According to Joe Leone, manger for quality control/gear grind, Milwaukee Gear has been in operation for 94 years and was founded by Emil Borisch and Walter Kohls. The two men started the company in a small, one-story, brick building in downtown Milwaukee, and served as the company’s salesmen, machinists, order clerks, and product inspectors.
Milwaukee Gear moved to their current sprawling 180,000 ft. facility in 1953, and was family-owned until 2008, when it was acquired by a private equity group. The company was subsequently sold in early 2012 to Regal Beloit Corp. Today, Milwaukee Gear operates as a unit of Regal Beloit America, Inc., and employs approximately 220 people.
Diversity and Experience
Leone explains: “We manufacture gears and pinions for a variety of industries—air and gas compression, oil, gas, and coal mining, construction equipment, cranes and hoists, different types of air moving equipment, fans and blowers, refrigeration chillers and speed reduction/increase gear cases. This is just a thumbnail of the gearing we do. Customers come to us with their design, our engineering group utilizes the latest gear ratings software to optimize their applications and then we manufacture the gearing to spec for them. In some cases, we will manufacture housings and do complete gearbox assembly. However, most of the time our customers do their assembly in their own facilities and we supply the loose gearing.” Figure 1
Leone says they basically work from the raw material stage to a finished component—machine, heat treat, and all the processes in between. “We work in steel, typically a carburizing grade of 9310, 4320, 8620 or 17Cr Ni Mo6 bearing quality. I’d say 90 percent of our gearing is carburized and hardened.
“We’ll use bar stock, die forgings, hand-hammered forgings—many different configurations of steel. We purchase the raw material and do all the pre-heat treat machining, turning of surfaces, drilling and threading, and machine keyways or splines if required. We have full in-house heat-treating capability and metallurgical control. The case hardening process involves gas carburizing and polymer or oil quench in an atmosphere-controlled integral furnace. And then we do all of the post-heat treat machining, which includes OD/ID grinding, and, of course, gear tooth grinding, which is our core competency.”
Leone says that Milwaukee Gear has always been proud of being a first-class organization and having the very best equipment that money can buy—and being second to none in advance technology investment. Grinding technology is no exception.
“We acquired a Studer S40 (United Grinding Technologies; Miamisburg, OH) in July of 2005. Not only is it still running today, seven years after first being installed, but the S40 is still operating as our primary OD grinding machine. Many of the parts that we manufacture have a dimensional size requirement of +/- 0.0002”, which is one of our tightest size tolerances. We confine the Studers to only our highest precision gears, pinions, and shafts. Once you attain size, the Studers are reliable and accurate and amazingly repeatable—piece after piece after piece. The size range on the Studer S40 is 15” in diameter by 63” in length. The S33 is a smaller machine with a 12.9” diameter and a length of 39.4”. Figure 2
Both CNC universal cylindrical grinders are designed for grinding medium-sized workpieces in individual and series production. The solid Granitan® S103 machine base forms the basis for a cylindrical grinding machine that is equipped with high quality components, and guarantees maximum precision, rigidity, superior dampening and elimination of thermal distortion. The Studer grinding software with proven pictogramming allows even less-experienced users to quickly optimize the potential of the machine. The Studer GRIND software enables efficient programming of special applications, such as form and thread grinding.
Changeover from grinding between centers to live spindle grinding is especially easy on the Studers. Only a few movements are needed to withdraw the tailstock to its “park” position and free up the space required for internal grinding. Reference points from grinding wheels to dressing tool and work piece can be registered very quickly with the help of Quick-Set, the software controlled setup device from Studer.
A Ferrari in the House
According to Venu “Vinny” Gupta, Studer operator and setup specialist, the absolute selling point for both Studers is the Quick-Set programming. “The Quick-Set allows us to grind any part as long as we have a program for it,” says Gupta. “With Quick-Set, you put the part in, bring the program down, offsets up and run the part. I can change from one part to another in 30 minutes, and this is especially true if we’re doing similar or a family of parts. Also, the Fanuc control has a library of up to 99 wheel programs. The S40 has the capability to also grind cams, threads, and lobes. It does all that through high-speed grinding. Our S40 would require additional software to do high-speed, but we don’t really need that for our current type of work. Still, we have the resident ability to do high-speed grinding. Figure 3
“Whether you’re running an S30, S40, or S33, all the software is identical. An operator can go from an S40 to the S33 with virtually no retraining. The Studers are a very precise and reliable machine. They’re the Ferrari of grinding. On surface finishes we can get 8-, 6-, or 4-micro—you name it, the Studers can deliver. Generally we’re getting a 6 micro requirement on surface finish.”
