Fast But Firm – Profile of Success: Koss Aerospace

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by Mary Scianna

Profilesof toolholding success in high speed machining

Machining speeds: Up to 33,000 rpm on Handtmann, Makino machines

Toolholder: Haimer Power Clamp Economic Plus NG shrinkfit machine and Tool Dynamic balancing machine

High speed machining with speeds of up to 50,000 rpm isn’t for everyone, but if your manufacturing requirements demand it, you need to invest in the right technologies to ensure success: a machine that can handle the speeds and tooling that won’t break off during machining. Ensuring your tooling won’t break off means you have to have the right toolholding system in place. Shop Metalworking Technology approached manufacturers involved in high speed machining and asked about their success strategies using toolholders in high speed machining applications.

Koss Aerospace has been in business since 1975, and from the beginning Drago Cajic, founder and president, has followed a philosophy of investing in the best technology to remain competitive.

ILjubisa Bodiroga, who works on the high speed machines at Koss Aerospace, is impressed with the Haimer shrinkfit toolholder technology.n 2015, the company moved into the high speed five axis machining arena, purchasing two Handtmann machining centres operating at speeds of up to 30,000 rpm. The machines produce aluminum aerospace parts, primarily structural parts like fuselage components.

“Since they were the first high speed machines, we needed different types of toolholders to handle the higher speeds,” explains David Cajic, vice president of Koss Aerospace. “We had been using some hydraulic chucks for critical operations on our other machines in the past, but we switched to the Haimer shrinkfit toolholders after observing the success we had in high speed machining with the Haimer products.”

Koss Aerospace selected Haimer’s Power Clamp Economic NG shrinkfit toolholder system and Haimer’s Tool Dynamic toolholder balancing machine. Now in operation for more than two years, Cajic and machinist Ljubisa Bodiroga, who works on the high speed machines and uses the Haimer toolholder systems, are impressed with the technology.

“I’ve never had any runout problem with this system. I like that it holds the tools and the toolholder very secure and we don’t have any problems,” explains Bodiroga.

The Haimer shrinkfit technology offers less than 0.00012 in. runout at three times diameter.

Cajic says he also likes the versatility of the universal Haimer shrinkfit unit that is designed with a flexible and modular system. While the system is used primarily on high speed machines, it’s also used, from time to time, on other machine tools in the shop.

“Shrinkfit eliminates vibration and chatter, so you get higher accuracies and because the technology holds tooling and toolholders so securely, it eliminates a lot of potential problems like tool breakage.”

Koss uses Haimer's shrinkfit technology on tooling for Koss' Handtmann high speed machining centres, one of which is seen here.Other advantages that Cajic and Bodiroga like are the gripping force–the chucks can grip the cutting tool 360° around the shank on multiple planes, providing very high gripping force, which in turn eliminates chatter during roughing and finishing operations–and setup consistency, which eliminates setup errors.

There are two other key attributes that contribute towards the Haimer shrinkfit toolholders’ anti-vibration properties. The holders are balanced to G2.5 at 25,000 rpm, which in turn helps to reduce the imbalance of the full assembly and reduce vibration. And specifically with the Power series holders, the design helps dampen vibration because of a thick wall at the clamping bore and a wider body construction.

Cajic says the outlook for Koss is good. In fact, the company recently purchased a Makino five axis horizontal milling machine, the MAG1, with machining speeds up to 33,000 rpm. Cajic says the company will use the existing Haimer shrinkfit system on tooling for the Makino for the short term, “but as we ramp up production with this new machine, we’ll be able to justify purchasing a second Haimer shrinkfit system.”

Koss employs 80 people and operates out of a 3,716 sq m (40,000 sq ft) manufacturing facility that houses a variety of CNC machines.

“We’re running three shifts so we’re able to handle the work, but space in our shop is at a premium and now that we’re investing in newer and, in some instances, larger machines, we need to make more efficient use of processes,” explains Cajic. “One way we’re doing that is replacing older machines with new ones as we get them. The newer machines usually take up less room and they can handle more work, so that’s making us more efficient.” SMT

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