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One of the biggest challenges of machining parts for off-road and civil construction equipment is the sheer size of the parts themselves. Their unusually large dimensions often go beyond the work planes of standard machining centers, requiring manufacturers to create work-arounds that are less than optimal in order to complete the job.
K-Fab, Inc. (Berwick, PA), was one of those manufacturers. The company, a 350-person general machine and fabricating shop that serves as a sole source manufacturer for a variety of industries, had seen its large construction parts manufacturing business increase over the past few years.
Yet it still had to machine those parts using a two-step operation on a small horizontal machining center. The company would initially machine two sides, and then turn the piece to finish the two remaining sides – a solution that was less than ideal.
"Being able to work only two sides at a time is a very time-consuming and labor-intensive process, especially on parts this large," says Randy Barnes, a manufacturing engineer at K-Fab. "Performing the set-up and machining twice would take us an hour and a half for a single piece. In a shop that’s running at full capacity 24 hours a day, seven days a week, that’s an eternity."
K-Fab knew that a larger horizontal machining center would be the answer, but they weren’t happy with the quality of the machines available. In early 2008, John Watkins and Mike Christ of JBM Technologies, an East Coast distributor, notified Barnes that Kitamura Machinery was introducing a new machine that seemed tailor-made for K-Fab.
It was the Mycenter HX1000i, a large horizontal machining center with a work table area of 39.37 in x 39.37 in that could accommodate work pieces as large as 80.81 in x 61.02 in. They said it also provided X-axis travel of 80.31 in, Y-axis travel of 51.97 in, Z-axis travel of 53.94 in, and had a fourth B-axis with a travel of 0 to 360 deg in one-degree increments.
"As soon as I heard it was coming out I said ‘we need one of those,’" Barnes remembers. "We purchased one of the first ones that was built, without even seeing a sample, because we were so confident it would do what we needed it to do." Part of the confidence in buying blind was driven by the company’s past experience with this brand of machines. K-Fab uses this brand exclusively in the shop and is familiar with their overall quality and construction.
"These machine tools use solid boxway construction, which is a lot more rigid than linear machines," explains Barnes. "It’s a little more expensive, but it makes a huge difference when it comes to precision and stability, which is important when building large, heavy-duty parts. This equipment also has gear-driven spindles that allow you to develop high torque at low rpm for the tough jobs. Our HX1000i can go from 8,000 rpm all the way down to 20 rpm if we need it to – and we do, from time to time."
Since bringing this machine tool online, K-Fab has been able to reduce cycle times on large parts by as much as 75 percent – even on large, high-durability parts manufactured from difficult to cut materials such as A572 grade 60, 80 and 100 structural steel. That’s four times the productivity they were previously achieving at that station while maintaining or even improving quality.
GET WHAT YOU PAY FOR
The solid boxway construction is a little more expensive than linear machines, but is much more rigid. That pays off big time in the precision and stability needed to build large, heavy-duty parts.
The plant has also seen its rejection rate drop to "statistical anomaly" levels. Currently less than one percent of all products produced on these machining centers are rejected, allowing the company to maintain its reputation as a quality supplier while not tying up machines on reruns. In fact, Barnes believes this success rate is as high as it can be. "There’s always the possibility something can go wrong," he notes, "but it’s rare. And when it does happen, it’s usually something in the materials, rather than the machining."
These machining centers have also impacted the bottom line in other ways, including capturing work that was previously being sent overseas.
"We’ve had work come back to us that was initially going to China," Barnes adds. "Also, one customer who was considering moving parts there ran the numbers for a comparison, including the expected rejection rates. When it was all said and done, he said it would be less expensive to do the work with us than to send it to China. That’s a great feeling."
K-Fab, Inc., 1408 Vine Street, P.O. Box 345, Berwick PA 18603, 570-759-1247, Fax: 570-759-0150, www.kfabinc.com.
JBM Technologies, 60 Vincent Circle, Ivyland, PA 18974, 215-672-8878, Fax: 215-672-8828, jbmtechnologies.com.
Kitamura Machinery, 847-520-7755, www.kitamura-machinery.com.