Production Process I

Production Process I

IntroductionA. Syllabus, paper pattern

Introduction

Market need

Concept design

Detailed design

Manufacturing

Sell

B. Introduction to the subject

Introduction

B. Introduction to the subject1. What is manufacturing?

IntroductionC. Classification of manufacturing processes

Solidification Process

Particulate Process

Deformation Process

Material removal Process

Module IMetal casting process

Metal Casting Process

1. Casting2. Mold3. Pattern

A. Fundamental of metal casting

Casting is a process in which the molten metal flows by gravity or forced into a mold, where it solidifies and finally after cooling, it acquires the shape of the mold cavity.

Open Mold Closed Mold

Metal Casting Process1. Casting2. Mold

2.1 Mold materials2.2 Constituent of Molding Sand2.3 Kinds of Molding Sand2.4 Properties of Molding Sand2.5 Steps involved in making Sand Mold2.6 Venting of Molds

3. Pattern

2. Mold

Depending upon the extraction of cast product, the casting process in divided into

Expendable mold - casting process Permanent mold - casting process•Sand mold casting

•Shell mold casting•Vacuum mold casting•Investment casting•Carbon dioxide mold casting

•Die casting•Centrifugal casting

Metal Casting Process1. Casting2. Mold


3. Pattern

2.1 Mold materials

Metal•Cast Iron•Mild Steel•Alloy steels

Non Metal

•Plaster of Paris•Graphite•Ceramics•Molding Sand

2. Mold

Sand Casting ProcessA. Fundamental of sand casting

Casting Terms :

•Mold: It contains a cavity whose geometry determines the shape of the cast part.•Cope: It is the upper half of the mold.•Drag: It is the bottom half of the mold.•Flask: A metal or wood frame, without fixed top or bottom, in which the mold is formed.



•Parting line: This is the dividing line between the two molding flasks that makes up the mold.•Pattern: It is the replica of the final object to be made. The mold cavity is made with the help of pattern.•Molding sand: Sand, which binds strongly without losing its permeability to air or gases. It is a mixture of silica sand, clay, and moisture in appropriate proportions.



•Facing sand: The small amount of carbonaceous material sprinkled on the inner surface of the mold cavity to give a better surface finish to the castings.•Core: A separate part of the mold, made of sand and generally baked, which is used to create openings and various shaped cavities in the castings.•Chaplets: Chaplets are used to support the cores inside the mold cavity to take care of its own weight.



•Pouring basin: A small funnel shaped cavity at the top of the mold into which the molten metal is poured.•Sprue: The passage through which the molten metal, from the pouring basin, reaches the mold cavity.•Runner: The channel through which the molten metal is carried from the sprue to the gate.•Gate: is that portion of runner through which the molten metal enters the mold cavity.


Sand Casting Process1. Fundamental of sand casting

•Riser: it serves as reservoirs to supply the molten metal necessary to prevent shrinkage during solidification.•Vent: Small opening in the mold to facilitate escape of air and gases.


Metal Casting Process2.2 Constituent of Molding Sand

1. Casting2. Mold


3. PatternThe main constituents of molding sand involve silica sand, binder, moisture content and additives.

Silica sand (88%-92%)•Silica sand form the main constituent of molding sand having enough refractoriness which can impart strength, stability and permeability to molding and core sand. •The silica sand can be specified according to the size (small, medium and large silica sand grain) and the shape (angular, sub-angular and rounded).•But along with silica small amounts of iron oxide, alumina, lime stone, magnesia, soda and potash are present as impurities.


1. Casting2. Mold


3. PatternBinder (6%-12%)•In general, the binders can be either inorganic or organic substance. •The inorganic group includes clay, sodium silicate etc. •In foundry shop, the clay acts as binder which may be Ball Clay, Fire Clay, Limonite, Fuller’s earth and Bentonite. •Organic group binders are dextrin, molasses, cereal binders, linseed oil and resins like phenol formaldehyde, urea formaldehyde etc.•Among all the above binders, the bentonite variety of clay is the most common.


1. Casting2. Mold


3. PatternMoisture (3%-6%)

•The effect of clay and water decreases permeability with increasing clay and moisture content. •The green compressive strength first increases with the increase in clay content, but after a certain value, it starts decreasing.


1. Casting2. Mold


3. PatternAdditivesSome common used additives for enhancing the properties of molding and core sands are discussed as under.

• Coal dust• Corn flour• Dextrin• Sea coal• Pitch• Wood flour• Silica flour


2.3 Kinds of Molding Sand1. Casting2. Mold


3. Pattern

•Green sand

• Dry sand

• Loam sand

• Facing sand

• Backing sand

• System sand

• Parting sand

• Core sand

Metal Casting Process2.4 Properties of Molding Sand

1. Casting2. Mold


3. Pattern

• Refractoriness

• Permeability

• Green Strength

• Dry Strength

• Collapsibility

• Cohesiveness

• Reusability

Metal Casting Process2.5 Steps involved in making Sand Mold

1. Casting2. Mold


3. Pattern• The first step in making mold is to place the pattern on the molding board.• The drag is placed on the board • Dry facing sand is sprinkled over the board and pattern to provide a non

sticky layer.• Molding sand is then riddled in to cover the pattern with the fingers; then

the drag is completely filled.• The sand is then firmly packed in the drag by means of hand rammers.

