What Is Foundry In Casting, Manufacturing And In Mechanical Engineering?
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| Foundry In Casting |
Foundry Introduction
A foundry can be defined as a factory which is involved in founding or manufacturing the casting process and providing related casting services.
85% of manufacturing produced today is produced from foundry facilities all around the world. China, India, Russia, Japan, Brazil, Korea and the United States of America are some of the largest producers of casting components.
The casting market is a 250 billion dollar market and has seen substantial growth over the years due to the high demand for manufacturing casting components in the automobile industry, aerospace industry, space industry, household appliances industry, marine industry and machine manufacturing industry.
The foundry is a facility where all the components are manufactured from raw metal ingots to highly finished products using production steps such as melting ingots, pattern making, mould making, pouring molten metal into various types of mould, fettling, cleaning of solidified casting and performing secondary manufacturing operations such as coating and surface finishing, packing and dispatching are done under the same roof.
The foundry consists of various production departments, production units, equipment and machines with the sole objective of producing excellent sound-quality casting. Each of these is discussed below in detail.
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Metal Foundry Factory Process
What is the foundry process in casting?
The foundry process in casting is a process of producing casting by melting the ingot in a furnace to pour it into a mould cavity (depending upon the type of casting process) to produce high-quality casting.
I have explained the step-by-step foundry process in casting below:
Casting Design Department
The design department takes input from the sales department to draw casting designs according to customers.
Initial designs about moulds and cores, casting simulation, thermal shock analysis, calibration, calculation of inflow of metal, pressure, mechanical stress and thermal analysis, defects.
After the design department finishes the work, the design is given to the production/manufacturing department for selection of the type of casting machines, metals, mould material and calculation of production time to further allow the manufacturing department to carry forward the production operations mentioned below.
Pattern-Making Unit In Foundry
There are many types of patterns used as a tool for making cavities in the sand, sand-resin, ceramic and plaster for the casting process.
Patterns are colour-coded in the foundry to be identified by the pattern maker and during the moulding process.
This unit consists of making patterns and prototypes for sand casting, shell casting and investment casting using various pattern-making materials such as wax, plastic, wood, rubber and foam material.
I have explained the entire step-by-step process of making patterns in the foundry, foundry engineers can read the process and steps in detail.
Patterns are manufactured using injection moulding machines, metal lathe machines, carpentry lathe machines, milling machines and welding machines.
Rapid prototyping, 3D- printing, selective laser melting, stereolithography, fused filament fabrication, powder bed print, additive manufacturing, NC and CNC machining.
Proper pattern material is selected based on pattern material properties and factors for selecting pattern material considerations and properties of pattern material. Required pattern allowance is given to the pattern to compensate for changes in dimensions during the solidification of liquid metal and during the pattern withdrawal step.
Mould And Core Making Department
The objective of making a mould is to give a desired space for molten metal to solidify in the mould cavity to form a final casting keeping in mind surface finish, tolerance and dimensional accuracy of the final casting.
Moulds used in the casting process are produced in the foundry and are of the following types:
- Sand Mould
- Die Mould
- Sand-Resin Mould
- Ceramic Mould
- Sand mould (green, dry, skin-dry) is used in the sand casting process.
- Die metal mould is used in the die casting process, slush casting process, permanent mould casting process, centrifugal casting process, squeeze casting process and continuous casting process.
- Sand-resin moulds are produced for the shell-casting process.
- Ceramic moulds are manufactured for producing moulds in the investment casting process.
Gating elements are carved in all the mould (eg sand mould, die mould etc) which includes a pouring basin, sprue, runner, gates and riser for proper flow of molten metal considering shrinkage distortion and proper solidification of molten metal in casting.
Various manual tools are used in the sand casting process to produce sand moulds.
The mould and core-making process consists of making a mould using different materials such as sand, ceramic, resin, metal and plaster for different casting processes such as sand moulding, die casting, investment casting, continuous casting, shell casting, centrifugal casting, permanent moulding and investment casting process.
In sand casting, there are options to make sand mould based on customers' requirements, there are green sand mould, dry sand mould and skin-dried sand mould considering the size, shape, surface finish, tooling and foundry capacity.
In the centrifugal casting and slush casting process, castings are manufactured without the use of a core. This process can also be called the coreless casting process.
Cores making is the process of making cores using sand, metal, fine resin sand and foam. Mould clamps are also used to clamp the split mould sections such as cope and drag together in case of sand and permanent mould manually to form a single casting mould.
These cores are made in the core box in the case of fully solid sand cores and resin shell sand cores. Disposal foam cores and 3D-printed foam are also high in demand considering their capacity to produce complex shapes.
