The Gear Chamfering Robot (GCR) is a portable powerhouse, designed to be flexible enough to fit a broad range of gear modules while also reliably carrying out its duties in daily production. Weighing in at just over 300 pounds, it is dwarfed by competing machines that demand large amounts of floor space, energy, and dedicated programmer/operators. Its “programless” functionality requires only four to six fields of input by an operator who can be trained to use this machine to its fullest potential in a matter of hours. From “in the crate” to “out of this world” in a few hours, the simplicity of this machine is a key selling point for those companies relying on semiskilled tradesmen to chamfer and deburr large-format gears in all markets across the globe.
The history behind the GCR starts in 2008 with Darryl Witte, who is vice president of sales at Banyan Global Technologies. His background in gear cutting tooling goes back some 20 years and covers a broad range of products for producing and finishing gear forms, which has given him a unique perspective on market trends and where opportunities may exist for new machine tools and processes.
“A few years ago we were seeing a rapid expansion in the wind energy market, with the large slew bearing gear production requests outpacing available production rates for existing machinery,” he says. “Though that has tapered off a bit, we continue to see expansion in sales activity through the off road, mining, and marine markets, which also produce gears of similar size.” Figure 1
Unfortunately, he continues, the cold economic climate in the U.S. has caused everyone to downsize personnel while trying to increase productivity. That’s where Banyan saw the most opportunity for the machine to help its customers. Before the invention of the GCR a customer only had a couple of choices. They could either set an operator with a pneumatic grinder in front of a gear for eight hours a day, dedicating him to that solitary operation and accepting a cosmetically inconsistent result, or they could invest in a large piece of expensive machinery with high cost of ownership and operation in order to achieve a suitably consistent geometry and surface finish. The Banyan GCR provides this high quality geometry and surface finish while eliminating the high cost of ownership. The advantage of a consistent chamfer is that it returns a more process-stable result from subsequent induction heat treatment, significantly reducing the chance of cracking.
The Banyan GCR is a completely self-contained machine with all electronics onboard for operation. With the connection of a power cord (208VAC – 20A is standard, other configurations available worldwide) and pneumatic line (90 PSI [6.2 BAR], clean and lubricated) via overhead umbilical, the machine is production-ready minutes after uncrating. Communications with the machine are via an onboard 6” touch screen, wired RJ-45 Ethernet, or via wireless data access point for remote configuration and troubleshooting. Integrated data storage allows for several thousand unique gear chamfering configurations to be recalled at the touch of a button. Figure 2
The brains and muscle of the GCR come from its multi-axis servo control system, precision accuracy drive transmission, and standard 3Hp direct drive custom-tuned spindle motor configured as a complete drive and positioning system. This positioning system senses spindle torque load and adjusts movement in two axes independently to ensure a smooth machine operation where the cutting tool remains fully engaged in the gear teeth at all times during the chamfer operation. It does this by solving multiple simultaneous equations involving the current torque of the pinion servo, force on the spindle, rotational velocity of the drive pinion, and linear velocity of the spindle traverse axis. This proprietary system is what contributes to the machine being nearly programless, save for a few parameters including the cutting speed and feedrate.
Banyan’s engineering department spent a significant amount of time and effort in the design of the live bearing and cam follower tools most common to the machine’s operation and success. Due to the relatively small root radius of most of the gears using this machine, it was impossible to integrate a strong enough bearing with sufficiently small outside diameter and lateral load bearing capacity to properly trace through the root and avoid plunge-cutting the entire root form with the cutting tool, which generally operates in the 6,000-8,000rpm range. The answer to the lateral load and diameter issue came in the form of an internal live cam-follower utilizing needle bearings, as well as thrust bearings for such tools that may experience an axial load, such as helical gears. The result of this effort is a cutting tool that easily handles the load vectors, cuts freely, and has a regrindable and replaceable cutting head, which reduces downtime and service to the perishable tooling. Though not required for every application, Banyan Global Technologies will custom design and manufacture a cutting tool specific to a customer’s application if an off the shelf solution doesn’t exist.
The drive mechanism that allows the GCR to traverse around the gear consists of the drive servomotor with encoder, high-precision zero-backlash drive transmission, high durometer idler roller wheels, and the main drive pinion. The machine is capable of chamfering gears as small in size as 48” in diameter and larger, both internal and external forms, and in spur and helical geometries. Due to the flexible nature of the gear chamfering robot and the high variability of gears across a wide range of sizes and configurations, it is important to note that a specific mating drive pinion needs to be purchased for each variant of module/pressure angle you intend to chamfer or deburr. This low-cost durable tool is available and can be specified by the customer or designed for particular applications by Banyan’s staff engineering department at no additional charge. Figure 3
With the correct drive pinion and cutting tool installed, the GCR machining operation itself is completely automated through its entire cycle. After pressing cycle start, the machine will find home for all axes of movement and will engage the drive spindle and locate the first tooth for chamfering by sensing the reaction force against the spindle caused by engagement. As the cutting tool engages the gear profile the machine will coordinate the infeed axis of the drive spindle with the drive pinion axis which allows the GCR to “walk” around the gear, chamfering each tooth to the depth specified on its digital display and ensuring a good quality and consistent surface finish. When it has completed one full machine cycle that entails chamfering all teeth the machine will come to a stop, disengage the chamfering tool from the gear profile, and stop the spindle. The standard red/green stack light will go to red, indicating that the machine cycle has ended. An optional automated Z-axis (spindle height adjustment) provides the ability for the GCR to increase the cutting depth for a second or third pass if the chamfering depth required exceeds single-pass capability. This optional equipment consists of programming an additional axis along with servomotor and ball screw installation. Figure 4
Included with the machine is a full set of operator manuals, electrical wiring diagrams, and spare parts list. It includes all removable safety covers for easy service in the field, and it also comes with a set of spindle collets and wrenches. The base machine includes one drive pinion and one set of perishable tooling, as well as onsite operator training at the time of machine qualification at the Banyan facility. This training will include instruction on setup and installation, configuration, use and care, preventive maintenance, and troubleshooting. Additional training at the customer’s facility is also available for an additional charge.
“We designed the GCR to revolutionize the gear chamfering and deburring market, totally changing the dynamic between operator, machine, and gear,” Witte says. “Instead of moving a multi-ton gear across the shop to a dedicated machine tool taking up valuable floor space, we decided to bring the deburring and chamfering process to the gear; the integral lifting bars make this task very simple and much safer.”