The ramming must be proper i.e. it must neither be too hard or soft.• After the ramming is over, the excess sand is leveled off with a straight

bar known as a strike rod.• With the help of vent rod, vent holes are made in the drag to the full

depth of the flask as well as to the pattern to facilitate the removal of gases during pouring and solidification.


1. Casting2. Mold


3. Pattern• The finished drag flask is now rolled over to the bottom board exposing

the pattern.• Cope of the pattern is then placed over the drag pattern with the help of

locating pins. • The dry parting sand is sprinkled all over the drag and on the pattern.• A sprue pin for making the sprue passage is located at a small distance

from the pattern. Also, riser pin, if required, is placed at an appropriate place.

• The operation of filling, ramming and venting of the cope proceed in the same manner as performed in the drag.

• The sprue and riser pins are removed first and a pouring basin is scooped out at the top to pour the liquid metal.


1. Casting2. Mold


3. Pattern• Then pattern from the cope and drag is removed and facing sand

in the form of paste is applied all over the mold cavity and runners which would give the finished casting a good surface finish.

• The mold is now assembled. The mold now is ready for pouring


1. Casting2. Mold3. Pattern 3.1. Objective of pattern 3.2. Type of pattern 3.3 Common pattern materials 3.4. Pattern Allowance

3. Pattern

Pattern is the replica of the final object to be made by the casting process, with some modifications.

The main modifications are the addition of pattern allowances . If the casting is to be hollow, additional patterns called cores are used to create these cavities in the finished product.

The quality of the casting produced depends upon the material of the pattern, its design, and construction.



3.1. Objectives of the Pattern

•A pattern prepares a mold cavity for the purpose of making a casting..•Runner, gates, and risers used for feeding molten metal in the mold cavity may form a part of the pattern.•Patterns properly made and having finished and smooth surfaces reduce casting defects.•A properly constructed pattern minimizes the overall cost of the castings.



3.2. Types of Pattern

•Single piece/solid pattern

•Two piece/split pattern

•Multi piece pattern

•Cope & drag pattern

•Loose piece pattern

•Match plate pattern

•Follow board pattern

•Gated pattern









3.3. Pattern material

Some materials used for making patterns are: • Wood • Metals and alloys like cast iron, brass & bronze, Aluminium alloys• Plaster of Paris,• Plastic and rubbers, • Wax, and resins.



3.3. Pattern material

To be suitable for use, the pattern material should be:

• Easily worked, shaped and joined• Light in weight• Strong, hard and durable• Resistant to wear and abrasion• Resistant to corrosion, and to chemical reactions• Dimensionally stable and unaffected by variations in temperature

and humidity• Available at low cost



3.4. Pattern Allowance

•Shrinkage or contraction allowanceLiquid Shrinkage & Solid Shrinkage

•Draft or taper allowancePositive allowance of 10mm to 20mm/m

•Machining or finish allowancePositive allowance of 3mm to 18mm

•Distortion allowance•Rapping allowance

Negative allowance of 0.5mm to 1mm

RISER

Considerations for Designing Riser

(A) Freezing time

(B) Feeding range

(C) Feed Volume Capacity

SOLIDIFICATION TIME

Chvorinov’s Rule

Chvorinov’s rule indicates that a casting with a higher volume-to-surface area ratio will cool and solidify more slowly than one with a lower ratio.

CASTING DEFECTS


1. Casting2. Mold & its types3. Patterns3. Advantages and disadvantagesAdvantages:

The metal casting process is extensively used in manufacturing because of its many advantages.

1.Molten material can flow into very small sections so that complicated shapes can be made by this process. As a result, many other operations, such as machining, forging, and welding, can be minimized or eliminated.2.It is possible to cast practically any material that is ferrous or non-ferrous.3.As the metal can be placed exactly where it is required, large saving in weight can be achieved.4.The necessary tools required for casting molds are very simple and inexpensive. As a result, for production of a small lot, it is the ideal process.5.There are certain parts made from metals and alloys that can only be processed this way.6.Size and weight of the product is not a limitation for the casting process.


1. Casting2. Mold & its types3. Advantages and disadvantages

A. Fundamental of metal casting

Limitations:

1.Dimensional accuracy and surface finish of the castings made by sand casting processes are a limitation to this technique. Many new casting processes have been developed which can take into consideration the aspects of dimensional accuracy and surface finish. Some of these processes are die casting process, investment casting process, vacuum-sealed molding process, and shell molding process.2.The metal casting process is a labor intensive process

Shell mold casting

Vacuum mold casting

Investment casting

Permanent mold casting

The basic permanent-mold process

DIE CASTING - Hot chamber die casting

DIE CASTING - Cold chamber die casting

Centrifugal casting

Production Process I

Documents

mold cavity

mold materials2

sand mold2

patternsand casting

patternsand casting

moldsand casting processa

properties of molding

kinds of molding sand2