Posted tagged ‘Surface’

MATERIAL HANDLING

August 23, 2011

Bases on Design features and operational characteristics, material handling equipment may be broadly classified as:

01-classification of material handling equipment

Hoisting Equipment’s:

01-hoisting equipments-Pillar-Type-Jib-Crane-cantilever crane

It constitute a group of equipment which are employed mainly for lifting or lowering of unit load or piece goods in batches. This group of equipment’s can be further sub classified into:

1. Pure Hoisting Machineries

    • Jack
    • Winches
    • Hand Hoists
    • Pulley Blocks

2. Cranes

    • EOT Crane
    • Jib Crane
    • Cantilever Crane

3. Elevators

    • Lift
    • Bucket Elevators

Conveying Equipment’s:

01-automatic conveyor system-material handling system-material handling equipments

It comprises of a number of equipment which are employed for handling principally bulk load (occasionally piece goods or unit load may also be handled) in continuous flow. Such machines do not have separate lifting or lowering gear. This group of equipment also can have further sub classifications as:

1. Belt Conveyor

2. Hydraulic Conveyor

3. Pneumatic Conveyor

4. Apron Conveyor

5. Screw Conveyor

6. Flight Conveyor

Surface/ Overhead Equipment’s:

01-Toyota_Forklift-surface equipment-handling unit load-bulk load

These are the group of equipment’s which are employed for handling unit load or bulk load in batches on a horizontal surface. This group of equipment may be further sub classified into:

1. Truck and Lorries

2. Railway Cars and Wagons

3. Fork Lifts

4. Overhead mono-rail / Equipment

5. Scrapers and Skidders

Types of Material Handling Equipment Loads:

It usually classified into:

1. Unit Load

2. Bulk Load

Unit Load:

Unit loads are those which are counted by numbers or units. A component of a machine, a complete machine, a structural element, a beam, a girder, building block are some examples of unit load.

01-hoisting machineries-niko_jib_crane_floor_mounted-cantilever cranes


Sometimes certain quantities of free flowing materials can be placed in a container and can be handled as unit load. Hoisting equipment are primarily used for handling unit load. Unit loads are usually specified by it’s weight.

Bulk Load:

When the load is in the form of particles or lumps of homogeneous materials or powder like materials, which can not be counted by numbers, it is called as “Bulk load”.

01-bulk load material handling equipment's-railway cars-railway wagons

Examples are:


Sand, Cement, Coal, Mineral, Stone, Clay etc.,

A bulk material may be classified by it’s:

1. Bulk Density

2. Lump-Size

3. Flowability

4. Abrasiveness

5. Miscellaneous Characteristics

FAILURE ANALYSIS

August 23, 2011

01-tank-failure-failure analysis-visual examination-scanning electron microscopy-metallography-materials technology


• Why ?

As the standards of our industry rise due to increasing globalization and competition, there is an ever growing need for consistency and reliability. Breakdown of any unit, system or equipment is an avoidable and costly occurrence and must be prevented or minimized. Analysis of such failures becomes a resourceful and affordable tool in addressing such unwanted occurrences.

To establish whether the cause of component failure lay on:

a) Service conditions
b) Design considerations
c) Material and its specification
d) Improper processing and assembly procedures or
e)  Combinations of these.

01-RootCause-root cause analysis cycle-problem solving steps-avoidance of recurring problems

Only the real “Root cause” can ensure the effectiveness of corrective and preventive actions and avoid recurrence of failure.

01-CauseEffect-analysis-bottom up predictive-ishikawa - fishbone diagram-prediction analysis

• Stages Of Failure Analysis

1. Understanding and assimilation of background data and selection of samples.
2. Examination and documentation of the failed part by the following

1. Visual examination of parts, location (if necessary) and relevant photographs as well.

01-visual examination-metallographic examination-appearance of the parts-calibrated metallurgical microscope equipment-image analysis-microstructure

2.  Non destructive testing by means of Radiography, Dye      penetrant, Magnetic particle testing etc.

01-NDT-non destructive testing-cold process-radiography-die penetrant techniques-magnetic particle testing
3. Mechanical Testing for various physical properties.

