Thursday 14 February 2013

Conventional Machining VS Non-Conventional Machining


Conventional machining usually involves changing the shape of a workpiece using an
 implement made of a harder material. Using conventional methods to machine hard
metals and alloys means increased demand of time and energy and therefore increases
in costs; in some cases conventional machining may not be feasible. Conventional
machining also costs in terms of tool wear and in loss of quality in the product owing to
induced residual stresses during manufacture. With ever increasing demand for
manufactured goods of hard alloys and metals, such as Inconel 718 or titanium, more
interest has gravitated to non-conventional machining methods.
Conventional machining can be defined as a process using mechanical (motion) energy.
Non-conventional machining utilises other forms of energy. The three main forms of
energy used in non-conventional machining processes are as follows :
• Thermal energy
• Chemical energy
• Electrical energy
One example of machining using thermal energy is laser. Thermal methods have many
advantages over conventional machining, but there are a few of disadvantages.
• Inconel 718, titanium and other hard metals and alloys have a very high melting
point. Using thermal methods will require high energy input for these materials.
• Concentrating heat onto any material greatly affects its microstructure and will
normally cause cracking, which may not be desirable.
• Safety requirements for thermal methods, especially laser, are demanding in
terms of time and cost.
• Machining large areas or many surfaces at the same time using thermal methods
is not normally possible.
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The methods using electrical energy are electrodischarge machining (EDM) and anodic
machining (AM), which are similar in practice. EDM, often refered to as spark erosion,
uses pulsed voltage to remove material from a workpiece and a non-conductive medium
to clear the debris. Because the medium is electrically inert the tool is a direct reverse of
the workpiece and no complicated tool design criteria are required. But the shock of
spark erosion can affect the microstructure on the surface of the workpiece. Also, EDM
has a lower material removal rate than AM.

The chemicals used in AM are non-toxic and the energy required is less than other nonconventional
machining processes. It has no effect on the microstructure of the

workpiece. The electrolyte can even be common sea water, enabling AM to be used in a
sub-sea capacity. The hardness and thermal resistivity of the workpiece material do not
matter therefore hard metals and alloys can be machined using tools made from softer
materials. The only disadvantage is that tool design is a little more complex than that of
EDM, but software is being developed to make this easier. The controllability,
environmental versatility, speed, safety and absence of change in workpiece
microstructure make AM a competitive manufacturing process.

1 comment:

  1. I am importing an .IGS file into Solidworks in order to render it using Photoworks. Right now it always looks like the thing is floating several feet above the "ground". I physically move the model down to where the "ground" appears to be and render it and it looks fine, but if i rotate the view and then render it once again looks as if it is floating. . . Can someone please tell me how to "drop" my model so its sitting on the "ground"?.

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