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Fast forward for servo gearheads
Novel heat-treating and a new tooth profile move precision gearing into the 21st century
By David J. Bak, Senior Regional Technical Editor -- Design News, August 26, 1996
"No way!" That's the skepticism Howard Lind, president of Bayside Controls Inc., expected when he laid out the company objectives for 1996. After all, the goals were a bit intimidating: Develop a new line of servo gearheads with:
• 30% more torque capability in the same frame sizes;
• less than 1/2 current backlash specifications;
• less than 65 db noise; • ability to accommodate input speeds reaching 10,000 rpm;
• and better than 90% efficiency.
His final requirement, however, was the killer: Be ready for product introduction at Chicago's International Manufacturing Technology Show in early September, nine short months away.
Fortunately, the engineers of Bayside's design, manufacturing, and marketing departments had done their homework. As a group, they had already spent several months scouring the marketplace for new technologies, as well as market trends. It was a process that took them to trade shows, seminars, and other manufacturing companies both in the United States and Europe.
Harvesting the fruits of these fact-finding missions provided the fuel for new product development. "We gathered information as a team," says electrical engineer and Marketing Manager Joe Panebianco, "and then asked ourselves, 'Where can we apply it?'" Such inter-departmental brainstorming sessions, he adds, not only preceded, but paralleled development of Bayside's new StealthTM gearheads for servomotors.
Novel heat treating. Consequently, when VP of Manufacturing Jack Dillon loaded a bunch of engineers in his van, and they headed out to educate themselves about new advances in metal cutting technology, their research took them beyond a solution to his immediate objective: implementing a more efficient method for cutting the slot in Bayside's ServoMount design (see sidebar).
"Investigation pointed to plasma, rather than abrasive cutting," he says, adding that "somehow along the way, the team also focused on plasma-assisted heat treating." Incorporating the latter into development of the Stealth line of precision gearheads resulted in two significant benefits: longer-lasting cutting tools and longer-lasting gear teeth.
"When they asked us for half the current backlash specifications," Dillon recalls, referring to the Stealth program objective, "I realized we would have to change our cutters twice as often. My next thought, since no two cutters are alike, was 'How are we going to hold tolerances with two times the variation?' "
Plasma-assisted case hardening, he claims, proved to be the answer--not only for extending cutter tool life, but for longer-life gearing as well. Because the process hardens the surface only, it protects against wear and pitting, yet avoids any brittleness that can result from conventional through-hardening processes. Adoption of the heat-treating process, new to precision gearheads, generated additional material improvements, focusing on alloy steels conducive to plasma-assisted case hardening.
Improved tooth profile. All the while, engineers in R&D were busy working on tooth geometries. "Our market research showed a definite trend towards higher speed servo motors," explains Panebianco. "We wanted Stealth to anticipate these high speeds, plus accommodate the shock loads that accompany rapid acceleration and deceleration."
Using advanced gear geometry algorithms, and ProENGINEER for CAD, Senior Design Engineer Yefim Khariton developed, and Bayside trademarked, the HeliCrownTM tooth design. Combining helical gear design with crowning, the new configuration offers the advantage of significant noise reduction, a 15% to 30% increase in torque capacity, and higher contact ratios for greater speed capability.
Barriers to implementation, states Khariton, involved manufacture and inspection. "A new profile is all well and good," he says, "but if there's no CNC equipment to cut and measure it, the profile remains on the shelf as another concept only."
Lucky for the engineers in R&D, Dillon--out and about searching for a software-driven machine to measure his cutting tools--was sitting on the answer. "We had been looking at analytical gear measurement systems in the U.S. as well as Europe, talking to companies such as Klingelnberg, Hofler, and M&M Precision," explains the manufacturing VP.
"I was really excited about the machinery we saw, and in one of our brainstorming sessions, told our design engineers that the equipment we found could measure any tooth profile," Dillon says. "But I was thinking spur gears, worm gears, and spiral bevel gears; I didn't realize engineering had a completely different concept, one never before applied to servo gearheads!" To Dillon's relief, the equipment he and his colleagues inspected turned out to be directly applicable to the accurate manufacture of the HeliCrown profile.
These and other examples of design, manufacturing, and marketing working concurrently from a clean sheet of paper, says Panebianco, allowed Bayside to meet its nine-month deadline--a goal that "wouldn't have been possible using traditional methods of product development." As Jack Dillon puts it, "It's amazing how one idea leads to another."
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