
    removed from the wheels following the casting
    process. From the dry sole furnace, the molten
    aluminium is transferred to the alloy induction
    furnaces via a feed channel to enable the mixing
    and smelting of the elements required in the
    preparation of the alloy AlSi 7.

NITC
7
  • A spectrometer equipped quality control
    laboratory is used during the process of alloy
    preparation to ensure the composition of the
    alloy meets the required specification during
    this stage of the preparation process.
    Spectrometer analysis sampling is also applied
    randomly to finished wheels.

NITC
8
  • Molten alloy is transferred to holding furnaces
    for eventual transfer to the casting machines.
    After the molten alloy has been tested for
    conformance to specifications, it is transported
    to the alloy treatment station where the alloy is
    submitted to three procedures performed by an
    automatic process control system. The treatment
    unit introduces salts into the molten alloy using
    a high-speed spinner, where the alloy
    purification is assisted by the use of nitrogen
    gas jets. The three procedures to which the
    molten alloy is submitted are-
  •          Degassing
  •          Refining
  •          Modifying

NITC
9
These processes are intrinsic to the removal of
all undesirable impurities in the molten alloy.
The automation of these processes improves the
product quality control, production rates and
importantly minimizes wastage by reducing the
possibilities of rejection of the finished
product. Following the procedures to ensure that
the molten alloy conforms to precise
specification, it is transported in holding
furnaces to the low pressure casting machines.
These furnaces are designed to produce casting by
employing pressurised air within a range of 0.3
1.0 atm., the pressurization being monitored and
varied by a computerized process control system
according to flow requirements 
NITC
10
Computerized process technology automatically
controls the casting process, and then, at the
end of the 4.5 minute casting cycle, cools and
ejects the wheel onto a catcher arm designed for
this purpose. Holding furnaces contain between
500-750kg of molten alloy - sufficient for up to
approx. 4 hours of casting operations. When the
holding furnace is exhausted it is exchanged for
a full replacement furnace using the transfer
shuttle - illustrated above - without
interruption to the casting process. Hydraulic
systems control many of the units operating
movements, and, due to high operating
temperatures many measures have to be taken to
enable minimization of risk and reduction of
maintenance of these systems. For example, it is
necessary for all hydraulic systems to employ
fire resistant fluids thereby eliminating fire
risk. Likewise, all hydraulic hoses have to be
metal covered and insulated against accidental
splashes of molten metal.
NITC
11
The operators of the Counter Pressure Casting
Machines perform an initial visual quality
control as the wheels are ejected from each unit
and palleted ready for transport to the Riser
cutting department. At this first stage in the
machining process following casting, the removal
of the gates and risers is carried out by
automated machines designed for this purpose
with a cycle time of 50 seconds per wheel. The
CNC riser-cutting unit performs the following
operations
NITC
12
  •          Pre-boring of the central hole of the
    wheel
  •          Removal of the channel burrs
    corresponding to the surface joints on the Dies
    moving parts
  •          Trimming upper and lower edges of the
    wheel
  • The working cycle of the Riser cutting unit is
    completely automated to improve both quality
    control and production rate per machine. All
    waste products are collected for recycling at the
    foundry. The machine operations are performed
    under a suction hood to remove aluminium dust and
    particulates from the environment in proximity to
    this unit.
  • Customarily, after the machining processes have
    been completed on the newly cast wheels, the
    wheels are passed to the quality control unit for
    examination under a variety of non-destructive
    and destructive tests. Batch sampling of the
    wheels may involve taking a 1-2mm scrape taken
    using a lathe, and running a spectrometer
    analysis of the resulting alloy sample.

