Instrumentation • Electronics
Fig. 2. The Southampton University Laser Sintered Aircraft (SULSA).
not come from 3D CAD may be retrieved in many different ways,” Schaeflein says.
Object geometry
“I am not just talking about classical 3D measurement but also laser and CT scanning, even in the mechanical area, and mathematical programs which are not really CAD. The approach to data generation is basically the same: you have a device that retrieves an object’s geometry, and by the way 3D measuring tables are used relatively rarely because they take forever and a day.” Turning to Verduijn’s assertion that CT scanning is not
used for metal parts, Schaeflein rejoins: “This is partially correct. There is also magnetic resonance imaging (MRI) scanning, but in practice this is more used for soft tissue. Metal objects are represented on a CT scan clearly, but such scans do not represent the internal structure of a metal part.” The data fed to a Stratasys is typically in the form of
a stereo lithography (STL) file, which Schaeflein claims is the easiest format to work with and which guarantees topologically correct surfaces or volumes. As 3D CAD technology has been around for 25 to 30 years, Schaeflein holds that that there are not many components today that do not have 3D data available. Schaeflein deduces: “I would say that reverse engineering
is of interest for measurement and quality control, but not really to redesign parts; more to verify that the output corresponds to the CAD file used for the input.” Ronen Sharon, CEO at Sharon Tuvia, an Israeli
manufacturer of aerospace mechanical assemblies, parts and components, claims that his company’s CMM measuring cycle has been shortened by using PAS CMM software that automates program writing time for the machine. PAS-CMM automatically creates a dimensional measuring interface
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specification (DMIS) program. Sharon continues: “It possible to use an optical measuring
system and compare it to the CAD file and have the deviation between the part and the CAD by using GOM optical measuring systems.” Gesellschaft für Optische Messtechnik (GOM) was founded in 1990 as a spin-off of the Technical University of Braunschweig.
Printed drone
At Farnborough 2012, EADS presented the prototype of a portable unmanned aerial vehicle (UAV) produced by ALM technology with a wingspan of approximately 1.5 metres, designed by students from the University of Leeds. However in July last year, Southampton University engineers flew what they claimed to be the world’s first ‘printed’ aircraft. The entire structure of the Southampton University Laser
Sintered Aircraft (SULSA) has been printed on an EOS EOSINT P730 nylon laser sintering machine, including wings, integral control surfaces and access hatches. The machine fabricates plastic or metal objects, building up the item layer by layer. The project was led by Professors Andy Keane and Jim Scanlan at the University’s computational Engineering and design group and resulted in an electric-powered aircraft with a two metre wingspan and a top speed of nearly 100 miles per hour. It is almost silent when cruising on autopilot. “There are four servos for the two wing surfaces and two
tail surfaces, an electric motor for the engine, an autopilot and a standard aero modeller receiver,” explains Professor Keane. “It is programmed to fly in a mission to different way points and then come back and land under its own steam - it does not need a ground pilot. “The whole craft was designed from scratch in CAD. We
decided how big we wanted it to be and then designed the aerodynamic shapes needed to create the parts, created the
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