High-Density Vises Reduce Part Machining Costs by 65% for Clutch System Component
Four Vises Hold 40 Components for Highest Density Machining
LITTLE FALLS, Min.—Super Torquer Systems, Inc., was able to reduce part machining costs by 65 percent recently by combining the benefits of an effective workholding setup with some intuitive process planning by the company's owners, Randy and Cindy Nouis. On the workholding side of the equation, Super Torquer utilized four Kurt HDM6 double station vises, mounted side by side on a vertical milling machine and utilizing quick change jaws. One might say it's an example of how the virtues of high-density workholding were made even better by a husband and wife team looking for the most cost-effective way to machine precision components.
The machined parts are critical components of the very popular and patented Heel Clicker Clutch weight used in snowmobiles and all-terrain vehicles. Randy and Cindy Nouis designed the clutch parts, which received a huge industry response that required them to develop the manufacturing output to meet demand. Unique and high-performance by design, the Heel Clicker kit has an exclusive, dual-quadrant flyweight design that transfers engine power into the highest horsepower output of any clutch kit currently on the market. "The Heel Clicker kit adds 20 percent more power to the average snowmobile," reports Randy Nouis, "and has become the clutch kit of choice by most leading snowmobile and ATV manufacturers."
As a new startup company, Super Torquer had to devise ways to manufacture and assemble its new clutch design in varying quantities to meet a range of vehicle sizes and applications. The clutch weights are used in snowmobiles built by Polaris, Arctic Cat, Yamaha, Kawasaki and Bombardier. The husband and wife team (and only employees of the company) decided to develop their own precision machining capabilities to improve quality, reduce costs, and control part inventory.
Both Randy Nouis and Cindy Nouis are degreed mechanical engineers with over 14 years of experience each with General Motors Corporation/Delphi Corporation. While short of hands-on machining experience, they were confident that they could develop a cost-effective machining process that included a workholding setup and machine programming to easily handle the broad platform of clutch components for their customers. As it turned out, the machining process improved turnaround time, quality, and profitability of the clutch product line.
Four-Vise Setup Provides Flexible Platform for Handling Irregularly-Shaped Parts
"We knew we could improve our machined part quality and turnaround time if we had the right equipment," said Randy and Cindy Nouis. "We settled on a new Hurco model VM1 vertical machining center and looked at various workholding options, including standard vise products and custom fixturing. We contacted our local Kurt sales representative, Mike Neeley, for his workholding recommendations, thinking that custom fixturing would be the answer."
For a more cost-effective and flexible alternative, Neeley suggested Kurt Manufacturing's HD vises, which provide many of the benefits of custom workholding but are far less costly. With carvable and changeable jaw options, they are well-suited for holding large and small, irregularly-shaped parts with high clamping rigidity, in line with the requirements for Super Torquer's products. After studying product prints, as well as tolerance and quantity requirements, Kurt's engineers recommended equipping the machining center with four Kurt HDM6 vises with machinable ductile iron jaws.
The key clutch component for machining in this setup is a continual variable transmission (CVT) flyweight or clutch cam arm. It is machined out of high carbon steel. The cam arm controls and distributes engine rpm into torque. A typical clutch arm measures 1 inch x 2 inch x ½ inch, with contoured precision surfaces. Each cam arm has a tapped and threaded hole and is matched in trios and quads to one-tenth gram weight. Critical surface areas must meet ± .001 tolerances to function properly—a challenge to machine but not rocket science.
The initial justification for the recommended setup was that four Kurt HD twin station vises provided high density for holding four of the cam arms per vise. These vises also provided a flexible platform using machined, changeable jaws for holding and machining other components in the clutch weight assemblies.
