How 5-axis machining is modernizing bevel gear cutting at Milwaukee plant.

A few short years ago, producing the bevel gearset for the Falk® V-Class® gear drive at Regal Rexnord’s Milwaukee-based plant looked like this:

A technician would spend about two hours setting up a cutter. Then, the technician would spend about another hour on the fixture setup. Once “set up,” the technician would spend an hour inputting and cross-checking data. Next comes the setup of the first piece and going through checks — on average, this takes about one hour; however, for larger bevel gears, it can take up to five hours. Next, an hour is spent validating inspection. Finally, after a minimum of six hours, the first piece is cut.

This is how bevel gearsets have been created for decades. The manpower required is heavy, but so is the technology itself. Bulky and cumbersome, these older machines use a series of cutters specific to each job, roughing the teeth prior to heat treatment.

Fast forward to today.

To cut a bevel gearset for a new V-Class drive, a technician at Regal Rexnord now walks over to a 5-axis machine. Depending on the size of the gear, the setup takes about 20 minutes. Cutter setup time is eliminated, as there is a dedicated tooling resident in the tool chain. (Tooling takes about 15 minutes to maintain.) Next, the technician spends about five minutes reviewing a computerized setup. An hour later, the technician is machining the part. About 30 minutes after that, the technician begins an hour-long inspection. 

In all, the technician spends about two hours on a single gear — and that’s on the high end of average.

A decade ago, gearing engineers, technicians, and managers wouldn’t have dreamed this type of technology could exist. But it has profoundly changed gear cutting — for the better.

What is a bevel gear?

A bevel gear is the heart of the gear drive, where power is transferred from a motor to the driven equipment. Simply put, it translates rotation and torque at a 90-degree angle. Bevel gears consist of two cone-shaped gears with intersecting axes. When the input gear rotates, the gear teeth engage and transfer the rotational motion to the output gear and shaft.

Bevel gears are typically made from steel, cast iron, aluminum, or bronze. (Choice of material depends on a variety of factors such as cost, load/speed conditions, noise requirements, and lubrication provisions.) Bevel gearbox assemblies are quite versatile, can handle large overhung loads, and can be highly modified. A light-duty load may use a spiral bevel gearbox made from aluminum, whereas a heavy-duty load with significant torque and speed may use a cast-iron gearbox with a forged bevel gearset. An example of an ideal application for a spiral gearset could be a small military robot, while a heavier duty forged gearset may make more sense for an overland conveyor.

The specific 5-axis machine at Regal Rexnord is dedicated to bored bevel gears, which are used in Falk V-Class gear drives.

V-Class drives are used worldwide and are involved in the extraction, transportation, and processing of raw materials and finished goods that affect daily life. From mines and mills to production equipment and critical infrastructure, innovative design and manufacturing of these gear drives and the components within promotes faster, efficient delivery of drives to be commissioned, and the reliability of drives in their operating lives.

And it all starts with a bevel gear.

The 5-axis vertical-spindle machine, manufactured by DMG MORI, accommodates workpiece diameters up to 508 mm. (Courtesy: Regal Rexnord)

The cost of traditional gear cutting methods

While the generator is not totally obsolete — some gearsets are simply too large otherwise — the 5-axis has become the preferred method for cutting new bevel gears. 

The primary challenges associated with older technology include:

  • Long setup times for cutters.
  • Complex and time-consuming fixturing setup. 
  • Specialized cutters needed for certain jobs are expensive and can have long lead times.
  • Blades are unique to the gear tooth. Because specific sets are needed for specific parts, facilities must have significant blade inventory.
  • Significant time is spent on data input and data checking during setup; this also adds to the risk of errors.
  • Multiple cutters are often needed for a single job, increasing setup complexity.
  • Inflexibility in the types of jobs it can handle due to limitations of the cutter system.
  • Requires more labor and operator expertise.

With both processes old and new, Regal Rexnord is taking the tooth form as close as possible to the finished size, allowing for finished grinding stock. This is typically a small amount of material; about a 10-thousandth per side on the tooth.

In the case of solid-on-shaft pinions, technicians are forced to use older technology. But when it comes to a bevel gear blank, they can move it into the 5-axis machine.