3. Vital specimens are selected, classified, and subjected to:

  1. Macroscopic examination and analysis. This involves examining the fracture surfaces, secondary cracks, deposits and other such elements
  2. Microscopic examination and analysis of fracture surface (by Scanning Electron Microscopy, if required).

01-scanning-electron-microscopy-vital specimens-fracture surfaces-secondary cracks-microscopic examination

4. Chemical analysis of material for conformation to specifications.

5. Chemical analysis of corrosion products, deposits, contaminants etc.

01-corrodedmetal-corrosion in metals-material technology-material science and metallurgy-iron oxidization-low affinity with oxigen-electrochemical corrosion-oxidation

6. The actual state of the failed part and the failure mode are established.

7.  Fracture mechanics study if found necessary.

01-connection_failure_analysis-comprehensive failure analysis-analysis and testing-investigation of failure-design life check-failure mechanisms-identification of causes of failure
8. A simulation of the identical working environment to determine if any external      factors have contributed to the failure

9. Conclusions are determined after compiling all evidences and analysis and       then the report is generated.
10. Follow-up recommendations are also provided.

INFRARED CURVING

August 23, 2011

01-infrared curing process-infrared spectrum wave-conduction, convection, radiation

The coatings and paint industries strive to provide high technology coatings while reducing volatile organic compounds and energy consumption to produce a finished coating. Conventionally Convection ovens are used to cure the coatings. But this process which uses electric heaters is not an optimal process and is associated with various disadvantages.

01-coating surface absorption-infrared energy -infrared curing

Improved technologies are available today, which can either replace or improve the convection curing process. Infrared Curing is such a technology which uses Infrared rays emitted by an Infrared emitter to provide the required cure. Infrared curing applies light energy to the part surface by direct transmission from an emitter. Some of the energy emitted will be reflected off the surface, some is absorbed into the polymer and some is transmitted into the substrate.

01-reduced cycle times on final cure-eliminating manual rack up time

This direct transfer of energy creates an immediate reaction in the polymer and cross linking begins quickly once the surface is exposed to the emitter. Infrared emitters are often custom manufactured to suit the production demand. The various aspects of Infrared curing and convection curing and the possibility of combining these two technologies into a singe system will be discussed in this seminar.

01-infrared wave-infrared heating-infrared emitter-infrared curing

How it Works

Infrared heating is a direct form of heating. The source of the heat (the infrared emitter or lamp) radiates: energy that is absorbed by the product directly from the emitter. That is, the heat energy is not transferred through an intermediate medium. This is one reason for  the  inherent high-energy efficiency of infrared systems. For  example, hot air heating  first needs to heat air; the air then heats the product by convection.

01-infrared emitter-infrared curing systems

Infrared  energy is directed  to  the  product. When  the  product absorbs this energy, it is then converted into heat. Infrared energy is dispersed from the source in much the same  way as visible light. Exposed product surfaces easily absorb  the  infrared  energy and  become  heated. Therefore, heating effectiveness is related to line-of-sight between the source and the product. Depending on the coating and/or product substrate material, this heat is further thermally conducted.


01-table-characteristics of commercially used infrared heat sources

The ability of the product to absorb energy is also known as its “emissivity”. A theoretical body that absorbs all energy is termed a “black body”. A black body has an emissivity of 1. A highly reflective body would have a low emissivity value, approaching 0. (Reflectivity is the inverse of emissivity).

The potential of a product to become heated with infrared is related to the following:
• Watt density (total output power) of the source
• Wavelength (temperature) of the source
• Distance from the source to the product
• Reflective characteristics of the oven cavity
• Air movement and temperature in the oven
• Time product is exposed to the source
• Ratio of exposed surface area to the mass of the product
• Specific heat of the product
• Emissivity of the product
• Thermal conductivity of the product

CURING

Curing is a process of baking surface coatings so as to dry them up quickly. Curing is a broad term which means all the techniques employed for the finishing operations incurred during part production. Curing essentially involves either the melting of the coating or evaporation of volatile fluids present in the coating by the application of heat energy.

