foundary
DESCRIPTION
faundaryTRANSCRIPT
Foundry-Basics
By
Rao Muhammad Zeeshan, (Mechanical Associate Engineer)
Instructor atWah British Institute of technology, Taxila
What is a Foundry?
• Casting is one of the oldest industrial processes • There are different casting processes.
The focus here is: “GREEN SAND” CASTING
A foundry is:a factory that pours molten metal into molds, producing cast metal objects.
Some typical cast
metal objects:
Turbine blades in jet engines
Engine blocks,axlesAluminum
pots
SAND-CASTING
Sand, mixed with clay binder &
water (so it will hold its shape) plus coal dust to
improve surface finish
Patterna copy of the shape you want to produce, made of wood, plastic or metal
Basic materials & equipment for green sand-casting
Container of molten metalfilled from furnace Top and bottom mold forms
made of metal, open at top and bottom
Rammertool to compact the sand; often a pressing machine is used
SAND-CASTING
MOLDING:Sand placed
into bottom mold form &
compacted
MOLDING: Pattern placed into mold
A very basic summary of the sand casting process. . .
First of all, mix the sand.
21THEN
SAND-CASTINGMOLDING: Add the top mold form
3
4 MOLDING: Fill top form with compacted sand.
RUNNER: A tube or pipe provides a path to pour the metal in
Pattern is still inside!
RISER: A tube or pipe provides a path to exhaust gases
SAND-CASTING
MOLDING: Take the top mold off and remove pattern & pipe
5
6 MOLDING: Replace the top mold and fasten socket!
Pouring hole
In the middle of the sand is a cavity shaped like the pattern!
SAND-CASTING
7 CASTING: Pour the metal (container is filled from furnace immediately before you are ready to pour)
8 Wait for the metal to cool(depending on the size of the casting)
SAND-CASTING
8 SHAKE OUT: Break apart the two halves of the mold & take out the part—usually requires vibrating or striking the mold to break apart the sand
CLEANING. Sand is cleaned off the part
9
A copy of the pattern has now been made in metal
10 Mold forms are reused
11Sand is broken up, screened to remove debris and clumps, and sent for remixing
SAND-CASTING
Sand-casting is simple in concept, but demanding in execution. It is a process essential to making basic and advanced products. . . it is also hazardous and energy-intensive!
Sand Casting: Parts of a Sand Mold (expendable mold)Key terms: Flask, Cope, Drag, Spur, Runner, Gate, Riser, Mold Cavity, Core, Parting Line, Draft (not shown).
Casting Terminology
Parting line
Sand Casting Configuration
Patterns
What is pattern?• Approximate duplicate of product • Patterns are made in the shape of the casting• Pattern Materials: Wood, Plastic or metal.• One piece or multiple piece pattern
Types of PatternsTypes of patterns used in sand casting: (a) solid pattern(b) split pattern(c) match‑palate pattern(d) cope and drag pattern
Pattern Making
One piece or Solid Pattern
Cope & Drag PatternMatch Plate Pattern
Split Pattern
Pattern AllowancesShrinkage AllowancePatterns are made larger than the casting to compensate contraction of the liquid while freezing.For internal cavities the allowances should be negative.
Machining AllowanceAllowance required to remove the rough cast surface. 2 to 25 mm (0.1 to 1’)
Draft Allowance To facilitate ease of removal, usually ½ to 2 deg.
Shrinkage allowance
Normal shrinkage: Cast iron 0.83 to 1.3%Aluminum - 1.3%
Cores
• Cores are used to create internal cavities.
• Should have similar properties as the mold.
• Shaken out after casting is produced.
Casting Process
1
Mould
2
3
Dolly
4
5
Sprue Pins
6
7
8
9
10
11
12
13