Permanent Mold Casting

Permanent mold casting is a metal casting process that shares similarities to both sand casting and die casting. As in sand casting, molten metal is poured into a mold which is clamped shut until the material cools and solidifies into the desired part shape. However, sand casting uses an expendable mold which is destroyed after each cycle. Permanent mold casting, like die casting, uses a metal mold (die) that is typically made from steel or cast iron and can be reused for several thousand cycles. Because the molten metal is poured into the die and not forcibly injected, permanent mold casting is often referred to as gravity die casting.

Permanent mold casting is typically used for high-volume production of small, simple metal parts with uniform wall thickness. Non-ferrous metals are typically used in this process, such as aluminum alloys, magnesium alloys, and copper alloys. However, irons and steels can also be cast using graphite molds. Common permanent mold parts include gears and gear housings, pipe fittings, and other automotive and aircraft components such as pistons, impellers, and wheels.

The permanent mold casting process consists of the following steps:

1. Mold preparation - First, the mold is pre-heated to around 300-500°F (150-260°C) to allow better metal flow and reduce defects. Then, a ceramic coating is applied to the mold cavity surfaces to facilitate part removal and increase the mold lifetime.
2. Mold assembly - The mold consists of at least two parts - the two mold halves and any cores used to form complex features. Such cores are typically made from iron or steel, but expendable sand cores are sometimes used. In this step, the cores are inserted and the mold halves are clamped together.
3. Pouring - The molten metal is poured at a slow rate from a ladle into the mold through a sprue at the top of the mold. The metal flows through a runner system and enters the mold cavity.
4. Cooling - The molten metal is allowed to cool and solidify in the mold.
5. Mold opening - After the metal has solidified, the two mold halves are opened and the casting is removed.
6. Trimming - During cooling, the metal in the runner system and sprue solidify attached to the casting. This excess material is now cut away.

Permanent Mold Casting

Using these basic steps, other variations on permanent mold casting have been developed to accommodate specific applications. Examples of these variations include the following:

• Slush Casting - As in permanent mold casting, the molten metal is poured into the mold and begins to solidify at the cavity surface. When the amount of solidified material is equal to the desired wall thickness, the remaining slush (material that has yet to completely solidify) is poured out of the mold. As a result, slush casting is used to produce hollow parts without the use of cores.
• Low Pressure Permanent Mold Casting - Instead of being poured, the molten metal is forced into the mold by low pressure air (< 1 bar). The application of pressure allows the mold to remain filled and reduces shrinkage during cooling. Also, finer details and thinner walls can be molded.
• Vacuum Permanent Mold Casting - Similar to low pressure casting, but vacuum pressure is used to fill the mold. As a result, finer details and thin walls can be molded and the mechanical properties of the castings are improved.

Advantages and disadvantages of shell molding casting

Shell molding casting is a main sand casting production process. The castings have good surface smoothness, less surface defects, and good dimensional accuracy. Our foundry has used this process for many years.

The followings are the advantages of shell molding castings:

1. Good surface quality

Because shell molding uses phenolic resin as the sand binder, so the smooth and hard surfaces of sand molds make the castings have good surface smoothness. The following photo could be taken as sample for the surface quality.

Moreover, this process have less sand residue during production, so could reduce some iron casting defects, such as sand inclusion, sand holes and air holes.

2. High rough casting dimensional accuracy

This molding material is a type of hard mold, so there will be less swell of sand molds, so the dimensional tolerance will be smaller. This advantage will be very useful for producing high accuracy rough castings, and reduce machining cost.

3. Thin wall thickness and complex castings

Less than 5mm wall thickness will be taken as very thin as for sand castings. Only shell molding process could produce these cast products.

In addition, hot shell and core molds are made by molding machines, so it could produce the castings with complex structures, especially complex inside structures.

4. Less manpower and molding skill requirements

Since the main works have been completed by the molding machines, so this process could be operated by women workers, and there is no special skill required. This is very different with green sand casting process.

The followings are the disadvantages of this process.

1. High production costs and casting prices

The phenolic resin sand is more expensive than green sand and furan resin sand, and it could not be recyclable. Therefore, shell molding castings will have higher prices.

2. High pattern costs

This process needs to use metal patterns (iron patterns), which will be more costly. So, it is not suitable for producing small quantity castings and small orders.

3. Size and weight limitation

The shells and cores of castings are produced by shell molding machines. These machines have dimensional limitation. So, most of shell molding castings will be less than 400mm length, and less than 20kg weight. Too long or too heavy can not be produced by this process.

