Free-form Rifle Stocks Reverse Engineered Quickly with Portable System

The Company: 

Keystone Sporting Arms, LLC, located in Milton, PA, is the fourteenth largest producer of sport rifles and rifle parts.  It prides itself in the excellent quality of its rifles and its tradition of promoting safe gun handling practices in its customers.

The Challenge: 

Keystone Sporting Arms started out as a service bureau customer of GKS Inspection Services, a division of Laser Design, Inc., when they were expanding their line of aftermarket rifle stocks. A new stock model had a more involved free-form shape than previously and they needed accurate and complete CAD data in order to mill the shape precisely. They took the GKS-produced CAD model straight to their MasterCAM system to make the new stocks.

Steve McNeal, Keystone Sporting Arms owner remarked, “GKS Inspection Services provided excellent 3D data from which to manufacture the new stock shape.” GKS Service Bureau Manager Larry Carlberg added, “Keystone was very impressed with how good the scan data was for processing into machining files using MasterCAM.  Their engineers examined the model and said they had never seen such good data from reverse engineering of parts.”

Around this time, Keystone acquired another rifle stock maker and wanted to continue producing their legacy models.  However, the defunct maker did not have CAD models of their stocks.  Keystone had already invested heavily in the machining equipment and needed to be able to quickly generate CAD data from scanning a master model of the stock. 

McNeal knew that laser scanning with the Laser Design system was able to produce excellent results to reverse engineer rifle stocks. He commented, “Laser scanning is well suited to creating CAD models for parts that have none.” Since they had many ongoing data acquisition projects, McNeal decided to purchase a portable Surveyor FA-Series scanner from Laser Design and bring the scanning work in-house to facilitate more flexibility and even greater speed in their design engineering work.  He also hired a scanning technician to scan the existing models and create new CAD data which could be used to generate the needed CNC toolpaths.  As an added benefit to Keystone, although the company now owned the system, GKS would still be available as a valuable support resource to them, especially for difficult projects.

The Solution: 

The Laser Design FA-Series 8-foot 7-axis Faro Platinum Arm was installed at Keystone Sporting Arms with Laser Design’s high-accuracy SLP-330 laser probe, and work was begun on scanning the 24 previously undigitized gun stocks.  When an object is hard to measure manually or with a touch probe due to its irregular surface contours, non-contact 3D laser scanning can produce accurate CAD data very quickly.

“The Laser Design – Faro arm system gives good scan data,” commented the scanning technician.  The scan setup for rifle stocks was quick and easy.  Only two full passes were needed to capture the majority of the gun stock geometry—first one side, then the other, plus the ends.  The portable 8’ Faro arm and laser probe scanning system allows scanning from all perspectives.

Scanning free-form shapes and irregular surfaces, such as curved gun stocks is an ideal application for a non-contact laser scanner on an articulating arm. Because the scanning system 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 problem of missing data on an irregularly shaped surface is minimal. The operator moves the laser line back and forth over the area until the complete surface is captured. The capture progress is continuously monitored by the operator on the computer screen. The system measures details and complex geometry so that the object can be exactly replicated digitally. Laser scanners measure articles quickly, picking up to 75,000 coordinate points per second, and generate huge numbers of data points without the need for templates or fixtures.

Most of the gun stock had a smoothly finished surface which produces excellent scan data with an accuracy of 25mm. The front end of the stock, the “leading area,” which is a rough wood grain, needed sanding to yield more usable 3D data.  A feature that was somewhat challenging to scan was a 1-½”hole in the stock. To capture the sides and bottom of the hole the scan technician positioned the laser directly over the top of the hole so the laser could “see” the bottom, then at a 45-degree angle for the sidewalls.

The raw scan data contained over 18 million data coordinates.  This enormous point cloud file was edited and the surface model was created using Geomagic Studio 10.  It was then exported to Master CAM as an IGES file to create the CNC toolpaths.  From start to finish, the project took only three hours for the scanning, data editing, and exporting to MasterCAM. 

The Results: 

According to owner Steve McNeal, “The work is going very well.”  The scanning process is fast, and exporting directly to Master CAM for milling is extremely efficient as well.  To maximize the quality of the data, the scanning technician carefully prepped and set up the rifle stock.  The result: “It turned out great,” he observed. He has been able to call upon the experts at GKS to help him create crisp well-defined edges and corners in the data files which is key in their reverse engineering process.

Keystone Sporting Arms has reproduced one model from scan data so far, and with it manufactured hundreds of stocks.  The quality and faithfulness of the reproduction is excellent.  As more of the stocks are scanned and experience is gained, the procedures will get even faster.  Eventually, the company wants to outsource creating the CAD models in MasterCAM; at that point, the data files will be absolutely perfect. In the meantime, being able to manufacture their rifle stocks rapidly and economically with the help of the Laser Design 3D laser scanning system is definitely a boon to Keystone’s business.

About Laser Design and GKS Inspection Services

Laser Design, Inc. and GKS Inspection Services has been the leading supplier of ultra-precise, 3D laser scanning systems and services for over 20 years.  Used for capturing the 3D shape of objects with complex geometries and free-form surfaces, Laser Design’s Surveyor line of automated and portable scanning systems are ideal for 3D scanning applications involving inspection and reverse engineering of complex shaped plastic and metal parts.  The company’s patented laser line-probe technology dramatically reduces scanning time by collecting data substantially faster and more accurately than conventional metrology technologies.  For more information contact us.