NITC
13
  • X-Ray analysis machine in Quality control
    department
  • Non-destructive testing is undertaken using
    radiography processes. It is common practice for
    the VM customers to include within their
    contractual requirements testing volumes and
    timescales (i.e. before or after machining). The
    X-ray control equipment can be pre-set with
    information from up to 1000 wheel designs, and
    wheels can be inspected on a wide variety of
    positions / angles (normally 20 position
    variants).
  • The wheel manipulator for handling the wheels
    during the inspection cycle has 5 fully
    computerized axes and a roller conveyor
    automatically provides loading/unloading of the
    machine with the wheels for inspection.
  • The X-Ray unit takes 2 wheels at a time - one in
    process of inspection cycle, and a second wheel
    in a holding position. As the testing machine
    completes the automated inspection cycle, it
    simultaneously ejects the inspected wheel, puts
    the second wheel into position for inspection and
    draws another wheel into the holding position.
    Thus the performance inspection cycle is enhanced
    to its maximum possibility. During an inspection,
    the operator monitors the x-ray image on a
    viewing console and has the possibility of
    magnifying the image or replaying the process
    to precisely identify any casting defect exposed
    by this machine.

NITC
14
  • The next stage of the quality control process is
    undertaken on Geometrical control benches where
    the physical dimensions of the wheels are
    compared with the specification standard using
    pantographs and micrometers.
  • The semi- finished product, having been submitted
    to various machining and quality control
    procedures are passed to the finishing dept.
    which - dependent upon client specification -
    either submits the wheels through an automated
    paint shop - or polishing line where a bright
    lacquer finish has been specified.
  • The finished wheels are then palleted and wrapped
    in polyethylene film - ready for transfer to a
    wheel/tyre assembly plant - prior to final
    shipment to the production lines of the VM
    customer

NITC
15
  • The pallet/box wrapping equipment consists of a
    motorized wrapping machine allowing pallets to
    be placed on a rotating turntable, and providing
    film wrapping through this rotation with a fixed
    unit holding the polyethylene roll.
  • The finished wheels are stored on pallets/boxes
    until shipping.  
  • COUNTER PRESSURE DIE CASTING MACHINES
  • The casting machines have evolved over 25 years
    of development and manufacturing experience of
    counter-pressure low pressure casting machines.
  • Simplicity of design, operating convenience and
    ease of maintenance are the core attributes that
    produce highest levels of egonomics and safety.
  • The above principles are well emphasised by the
    rugged vertical tie-bar construction
    incorporating an integral holding furnace.
  • The well tried and proven technical solutions
    provide stability, accuracy in guiding and
    controlling the precision of the moving parts,
    and include essential rigidity, operational
    dependability and longevity of the machines.
  • All machines are designed to withstand heavy-duty
    service in foundries operating continuous 24 hour
    cycles.

NITC
16
NITC
17
INSPECTION OF CASTINGS
  • SEVERAL METHODS
  • VISUAL
  • OPTICAL
  • - FOR SURFACE DEFECTS
  • SUBSURFACE AND INTERNAL DEFECTS THROUGH NDTs
    DTs
  • PRESSURE TIGHTNESS OF VALVES BY SEALING THE
    OPENING AND PRESSURISING WITH WATER

NITC
18
CASTING DEFECTS
  • SURFACE
  • METALLIC PROJECTION (4)
  • DEFECTIVE SURFACE (11)
  • CHANGE IN DIMENSION- WARP
  • INCOMPLETE CASTING
  • MISRUN, RUNOUT
  • CAVITY-
  • BLOWHOLES, SHRINKAGE
  • PINHOLES
  • DISCONTINUITY
  • HOT CRACK
  • COLD SHUT, COLD CRACK
  • SUBSURFACE
  • SUBSURFACE CAVITY
  • INCLUSIONS
  • DISCONTINUITY

NITC
19
NDTs
  • Methods of testing
  • Destructive-
  • Non destructive-
  • Radiagraphic
  • Ultrasonic

NITC
20
  • Non Destructive Testing
  • with Ultrasonics
  • for flaw Detection in Castings,
  • Weldments, Rails, Forged Components etc.

NITC
21
ULTRASONIC TESTING
NITC
22
Why Ultrasonics ?
  • Flaw detection in metals and nonmetals
  • Flaw measurement in very thick materials
  • Internal and surface flaws can be detected
  • Inspection costs are relatively low.
  • Rapid testing capabilities and portability.

