Increasing Grinding Capabilities

Thanks to Reishauer, a new technology is enabling manufacturers to take the lead in expanding market segments, increasing both flexibility and capabilities.

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As the owner of Michigan Automatic Turning—which specializes in manufacturing gears and shafts, primarily for off-road and agricultural machinery—Peter Lazic had come to rely on Ann Arbor Gear for its high-end grinding capabilities. When he found out they were planning to close their doors three years ago, he immediately picked up the phone and made his feelings known. “No,” he said, “you just can’t do it.”

The reason he felt so strongly about his longtime service supplier was because their precision grinding filled the need for a capability he didn’t possess in-house at the time. “We needed their capacity,” Lazic says. “Because of the quality requirements and volume of parts they were supplying, there just wasn’t anyone else in town who could keep up with us.” Figure 1

His solution? He bought the company, renaming it AA Gear. Along with the acquisition came the reason for the company’s superior grinding capabilities: a Reishauer RZ400 gear grinder. Lazic recognized that this machine was critical to sustaining both the throughput and quality the he and his customers had come to expect in the finished gears.

The RZ400 was Lazic’s first exposure to the Reishauer’s unique hard gear finishing process. He came to understand that the RZ400 delivered great quality while at the same time being very cost effective. It enabled AA Gear to grind both small batches and large volumes of parallel access gears that range in size from 20 mm to 400 mm in diameter. In addition to supporting Michigan Automatic Turning’s off-road and agricultural transmission shafts and gears, AA Gear also provides contract gear grinding to numerous customers, resulting in a reliable revenue stream.

As Lazic began to grow this segment of the business, he landed a couple of high-volume production jobs that began to outstrip the capacity of the RZ400. “We went out on the market and really researched it. We looked at half a dozen options and decided on purchasing another Reishauer,” Lazic recalls, adding that he decided to focus on Reishauer’s newly introduced model RZ260. “It became clear to us that this machine was the most cost effective and efficient gear grinder per output for our style of work that’s currently available on the market.”

Meeting Production Demands
One of the key features that Lazic discovered about the Reishauer RZ260 was the new dual spindle configuration. This important design feature enables AA Gear to adapt to different production requirements, depending upon the customer’s individual needs. He found that loading times were greatly minimized with two spindles, while overall production output was increased. The machine presents one part for grinding while the other station is loaded, unloaded, and synchronized. Figure 2

The RZ260 is also equipped with a CNC-controlled axis for swiveling the dressing tool. With this option the flexibility of the dressing tools can be increased since the same tool can be used for a range of gears, as compared to the fixed dresser where the tools are usually workpiece-specific. While the machine can be equipped with robotic automation, AA Gear hasn’t yet gone that route. “We don’t have automation at this point,” Lazic explains. “Due to the variety of the parts that we carry, we were looking for a machine that was efficient without the automation. That was one of the criteria we needed, because it’s not unusual for us to run three or four different jobs a week through that machine.”

While a production run can be anywhere from 20 to 50,000 pieces, he says that even at 20 pieces he could make a business case for the RZ260. “It’s the combination of cycle time and quality, he says, “and the quality of gears we’re getting is phenomenal.”

Lazic also mentioned the ability of the RZ260 controller to store a variety of special tooth forms. In addition to standard tooth forms, it has the ability to line dress any kind of form required. “As long as you have the right dressing diamonds, changeovers are fairly quick.”

