A 3-D comparison in Geomagic Qualify shows deviation between the sand mold, the casting and the resulting part. ITT Goulds Pumps calls this the “eureka moment,” as the analysis filters out everything but the variation, which is what most interests quality engineers. Source: Geomagic
Like most other companies obsessed with quality, Six Sigma and other proven methodologies are essential at ITT’s Goulds Pumps Division (Seneca Falls, NY), a pump manufacturer in business for more than 150 years.
But when it comes to implementing new technologies, Robert Kilmer, product engineer with Goulds, sometimes veers off the beaten path. Kilmer has found that digital shape sampling and processing (DSSP) based on Geomagic (Triangle Park, NC) software is a critical ally in opening up new and productive ways of analyzing product quality.
DSSP describes the use of 3-D scanning technologies to close the loop between physical products and their digital representations. The key DSSP component for Goulds is Geomagic Qualify, computer-aided inspection software that enables operators to perform a complete inspection of every type of shape and feature that characterizes an object, saving time and increasing inspection accuracy.
“DSSP using Geomagic has opened up new areas of learning and investigation,” says Kilmer. “It has made my job more pleasurable because when we make that breakthrough, it’s very satisfying.”
During the past few years, Goulds has had its share of breakthroughs, including new processes to improve impeller balance and determine foundry process variation.
A 3-D analysis of an impeller in Geomagic Qualify used by ITT’s Goulds Pumps to assess rotational symmetry. Source: Geomagic
Throwing Out the Book
During the project to improve impeller balance, Kilmer and his team deviated from standard practice that combines DSSP with computer-aided design (CAD) for quality assurance.“We took a big departure from the conventional approach outlined in recent publications,” he says. “All processes seem to start or end with a CAD model. We threw that book out the window and we only use the Geomagic models-there are no CAD models used or created anywhere in the process.”
Precision balance of impellers affects the operation and lifespan of every pump. The challenge for Goulds was to reduce the time to balance impellers and increase material flow.
The standard DSSP method called for Goulds to scan the impeller, convert it from point clouds to polygons to non-uniform rational basis spline (NURBS) surfaces in Geomagic, and measure solids’ properties in Pro/Engineer. Kilmer’s team tried that and even though it only took hours-compared to the days it would likely take using CAD alone-it was too long for Goulds.
“For the purpose of understanding the factors that affect balance,” says Kilmer, “this took too long, particularly considering the large number of impellers we wanted to study.”
A comparison of a pattern tool and the sand mold made from the tool reveals that the two are not identical, shattering conventional wisdom. Source: Geomagic
From Hours to Minutes
The process that Goulds came up with is deceptively simple, and takes about 10 minutes for each impeller. Scans of the same impeller are imported into Geomagic Qualify twice, so that two copies of the scan exist in the same 3-D space. Within Qualify, one object is rotated 180 degrees, and then a procedure called “fine adjustment best fit” is performed on the two copies. After that, a 3-D comparison is made. Differences that affect balance are visible immediately.At the time of this project, Goulds was analyzing around four impellers a day, so the accumulative timesavings during the course of a month using the new process amounted to several days. Those savings multiplied during the life of the project, which lasted about 18 months.
“It’s a very simple process that reflects the essence of what we need to measure: rotational symmetry,” says Kilmer. “The underlying message is that DSSP can have significant value for companies and industries even if they don’t rely on 3-D models.”
The greater volume of analysis in less time leads to faster learning curves, according to Kilmer. “Trends are more observable when you can look at many units in succession as opposed to one at a time,” he says.
Besides speed, the new process delivered the ability to differentiate between casting-induced unbalance and machining-induced unbalance.
“This is unprecedented,” says Kilmer. “We learned that machining-induced unbalance is relatively uncommon, but there is a big advantage in seeing and demonstrating it when it does happen. We are now able to use Geomagic Qualify visualizations to improve our suppliers’ machining processes and optimize part balance.”
This 3-D map shows the wall thickness of an impeller. In this case, the bottom is slightly thicker than the top section. Source: Geomagic
A Breakthrough in Wall Thickness
The ability to identify wall thickness variance is another big breakthrough for Goulds. Variations in wall thickness are caused by differences in the shapes of the casting, mold and pattern tool. Comparing scans of these three related objects within Geomagic Qualify enables Goulds to pinpoint the magnitude and source of variations. The process is so accurate that it can measure small differences in wall thickness due to molten metal flowing into and filling sand molds.“Qualify clearly shows that sand castings are not necessarily perfect replicates of the molds from which they are produced,” says Kilmer. “We can now measure variation and its source down to a level at which it is not economically viable to reduce any further. There is a huge value in knowing that we can control all important factors and be aware of other factors that we might not want to control for cost/benefit reasons.”
The ability to quickly and accurately make direct measurements and comparisons of wall thickness has extended to other projects at Seneca Falls. For example, it is helping to uncover potential production issues with older pattern tools that do not have associated 3-D models.
“We can scan the tooling pieces, assemble them electronically in Geomagic Qualify to create a polygon model of the casting, and then compare the model to a scan of an actual production casting,” says Kilmer. “Using several Qualify analysis processes along the way, we can identify all possible tooling issues and differentiate them from process-induced issues.”
Pervasive Quality Impact
Kilmer says that although many of the benefits of DSSP are difficult to quantify by numbers, they are nonetheless concrete.“The biggest qualitative measure is our reliance on these technologies throughout ITT’s Goulds Pumps,” says Kilmer. “DSSP with Geomagic Qualify has allowed us to see foundry process variation that we could not see previously because of the complex geometries required for hydraulic designs. We can also ‘see through’ the complexity of the pattern tooling and the sheer number of factors that influence foundry operations. With DSSP, we can focus our efforts on the factors that directly influence the quality of our castings.”
Kilmer points out one other qualitative measure: ITT awarded the Seneca Falls Foundry the Gold Ring of Quality, the highest quality recognition within the company.
“It is due in large part to lots of hard work by the foundry staff,” says Kilmer, “but I also believe that DSSP contributed to that award.”
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