Curing is given to a wide range of materials both organic and inorganic. Usually curing is given to materials like ,

” Paints
” Enamel
” Liquor
” Powder coatings
” Varnishes
” Epoxy coatings
” Acrylic coatings
” Primers Etc.

Curing is also given to Rubber and Latex .The principle used for curing can also be used for drying rice and grains.

01-infrared technology-infrared-convection systems-tunnel system

CONVECTION CURING

Convection ovens are usually used for curing purposes. Traditional convection ovens use heated forced air to provide the necessary cure. Convection ovens consist of a chamber lined on the inside with Electric heaters. The shape of the chamber will be in accordance to the shape or geometry of the part being cured. A series of blowers circulate the heated air around providing the required cure. This process depends on convection to transfer heat from hot air to body surface and conduction to transfer heat to the interior of the surface. The air being delivered is held at temperature using closed-loop control, which provides predictable, repeatable results. Typically a temperature of around 250-500 degree Fahrenheit is required for paint or powder. Though convection ovens are widely used today they have certain disadvantages, which chokes the overall productivity of a company
Disadvantages of convection ovens :

” Fairly long heating times:-

Convection is a slow process. It takes a considerable amount of time for the heaters to heat up and raise the temperature of air to the required level. This causes a lag in the process and hence the curing time increases. Longer curing time spells reduced assembly line movement. This in turn reduces productivity.

” High energy consumption:-

A convection column dryer uses around 2000 BTU(British Thermal Unit) of energy to remove 1 pound of moisture. They use around 7.7 KW of electrical energy to dry a ton of rice. These are significantly larger figures for any company trying to bring energy consumption under control. The additional use of blowers and compressors further increases energy consumption.

” Large floor area required:-

Convection ovens are bulky in nature. Due to the presence of compressors and blowers, additional space is needed, which in turn increases the floor area requirement.

” Air circulation is required:-

Convection heating requires a medium for transmission of heat. Hence blowers are employed for good circulation of heated air. This increases the overall cost of the equipment.

CRYSTAL SYSTEM

August 23, 2011

Crystalline Materials:

  • A crystalline material is one in which the atoms are situated in a repeating (or) periodic array over large atomic distances.

01-space-lattice-unit-cell-represenatation

 

 

Non Crystalline Materials:

  • Materials that do not crystallize are called non-crystalline (or) Amorphous materials

 

Space Lattice:

  • Lattice is the regular geometrical arrangement of points in crystal space.

01-lattice-crystal structure

 

  • The atoms arrange themselves in distinct pattern in space is called a Space Lattice.
  • Atoms in crystalline materials are arranged in a regular 3 – Dimensional repeating pattern known as Lattice Structure.
  • They are divided by network of lines in to equal volumes, the points of intersection are known as Lattice Points.

 

Unit Cell:

01-unit cell

  • It is the smallest portion of the lattice which repeated in all directions.
  • 3D visualization of 14 Space Lattices are known as Bravai’s Space Lattice.
  • If a unit cell contains lattice points only at it’s corners, then it is called Primitive Unit Cell (or) Simple Unit Cell.
  • Three edge length x,y, & z and three interaxial angles α, β, & γ are termed as Lattice Parameters.

 

Crystal System:

  • It is a scheme by which crystal structures are classified according to unit cell geometry.

 

Types of Crystal Systems:

    • Cubic
    • Tetragonal
    • Hexagonal
    • Orthorhombic
    • Rhombohedral
    • Monoclinic
    • Triclinic

 

Crystal Systems

image


Simple Crystal Structure:

Body Centered Cubic Structure (BCC)

  • Unit cell contains 2 atoms
  • Lattice Constant a= 4r / √3, where r is atomic radius
  • Atomic packing factor APF = 0.68
  • Metals are Vanadium, Molybdenum, Titanium, Tungsten

0I-bcc-structure-body center cubic02-bcc-structure-body center cubic

03-bcc-structure-body center cubic

 

Face Centered Cubic (FCC)

  • Unit cell contains 4 atoms
  • Lattice Constant a= 4r / √2, where r is atomic radius
  • Atomic packing factor APF = 0.72
  • FCC structures can be plastic deformed at severe rates
  • Metals are Copper, Aluminum, Phosphorous, Nickel, Cobalt etc