Although shell and core molding process has these disadvantages, but its advantages are also very important. So, more and more iron foundries in China are using it to produce small and middle iron castings. As we know, in other countries, many metal foundries are using it to produce steel castings to replace lost wax casting process.

Shell Mold Casting

Shell mold casting is a metal casting process similar to sand casting, in that molten metal is poured into an expendable mold. However, in shell mold casting, the mold is a thin-walled shell created from applying a sand-resin mixture around a pattern. The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds. A reusable pattern allows for higher production rates, while the disposable molds enable complex geometries to be cast. Shell mold casting requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal.

Shell mold casting allows the use of both ferrous and non-ferrous metals, most commonly using cast iron, carbon steel, alloy steel, stainless steel, aluminum alloys, and copper alloys. Typical parts are small-to-medium in size and require high accuracy, such as gear housings, cylinder heads, connecting rods, and lever arms.

The shell mold casting process consists of the following steps:

1. Pattern creation - A two-piece metal pattern is created in the shape of the desired part, typically from iron or steel. Other materials are sometimes used, such as aluminum for low volume production or graphite for casting reactive materials.
2. Mold creation - First, each pattern half is heated to 175-370°C (350-700°F) and coated with a lubricant to facilitate removal. Next, the heated pattern is clamped to a dump box, which contains a mixture of sand and a resin binder. The dump box is inverted, allowing this sand-resin mixture to coat the pattern. The heated pattern partially cures the mixture, which now forms a shell around the pattern. Each pattern half and surrounding shell is cured to completion in an oven and then the shell is ejected from the pattern.
3. Mold assembly - The two shell halves are joined together and securely clamped to form the complete shell mold. If any cores are required, they are inserted prior to closing the mold. The shell mold is then placed into a flask and supported by a backing material.
4. Pouring - The mold is securely clamped together while the molten metal is poured from a ladle into the gating system and fills the mold cavity.
5. Cooling - After the mold has been filled, the molten metal is allowed to cool and solidify into the shape of the final casting.
6. Casting removal - After the molten metal has cooled, the mold can be broken and the casting removed. Trimming and cleaning processes are required to remove any excess metal from the feed system and any sand from the mold.

Shell Mold Casting

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns,Mechnical Previous Years Gate Question Papers ,Mechanical-old-question-paper,Core and Core Box,Shell Moulding

 

CORE AND CORE BOX

CORE AND CORE BOX

A core is a preformed baked sand or green sand aggregate inserted in a mold to shape

the interior part of a casting which cannot be shaped by the pattern.

A core box is a wood or metal structure, the cavity of which has the shape of the desired core which is made therein.A core box, like a pattern ismade by the pattern maker.Cores run from extremely simple to extremely complicated.

A core could be a simple round cylinder form needed to core a hole through a hub of a wheel or it could be a very complicatedcore used to core out the water coolingchannels in a cast iron engine block along with the inside of the cylinders.

Dry sand cores are for the most part made ofsharp, clay-free, dry silica sand mixed with a binder and baked until cured;the binder cements the sand together.

When the metal is poured the core holds together long enough for the metal to solidify, then the binder is finely cooked, from the heat of the casting, until its bonding power is lost or burned out.

If the core mix is correct for the job, it can be readily removed from the castings interior bysimply pouring it out as burnt core sand.

This characteristic of a core mix is called its   collapsibility.

The size and pouring temperature of acasting determines how well and how long the core will stay together.

Dry sand core with support wire.

The gases generated within the core during pouring must be vented to the outside of the mold preventing gas porosity and a defect known as a core blow.

Also, a core must have sufficient hot strength to be handled and used properly.

The hot strength refers to its strength while being heated by the casting operation.

Because of the shape and size of some coresthey must be further strengthened withrods and wires.

A long span core for a length of cast iron pipe would require rodding to prevent the core from sagging or bending upward when the mold is poured because of the liquid metal exerting a strong pressure during pouring.

 

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns,Mechnical Previous Years Gate Question Papers ,Mechanical-old-question-paper,

Mechanical Old Question papers

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-2004.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-2003.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-2002.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-2002.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-2000.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1999.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1998.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1996.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1995.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1994.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1993.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1992.pdf

http://cdn0.gateforum.com/wp-content/uploads/2013/01/ME-1991.pdf

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns,Mechnical Previous Years Gate Question Papers

Mechnical Previous Years Gate Question papers

ME-GATE-2012

ME-GATE 2013

ME-GATE-2011

ME-GATE 2010

ME-GATE 2009

ME-GATE 2008

ME-GATE 2005

ME-GATE 2006

ME-GATE 2007

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns,Mechnical Previous Years Gate Question Papers

Gate syllabus

GATE 2014 Syllabus

Aerospace Engineering (AE)

Agricultural Engineering (AG)

Architecture and Planning (AR)

Biotechnology (BT)

Civil Engineering (CE)

Chemical Engineering (CH)

Computer Science (CS)

Chemistry (CY)

Electronics and Comm Engg (EC).

