Short-run, close-tolerance work for medical or aerospace parts is there to be had by manufacturers that can meet the performance requirements.

For KBK Tool & Manufacturing Inc. (Skokie, IL) that meant finding the right equipment to do what its conventional equipment could not do by reaming or boring, i.e. hold total tolerances of 0.0005'' (0.0127 mm) on shallow bores 0.1125'' (2.86-mm) deep and 0.375'' (9.53-mm) diam.

Owner Ken Hedeen explains: "I really wanted to do these bores with an end mill and interpolate, but couldn't do it with our present equipment. So I began to consider new equipment to tackle this type of work."

For more than two decades, KBK has specialized in CNC milling arjd turning of basically any type of material, including stainless steel, carbon steel, aluminum, heat-resistant steel, titanium, and plastic. "Just about anything that's machinable," says Hedeen.

Right now, KBK's business mix is about 75% medical, 15% aerospace, 5% office equipment, and another 5% miscellaneous work. The company's capabilities extend from prototyping to volume production with the ability to meet military specs for heat treating, welding, lapping, NDT, painting, and finishing.

For its medical device customers, the company produces about 70% of the machined parts that go into medical diagnostic equipment and surgical instruments. "These kinds of customers expect and require very close tolerance, ultraprecision parts and are pretty uncompromising," says Hedeen.

KBK selected a Bridgeport 760 XP^sup 3^ VMC from Hardinge Inc. (Elmira, NY) to meet the demanding machining required of it. "At the beginning of my search for a machining center, I was unaware that Bridgeport offered such high-end solutions with their XP^sup 3^ line."

KBK needed the new machine right away and didn't have time to look through the manuals thoroughly to become familiar with machine capabilities. The new 760 XP^sup 3^ was put to work making parts and holding the tolerances it promised.

"My programmer came up to me and told me he is holding true position of 0.001'' [0.03 mm] and that he programmed the first part and it came out perfect. He'd had to make no adjustments whatsoever, and, in all his years of programming experience, he had never been able to do that," Hedeen says.

Once KBK became aware of the high-speed options of the XP^sup 3^, the company was able to speed interpolation feed rate from 6 ipm (152 mm/min) to 30 ipm (762 mm/min), and reduce cycle times by one-third. "These parts are aluminum, and the cycle times had been 45 to 50 minutes," says Hedeen. "Now that time had been cut by 30%. We had run a lot of these parts and the job was just about done. I know I left a lot of money on the table on that job, but that's what happens when you buy|a machine like this and have to put it to work right away, and don't have the time to really investigate all the options and capabilities. We just had to get it in and begin producing parts right away," Hedeen explains.

Gaining experience with the XP^sup 3^ enabled Hedeen to develop the best machining strategy for his operation and turn jobs around quickly for KBK's customers. "We often use fixture plates on the machine, especially if we know we're going to be repeating the job," says Hedeen.

"With repeat work, we throw the fixture on, call up the program, and go. And one of things I really like, for a couple of reasons, is the 30-tool side-mounted swing-arm ATC. It's really handy because we can leave some tools in the changer, and when those jobs repeat, our setup time is negligible. The tools are already there, and the program has been loaded in the control. A job that may have taken four to eight hours to program and set up has now been replaced by putting a fixture plate on and calling up the program. The difference is time-in-cut instead of idle time."

The other thing that Hedeen likes about the Bridgeport toolchanger is that it's mounted to a fully supported shoulder on the machine's column, which is engineered to support its weight, thus eliminating the transfer, of vibration into the cutter while the toolchanger is rotating.

Consistency between parts made at the beginning of the day and parts made at the end of the day has been improved by two features of the XP^sup 3^ machining center: a cooling system that reduces heat in the head, and a thermal compensation system.

"The Bridgeport has allowed us to go after work we couldn't previously do," says Hedeen. "I'll be honest, I quoted jobs that I really thought I could do, but no matter what we tried, until the Bridgeport, we couldn't actually run some of these jobs."

After acquiring the Bridgeport, KBK acquired a Zeiss CMM to provide complete traceability for medical and aerospace parts, certifying the material, and any grinding or heat treating that's done to the part.

The 760XP^sup 3^ has extended KBK's capacity for demanding precision machining jobs. "We're able to go after jobs we wouldn't have thought about before the Bridgeport. We're typically hitting tolerances of 0.0005'' [0.0127 mm], total not plus or minus, and we hit 0.0003'' [0.0076 mm] as well." 

http://cnc-info.blogspot.com/2007/01/vmc-delivers-precision-jobs.html

For more information visit CNC Resources category