Machine Specifications
The RZ260 bed is a robust construction that was designed for very high stiffness to withstand the stresses encountered during the grinding and dressing process. Both the control panel/pendant and hydraulic/lubrication components are integrated into the basic machine structure taking up a mere 55 square feet (machine) of floor space. The machine requires only a small amount of valuable shop real estate, the smallest foot print for a machine of this type despite its impressive performance. Figure 3

As for the concept and design, the RZ260 three-position turret assembly provides for the shortest possible time between loading (approximately four seconds) and facilitates the wheel dressing operation. Not only is loading and unloading done in parallel to the machining cycle, the workpiece is pre-synchronized to the grinding wheel, minimizing the idle time during the grinding portion of the cycle time. The machine can be equipped with up to 13 numerically controlled axis that take their orders from a Siemens 840D control, a Reishauer MMI, and an electronic gear box that has been perfected over the last two decades. Most NC-axes are equipped with absolute encoders resulting in fewer referencing movements at machine start up and provides the basis for the unique Siemens security system. The machine is completely enclosed providing a pleasant shop environment for operators and plant staff.

Flexibility does not take a back seat to productivity, as the RZ260 is available in four versions. In the basic model equipped with a single workspindle, the spindle is automatically moved to an easily accessible position for manual loading. When large lot sizes are called for, the machine is equipped with two work spindles. The machine is configured with a fixed dressing unit if a limited variety of profile modifications are to be produced using workpiece specific dressing diamond tools. When maximum flexibility is called for to produce a large range of different gears, a pivoting dressing unit is the more appropriate choice.

The grinder is equally adept at grinding shafts as it is bore type parts. Shafts are usually supported with the optional tailstock(s), while there is normally no need to support bore type parts with a tailstock due to the inherent design stiffness of the workspindle(s).

• OD ≤ 260 mm
• Maximum face width ≤ 150 mm
• Maximum length for shafts  ≤ 490 mm
• Module .5 to 4 mm
• Maximum module for form grinding 6 mm
• Helix angle ± 45°
• Diameter of grinding wheel 275-205 mm
• Small profile spindle wheel diameter ≥ 60 mm
• Maximum wheel width 125 or 160 mm

Entering New Markets
At a time when new gearing will be required for emerging technologies involving automotive designs powered by fuel cells, gas, diesel, and electric engines—as well as the advances being made in larger off-road and agricultural machinery—forward-thinking businesses are realizing the value of getting involved in the early stages. “Recently, AA Gear has been playing a fairly large role in the research and development field,” Lazic says. “The requirements on gears as far as noise, durability, and load bearing capability are continuously getting more stringent.” Figure 4

He goes on to say that another significant reason for the selection of the RZ260 was that it accommodates bias control, a key feature with newer gear designs. “What that enables us to do is correct for naturally occurring bias that’s inherent in the manufacturing process,” Lazic explains, adding that whatever they can deliver in prototypes can be consistently replicated through high production runs, as well. “Not only can we correct for it, we can compensate in the opposite direction for whatever the need might be, whether it’s load deflection or manufacturing/design/variances of the parts and improve the contact between the gears.”

Lazic is proud of his company’s increasing role in prototype development to meet new market demands. “It’s a very unique feature, and I don’t know of any other company our size that has that capability.” In addition to the bias control, he also appreciates how the RZ260 utilizes advanced machine technology, including LNS™ Low Noise Shifting, resulting in very low gear noise emissions. As a result the company has been able to get significantly higher gear life by applying low noise shifting grinding, which also results in higher residual stresses and much quieter gears. Figure 5

AA Gear is in the process of moving into a new 112,000 square-foot facility. “We’re going to stay focused on the new technology and evolution of manufacturing processes. Our whole goal as a company, and what you’ll find in our mission statement, is that we want to be the most efficient gear and shaft manufacturer serving our particular markets.”

Partnering with Reishauer has provided the perfect means for achieving this. “It’s about constantly striving to be more efficient and learning how to do a better job, and you want your customers to know that’s how you do business,” Lazic says. “And that’s exactly how I feel about Reishauer.”   

References:
1) V.Rudnev, D.Loveless, et.al., Handbook of Induction Heating, Marcel Dekker, NY, 2003.
2) K.Shepelyakovskii, Induction Surface Hardening of Parts, Mashinostroenie, Moscow, 1972.
3) ERS Engineering Inter-Company Report, 2010.