Manufacturing Process

A sequence of operations, often done on a machine or at

a given areaDuring a manufacturing process, we add,

subtract, or form materials in order to give a desired property/shape to the workpiece.

Therefore, different manufacturing processes, manufacturability of a material, processing tools, environmental aspects etc., have become important issues for manufacturing processes.

Manufacturing Tools & Techniques

For the purposes of this subject, Manufacturing Technology can be broken down into the following sub-sets.

Material removal and tooling

Material forming

Additive processes

Controls/Software

Plastics technology

Material Removal and Tooling

The vast majority of tools and techniques within Manufacturing Technology fall within ‘machining processes’ and perhaps form the basis of the public perception of ‘Manufacturing’.

MillingTurning

Boring

Broaching

Drilling

Electrical Discharge

MachiningGrinding

Cutting

Cutting

Cutting is the most common material removal and machining processes.

Cutting is typically achieved using a cutting blade with hardened teeth to cut through (or ‘Saw’) the workpiece.

Drilling

Like cutting, drilling is one of the most common material removal and machining processes. It is estimated that over two-thirds of all metal-cutting material removed comes from drilling operations.

Drilling is an operation that uses a hardened rotating tool to produce a round hole in a workpiece. This is accomplished most typically by using a twist drill.

Drilling is generally performed before machining operations such as boring, reaming, tapping, counterboring, countersinking and spotfacing.

Turning & Boring

Turning is one of the basic machining processes and produces solids of revolution which can be tightly toleranced because of the specialized nature of the operation.

The turning process is performed on a machine called a ‘Lathe’ in which the work piece is mounted on the chuck, which rotates relative to the stationary tool.

Milling

Milling is as fundamental as drilling among the powered metal cutting processes and uses a rotating cutter that is moved laterally to remove material from the work piece.

Milling is versatile for a basic machining process, but because the milling set up has so many degrees of freedom, milling is usually less accurate than turning or grinding.

Grinding

Grinding is a ‘finishing’ process used to improve the surface finish, abrade hard materials, and tighten the tolerance on flat and cylindrical surfaces by removing a small amount of material.

In grinding, an abrasive material rubs against the component to remove material and is typically on the surface of a wheel or belt.

The excessive heat produced during the grinding process, requires the use of fluid within the cutting area to prevent the workpiece becoming damaged or distorted.

Material Forming

Not all components can be manufactured through the use of Material Removal tools & techniques.It is often advantageous to use Material Forming techniques, where it is easier to manufacture more complex components maintaining the material properties.Material forming techniques include;

BendingExtrusion Forging

CastingPressing

Bending

Another of the basic manufacturing processes, bending is one of the most common material forming processes.

If a bend is required in a workpiece

(be it sheet metal, bar or tube), a

Bending Machine is used to apply

a strain at the desired location to

form the designed bend.

ForgingForging is the term for shaping metal by using localised compressive forces.

Cold forging is done at room temperature or near room temperature, while Hot forging is done at a high temperature, which makes metal easier to shape and less likely to fracture.

Warm forging is done at an intermediate temperature between room temperature and hot forging temperatures. Forged parts can range in weight from less than a kilogram to 170 metric tons.

Forged parts usually require further processing to achieve a finished part.

Casting

Casting is a process by which a liquid material is poured into a mould, which contains a hollow cavity of the desired shape, and then allowed to solidify.

The solidified part is known as a casting, which is ejected or broken out of the mould to complete the process. Casting materials can be metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and clay.

Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods.

ExtrusionExtrusion is a process used to create objects of a fixed cross-sectional profile, where the base material is pushed or drawn through a die of the desired cross-section.

The two main advantages of this process over other manufacturing processes are;

Its ability to create very complex cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses.

It also forms finished parts with an excellent surface finish.

The extrusion process may be continuous or semi-continuous and can be done with the material hot or cold.

METAL CASTING PROCESSES

1. Sand Casting2. Other Expendable Mold Casting Processes3. Permanent Mold Casting Processes4. Foundry Practice5. Casting Quality6. Metals for Casting7. Product Design Considerations

Steps in Making Sand Castings

There are six basic steps in making sand castings:

PatternmakingCore makingMoldingMelting PouringCleaning

Pattern making

The pattern is a physical model of the casting used to make the mold.

The mold is made by packing some readily formed aggregate material, such as molding sand, around the pattern.

When the pattern is withdrawn, its imprint provides the mold cavity, which is ultimately filled with metal to become the casting.

If the casting is to be hollow, as in the case of pipe fittings, additional patterns, referred to as cores, are used to form these cavities.

Core making

Cores are forms, usually made of sand, which are placed into a mold cavity to form the interior surfaces of castings.

Thus the void space between the core and mold-cavity surface is what eventually becomes the casting.

Molding

Molding consists of all operations necessary to prepare a mold for receiving molten metal.

Molding usually involves placing a molding aggregate around a pattern held with a supporting frame, withdrawing the pattern to leave the mold cavity, setting the cores in the mold cavity and finishing and closing the mold.

Melting and Pouring

The preparation of molten metal for casting is referred to simply as melting.

Melting is usually done in a specifically designated area of the foundry, and the molten metal is transferred to the pouring area where the molds are filled.

Cleaning

Cleaning refers to all operations necessary to the removal of sand, scale, and excess metal from the casting.

Burned-on sand and scale are removed to improved the surface appearance of the casting.

Excess metal, in the form of fins, wires, parting line fins, and gates, is removed. Inspection of the casting for defects and general quality is performed.