NITC
23
Ultrasonic waves are simply vibrational waves
having a frequency higher than the hearing range
of the normal human ear, which is typically
considered to be 20,000 cycles per second (Hz).
The upper end of the range is not well defined.
Frequencies higher than 10 GHz have been
generated. However, most practical ultrasonic
flaw detection is accomplished with frequencies
from 200 kHz to 20 MHz, with 50 MHz used in
material property investigations. Ultrasonic
energy can be used in materials and structures
for flaw detection and material property
determinations.
NITC
24
  • Ultrasonic waves are mechanical waves (in
    contrast to, for example, light or x-rays, which
    are electromagnetic waves) that consist of
    oscillations or vibrations of the atomic or
    molecular particles of a substance about the
    equilibrium positions of these particles.
    Ultrasonic waves behave essentially the same as
    audible sound waves. They can propagate in an
    elastic medium, which can be solid, liquid, or
    gaseous, but not in a vacuum.

NITC
25
In solids, the particles can (a) oscillate along
the direction of sound propagation as
longitudinal waves, or (b) the oscillations can
be perpendicular to the direction of sound waves
as transverse waves.   At surfaces and
interfaces, various types of elliptical or
complex vibrations of the particles occur.
NITC
26
THEORY OF TESTING
NITC
27
MACHINE SPECIFICATIONS
  • Make
  • Weight
  • Calibration range upto 9999 mm.
  • Choice of Frequency range
  • Provision for adjusting gain.
  • Documentation possibility via printer
  • Limitation.

NITC
28
Probe
NITC
29
SCANNING TECHNIQUES
  • Pulse Echo method
  • Straight beam method
  • Angle beam method

NITC
30
PULSE ECHO METHOD
NITC
31
Inspection of
  • Gas porosity
  • Slag Entrapment
  • Cracks

NITC
32
With the exception of single gas pores all the
defects listed are usually well detectable by
ultrasonics.     Ultrasonic flaw detection has
long been the preferred method for nondestructive
testing , mainly in welding applications.   This
safe, accurate and simple technique has pushed
ultrasonics to the forefront of inspection
technology.
NITC
33
The proper scanning area for the weld First
calculate the location of the sound beam in the
test material.   Using the refracted angle, beam
index point and material thickness, the V-path
and skip distance of the sound beam is found.  
Then identify the transducer locations on the
surface of the material corresponding to the
crown, sidewall, and root of the weld.
NITC
34
NITC
35
NITC
36
Inspection of Rails
NITC
37
NITC
38
  • New trend
  • Ultrasonic Simulation - UTSIM
  • UTSIM is a user interface integrating a CAD model
    representing a part under inspection and an
    ultrasound beam model.

NITC
39
NITC
40
NITC
41
Ultrasonic sizing of small flaws with the
distance-amplitude-correction (dac) curve
NITC
42
Casting Defects
  • Metal casters try to produce perfect castings.
  • A few castings, however, are completely free of
    defects.
  • Modern foundries have sophisticated inspection
    equipment which can detect small differences in
    size and a wide variety of external and even
    internal defects. For example, slight shrinkage
    on the back of a decorative wall plaque is
    acceptable whereas similar shrinkage on a
    position cannot be tolerated.
  • No matter what the intended use, however, the
    goal of modern foundries is zero defects in all
    castings

43
  • Scrap castings cause much concern.
  • In industry, scrap results in smaller profits for
    the company and ultimately affects individual
    wages.
  • Scrap meetings are held daily. Managers of all
    the major departments attend these meetings. They
    gather castings that have been identified as
    scrap by inspector. The defect is circled with
    chalk. An effort is made to analyze the cause of
    the defect, and the manager whose department was
    responsible for it is directed to take corrective
    action to eliminate that specific defect in
    future castings.
  • There are so many variables in the production of
    a metal casting that the cause is often a
    combination of several factors rather than a
    single one.
  • All pertinent data related to the production of
    the casting (sand and core properties, pouring
    temperature) must be known in order to identify
    the defect correctly.
  • After the defect is identified attempt should be
    to eliminate the defect by taking appropriate
    corrective action.