Depending upon the type of applications, surface finish and customers' requirements moulds are manufactured in foundry.
Ingot Melting Unit
This unit consists of furnaces used to melt pure, ferrous, non-ferrous and alloy metals. This process is also called charging which consists of heating metals above their melting point. The metal is carried to moulds using the ladle.
Types of furnaces used in this process are electric arc furnaces, cupula, oil-fired furnaces and coal furnaces.
In the case of a hot chamber die casting melting metal and casting operation happens at the same casting station.
Degassing Process
Producing defect-free porosity and inclusions-free casting reduces rejection from the customer's side and also improves the profit of the foundry.
To produce the defect-free low porosity gas defect casting degassing becomes an important step as this process removes the unwanted gases from the molten metal.
This process is done after the ingot has been melted in the furnace and before pouring molten metal into the mould cavity.
A metal degassing unit (MDU) machine is used to inject argon into molten metal using a ceramic rotor which rotates in the molten metal continuously.
This argon combines with the hydrogen gas in the metal and releases it into the atmosphere directly.
Degassing plays an important role in the casting process to manufacture sound casting. This step reduces the porosity and gas defects in the final casting increasing the strength and quality of casting.
In addition to the regular degassing process, this process can be done in a vacuum chamber promoting a cleaner environment for the process.
The advantage of this process is that flux can be added during the degassing process, this is done to reduce oxides and impurities for the non-ferrous castings, steel, copper, brass and aluminium.
Inclusion Process
Ingots used in the casting process of required metal do not have all the important mechanical properties due to improper grain structure to produce solid sound in the final casting.
Commonly used inclusions that are added to the molten metal are ferroalloy inclusions such as ferrosilicon, lanthanum, cerium, ferromanganese and calcium-based inclusions to reduce the chilling effect during the casting process.
Inclusions change the metallurgical and chemical properties of the molten metal improving the mechanical properties of the final casting.
This method is more prominent for producing ductile iron casting as it has less graphite in it. Iron formed after the inclusion is a strong spheroidal graphite structure.
To solve this casting process silicon alloys are mixed into the molten metal to improve its graphite distribution and improve the mechanical properties of the casting.
This process is done by mixing silicon alloys in the ladle, or in mould directly or through automatically in the stream during the casting process through feeders.
Mould Pre-Heating Unit
This unit consists of ovens and flame torches to pre-heat sand mould and metal die mould.
Moulds are pre-heated to avoid the soldering of hot liquid molten metal and cold die/sand mould that can cause uneven surface defects in solidified casting.
Pre-heating also eliminates any moisture in the sand and die surface reducing porosity in the casting and gas defects in castings.
Casting Machine Station
This station is a workstation consisting of a casting machine where molten metal is poured into the casting moulds to solidify casting, this station consists of a mould cooling system where mould is cooled uniformly to achieve directional solidification in case of sand, plaster, and ceramic sand mould.
Inspection And Testing Unit
This unit consists of inspection and testing of casting for dimensional accuracy, tolerance, cracks, defects, surface finish, deformity, unevenness, uniformity, desirable shape and size.
The inspection and testing unit does multiple casting inspections and testing methods to check for casting defects in the casting process.
Various non-destructive testing (NDT) and destructive testing (DT) testing methods such as visual inspection testing, eddy current testing, ultrasonic testing method, magnetic particle testing, dye penetration testing methods, water and air penetration testing, X-ray and Ɣ-ray radiography testing, mechanical testing method, metallurgical testing and spectrographic atomic absorption testing method.
All the above-mentioned casting inspection and testing methods are discussed and explained in the casting inspections and testing methods article.
Casting Cleaning And Shakeout Unit
This unit's objective is to clean castings from sand, ceramic, plaster and resin.
Remove burr, flash and oxides from the casting completely using shot blasting, pressurized air, glass beading, bead blasting and tumblers.
Casting Fettling Unit
This unit engages in separating the final casting from the gating system elements such as sprue, runner, riser and gate. This process is also called degating.
Degating is separating the gating system from the final casting that is to be dispatched to the customers.
This is done to send casting further to process casting components for secondary manufacturing processes which I have mentioned below.
Heat Treatment And Metallurgical Unit
Solidified casting taken out of machine/mould does not have full mechanical properties, characteristics and strength.
To improve casting products various heat treatment processes are carried out to improve mechanical properties, strength, metallurgical quality of casting, hardness, ductility, tensile strength, shear strength and compressive strength of castings.
This department ensures mechanical properties of casting improve by using heat treatment processes such as hardening, normalizing, annealing, tampering, case hardening, quenching, soaking and carburizing.
