Ready For Harvest

By using laser scanning technology, Harvest Technologies creates products without much of the waste that comes with introducing the human element to measurement practices.

By using laser scanning technology, Harvest Technologies creates products without much of the waste that comes with introducing the human element to measurement practices.

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Generally speaking, engineers are pragmatists. Find the best way to complete a task accurately, quickly, and easily -- or easily enough – and run with it. To that end, those same engineers have utilized laser technologies for years in order to expedite and improve everything from cutting to measuring.

These days, a growing number of engineers are utilizing laser scanners to help create prototypes for new products and ensure conformity to original CAD designs -- and they're doing so more quickly and accurately than ever before.

In the process known as additive manufacturing (AM) -- accepted industry nomenclature that encompasses both rapid prototyping and direct 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 deliverable:

Stereolithography (SL) utilizes a 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.

Other processes such as CNC machining are used to whittle-down solid blocks of material to arrive at a finished part quickly and inexpensively.

At the end of the day, 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.

Harvest Technologies is an AM firm located in Belton, Texas. Formed by father and son David E. and David K. Leigh, the firm has been engineering prototypes and production parts for customers around the world since 1995.

Harvest had mastered the techniques involved with rapid prototyping, but sought a way to improve the speed and accuracy with which they checked and ensured the finished products. Referred by a customer, Harvest contacted Lake Mary, Florida-based FARO Technologies about their FARO Laser ScanArm. Laser scanners, like the one FARO provides, offer the ability capture both 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 ScanArm captures up to 19,200 points per second and can be used to measure complex parts. 

A 3D laser scanner's technology is simple. The scanner 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.  

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Harvest Technologies was recently tasked with performing dimensional inspection of a prosthetic foot prototype.

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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 then uses Geomagic software to place the completed prototype scans into CAD files and the scanned prototypes are 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.

Recently, Harvest was tasked with performing dimensional inspection of a prosthetic foot prototype. The human foot is very curvy, which makes it difficult to obtain traditional XYZ measurements. Utilizing the scanning 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," explains 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 utilizing laser scanning technology, Harvest can create and analyze more products without much of the waste that comes with introducing the human element to measurement practices. 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.

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