process development
Research into metallic
feed systems started
in the late 1980's using
MIG welding torches fitted
to multi-axis robots, as a
way of building up material
onto expensive damaged
parts, such as turbine
blades or mould tools. In
the 1990's welding wire
was replaced with blown
powder, which although
much slower, enabled far
better melt-pool control
and subsequent part
accuracy.
A wide range of
production
engineering metals for
components such as these
hip joint cups have been
processed using powder
bed ALM systems
RAPID Manufacturing (RM) describes the
production of ‘series’ or ‘end-use’ component parts
made using Additive Layer Manufacturing (ALM)
processes. Traditionally, these were used to make
prototypes and casting patterns, but advances in ALM
technologies and materials now allow manufacture of
parts in polymers, ceramics and metals for many
production applications.
How Does Additive Layer Manufacturing Work?
The principle is simple. As opposed to machining,
where material is removed from solid block, or casting
where material is melted and forced into a cavity, it
works by building-up the required geometry particleby-particle,
layer-by-layer, from the bottom-up. There
are many different mechanisms for generating a single
layer, or for bonding layers together. In some simple
systems, layers are cut from sheet material and bonded
using adhesives or ultrasonic welding type processes. In
others, layers are generated by melting fine powder
using a laser or electron beam, and consolidating the
new layer onto the previous layer by remelting. There
are over 30 different ALM processes marketed by over
40 different companies around the world. Most focus
on polymeric materials.
Why is RM becoming important to the economy?
Some see it as one of the most important emerging
technologies to the future manufacturing economy. A
notable advantage is the potential elimination of
62 MWP march 2008
Direct rapid manufacturing of
metallic parts - the technology
of the future? Or is it here and
now? We offer a UK industry
overview. (for a full version go
to www.mwponline.com)
By Phil Reeves
It adds up
tooling. Without the constraints of casting or moulding
tools, or machining jigs and fixtures, RM enables
manufacturers to produce cost effective batches of one,
or to make parts at multiple locations or with multiple
product design iterations at no extra cost..
Why is RM different to traditional manufacturing?
Because it uses layer-wise manufacturing, many of the
traditional Design for Manufacture (DFM) principles
no longer need apply. RM components can be
manufactured with no split lines, or with complex
internal and re-entrant features. It therefore allows for
significant part consolidation, reducing
manufacturing, assembly and inspection costs; and for
the manufacture of topologically optimised
components - ‘manufactured-for-design’ as opposed to
‘designed-for-manufacture’. This can eliminate many
secondary manufacturing steps such as internal
machining ops or secondary fabrication.
How will RM affect the traditional supply chain? In
principle, RM can reduce or eliminate many stages of
the traditional supply chain, reducing lead times,
inventory and supply chain transaction and logistics
costs. Moreover, little if any waste material is generated
- this is particularly true of the newer metallic
processing technologies. Additive processes are lean yet
agile, allowing manufacture of low volume component
batches, with little manual intervention.
So who is using RM today? There has been an
almost exponential increase in the number of
companies using RM, across many sectors. Applications
include aerospace and automotive components,
packaging, medical implants, hearing aid shells and
surgical guides, and consumer products as diverse as
furniture and football boots.
How did we get to where we are today? The
technologies behind RM have existed since the mid
1980s, when processes such as Stereolithography (SLA),
Fused Deposition Modelled (FDM) and Selective Laser
Sintering (SLS) were introduced to make prototype
parts directly from 3D CAD data - the term Rapid
Prototyping (RP) was coined. However, the processes
produced exclusively polymeric or paper parts. As the
accuracy and repeatability of the early systems
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