Secondary Manufacturing Process Unit
One casting is degated and casting goes through the heat treatment process to improve its mechanical properties it becomes important now to machine the casting according to its exact dimensions, cavities, surface finish, shine, surface texture, coatings, size, shape and accuracy that is mentioned in the drawing given to production departments from designed department according to customers requirement.
This includes machining, trimming, sawing, welding, reaming, drilling, turning, milling, boring, cutting, joining, surface coating, grinding, advanced surface finishing, visual appearance, corrosion resistance coating, repair, rework, powder coating and painting.
Secondary Manufacturing Machines
Casting cannot be manufactured with exact surface finish, shine, holes, cavities, treading, drill depth and bores accurately. To do this machines are used for machine operations which will produce holes, cavities, drills and treading in final casting.
Many big foundries consist of machines used to produce casting in required dimensions once solidified casting is taken out of the die and sand mould while small foundries outsource these casting to small machine workshops for machining operations.
The secondary manufacturing casting operations are carried out using lathe machines, milling, boring, drilling, grinding, welding machines, soldering, electrical chemical machines, chemical machines, ultrasonic machines, abrasive jet machines, water abrasive jet machines, water jet machines and laser machines.
Material Handling And Transporting Equipment
This consists of material handling equipment used in the foundry such as such as conveyors, ladles, forklifts, cranes and automatic guided vehicles.
Casting And Mould Storage Facility
The facility also has casting storage units to store casting until dispatch according to orders of customers.
Maintenance Department
The objective of this unit is to maintain die-casting machines, continuous-casting machines, repair sand and metal moulds, furnaces, ladles, conveyors, secondary manufacturing machines and the equipment mentioned above.
Safety Department
This unit comes under the safety department of the foundry which specializes in reducing injury, accidents, fire and hazards in the foundry to operators.
Care is taken that foundry gases are exhausted out and the foundry is ready to fight any accidental fire with fire retardant equipment ready.
This department also ensures proper safety glasses, helmets, aluminized clothing and eye and face protection shields are given to the operators on the foundry floor.
Foundry Application
- Automobile Parts And Components: Engines, engine blocks, shift knobs, strut, steering shaft, crankshafts, clutch, gear lever, spark plug, ignition system, housing and casings, motors, cover, fuel tank, battery plate, flywheel, door handles and knobs, steel frame panels, camshaft, brake pump, bearing, fasteners, engine valves, cam and followers, car chassis, rocker arm, pistons, cylinders, grab handle, brake, cylinder head, drive unit, radiator components, exhaust manifold, transmission unit, gears, gearbox, housing.
- Construction Industry: Steel beams (I, C, T, L and section, ), cast iron domes, trusses, drum rollers, large pipes, pumping systems, metal cladding, lifts, bridge structures, structural steelwork, stairways, metal blocks and plates used in highways, diggers, excavators, tower cranes, planers, pavers, loader and unloaders, construction equipment, components of the HVAC system, parts of construction equipment, mixing containers, plumping chambers rods, large exhaust pipes, tubes and tanks.
- Agricultural Industry: Agrical equipment such as shoves, feed equipment, planters, harvest equipment, components of milk machines, sprayers, cultivators and harrows, balers, manure spreading machine components, agricultural machines, irrigation system components, containers, reservoirs, water systems, pickers and ploughing.
- Art And Craft: Sculptures, ornaments, jewellery, statues, antique pieces, decorative brass bowls, showpieces, die-cast cars, bells, decorative door handles, grab bars and bronze art objects.
- Household Equipment: Components of washing machines, refrigerator parts, pans, vessels, mixing bowls, containers, skillets, ovens, toasters, table lamp stands, stoves, grinders, mixers, blenders, vacuum cleaners, lawn movers, and kettles.
- Household Repair Kits: Components of drilling machine, rails, large fasteners, anti-rust hammers, punching machine, wrenches, spanners, fittings and pliers.
- Industry Equipment: Valve, brackets, housing, brackets, bearing, connecting shafts, covers, regulators, actuators, components of compressor, pumps, generators, alternators, electric motors and servomotors.
- Marine Industry: Ornamental tubing, impellers, suction pump, propellers and propellers shaft, stainless steel tanks, exhaust manifolds, watertight doors, stern frames, manifolds, hulls, steering system, engine blocks, engine housing, cylinder and pistons,
- Machine And Machine Tool Components: Parts of machine bed, rods, motor housing, parts of milling machine, rotating shaft, lathe machine grinding machine, planner machine, shaper machine, die casting machine, blanks used for machining, continuous casting machine and metal moulds.