Non Traditional Manufacturing Processes
Introduction
Non-traditional manufacturing processes is
defined as a group of processes that remove excess material by various
techniques involving mechanical, thermal, electrical or chemical energy
or combinations of these energies but do not use a sharp cutting tools
as it needs to be used for traditional manufacturing processes.
Extremely hard and brittle materials are
difficult to machine by traditional machining processes such as
turning, drilling, shaping and milling. Non traditional machining
processes, also called advanced manufacturing processes, are employed
where traditional machining processes are not feasible, satisfactory or
economical due to special reasons as outlined below.
- Very hard fragile materials difficult to clamp for traditional machining
- When the workpiece is too flexible or slender
- When the shape of the part is too complex
Several types of non-traditional machining
processes have been developed to meet extra required machining
conditions. When these processes are employed properly, they offer many
advantages over non-traditional machining processes. The common
non-traditional machining processes are described in this section.
Laser–Beam Machining (LBM) Introduction
Laser-beam machining is a thermal
material-removal process that utilizes a high-energy, coherent light
beam to melt and vaporize particles on the surface of metallic and
non-metallic workpieces. Lasers can be used to cut, drill, weld and
mark. LBM is particularly suitable for making accurately placed holes. A
schematic of laser beam machining is shown in Figure 12.
Different types of lasers are available for manufacturing operations which are as follows:
- CO2 (pulsed or continuous wave): It is a
gas laser that emits light in the infrared region.? It can provide up
to 25 kW in continuous-wave mode.
- Nd:YAG:? Neodymium-doped
Yttrium-Aluminum-Garnet (Y3Al5O12) laser is a solid-state laser which
can deliver light through a fibre-optic cable. It can provide up to 50
kW power in pulsed mode and 1 kW in continuous-wave mode.
Figure 12: Laser beam machining schematic
Applications
LBM can make very accurate holes as small as
0.005 mm in refractory metals ceramics, and composite material without
warping the workpieces. This process is used widely for drilling and
cutting of metallic and non-metallic materials. Laser beam machining is
being used extensively in the electronic and automotive industries.
Laser beam cutting (drilling)
- In drilling, energy transferred (e.g., via a
Nd:YAG laser) into the workpiece melts the material at the point of
contact, which subsequently changes into a plasma and leaves the
region.
- A gas jet (typically, oxygen) can further facilitate this phase transformation and departure of material removed.
- Laser drilling should be targeted for hard materials and hole geometries that are difficult to achieve with other methods.
A typical SEM micrograph hole drilled by laser beam machining process employed in making a hole is shown in Figure 13.
Figure 13: SEM micrograph hole drilled in 250
micro meter thick Silicon Nitride with 3rd harmonic Nd: YAG laser
Laser beam cutting (milling)
- A laser spot reflected onto the surface of a workpiece travels along a prescribed trajectory and cuts into the material.
- Continuous-wave mode (CO2) gas lasers are
very suitable for laser cutting providing high-average power, yielding ?
high material-removal rates, and smooth cutting surfaces.
Advantage of laser cutting
- No limit to cutting path as the laser point can move any path.
- The process is stress less allowing very fragile materials to be laser cut without any support.
- Very hard and abrasive material can be cut.
- Sticky materials are also can be cut by this process.
- It is a cost effective and flexible process.
- High accuracy parts can be machined.
- No cutting lubricants required
- No tool wear
- Narrow heat effected zone
Limitations of laser cutting
- Uneconomic on high volumes compared to stamping
- Limitations on thickness due to taper
- High capital cost
- High maintenance cost
- Assist or cover gas required
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