Advanced Manufacturing Flashcards
Electro Discharge Machining (EDM)
- Two electrodes (the tool and the workpiece) are:
–immerged in a dielectric fluid,
–submitted to an electrical current
–Separated by a gap
- If the gap is small enough (< spark gap)
–Electrical discharges occur
»Creating Craters on the workpiece and on the tool
–Material removal occurs through the accumulation of craters produced by electrical discharges
- Can machine any (only) conductive material regardless of its hardness
Die Sinking EDM
The electrode moves up and down and creates a negative version of of the shape in the workpiece.
Higher energy used = faster process but bigger spark gap + rougher surfaces
Dielectric Flushing - removal of debris
- Limitations
–Tools can be difficult to produce
–Wear on the tools can be difficult to control
–Slow process => expensive
- Advantages
–High quality surfaces
- Main application: Moulds for injection moulding.
Wire EDM
Removal by craters produced by electrical discharges between a wire and the work-piece.
- Limitations
–Produces mainly 2D shapes
–Corners Diameter limited by the Wire Diameter (+spark gap)
- Advantages
–No wear compensation needed
–Easy flushing (brought by the movement of the wire)
EDM Drilling
Can produce very deep holes
– Aspect ratio > 100 (e.g. Ø1mm 100mm
deep)
– Flushing is crucial to remove debris
* Hollow Electrodes
EDM milling
- Can produce complex 3D shapes with features down to 5μm
- Compared to Die sinking
– Improved flushing more accurate geometry
– Extremely Time consuming
– Mostly used for cavity smaller than 100mm2
Laser machining applications
Almost any Material - Metals/Plastics/Ceramics
- Sharp corners to be avoided, difficult to produce
- Deep cuts produce tapered walls
- Dull and unpolished surfaces preferable
- Heat-affected zone, high local temperatures might affect material
properties - Clean operation
- Flexible process
- Simple fixtures
- Low set up times
But slow process when compared to standard CNC machines
Abrasive Water Jet Machining
momentum change of a stream
of water with particles which produces a high
force
Clean Operation
* Good for heat sensitive material
* Complex 2D shapes can be manufactured
economically
* Min hole diameter is around 0.4 mm
* Max hole depth is around 25 mm
Chemical Machining
- Produces shallow cavities on plates, sheets, forgings and extrusions
Water Jet
momentum change of a stream of water which produces a high
force
compared to wire edm
* Cleaner operation - Environmentally safe
* More Efficient
* Material does not have to be conductive
– Used in food-processing industry (cutting/slicing food)
* No heat
* Cut can start at any location - No need for start hole
- Rougher surface
- Not as accurate
Shrinkage + Warping
Warping – waviness on the surface
Uneven pressure, solidification before a mould is packed out
Shrinkage
Reduction in sizes after cooling
Factor ratio varies between materials
( typically around 1%)
To compensated during mould design
by increasing dimensions. Not an exact science.
Injection moulding
Melting the Granules of desired Material
Filling up the mould with melted material
Solidifying the Material
Demoulding
Thermoplastics#
Mould and Component design - Many design rules
* To Facilitate Demoulding
* To Deal with deformations occurring during cooling
(e.g. Warping, Shrinkage)
* Reduce stress (avoid sharp corners)
* Minimise additional defects (e.g. ejector pins, flash
or sink marks)
Fabrication of Microelectronic devices MEMS
Micro Chip
Integrated circuits technology
Clean room environment
* Essential for the
production of
integrated circuits due
to the processing of nm
dimensions
Photolithography
Mask: glass/quartz plate with a pattern to be replicated on the
wafer
– Mask image
is enlarged
10 x
– Enlarged
image is
focused
3d printing
