Manufacturing Processes: EDM, Water Jet Cutting, Sheet Metal Bending, Powder Metallurgy

SOLUTION TO THE QUESTIONS
1. Discussion on manufacturing processes:
(a) Electrical discharge machining
Normally there is an electric gap between the work piece and the electrode such that
the electric gap is filled with dielectric fluid such that it establishes a conductivity
bridge.
The process causes surface erosion on the selected work piece. There is a constant
gap being maintained between the work piece and the electrode. Electric field is set
up between the two electrodes such that electrons are attracted to the positive
terminal. Some pieces are ionized to form a strip. As temperature and pressure
increase, the spark develops such that materials are vaporized and a burble comprised
of vaporized materials rapidly expands and grow outwards from the channel. Finally
the burble disappears and dielectric fluid rushes into gap flushing away the loosened
materials from the surface.
(b) Thermal and abrasive water jet cutting
Thermal cutting utilizes heat to cut metals into two pieces within a predetermined
profile. Normally it is limited in that: it creates the heat affected zone which makes
the resulting material to have more non-uniform properties. It is also less accurate
hence challenges in tolerance levels. Besides, it is labor intensive such that secondary
finishing operation is required such as slug removal. Safety concerns regarding fuel
gases and cutting flumes can be flammable, electrical shock, high noise level, hot slug
and intense laser light.
(c) Sheet metal bending
A metal piece is placed between a set of dies which comprises upper and lower dies
such that the ram is forced to move downwards and press on the work piece.
As the material is being pressed, it bends to the required shape and angle. The male
component of the die sandwiches the work piece with the female component being
used to provide the required shape. The larger the die opening, the smaller the force
required to cause bending. The most common technical terminology used include:
bending angle and bending radius. However, there is normally a phenomenon called
Spring back. This refers to the tendency of the stretched material regaining it shape
and size once force causing the bending is retrieved. It normally ranges between 2 to
4 o. Therefore, it is imperative for the bending design to consider this prior to
bending.
(d) Powder metallurgy
This is a material forming technique in which given properties of powdered
compounds are mixed to form a homogeneous compound for parts production.
Binders and lubricants are normally added. Powder consolidation is then carried out
in a mold. Shaping follows such that they are made into compacted material. Heat