Gunmaker Blasts Scrap Rates

Gunmaker Blasts Scrap Rates

Smith & Wesson significantly reduced scrap rates for its .44 Magnum revolver product line.


Smith & Wesson scans its forged handgun frames with a Romer laser scanning system, then using PolyWorks software produces a color map denoting varying degrees of deviation.


Shop forgers easily spotted irregularities or mismatches using hand-held measuring tools, keen eyes and years of experience, but often, small nuances undetected by the human eye would slip by. That resulted in scrapped parts that weren't found until subsequent manufacturing operations. To remedy the situation, Smith & Wesson (www.smith-wesson.com) installed an integrated industrial inspection system.

Since it deployed the inspection system, the company's forging area significantly reduced scrap. "Our goal in this department is to get our scrap rate down to almost nothing," said Joe Dombkowski, forge manager at Smith & Wesson. "Just a few years ago, our scrap per unit produced was 12 cents. We have since lowered that to 2 cents per unit produced. Percentage wise, we have made substantial progress due to the new inspection system together with the experience of our forgers and better practices in place to spot possible problems."

Smith & Wesson's inspection system consists of a Romer Inc. (http://us.romer.com) Laser Scanning Inspection (LSI) unit and the PolyWorks point-cloud processing software from InnovMetric (www.innovmetric.com). Smith & Wesson first applied the system to its .44 Magnum revolver product line, the line that generated the most scrap. The company said the system makes its forging process visible down to the tiniest deviation.

A separate room directly off the forging area houses Smith & Wesson's quality assurance operation. Along with the LSI unit and a laptop computer loaded with the PolyWorks software, there is a Romer Infinite 7-axis portable coordinate measuring machine scanning arm and a Perceptron laser scanner. This combination of articulating arm measurement with laser scanning enables maximum workpiece-surface inspection.

The non-contact scanning system acquires more than 23,000 points per sec for detailed inspection of both geometric and surface features. The setup also allows for point data capture with contact probes when needed, and the Infinite scanning arm measures within an 8-ft work volume. To reduce operator fatigue, the articulated carbon-fiber arm functions with a low-profile, ergonomic Zero-G counterbalance for one-handed operation.

Resting on a solid granite plate mounted to a rolling cart, the LSI system easily moves anywhere within the Smith & Wesson factory. Near the Romer arm, an ordinary clamp fixture holds handgun frames for the scanning procedure, and integrated Wi-Fi communication during the touch probe mode adds to system mobility.

While typical forging tolerances at Smith & Wesson are 0.020 in., the Romer inspection system delivers measuring accuracies to 0.002 in. The laser scanner's accuracy runs at 50 microns, and the articulated arm with a probe is 25 microns, for an entire system spec accumulating to 75 microns.

The main component of a Smith & Wesson revolver-style handgun is a carbon steel frame forged in lots of 500 to 1,000 at a time. Before each of the shop's three work shifts begins a frame production run, forgers conduct a sample run of 5 to 10 pieces then walk a cooled setup frame to the inspection room where the part is mounted in the holding fixture for scanning.

Inspection technicians orient the laser scanner perpendicular to the part and, within two or three scans and in less than 5 min., digitize the entire surface of the part. The scanning motion used by the technicians resembles spray painting movements, and as data is captured, a dense 3D point cloud appears on a computer screen. Audio cues guide technicians during scanning routines to ensure the results are valid.

At this point, the inspection template automates a 5-point process — align, inspect, output, create a PDF file and send to file folder. Technicians use a 3D solid model of the handgun frame as a reference model for new forgings. Once the solid model is imported into PolyWorks, the software's IMAlign module evaluates the point cloud and creates a PSL file, data then is aligned roughly to the CAD file.

The software macro pulls up key reference points for precise alignment of CAD model and scanned part, then creates inspection points.

The PolyWorks IMInspect module analyzes both sets of data and generates a visual 3D roadmap that is colored to denote varying degrees of deviation. In Smith & Wesson's case, if the forger sees a predominance of red and green areas on the model, he gives the ok for the department to run handgun-frame production.

According to Smith & Wesson, a forger can look at the visual 3D model derived from the CADcompare analysis and quickly make a pass or fail decision 99 percent of the time. Every hour, forge personnel pull three parts for dimensional checks on five inspection points in critical areas of the frame. After heat treating and coining processes, technicians once again inspect frames prior to machining.

Nick Shah, manufacturing engineer at Smith & Wesson, said that his people can interrogate parts in PolyWorks in ways that they were never able to do before. They analyze 18 calipers, 6 cross sections, and 12 mismatch points among other inspection functions. They also can dissect parts and conduct GDT and primitive checks. Eventually, the company plans to build similar quality-assurance templates for all models of its semi-automatic-type pistols.

Shah worked with Vincent Tiernan, senior metrologist at Measurement Solutions Group (www.measurementsolutionsgroup.com), to devise the powerful intuitive inspection routine that captures, aligns and analyzes scanned data from a handgun frame then compares it to the related 3D CAD file. The two also developed the virtual fixture that aligns frames to the same positions as they would be machined.

In addition to its forging operations, Smith & Wesson plans to expand inspection into its handgun-frame machining operations. The company's goal is to pass to the CNC machining process a frame that is within 0.001 in. or 0.002 in. of the allowed machining window tolerance. By doing so, the shop hopes to eliminate waste and reduce material usage on forgings while reducing machine run time and tool use and while increasing production output.

The key to the integration is to create virtual inspection-fixture reference points and critical points for replicating the fixture used in machining. Three bedding points on the frame are critical for troubleshooting, and locating the frame properly via these points should eliminate problems for machinists. On the other hand, if those holes are not properly drilled, the problem is compounded downstream, and at the end of the day, if the critical datum was in the wrong place, the part is scrapped.

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