44
CASTING DEFECTS
  • SURFACE
  • METALLIC PROJECTION
  • Swell, Crush, Mould Drop, Fillet Vein
  • DEFECTIVE SURFACE
  • Erosion Scab, Fusion, Expansion Scab, Rat tails,
    Buckle, Seams, Gas Runs, Fillet Scab, Rough
    Surface, Slag Inclusion, Elephant Skin
  • CHANGE IN DIMENSION-
  • Warped casting
  • INCOMPLETE CASTING-
  • Misrun, Run out
  • CAVITY-
  • Blow Holes, Shrinkage cavity, Pinholes
  • DISCONTINUITY-
  • Hot6 Cracking, Cold Shut, Cold Cracking
  • SUBSURFACE
  • SUBSURFACE CAVITY-
  • Blow Holes, Pin Holes, Shrinkage
  • Porosity, Internal Shrinkage, Severe
  • Roughness
  • INCLUSIONS-
  • Gas Inclusions, Slag, Blow Holes
  • DISCONTINUITY-
  • Cold Shuts

NITC
45
Repairability
46
(No Transcript)
47
  • FINS OR FLASH ON CASTINGS -AsMetallic Projections
  • Joint flash or fins. Flat projection of irregular
    thickness, often with lacy edges, perpendicular
    to one of the faces of the casting. It occurs
    along the joint or parting line of the mold, at a
    core print, or wherever two elements of the mold
    intersect.
  • Possible Causes
  • Clearance between two elements of the mold or
    between mold and core
  • Poorly fit mold joint.
  • Remedies
  • Care in pattern making, molding and core making
  • Control of their dimensions
  • Care in core setting and mold assembly
  • Sealing of joints where possible.

48
  • Flask was disturbed while investment was setting.
  • Base was removed too soon.
  • Flask was allowed to partially dry before
    dewaxing.
  • Incorrect dewaxing or a furnace malfunction.
  • Flask burned out and allowed to cool below (500oF
    (260oC) before casting reheating, flask allowed
    to cool between dewax and placement in preheated
    oven.
  • Flask was improperly handled or dropped.
  • Speed was set too high on centrifugal casting
    machine.
  • Patterns were placed on one plane. The should be
    staggered on top rack.
  • Incorrect water powder ratio was used.
  • Not enough investment was placed over the
    patterns.
  • Flask was placed too close to heat source in
    burnout oven.
  • Flasks were not held at low burnout temperature
    long enough.

49
(No Transcript)
50
DEFECTS IN CASTINGS- CAN BE ELIMINATED/MINIMISED
BY PROPER DESIGN, MOLD PREPARATION, PROPER
POURING.
NITC
51
(No Transcript)
52
DEFECTS IN CASTINGS- AS HOT TEARS - DUE TO
CONSTRAINTS IN LOCATIONS, CASTINGS CANNOT SHRINK
FREELY
NITC
53
  • Cavities
  • Blowholes, pinholes. Smooth-walled cavities,
    essentially spherical, often not contacting the
    external casting surface (blowholes). The largest
    cavities are most often isolated the smallest
    (pinholes) appear in groups of varying
    dimensions.
  • The interior walls of blowholes and pinholes can
    be shiny, more or less oxidized or, in the case
    of cast iron, can be covered with a thin layer of
    graphite. The defect can appear in all regions of
    the casting.

54
  • Possible Causes
  • Because of gas entrapped in the metal during the
    course of solidification
  • Excessive gas content in metal bath (charge
    materials, melting method, atmosphere, etc.)
    Dissolved gases are released during
    solidification.
  • In steel and cast irons formation of carbon
    monoxide by the reaction of carbon and oxygen,
    presents as a gas or in oxide form. Blowholes
    from carbon monoxide may increase in size by
    diffusion of hydrogen or, less often, nitrogen.
  • Excessive moisture in molds or cores.
  • Core binders which liberate large amounts of gas.
  • Excessive amounts of additives containing
    hydrocarbons.
  • Blacking and washes which tend to liberate too
    much gas.
  • Insufficient evacuation of air and gas from the
    mold cavity -insufficient mold and core
    permeability.
  • Entrainment of air due to turbulence in the
    runner system.

55
  • Remedies
  • Make adequate provision for evacuation of air and
    gas from the mold cavity
  • Increase permeability of mold and cores
  • Avoid improper gating systems
  • Assure adequate baking of dry sand molds
  • Control moisture levels in green sand molding
  • Reduce amounts of binders and additives used or
    change to other types -use blackings and washes,
    which provide a reducing atmosphere -keep the
    spree filled and reduce pouring height
  • Increase static pressure by enlarging runner
    height.

