Reverse
engineering has come a long way from the days when manufacturers used
it to side-step design and R&D processes and get to market by
copying a competitor's product. What gave reverse engineering
respectability was the rise of rapid prototyping. OEMs, manufacturers,
fabricators, and service shops were all quick to recognize that reverse
engineering speeds up numerous internal processes, particularly rapid
prototyping. Thus was removed the "copycat" label from a process that
has many legitimate benefits when applied to projects where no
intellectual property rights are involved.
Today, reverse engineering is seen as the fastest way of translating
the dimensions of a physical model or shape into the digital realm so
that where manufacturing, machining, or repair plans can be written for
it. In concept, it is fairly simple. An object, such as a pump housing,
plastic frame, boat hull, or aircraft nacelle is measured physically.
Then the measurements are transcribed into a digital medium (a
CAD-compatiblc platform) as an image of dots, streaming lines, or wire
frames. Subsequently, this image can be enhanced for its end use via
one or more software packages such as surfacing, stress analysis, human
factors, ergonomics, plant layout, or product flow.
Typical applications
There are a wide variety of reasons to use reverse engineering:
* Design-adapting a structure to a mating surface to compress the time-to-market cycle
* Development-rapid prototyping and prototype testing for ergonomic, flow testing, or other evaluations
* Tool making-reduce the time required to develop tooling and improve tool accuracy
* Repair-create new parts from old, fractured, or worn originals
* Fabrication-create elements of material-handling systems or other processes
* Manufacturing-develop one-off pieces of equipment or structures.
For a new design, the dimensions of a mechanical model-from clay,
plastic, wood, or wax-are copied digitally, then embellished via
surfacing, ergonomie, or other programs.
For a product modification, reverse engineering is used to capture
the existing mounting or mating structure as a drawing file
(IGES-compatible format), then manipulated in CAD or similar program to
complete the adaptation.
A good example of reverse engineering involves a sheet-metal
fabricator that modifies military vehicles to carry external items,
from auxiliary gasoline tanks to mounts for communications systems.
They digitize the surface where a bracket is to be attached-including
potential hole positions-and bring this image into their design
software where it is used to shape the bracket.
In repair applications, parts for which no drawings exist can be
recreated by reverse engineering. This includes equipment that is old
enough so that original drawings are lost, or that was built as a
one-off time and never documented in the first place. For example,
after years of service that included exposure to mild corrosion, a
blade on an impeller for an air supply compressor cracked off. Ordering
a new one from the manufacturer would take eight months. Plant
engineers decided to reverse engineer a new one from the original. They
measured the dimensions of the original to digitally capture the
location of the blades, including the one that broke off. Shaft and
bearing dimensions were also recorded. This data was downloaded into a
CAM program and a machining plan was written to cut the new impeller.
Actual milling was done in a machining center where the new impeller
was cut from a blank of aluminum alloy that would have toughness and
corrosion resistance that was at least equal to that of the original.
From start to finish, the project took three weeks.
Tool making and product testing also benefit from reverse
engineering. Using a physical model, dimensions can be taken to create
everything from molds to fixtures for robotic welders. The same process
is used to adjust tooling to dial in specifications. For some complex
automotive assemblies, fabricators have cut almost a year off the time
to qualify "first article" parts. In applications where software is
used to evaluate a design-for stress analysis, flow characteristics,
ergonomics etc.-the recreated image becomes the test object, providing
feedback on parameters such as flow patterns, material throughput, and
critical stress points.
Translation technology
If you can measure an object, you can reverse engineer it. The key
is to be able to measure with sufficient accuracy to capture the degree
of detail-in three dimensions-necessary for faithful reproduction.
In the past, this was accomplished with some novel techniques,
including one known as "stock building." As the name implies, a
measurement from one point on an object was taken using calipers,
rules, depth gages, etc. and a model was built with sticks, each stock
representing an individual measurement. The accuracy of the model
depended entirely on the skill of the model maker and the process
usually required weeks to get it right.
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