Electrical Engineering (EE)

Geology and Geophysics (GG)

Instrumentation Engineering (IN)

Mathematics (MA)

Mechanical Engineering (ME)

Mining Engineering (MN)

Metallurgical Engineering (MT)

Physics (PH)

Production and Industrial Engg (PI)

Textile Engg and Fibre Science (TF)

Engineering Sciences (XE)

Life Sciences (XL)

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns

Gate mechanical syllabus 2014

Syllabus for Mechanical Engineering (ME)

ENGINEERING MATHEMATICS

Linear Algebra: Matrix algebra, Systems of linear equations, Eigen values and eigen vectors.

Calculus: Functions of single variable, Limit, continuity and differentiability, Mean value theorems, Evaluation of definite and improper integrals, Partial derivatives, Total derivative, Maxima and minima, Gradient, Divergence and Curl, Vector identities, Directional derivatives, Line, Surface and Volume integrals, Stokes, Gauss and Green’s theorems.

Differential equations: First order equations (linear and nonlinear), Higher order linear differential equations with constant coefficients, Cauchy’s and Euler’s equations, Initial and boundary value problems, Laplace transforms, Solutions of one dimensional heat and wave equations and Laplace equation.

Complex variables: Analytic functions, Cauchy’s integral theorem, Taylor and Laurent series.

Probability and Statistics: Definitions of probability and sampling theorems, Conditional probability, Mean, median, mode and standard deviation, Random variables, Poisson,Normal and Binomial distributions.

Numerical Methods: Numerical solutions of linear and non-linear algebraic equations Integration by trapezoidal and Simpson’s rule, single and multi-step methods for differential equations.

APPLIED MECHANICS AND DESIGN

Engineering Mechanics: Free body diagrams and equilibrium; trusses and frames; virtual work; kinematics and dynamics of particles and of rigid bodies in plane motion, including impulse and momentum (linear and angular) and energy formulations; impact.

Strength of Materials: Stress and strain, stress-strain relationship and elastic constants, Mohr’s circle for plane stress and plane strain, thin cylinders; shear force and bending moment diagrams; bending and shear stresses; deflection of beams; torsion of circular shafts; Euler’s theory of columns; strain energy methods; thermal stresses.

Theory of Machines: Displacement, velocity and acceleration analysis of plane mechanisms; dynamic analysis of slider-crank mechanism; gear trains; flywheels.

Vibrations: Free and forced vibration of single degree of freedom systems; effect of damping; vibration isolation; resonance, critical speeds of shafts.

Design: Design for static and dynamic loading; failure theories; fatigue strength and the S-N diagram; principles of the design of machine elements such as bolted, riveted and welded joints, shafts, spur gears, rolling and sliding contact bearings, brakes and clutches.

FLUID MECHANICS AND THERMAL SCIENCES

Fluid Mechanics: Fluid properties; fluid statics, manometry, buoyancy; control-volume analysis of mass, momentum and energy; fluid acceleration; differential equations of continuity and momentum; Bernoulli’s equation; viscous flow of incompressible fluids; boundary layer; elementary turbulent flow; flow through pipes, head losses in pipes, bends etc.

Heat-Transfer: Modes of heat transfer; one dimensional heat conduction, resistance concept, electrical analogy, unsteady heat conduction, fins; dimensionless parameters in free and forced convective heat transfer, various correlations for heat transfer in flow over flat plates and through pipes; thermal boundary layer; effect of turbulence; radiative heat transfer, black and grey surfaces, shape factors, network analysis; heat exchanger performance, LMTD and NTU methods.

Thermodynamics: Zeroth, First and Second laws of thermodynamics; thermodynamic system and processes; Carnot cycle.irreversibility and availability; behaviour of ideal and real gases, properties of pure substances, calculation of work and heat in ideal processes; analysis of thermodynamic cycles related to energy conversion.

Applications: Power Engineering: Steam Tables, Rankine, Brayton cycles with regeneration and reheat. I.C. Engines: air-standard Otto, Diesel cycles. Refrigeration and air-conditioning: Vapour refrigeration cycle, heat pumps, gas refrigeration, Reverse Brayton cycle; moist air: psychrometric chart, basic psychrometric processes. Turbomachinery:Pelton-wheel, Francis and Kaplan turbines — impulse and reaction principles, velocity diagrams.

