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Laser Scanning Helps Rapid Prototyping and Manufacturing Specialist Ensure Quality
LAKE MARY, Fla.--In the process known as additive manufacturing, complex three-dimensional objects are created in a short period of time--think days rather than weeks. There are many ways to produce and form the object. Stereolithography (SL) uses an ultraviolet (UV) laser to photo-cure epoxy-based resins and grow objects, layer-by-layer, from three-dimensional electronic data. Similar to SL, laser sintering (LS) also builds prototypes in layers, but instead uses a CO2 laser to fuse myriad thermoplastic and metal powders to generate a finished product. At the end of the day though, even prototypes produced by the most accurate and advanced methods need to be measured and checked against CAD designs to ensure accuracy for the customer. Enter laser scanning technology.
Engineers have used laser technologies to expedite and improve a variety of processes, from cutting to measuring, for years. Today, a growing number of engineers are employing laser scanners to help them create prototypes for new products and ensure their conformity to original CAD designs, and they're doing so more quickly and accurately than ever before.
Harvest Technologies (www.harvest-tech.com), an additive manufacturing firm located in Belton, Texas, has been engineering prototypes and production parts for customers around the world since 1995, when it was formed by father and son David E. and David K. Leigh. After having mastered the techniques involved with rapid prototyping, Harvest sought a way to improve the speed and accuracy with which they checked and ensured the finished products. Referred by one of its customers, Harvest contacted Lake Mary, Florida-based FARO Technologies (www.faro.com), maker of the FARO Laser ScanArm®.
Laser scanners like the one FARO provided to Harvest Technologies offer the ability capture high-end and fine surface measurements for use in SL and other files. Where calipers sufficed in capturing the measurements on simple box dimensions, the Laser ScanArm captures up to 19,200 points per second and could be used to measure very complex parts.
A scanner like the one used by Harvest attaches to a portable coordinate measuring machine (CMM), which, in Harvest Technologies' case, was a Platinum FaroArm. The device then projects a laser line on the subject and uses a camera to look for the location of the laser line silhouette. Depending on how far away the laser strikes a surface, each point on the laser line profile appears at different places in the camera's field of view. Data is collected one "slice" or cross-section at a time and triangulated. The CMM acts as a referencing device -- or "localizer" -- that tracks and communicates to the host application software the position of each cross-section in space. As the laser stripe is swept across an object, hundreds of cross-sections are instantly captured and rendered collectively in a CAD environment. The end result is a full 3D digital representation of the object.
Harvest Technologies now uses Geomagic® (www.geomagic.com) software to place its completed prototype scans into CAD files. The scanned prototypes are then compared to an original 3D model. Tolerances in this line of work are tight, so Harvest's ability to quickly transform an existing part into a digital representation and remove the human error element from CAD-to-part inspections is a big advantage for them.
Recently, Harvest was tasked with performing dimensional inspection of a prosthetic foot prototype by one of its customers. Clearly, the human foot is very curvy, with rounded ends that make it difficult to obtain traditional XYZ measurements. Utilizing their arm, Harvest engineers were able to perform a complete inspection across multiple dimensions. This allowed them to not only check length, width, and height of the prototype, but also several other critical dimensions.
"With something as complex as a prosthetic, where appearance is very important, having this ability ultimately gave us the chance to produce a product that was as realistic as it could possibly be," explained Lewis Simms, marketing and business development representative for Harvest Technologies. "We were able to cover everything, from the size of the toes to the curvature of the heel."
By using laser scanning technology, Harvest Technologies creates and checks products in less time, more cost effectively, and without much of the waste that comes with introducing the human element to measurement practices. Perhaps most importantly, errors in a prototype are caught early, before the product is passed along to the customer or valuable material is wasted on a flawed production run.
"[The ScanArm] is a great tool," said Stereolithography Production Manager Jason Morgan. "Well worth its weight in gold."
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