02-fcc-structure-face center cubic-unit cell

0I-fcc-structure-face center cubic-unit cellHexagonal Closed Packed Structure (HCP)

  • Unit cell contains 3 atoms
  • Axial ratio c/a, where ‘c’ is Distance between base planes, ‘a’ is Width of Hexagon
  • Axial Ratio varies from 1.58 for Beryllium to 1.88 for Cadmium (Therefore  a=2.9787, c=5.617)
  • Atomic packing factor APF = 0.74
  • Metals are Zinc, Cadmium, Beryllium, Magnesium etc

0I-hcp-structure-Hexagonal close packed-unit cell

0I-hcp-structure-hexagonal close packed

0I-hcp ball-structure-Hexagonal close packed-unit cell

 

 

Crystallographic Planes and Directions

The Layers of atoms in the planes along which atoms are arranged is known as “Atomic” (or) “Crystallographic planes”.

Miller Indices:

Miller Indices is a system of notation that denotes the orientation of the faces of a crystal and the planes and directions of atoms within that crystal.

Miller Indices for Planes:

1. The (110) surface

02-miller indices-crystalographic planes

 

Intercepts :   a , a , ∞

Fractional intercepts :   1 , 1 , ∞

Miller Indices :   (110)

 

2. The (111) surface

03-miller indices-crystalographic planes

 

Intercepts :   a , a , a

Fractional intercepts :   1 , 1 , 1

Miller Indices :   (111)

The (100), (110) and (111) surfaces considered above are the so-called low index surfaces of a cubic crystal system.

 

3. The (210) surface

04-miller indices-crystalographic planes

 

Intercepts :   ½ a , a , ∞

Fractional intercepts :   ½ , 1 , ∞

Miller Indices :   (210)

CASTING

August 23, 2011

Methods are:

    1. Pressing
    2. Centrifugal Casting
    3. Slip Casting
    4. Extruding
    5. Gravity Casting
    6. Rolling
    7. Iso-static Moulding
    8. Explosive Compacting
    9. Fibre Metal processes

Pressing:

The function principles of the mechanic press machines differ in how to ensure the upper punch main movement by cams, spindles and friction drives, eccentric, knuckle-joints or by the round table principle, independent if the die or lower punch movement is realized by cams  or eccentric systems or other mechanically or hydraulically combined systems. The executions of auxiliary movements are also not decisive for a term-classification. These auxiliary movements can also base on pneumatic and hydraulic principles. In comparison to hydraulic press machines the maximum compaction forces of mechanical powder presses are limited and are placed in the range </= 5000 kN. For the requirements of wet and dry pressing techniques in the field of Technical Ceramics cams, eccentric, knuckle joint as well as round table presses have proved and tested, whereas cam presses especially used for wet-press-techniques of pourable materials. The range of compaction force of mechanical presses for products of the Technical Ceramics is < 2500 kN, what is caused from the less density of the ceramic materials. Normally the upper punch, lower punch and die systems of mechanical presses don’t work on base of multi subdivided punches.

01-powder pressing-metallurgy

Centrifugal Casting:

It employed for compacting heavy metal powders such as Tungsten Carbide. The powder is twirled in a mould and packed uniformly with pressures up to 3 MPa. The uniform density is obtained as a result of centrifugal force, acting on each particle of powder.

06-centrifugal-casting-process

05-centrifugal-casting-mold-metal-parts

Slip Casting:


Green compact of metal powder may be obtained by slip casting. The slurry, consisting of metal powder is poured in to porous mould. the free liquid in a slurry is absorbed by the mould tearing the solid layer of material on the surface of mould. The mould may be vibrated to increase the density of component. The Components are dried and sintered to provide sufficient strength.

07-slip casting-process-powder metallurgy

Extruding:

It employed to produce the components with high density and excellent mechanical properties.

Both hot and cold extrusion processes are used for compacting special materials. In cold extrusion the powder is mixed with binder and the mixture is often compressed into billet before being extruded. The binder must be removed before or during sintering. In hot extrusion the powder is compacted in to billet and is then heated to extruding temperature in non oxidizing atmosphere.