56
  • Discontinuities
  • Hot cracking. A crack often scarcely visible
    because the casting in general has not separated
    into fragments. The fracture surfaces may be
    discolored because of oxidation. The design of
    the casting is such that the crack would not be
    expected to result from constraints during
    cooling.
  • Possible Causes
  • Damage to the casting while hot due to rough
    handling or excessive temperature at shakeout.
  • Remedies
  • Care in shakeout and in handling the casting
    while it is still hot
  • Sufficient cooling of the casting in the mold
  • For metallic molds delay knockout, assure mold
    alignment, use ejector pins

57
  • Defective Surface
  • Flow marks. On the surfaces of otherwise sound
    castings, the defect appears as lines which trace
    the flow of the streams of liquid metal.
  • Possible Causes
  • Oxide films which lodge at the surface, partially
    marking the paths of metal flow through the mold.
  • Remedies
  • Increase mold temperature
  • Lower the pouring temperature
  • Modify gate size and location (for permanent
    molding by gravity or low pressure)
  • Tilt the mold during pouring
  • In die casting vapor blast or sand blast mold
    surfaces which are perpendicular, or nearly
    perpendicular, to the mold parting line.

58
  • Incomplete Casting
  • Poured short. The upper portion of the casting is
    missing. The edges adjacent to the missing
    section are slightly rounded, all other contours
    conform to the pattern. The spree, risers and
    lateral vents are filled only to the same height
    above the parting line, as is the casting
    (contrary to what is observed in the case of
    defect).
  • Possible Causes
  • Insufficient quantity of liquid metal in the
    ladle
  • Premature interruption of pouring due to
    workmans error.
  • Remedies
  • Have sufficient metal in the ladle to fill the
    mold
  • Check the gating system
  • Instruct pouring crew and supervise pouring
    practice.

59
  • Incorrect Dimensions or Shape
  • Distorted casting. Inadequate thickness,
    extending over large areas of the cope or drag
    surfaces at the time the mold is rammed.
  • Possible Causes
  • Rigidity of the pattern or pattern plate is not
    sufficient to withstand the ramming pressure
    applied to the sand. The result is an elastic
    deformation of the pattern and a corresponding,
    permanent deformation of the mold cavity. In
    diagnosing the condition, the compare the
    surfaces of the pattern with those of the mold
    itself.
  • Remedy
  • Assure adequate rigidity of patterns and pattern
    plates, especially when squeeze pressures are
    being increased.

60
  • Inclusions or Structural Anomalies
  • Metallic Inclusions. Metallic or intermetallic
    inclusions of various sizes which are distinctly
    different in structure and color from the base
    material, and most especially different in
    properties. These defects most often appear after
    machining.
  • Possible Causes
  • Combinations formed as intermetallics between the
    melt and metallic impurities (foreign
    impurities)
  • Charge materials or alloy additions which have
    not completely dissolved in the melt
  • Exposed core wires or rods
  • During solidification, insoluble intermetallic
    compounds form and segregate, concentrating in
    the residual liquid.
  • Remedies
  • Assure that charge materials are clean eliminate
    foreign metals
  • Use small pieces of alloying material and master
    alloys in making up the charge
  • Be sure that the bath is hot enough when making
    the additions
  • Do not make addition too near to the time of
    pouring
  • For nonferrous alloys, protect cast iron
    crucibles with a suitable wash coating

61
  • INCLUSIONS (FOREIGN PARTICLES) IN CASTINGS
  • Patterns were improperly sprued to wax base or
    tree or not filleted, causing investment to break
    at sharp corners during casting.
  • Flask was not sufficiently cured before placing
    into burnout oven.
  • Improper dewaxing cycle was used.
  • Flask was not cleaned from prior cast.
  • Loose investment in sprue hole.
  • Molten metal contains excess flux or foreign
    oxides.
  • Crucible disintegrating or poorly fluxed.
  • Improperly dried graphite crucible.
  • Investment was not mixed properly or long enough.
  • Contaminants in wax pattern.
  • Flask was not held at low burnout temperature
    long enough.
  • Flask was placed too close to heat source in
    burnout oven.