Maximizing Vise Clamping Station Real Estate
When the Nouis team started to plan the changeable jaw setup for the four vises, they saw an opportunity to really maximize the productivity of the setup. Conventional wisdom would have individual cut blanks inserted into the carved vise jaw pockets for a sequence of machining operations. Sequentially, machined components would be removed, repositioned, and reclamped individually in each adjacent vise, machining different part sides in all four vises in a series until parts were completed, eight per cycle and removed completed from the fourth vise. In a conventional sequence, unfinished blanks are inserted as finished ones are removed, thus keeping all 32 clamping stations loaded and progressively moving through the machining process.
However, with the Nouis team, conventional wisdom doesn't apply, and that's where the virtues of the multiple Kurt HD vise setup got even better. Instead of machining 32 individual cam arms in the four vises, they upped the number to 40. They accomplished this by using solid 2-½ inch x 1-¼ inch x ¾- inch, high-carbon steel blanks, each blank yielding five finished parts. Jaws are designed with datum points, so the blanks align exactly the same in each of the four vises, insuring part repeatability. Working left to right, the blank is inserted in the farthest left vise with the jaws carved with pockets to accommodate it. Jaws in vises two, three, and four also are custom carved to align and hold the semi-finished part as it progresses through the machining process.
Ninety-five percent of the machining for most of the cam arms is end milling on 3 sides, with the remainder drilling, reaming, and tapping with accuracy to 0.001 inch. A full cycle of 40 cam arms is completed in just under 20 minutes. Lot sizes average 3000.
What's really clever about this approach is that the work blank remains a solid piece until the end of the machining cycle in the fourth vise. At that point, the five individual cam arms are cut apart and finish machined and removed from the vise.
Another clever aspect of this process is that adjacent cam arms are machined at one time by the same ½-inch end mill. Staggered and located closely together, the parts align in a tight pattern to allow simultaneous end milling on two parts. Much is accomplished doing it this way, including machining at a top speed of 10,000 rpm, minimizing spindle travel part to part, and reducing individual part handling and load/unload operations while maximizing all machinable area on the components held in the vise jaws.
Vise Rigidity an Important Factor in Clamping Repeatability
When held in conventional vise setups, small and relatively narrow parts that are made of hard materials, such as Super Torquer's high-carbon steel, tend to creep upward during aggressive machining operations. Tight tolerance is lost and scrap parts result. Not so with Kurt's HD vises, the manufacturer says. The Anglock® jaws are said to prevent parts from creeping up and misaligning. Also, the vise bodies and jaws are made of durable 80,000-psi ductile iron, which provides rugged strength, rigidity, and long-term accuracy while absorbing machining vibration. Four of the vises (each 13.750 inches x 6 inches) lock solidly to the Hurco 30-inch x 14-inch machine table above its rugged 6,200-lb solid frame and are integrated as a single, immovable unit. With clamping force up to 5556 lbs at 70 foot lbs of input torque, these vises are said to provide repeatable accuracy to 0.0002 inch, well within the Nouis's tolerance requirements.
Credit Cindy Nouis for Creating the Innovative Machining Programs
Their strong work backgrounds in design and manufacturing have given Randy and Cindy Nouis an excellent understanding of manufacturing processes. And as engineers, the Nouis team understood the capabilities of their machining center and its potential when equipped with the four Kurt HD vises. It was another matter getting it to operate the way they envisioned, and that's where Cindy Nouis's previous computer skills and outside machine programming training made the difference.
"Basically, we were working on a clean sheet of paper, not having seen this done before," stated Cindy Nouis. "Also, it was new to Kurt and they urged us forward when they saw its potential. I read programming books, took classes, and did some trial and error programming. We planned each clamping station in such a way that all sides of the vise jaws are carved to hold various size part configurations, thus maximizing the available clamping area of each vise jaw. The staggered part pattern also allowed us to machine five cam arms in each vise, where originally there was space for only four. Once set, the part programs were reverse engineered for carving each of the jaw clamping stations. We carved the ductile iron jaws ourselves, so nothing was lost in the translation."
For information about Super Torquer capabilities, log on to www.heelclickerclutching.com.
For more information about Kurt workholding products, visit www.kurtworkholding.com.
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