MANUFACTURING AND INDUSTRIAL ENGINEERING

Engineering Materials: Structure and properties of engineering materials, heat treatment, stress-strain diagrams for engineering materials.

Metal Casting: Design of patterns, moulds and cores; solidification and cooling; riser and gating design, design considerations.

Forming: Plastic deformation and yield criteria; fundamentals of hot and cold working processes; load estimation for bulk (forging, rolling, extrusion, drawing) and sheet (shearing, deep drawing, bending) metal forming processes; principles of powder metallurgy.

Joining: Physics of welding, brazing and soldering; adhesive bonding; design considerations in welding.

Machining and Machine Tool Operations: Mechanics of machining, single and multi-point cutting tools, tool geometry and materials, tool life and wear; economics of machining; principles of non-traditional machining processes; principles of work holding, principles of design of jigs and fixtures

Metrology and Inspection: Limits, fits and tolerances; linear and angular measurements; comparators; gauge design; interferometry; form and finish measurement; alignment and testing methods; tolerance analysis in manufacturing and assembly.

Computer Integrated Manufacturing: Basic concepts of CAD/CAM and their integration tools.

Production Planning and Control: Forecasting models, aggregate production planning, scheduling, materials requirement planning.

Inventory Control: Deterministic and probabilistic models; safety stock inventory control systems.

Operations Research: Linear programming, simplex and duplex method, transportation, assignment, network flow models, simple queuing models, PERT and CPM.

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns

PSUs Job List Through GATE 2014

PSUs Job List Through GATE 2014

All PSU's  like NTPC, NHPC, HPCL, BHEL, Power Grid etc. recruiting through GATE 2013 are mentioned below. All those candidates who are looking for PSU recruitment through GATE 2014, they are at the right place. The full details about PSU recruitment have been provided here. 

NTPC Recruitment – National Thermal Power Corporation (NICL) Executive Trainee recruitment through GATE 2014.

NHPC Recruitment – National Hydroelectric Power Corporation (NHPC) Trainee Engineer recruitment through GATE 2014

BPCL Recruitment – Bharat Petroleum Corporation Limited (BPCL) Management Trainee Recruitment through GATE 2014.

HPCL Recruitment – Hindustan Petroleum Corporation Limited (HPCL) Graduate Engineers recruitment through GATE 2014.

PGCIL Recruitment – Power Grid, the central transmission utility (PGCIL) Executive Trainee (Electrical) recruitment through GATE 2014.

BEL Recruitment – Bharat Electronics Limited (BEL) Probationary Engineer recruitment through GATE 2014.

GAIL Recruitment – Gas Authority of India Limited (GAIL) Executive Trainee recruitment through GATE 2014.

MECL Recruitment – Mineral Exploration Corporation Limited (MECL) Trainees/Officer Trainees  recruitment through GATE 2014.

IOCL Recruitment – Indian Oil Corporation Limited (IOCL) Officers/ Graduate Apprentice Engineers (GAEs) recruitment through GATE 2014.

HECL Recruitment – Heavy Engineering Corporation Ltd (HECL) Executive Trainee recruitment through GATE 2014.

DDA Recruitment – Delhi Development Authority (DDA) Assistant Executive Engineer recruitment through GATE 2014.

CONCOR Recruitment – Container Corporation of India Ltd. (CONCOR) Management Trainee recruitment through GATE 2014.

MECON Recruitment – Metallurgical & Engineering Consultants (MECON) Management Trainee recruitment (Technical) through GATE 2014.

NALCO Recruitment – National Aluminium CompanyLimited (NALCO) Graduate Engineer recruitment through GATE 2014.

MDL Recruitment – Mazagon Dock Limited (MDL) Executive Trainee recruitment through GATE 2014.

NFL Recruitment - National Fertilizers Limited (NFL) Management Trainee recruitment through GATE 2014.  

Other Topics

IC engine, Air Standard Cycles, Method of Ignition, Gear Types, External Gear Pump, mechanical Engineering, Gears, spur gears,Helical gears,herringbone gear,Worm gears,English books,Photoshop tutorials,Physics files,Thamizh,Manufacturing,Gears pdf,Computer science,Harry potter,Best 100 english books,Rack and pinion,Face Gears,Involute Splines,Straight sided Spline, Bush Roller Chains,IC engine,Metal Casting,Metal Casting Terms,Categories of metal casting processes,Sand casting,SAND Casting Quiz,Casting patterns quiz,Sand Casting Process,Patterns