62
  • POROSITY
  • Pattern is improperly sprued.  Sprues may be too
    thin, too long or not attached in the proper
    location, causing shrinkage porosity.
  • Not enough metal reservoir to eliminate shrinkage
    porosity.
  • Metal contains gas.
  • Mold is too hot.
  • Too much moisture in the flux.
  • Too much remelt being used.  Always use at least
    50 new metal.
  • Metal is overheated.
  • Poor mold burnout.

63
  • ROUGH CASTINGS
  • A poor quality pattern
  • Flask was not sufficiently cured before placing
    into burnout oven.
  • Flask was held in steam dewax too long.
  • Metal, flask or both were too hot.
  • Patterns were improperly sprued.
  • Flask was placed too close to heat source in
    burnout oven.

64
  • BUBBLES OR NODULES ON CASTINGS
  • Vacuum pump is leaking air.
  • Vacuum pump has water in the oil.
  • Vacuum pump is low on oil.
  • Investment not mixed properly or long enough.
  • Invested flasks were not vibrated during vacuum
    cycle.
  • Vacuum extended past working time.

65
  • SPALLING (an area of the mold wall flakes into
    the mold cavity)
  • Flask was placed into a furnace at low
    temperature (below 150oC) for an extended period.
  • Flask was placed too close to the source of heat.
  • Sharp corners are struck by metal at high
    centrifugal velocities.
  • Improper burnout cycle was used.

66
  • NON-FILL OR INCOMPLETE CASTINGS
  • Metal was too cold when cast.
  • Mold was too cold when cast.
  • The burnout was not complete.
  • Pattern was improperly sprued, creating
    turbulence when casting in a centrifugal casting
    machine.
  • Centrifugal casting machine had too high
    revolution per minute.

67
  • GROWTH-LIKE ROUGH CASTING THAT RESISTS REMOVAL IN
    PICKLING SOLUTION
  • Burnout temperature too high.
  • Mold temperature was too high when casting.
  • Metal temperature was too high when casting.

68
  • SHINY CASTINGS
  • Carbon residue was left in the mold, creating a
    reducing condition on the surface.

69
AVERAGE SURFACE ROUGHNESS VALUES BY VARIOUS
PROCESSES
NITC
70
DESIGN CONSIDERATIONS
  • CAREFUL CONTROL OF LARGE NUMBER OF VARIABLES
    NEEDED-
  • CHARACTERISTICS OF METALS ALLOYS CAST
  • METHOD OF CASTING
  • MOULD AND DIE MATERIALS
  • MOULD DESIGN
  • PROCESS PARAMETERS- POURING, TEMPERATURE,
  • GATING SYSTEM
  • RATE OF COOLING Etc.Etc.

NITC
71
  • Poor casting practices, lack of control of
    process variables- DEFECTIVE CASTINGS
  • TO AVOID DEFECTS-
  • Basic economic factors relevant to casting
    operations to be studied.
  • General guidelines applied for all types of
    castings to be studied.
  • DESIGN CONSIDERATIONS

NITC
72
CORNERS, ANGLES AND SECTION THICKNESS
  • Sharp corners, angles, fillets to be avoided
  • Cause cracking and tearing during
    solidification
  • Fillet radii selection to ensure proper liquid
    metal flow- 3mm to 25 mm.
  • Too large- volume large rate of
    cooling less
  • Location with largest circle inscribed critical.
  • Cooling rate less
  • shrinkage cavities porosities
    result-
  • Called HOT SPOTS

NITC
73
  • DESIGN MODIFICATIONS TO AVOID DEFECTS-
  • AVOID SHARP CORNERS
  • MAINTAIN UNIFORM CROSS SECTIONS
  • AVOID SHRINKAGE CAVITIES
  • USE CHILLS TO INCREASE THE RATE OF COOLING
  • STAGGER INTERSECTING REGIONS FOR