When Milwaukee Gear was looking at CNC universal grinders with ID and OD grinding capability, they considered a number of key requirements: accuracy and repeatability, a rigid, vibration dampening machine bed, multiple grinding wheels, a swiveling workhead, an operator-friendly, robust programming software package, and superior after-sale service. After all, investing in advanced high technology grinding equipment is not like picking a machine builder’s name out of a hat—it requires research, machine comparisons, conversing with those who’ve had to make similar decisions, and knowing down to the finest detail what you need and want, not just for today, but for your future needs. The last thing you want to do is invest in technology that will become obsolete in three or so years. What you do want is technology that will handle shifting markets and market demands, and this requires grinding technology that’s flexible, reliably precise, and capable of adapting to your changing needs.
“After considering a number of machine offerings from various builders, we decided to go with Studer,” Leone says. “We went with the S40, largely because of Studer’s strong reputation for quality, precision, and repeatability. What really swung the decision was the Quick-Set package, which allows us to set up and start running a job sooner. Keep in mind we’re a job shop. We are not running the same product line day after day as you might find in the automotive industry. We have lots of setups and part turnovers. Because of our small lot sizes, setup and changeover are not just measurements in time, but an indicator of our overall efficiency. That’s what sold us on the purchase of the S40. In all my experience at Milwaukee Gear—and I have been here 33 years—the first Studer sold the second one, the S33. We watched for seven years what the S40 could do for us and saw the quality it produces, the tolerances it consistently holds, and it just made sense to buy another Studer and not look elsewhere.” Figure 4
“The B-axis on the S40 can swivel in any direction with a positioning resolution of 0.0001° to grind tapers, angles, contours—whatever you need, you can grind,” says Gupta. “We have two grinding wheels on both machines, so we can put different size wheels with different radii configurations, thus giving us considerably more capability and adding to not only the efficiency of these machines but to our overall efficiency.”
Precision Compressor Pinions
“We produce gearing for the high-speed compressor industry, which is one quality level down from aerospace gearing,” Leone says. “To get maximum efficiency, the OEM will utilize a drive ratio with a 1–1/2” diameter gear tooth pinion driven with a 35” diameter gear. These pinions can run up to 75,000 RPM. There are impellers assembled and precision balanced, and there are very tight fits within the housing of the compressors, so the diameter sizes have to be tightly toleranced and controlled—again, +/- 0.0002” is a common tolerance for these pinions, and concentricity of these diameters is, again, 0.0002” as well. A surface finish of 6 micro is common. There is an electronic probe (vibration sensor) assembled into the compressors so if the bearings start to wear, and these pinions start to shimmy and shake, when they reach a certain threshold, the compressor will shut down. So, for that industry the tolerances are critical, and this is probably some of the tightest tolerance work we do here. Again, being a job shop, we do a lot of compressor gearing for different OEMs.”
When purchased, the S33 was installed in a temperature controlled area of the facility where the gear tooth grinders have been for several years, and before the end of this year, the S40 will be placed in that same controlled environment to improve the efficiencies and capabilities of the Studer machines.
“In our process,” Leon explains, “we are doing OD grinding on both Studers. The S40 was purchased as a universal grinder to do many different types of parts, while the S33, which is more of a base machine, was purchased to do a specific line of parts. Gear tooth grinding is done on an entirely different machine, one specifically designed to grind precision gear teeth.” Figure 5
Partners in Service
According to Gupta, United Grinding Technologies handles all service and parts. “They’re very responsive,” he says. “If something goes wrong on one of the Studers, and it’s beyond the grasp of our in-house maintenance technicians, and we can’t work through a solution over the phone, United Grinding will send a service tech in to resolve the issue. With the S33, for example, when you bring a new piece of high tech grinding technology in, there are bound to be some things that need tweaking—which is entirely normal and to be expected. United Grinding has been right on the spot when we needed them.
“The S40 has been another story. We have had no major problems, and the machine runs three shifts a day, five or six days a week. All we have had to do on the S40 is change hydraulic fluid, coolant, and a belt here and there—which is amazing when you consider it’s going on eight years old, and it performs tirelessly around the clock. It’s true, Studer is the Ferrari of grinding, but unlike its automotive counterpart, it does not require kid gloves and delicate handling. Studer’s probably faster off the mark, too.”