04-extrusion-direct-indirect-rod-pipe-process

Gravity Casting:

It used for making sheets having controlled porosity, the powder is poured on a ceramic tray to form a uniform layer and then sintered up to 48 hrs in Ammonia Gas at high temperature. The sheets are then rolled to desired thickness and to obtain a better surface finish. Porous sheets of stainless steel, made by this process are used for filters.

09-gravity-casting-metal-mould

10-indirect-gravity-casting-metal-mould

Rolling:

It employed for making continuous strips and rods having controlled porosity with uniform mechanical properties. In this method the metal powder is feed in to two rolls, which compress and interlock the powder particles to form a sheet of sufficient strength. It is then sintered, re-rolled and heat treated if necessary. Metal powders which can be compacted in to strips include Copper, Brass, Bronze, Nickel, Monel and Stainless Steel.

08-cold-rolling-process-plate-sheet-foil

Iso Static Moulding:

It used to obtain the products having uniform density and uniform strength in all directions. metal powder is placed in elastic mould (Deformable Mould) which is subjected to Gas pressure (65 to 650 MPa). After pressing the compact is removed.

02-cold-iso-static-pressing-compacting

Explosive Compacting:

It employed for pressing hard particles. The metal powder are placed in water proof bags which are immersed in water. It contained in a cylinder having wall thickness. Due to sudden deformation of change at the end of cylinder the pressure in the cylinder increases. The pressure used to press the metal powders to form green compact.

11-explosive-moulding-compacting

Fibre Metal Processes:

In this process, the metal fibers (Fine wires of Convenient length) are mixed with a liquid slurry and poured over a porous bottom. The liquid is drawed off leaving the green mat of fibre. The mat in which the fibers are randomly distributed is pressed and sintered. The products are mainly used for Filters, Battery Plates and Damping’s.

 12-fibre-metal-processes

BLOW MOULDING PROCESS

August 23, 2011

Today, when walking in your supermarket, it is increasingly difficult to find items packed in glass and jars.  Packaging for soft drinks, healthcare and beauty products, household chemicals and medicines, among other products, have switched from glass or metal to plastics.  Today the Blow Molding industry has expanded from simple plastic containers to plastic drums, gas tanks, automobile parts and toys in all shapes and sizes.

01-blow-molding-extrusion blow molding-injection blow molding-parison extrusion


Blow Molding (BM) process makes it possible to manufacture molded products economically, in unlimited quantities, with virtually no finishing required.  The basic process of blow molding involves a softened thermoplastic hollow form which is inflated against the cooled surface of a closed mold.  The expanded plastic form solidifies  into a hollow product.

Blow molded components are now seen all over the markets and industries for traditional materials, particularly in liquid packaging applications.  The last few decades saw the introduction of  Poly Ethylene (PE) squeeze bottles for washing liquids, Poly Vinyl Chloride (PVC) for cooking oil and fruits squash bottles, and Poly Ethylene Terephthalate (PET) for carbonated beverage bottles.  Nowadays, it is also used for the production of toys, automobile parts, accessories and many engineering components.

There are basically four types of blow moulding used in the production of plastic bottles, jugs and jars. These four types are:

  1. Extrusion blow molding,
  2. Injection blow molding,
  3. Stretch blow molding and
  4. Reheat and blow molding.

Extrusion blow molding is perhaps the simplest type of blow molding, whereby a hot tube of plastic material is dropped from an extruder and captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the walls of the mold the material “freezes” and the container now maintains its rigid shape. There are various types of shuttle, reciprocating and wheel style machines for the production of extrusion blown bottles. Shuttle or reciprocating type machines can be used for small, medium and high volume production with wheel machines being the most efficient for huge volume production of certain resins.


01-petblow-plastic products manufacturing-PET Preform-PET bottles-stretch blow molding

A typical apparatus consists of following major components i.e. blow pin, plunger, accumulator and lastly a mold.

Actually the process utilizes air pressure to inflate softened thermoplastic tube which is sealed at one end (also called as parision). This parision is constantly inflated and extruded. Then later on it is cut according to required dimensions. The temperature in Accumulator is maintained around 400 degree Celsius or so.