  • UNIFORM CROSS SECTIONS
  • REDESIGN BY MAKING PARTING LINE STRAIGHT
  • AVOID THE USE OF CORES, IF POSSIBLE
  • MAINTAIN SECTION THICKNESS UNIFORMITY
  • BY REDESIGNING
    (in die cast products)

NITC
74
  • LARGE FLAT AREAS TO BE AVOIDED- WARPING DUE
    TO TEMPERATURE GRADIENTS
  • ALLOWANCES FOR SHRINKAGE TO BE PROVIDED
  • PARTING LINE TO BE ALONG A FLAT PLANE-
  • GOOD AT CORNERS OR EDGES OF CASTING
  • DRAFT TO BE PROVIDED
  • PERMISSIBLE TOLERANCES TO BE USED
  • MACHINING ALLOWANCES TO BE MADE
  • RESIDUAL STRESSES TO BE AVOIDED
  • ALL THESE FOR EXPENDABLE MOULD
    CASTINGS.

NITC
75
DESIGN MODIFICATIONS TO AVOID DEFECTS- AVOID
SHARP CORNERS TO REDUCE STRESS CONCENTRATIONS
NITC
76
DESIGN MODIFICATIONS TO AVOID DEFECTS- MAINTAIN
UNIFORM CROSS SECTIONS TO AVOID HOT SPOTS AND
SHRINKAGE CAVITIES
NITC
77
DESIGN MODIFICATIONS TO AVOID DEFECTS- GOOD
DESIGN PRACTICE
NITC
78
DESIGN MODIFICATIONS TO AVOID DEFECTS-
STAGGERING OF INTERSECTING REGIONS
NITC
79
DESIGN MODIFICATIONS TO AVOID DEFECTS- SECTION
THICKNESS UNIFORMITY MAINTAINED THROUGHOUT PART
NITC
80
DESIGN MODIFICATIONS TO AVOID DEFECTS
NITC
81
DESIGN MODIFICATIONS TO AVOID DEFECTS- USE OF
METAL PADDING (CHILLS) TO INCREASE RATE OF
COOLING
NITC
82
DESIGN MODIFICATIONS TO AVOID DEFECTS- MAKING
PARTING LINE STRAIGHT
NITC
83
DESIGN MODIFICATIONS TO AVOID DEFECTS-IN DESIGN
NITC
84
INSPECTION OF CASTINGS
  • SEVERAL METHODS
  • VISUAL
  • OPTICAL
  • - FOR SURFACE DEFECTS
  • SUBSURFACE AND INTERNAL DEFECTS
  • THROUGH NDTs
    DTs
  • PRESSURE TIGHTNESS OF VALVES BY SEALING THE
    OPENING AND PRESSURISING WITH WATER

85
(No Transcript)
86
(No Transcript)
87
(No Transcript)
88
EXERCISE
89
PROCESS FLOW CHART
  • RECEIPT OF ORDER
  • (REVIEW)
  • ARE THE TERMS ACCEPTED? NO COMMUNICATE-
    NEGOTIATE
  • YES
  • PREPARE WORK ORDER
  • WORK ORDER TO Q.C, INSPECTION, PLANNING, METHODS,
    PRODUCTION AND DESPATCH

90
  • PRODUCTION PLAN
  • METHOD DRAWING, QA DATA, PATTERN PLAN
  • MOULDING
  • WORK ORDER, CORE MAKING, HEAT CONFORMATION
  • MELTING AND POURING
  • FOR THESE, LAB
    TEST REPORTS
  • KNOCK OUT
  • STAGE ISPECTION- NOT OK, REJECT
  • OK, SHOT BLASTING, GAS CUTTING/ARC
    CUTTING
  • ASTM
    STANDARDS
  • HEAT TREATMENT
  • ROUGH FETTLING, FINISH FETTLING,
  • INSPECTION

91
  • NDT- CUSTOMER REPORT, NOT OK,
    WELDING RECTIFICATION
  • WELDING LOG SHEET
  • RE-INSPECTION, NOT OK-
    REJECT
  • MACHINE - IF REQUIRED
  • STRESS RELIEF
  • HYDRAULIC TESTS Etc.
  • TEST CERTIFICATE DESPATCH DOCUMENTS, PACKING,
    Etc. Etc.
About PowerShow.com