The company, based in Rochester, New York, specializes in miniature pattern-making and spin-casting of scale model parts and manufactures scale-model kits for hobbyists and collectors. 

The model company had just begun using computer modeling in conjunction with computerized machining (CNC) and 3D digital printing for producing scale model parts and patterns.  The company owner commented, “I had read about laser scanning in a trade magazine but thought it might be too expensive to justify using in my business.  Further investigation of this process led me to GKS Inspection Services, a provider of 3D laser scanning services.”

Reverse engineering of a complex free-form shape became an urgent need when a customer placed an order and requested a quick turnaround. The order was for the patterns, tooling, and cast parts for production of a 1:4 scale model outboard boat kit. The parts were to be spin-cast in Britannia metal, a silvery pewterlike material. “The boat propeller had complex shapes that would be difficult to replicate,” said the owner.  “I contacted GKS Inspection Services to see if laser scanning would be a feasible option to use for this application.”

The engineers at GKS, a division of Laser Design, Inc., knew that laser scanning would provide the ideal solution to the problem.  GKS’s non-contact laser system could easily scan and digitize the complex curves of the propeller blade. The laser projects a line of laser light onto surfaces, while cameras continuously triangulate the changing distance and profile of the laser line as it sweeps along the part to capture the complete surface of the part. The problem of missing data on free-form, irregularly shaped complex parts like the surface of the propeller blade is greatly reduced. The scanning system measures fine details and captures complex geometry so that the propeller could be exactly replicated. Laser scanners quickly measure components, picking up tens of thousands of points per second, and generating huge numbers of 3D data coordinates without the need for templates or special fixtures.

The results of the 3D laser scan of the full size outboard motor propeller would be adjusted for a 1:4 scale model and used in a stereolithography (STL) process, to “3D print” a precise pattern to make a mold of the part.  This mold would be used to spin-cast the model propeller in metal.  Spin-casting uses silicone rubber molds capable of casting tin-based alloys, zinc-based alloys, and urethane resin.  While the mold is spinning, metal or resin is poured into the center of the mold with centrifugal force filling the radial mold cavities.  This process uses low-cost molds and produces high-quality castings, perfect for scale models.

Solution:

GKS performed a 3D laser scan of a full-scale propeller from the outboard being modeled. The Laser Design Surveyor WS-2030 with the SLP-250 ultra-accurate laser probe was used to capture the curves and details precisely.  The propeller was set up on a rotary stage so that it could be scanned from every perspective to create a complete 3D model. The GKS engineer commented, “Having the ability to scan the part from several angles allows us to capture all the geometry in one set-up versus two or three repositionings of the part.”

The set-up and scanning process took under an hour, and the point cloud processing to the STL file format took another 45 minutes with Geomagic Studio 10.  The GKS team edited the insides of the small holes on the STL file using Geomagic Studio because the laser could not “see” the entire bottom of the hole during the scan.  When data is missing from a model, Geomagic can re-create the features, like these small holes, to an exactly designated size within the software.

“I received the STL data in less than a week and the cost was far less than the machining and fabrication time in my shop,” commented the owner. “I worked with the STL file supplied by GKS and scaled it down using Rhino 3D Modeling Software.  Once satisfied with the scaled 3D computer model, it was exported and sent to a 3D printing service.” 

If the model company had manually measured the propeller, it would have taken them many days or potentially even weeks to gather enough data points to create a model accurately representing the propeller.  GKS delivered the STL file in a few days.

A scaled part was made from the STL file using a 3D printing process. Small imperfections in the 1:4 scale part were filled in, sanded, and painted to provide a smooth finish.  The part was then used as a pattern to produce a mold cavity in a RTV (room-temperature vulcanized) silicone rubber spin-casting mold.   Once the mold was cured and processed, it was used to produce spin-cast Britannia metal parts.  

Results:

The company owner remarked, "The use of 3D laser scanning from GKS Inspection Services cut the labor cost of making the tooling for this part substantially since there was less CAD/CAM/CNC time involved. … The service provided by GKS was rapid and of excellent quality.”

The GKS engineer commented, “The high-accuracy SLP-250 laser probe was able to pick up excellent detail on the sharp edges of the propeller blade, providing very clean results. Because the laser scanning system projects a line of laser light on to surfaces, problems of missing data on free-form irregular surfaces are eliminated.  The SLP-250 accurately scanned the propeller providing a data file requiring minimal post-processing.”

“The technology GKS provided with their laser scanner saved me valuable time and produced a superior part for my customer,” concluded the owner.

More Informtion about GKS

GKS Inspection Services has been a leading provider of dimensional inspection, 3D laser scanning and terrestrial scanning services for over 25 years.  The company’s Plymouth, MI lab (Detroit metro area) is accredited by the A2LA for Mechanical Testing and Calibration and features numerous CMMs, vision systems, 3D laser scanners, surface analyzers and other inspection equipment.

For additional information about GKS Inspection Services, call 734-357-5229, send e-mail to measure@gks.com.