How the new machine works

The 5-axis vertical-spindle machine, manufactured by DMG MORI, accommodates workpiece diameters up to 508 mm. With its robust, high-torque/high-power spindle design, the machine creates an optimal environment for using a variety of highly productive, inserted milling cutters.

The technology enables heavy milling of forged raw parts, profiling, protuberance machining, flank finishing, and profile finishing of hardened gears — effectively completing the gear machining process from a blank in just a couple of hours.

The machines are equipped with a zero-point workholding system, which greatly reduces non-productive workpiece setup time by simplifying typically tedious manual workpiece setup and alignment. Also, a first part checking probe is integrated in the machine to automate that critical step in the setup process.

The probe will touch off the blank to automatically update machine coordinates. The machine will precision align itself to the blank, taking any human error out of the process. This step assures a consistent and repeatable outcome in the machining process.

For many years Regal Rexnord used a conventional, tooling-dependent generator to produce bevel gears. This older technology typically requires six to seven hours of setup and processing work for production. (Courtesy: Regal Rexnord)

Trusting computers to get the job done

The 5-axis machine technology is not only fundamentally different in its design and setup, it is also computer-based. Using proprietary software, a computer generates the code required to mill out the tooth form on the bored pinions. (Regal Rexnord uses a unique mill to the gearing industry, a Sandvik InvoMill. Those are used for roughing the teeth.)

The 5-axis computer (controller) does a few key things:

  • It allows tool paths to be modeled and programmed offline using HyGEARS software outside of the machine, to get a more predictable setup and result. This reduces the setup and programming work required by operators on the machine.
  • It calls up the pre-programmed tool paths for the specific part being machined. This takes about five minutes for the technician to load vs. more complex data input required on the generator.
  • It has in-machine probing capabilities to automatically qualify and verify the exact location of the part within the machine before cutting begins. This helps ensure accuracy.
  • It controls the 5-axis movement of the machine during cutting to machine the complex tooth forms based on the pre-programmed tool paths.
An operator at Regal Rexnord’s Milwaukee gear production facility uses the new 5-axis bevel cutting machine. (Courtesy: Regal Rexnord)

Positive impact on labor, operational efficiency, and innovation

Most, if not all, manufacturing companies are facing challenges attracting and retaining workers. Because the 5-axis machine only requires one technician (the generator requires several for setup and operation), the adoption of this new equipment has allowed Regal Rexnord to cut more gears with fewer workers.

Additionally, training on the 5-axis is simpler and faster. Programming can be done offline, so technicians don’t have to spend as much time doing complex data input at the machine. The automated probing and pre-programmed tool paths also make operation easier. Because workholding is fixed, technicians do not need to change fixtures during the cutting process.  Ultimately, there is less to learn — and less time spent learning. Most machine technicians can use the 5-axis with minimal upfront design knowledge.

At a facility management level, adopting the 5-axis machine has allowed Regal Rexnord to redistribute resources. Now the company can spend more time focusing on highly customized specialty components.

Finally, because technicians are spending less time setting up and operating the generator, Regal Rexnord can focus more on innovation. Specifically, the Milwaukee gearing team is pursuing “green grinding,” an alternative method for roughing gear teeth. Rather than milling the tooth form, it involves roughing the gear teeth directly in a grinder. This approach reduces variability and can lead to a better-quality product because the same machine is programming throughout the process.

Looking ahead to the future

The ability to quickly adapt and optimize the features of the 5-axis ensures Regal Rexnord maintains a competitive edge and continues to meet the high standards of quality and efficiency the company is known for. This strategic investment not only enhances operational capabilities but also reinforces a commitment to technological advancement and superior craftsmanship in gear manufacturing.

Sometimes it’s hard to fathom what dramatic changes can occur in this line of work. Isn’t gear cutting so simple?

Not so. Having a growth mindset and being willing to change and adapt are paramount to the future of the industry — from the bevel gear to beyond. 

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Mark Schultz is the manager of Manufacturing Engineering at Regal Rexnord, a global company that creates sustainable solutions to power, transmit, and control motion. Schultz has more than 24 years of experience in manufacturing engineering and management, particularly in the fluid power/hydraulics sector. He manages a diverse team involved in gear production, including engineers, CNC programmers, technicians, and tooling specialists.