Stretch_blow_mold-dies-PET Pre form mold-household appliance mold

The mold consists of two split parts which have a semi-circular cross-section. Usually the air pressure which is applied in low pressure molding is about 50 to 250 psi. Various forms of blow molding used in industry today on a wide scale are Injection Blow Molding.

Injection Blow Molding though not used in industry, has very limited and specific applications like making small medicine plastic bottles etc. Extrusion blow molding is the simplest form of blow molding. A tube of plastic material which is generally maintained hot, is dropped from an extruder only to be captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container and the tube is inflated just like a balloon. When the hot plastic material is blown up and touches the walls of the mold the material is cooled and the container now maintains a solid, rigid shape.

Now Stretch blow molding, this process requires the raw material to be formed in a pre-form using injection molding and later on stretch blow molding process can be applied.

The product range varies from various cylindrical components like bottles, cans, floats heater ducts in automobile parts and various small pipe fittings and hollow cylindrical parts can be produced in mass production.

The advantages are many like the tooling costs are very less as compared to injection molding, the part performance is excellent under pressure. Then the products have excellent environmental stress crack resistance. The products also perform excellently in high speed impact strength than even the metal components the process can be automated and used in mass production.

The disadvantages mainly raise environmental concerns. It depends on petroleum industry as any plastic industry depends. Also the cylindrical shapes are delicate so if the dimensions are not accurate then they result in scrap.

QTC

August 23, 2011

01-3D tablet-touch screen-force sensitive touch screen-quantum tunnelling composite

QTC is a composite made from micron-sized metallic filler particles (Silicone Rubber) mixed into an elastomeric matrix. Quantum tunnelling composite is a flexible polymer that exhibits extraordinary electrical properties. In its normal state it is a perfect insulator, but when compressed it becomes a more or less perfect conductor and able to pass very high currents.

01-QTC-Graph-resistance vs force - quantum tunnelling composite

History:

First produced in 1996, QTC is a composite material made from conductive filler particles combined with an elastomeric binder, typically silicone rubber. The unique method of combining these raw materials results in a composite which exhibits significantly different electrical properties when compared with any other electrically conductive material.

01-QTC pills-variable resistor-applications of QTC using pills-touch switches

Types of QTC:

1. Elastomeric (Material: Silicone Rubber) (The particle move close together)

2. Ink / Coating Solvent or Aqueous Polymer

3. Granular Sensors

Working of Quantum tunnelling composite:

01-quantum tunnelling composite-QTC-smart flexible polymer-silicone rubber-pressure switching-sensing-metal like conductor-variable inductance principle-QTC working-QTC operation

QTC usually comes in the form of pills or sheet. QTC pills are just tiny little pieces of the material. The sheets are composed of one layer of QTC, one layer of a conductive material, and a third layer of a plastic insulator. While QTC sheets switch quickly between high and low resistances, QTC pills are pressure sensitive variable resistors.

Application:

01-QTC touch Screen-pills-force or pressure sensors-quantum tunneling composite screen-pressure sensitive variable resistors

– Touch switches (sheet)
– Force/pressure sensors (pills)
– Motor speed control using force (pills)

Benefits:

  • QTC is a pressure/force sensing material. It can be easily integrated into existing products to enable force sensing opportunities and solutions.
  • Product surfaces can be incorporated, coated or impregnated with QTC to impart the properties of force sensing into or onto the host surface.
  • QTC material can be formed or moulded into virtually any size, thickness or shape, permitting redesign of product interfaces and providing improved ergonomics, aesthetics and user comfort.
  • QTC is an enabling technology which is simple and reliable to use.
  • QTC material is durable – it has no moving parts to wear out.
  • QTC material is mechanically strong.
  • QTC material can be made to withstand extreme temperatures limits.
  • QTC material is versatile, both electrically and physically e.g. Its range and sensitivity can be altered. QTC material is also intrinsically safe – the material is a contactless switch, ideal for sparkless operation.
  • QTC material can be directly interfaced to standard electronic and electrical devices.
  • QTC material and/or technology can be customized for customer requirements, applications and products.