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 MEC 2040:
Computer Aided Technology

 
MEC2040
Rapid Prototyping
SLA
SLS
FDM
LOM
CNC machining
What it stands for
Stereolithography

(apparatus)

Selective Laser Sintering
Fused Deposition Modeling
Laminated Object Manufacturing
Computer Numerically Controlled
How it works
Laser scans and solidifies layers of liquid plastic
Laser scans and solidifies layers of powdered material
Double barreled ‘glue gun’ lays down layers of molten material
Laser cuts out layers of glue-backed paper
Cutting Tool moves to series of coordinate points
How the parts are fixtured in fabrication
Thin walled breakaway structure 
Remaining Unsintered powder on each layer-
Second barrel shoots non-bonding material to fill spaces under part
Cross-hatched paper breaks away outside of model
Vises, clamps, screws, epoxy nests, machined shapes etc.
Materials
Unique, brittle, messy and expensive
Metals, ceramics and thermoplastics
Common thermoplastics and wax
Paper (wood)

Some plastic and metal laminates

Just about anything
Cost
High
Medium to high
Dirt
Low
Medium to High
Accuracy
Excellent
Fair
Fair
Fair/Poor in z

Absorbs moisture if not sealed.

Good and potentially the best
Support for molding
Quickcast process makes easy burn honeycomb interior
No casting masters but none necessary for direct mold fabrication
Easy melt wax casting masters
No special way of making masters
Casting masters for undercut molds are difficult
Surface finish
Good - small steps sand smooth
Poor - granular steps tough to fix
Poor - tough to fill smooth
Good - small steps sand smooth
Outstanding
Pros
Fine detail
Strong materials
Compact machine,

Strong ‘fibered’ parts

Fast for big parts,
strong like wood
Many – see above, production speeds
Cons
Requires ‘lab’ set-up
Poor on fine detail
Poor on detail
Can’t build hollow parts
Slow programming

P Johnson referencing www.efunda.com


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