Twin Kurt Vise Setup Clamps 1500 Lb. Hammer Dies Vertically For Precision Machining
-- Setup Time Reduced By 50 Percent Over Dedicated Fixtures At Impact Forge, Inc.
Columbus, Indiana: Impact Forge, Inc. is an innovative forge group of four companies offering a broad range of forging technologies with an ongoing commitment to improving its manufacturing processes. One of its offerings includes the production of hammer dies requiring large milling operations. Positioning and clamping these dies in a machining center is a challenge because they are heavy and bulky.
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| 1500 lb. Hammer die clamped vertically in twin Kurt Model 640XLS vises for precision machining in Okuma horizontal machining center. |
Front view of completed hammer die in the side-by-side Kurt vise setup, which replaces expensive custom fixturing. |
Weighing up to 1,500 lbs. and ranging in size up to 24 inch x 26 inch x 12 inch, positioning the dies in a machining center fixture requires an overhead crane and skillful maneuvering so as not to damage the part, fixture or machine. Holding and clamping these dies are equally challenging with most manufacturers relying on some form of custom built fixtures that are designed with the right amount of mass and clamping points to securely hold the die through long and complex milling cycles. Standard, off-the shelf holding devices such as vises traditionally were not considered a practical method for positioning and clamping the hammer dies. That is until Impact Forge decided to look for a better alternative to its expensive, custom holding fixtures.
Impact Forge Challenges The Use Of Traditional Custom Fixtures With An Innovative Use Of Kurt Vises
Founded in 1986 as a "greenfield" startup by six owners/managers, Impact Forge has prided itself in leading the way with ever-improving processes and higher quality. For example, Impact Forge was one of the first 300 companies in the world registered to QS-9000 (ISO 9002: 1994/ QS-9000: 1996) and all of its four companies have been recipients of the prestigious State of Indiana Quality of Excellence Award. These lofty achievements have been possible because the company constantly challenges its workers to find new and better ways to improve quality and productivity. In the area of workholding, it saw an opportunity to reduce setup time while increasing finished product output.
"Our custom fixtures worked well enough but they were slow to setup," reports Doug Lynch, applications engineer of Impact Forge. "We wanted something we could buy out of a catalog and looked into different types of vises as well as modular fixturing. There are a lot of standard products out there and we wanted to investigate all of the alternatives to see if we could reduce die setup time while reducing the front-end costs for these fixtures. We also saw our hammer die volume expanding, so we wanted the most cost-effective workholding solution so we could replicate it in a similar, second machine setup."
Impact Forge settled on Kurt because, as Lynch describes, "They offer a lot of vise sizes, plus we were familiar with the heavy duty Anglock design for accurately centering and gripping heavy parts for machining."
Under 10 Minute Setup Time Beats Old Method By 50 Percent
The vises chosen were two Kurt 640 XLS models, which have an open jaw capacity up to 14.00 inches, well within Impact Forge's capacity requirements. Also, all sides of these vises are machined accurate to within .001 inch for precise alignment in the type of setup Impact Forge has. Mounted vertically on a die plate, the jaw openings of the vises also provide a clear path for the hammer die as it is lowered and moved into the jaw openings by the overhead crane.
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| Two of these Kurt 640XLS vises are used in Impact Forge's setup. All sides of these vises are accurate to .001 inch for precise, easy alignment in multiples. |
Drawing shows how the two vises are mounted vertically on a subplate. Note the round dowel in the center, which acts as a locator for the hammer die when positioned in the two vises. |
"The crane picks the die up on its side and lowers it into the dual vise fixture," reports Lynch. "A round dowel centered between the two vises acts as a locator, which matches up with a dowel pocket in the hammer die, guiding and centering the die in front of the two vise jaw openings. Once moved into the open jaws, both vises are tightened manually by the operator who then drops the load and retightens, then removes the crane from the machining center work area. At this point the milling operations begin. With the old custom fixture, positioning the die was more difficult with several knobs to adjust and tighten in order to get everything aligned just right. The new way is easier for the operator and 50 percent faster. The machine operators really like the way the vises work."
Lynch said he considered hydraulic clamping for the setup because it would "remove some of the human element and chance for error from the setup operation. We decided against that route because hydraulic failure could cause a heavy die to come loose from the fixture and fall into the machine. The manual vise setup is simple enough for our machinists to operate plus we get all of the clamping force needed to hold the dies securely. And the setup has worked without a problem for over two years."
Vise Setup Is The Ultimate Strength Test Of The Anglock Clamping Design
Delivering up to 6,877 lbs precision clamping force, the Anglock design actually helps to automatically position the die in the vise jaws. As clamping force is applied, the die is pushed down and onto the base, which also aligns it accurately. The Anglock design also resists any tendency for part lift during milling. And the 80,000-PSI ductile iron vise body provides stability so possible chatter or vibration is eliminated from the process.
"Holding a die vertically that weighs up to 1500 lbs for several hours of continuous machining is the ultimate test of the Anglock design," reports Lynch, "and it's really stood the test with flying colors."
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| Anglock design works equally well in vertical or horizontal position. It clamps with up to 12,000 lbs precision force to securely hold very heavy parts like Impact Forge's hammer dies. |
Kurt's Model 640XLS has large jaw capacity of 14 to 18.70 inches |
The machining center used is an Okuma MA60H, a good choice for Impact Forge's requirements. The system has feeds and speeds of 150 inches a minute with the spindle turning up to 12,000 rpm. Roughing the larger areas with 3 inch face mill 50 inches a minute 700 rpm, this is where the stiffness of the fixture is put to the test. Most operations are finish milling all done using 1/8 inch to 1 inch ball cutters with carbide inserts in the larger sizes. One to one-half hammer dies are completed per 8 hour shift with the system operated 24/6.
"We're really pleased with the results of the change to Kurt vises from custom fixtures," reports Lynch. "We're maxed out with the present system, so we're on our way to installing a second machining system with a similar Kurt vise setup.
For more information about Impact Forge products, visit www.impactforge.com. Or call 1-812-342-4437.
For more information about Okuma products, visit www.okuma.com Or call 1-704-588-6503.
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