Today’s consumers take for granted that their cars’ transmissions — whether manual, automatic, or differential, luxury or entry level — will operate quietly, smoothly, and dependably. But behind the scenes, auto manufacturers, gear designers, and suppliers have worked hard to design, develop, and produce the high-quality transmission gears and shafts that make it all possible. Quality requirements are such that many of these gears are routinely hardened and then finished with threaded wheel grinding or honing. The reliability and productivity of these “hard” processes, as well as the manufacturers’ ability to master them while driving down cost and delivery times, are dependent on the technologies used for the “soft” processes performed upstream: hobbing, chamfering, and deburring.
Hobbing with integrated chamfering and deburring
It’s well-known that a completely burr-free tooth slot and a precisely defined chamfer are fundamental prerequisites for the honing process that’s used most often with shaft-type parts where minimal clearance prohibits grinding and to reduce the noise issues that may result from a ground shaft running with ground gears. For both gears and shafts, generating a chamfer to precise customer specification for size, shape, and angle is of critical importance in order to minimize the potential for sharp, brittle edges after heat treat, as well as to optimize material and conditions in the tooth flank prior to the finishing operations. Additionally, excessive stock and hardened burrs can diminish honing tool life and significantly increase cost per piece.
Today, Gleason is meeting the challenge for making these operations more efficient by fully integrating them into two new horizontal hobbing machine solutions: the P90CD for disc-type parts, such as planetary pinions, sun gears, and small shift gears, and the P90iC for shaft-type parts. In both cases, the aforementioned chamfering/deburring operations — often still performed on separate machines in multiple setups — now can be accomplished on a single machine. Customer benefits include improved cycle times, lower equipment costs, and more consistent quality.
Both of these new solutions are based on Gleason’s well-known small horizontal hobbing machines, which are operating now in nearly 1,000 installations worldwide. Horizontal machines, with optimized chip flow away from the work area, are ideal for the dry cutting conditions preferred today in many of the world’s high-volume manufacturing environments. The P90 platform offers a hob head design that delivers the torque and rpm needed to take full advantage of Gleason’s most advanced solid carbide or G90 hobs, featuring AlCroNite®Pro coating, for dry, high-speed cutting.
The P90CD features a chamfering/deburring unit that gives users the ability to perform chamfering/deburring in parallel with hobbing, resulting in a remarkable cycle time of just 10 seconds chip-to-chip using high-speed gantry load/unload automation and Gleason workholding with a fast clamp/unclamp capability. The gear is hobbed and the rough burr that results from hobbing is removed in a single setup. Then the gear is unloaded by the gantry and loaded into the chamfering/deburring station, where rotary chamfering with deburring is performed simultaneously while another gear is hobbed. The gantry then unloads the finished gear onto input/output automation and picks up a blank to repeat the process.
The P90iC also integrates chamfering/deburring, but it is configured differently to accommodate shaft-type parts and to eliminate the burrs typically formed by rotary chamfering in the tooth flanks in a subsequent second cut. As a result, the processing of workpieces on the P90iC is sequential, but performed in a single setup: load; first hob cut including removing the rough burr; rotary chamfering and deburring; second hob cut to remove the burr on the tooth flank and to generate the required scallop depth; unload; and repeat.
In conjunction with these machines, Gleason offers a wide array of rotary chamfering and deburring tools. Solutions range from simple chamfer tools for basic chamfer requirements to highly sophisticated chamfering tools that include burnishing options for producing precise chamfers with very tight tolerances.
Versatile automation systems
Both machines are easily adaptable to different customer stocking systems, from simple input/output conveyors to much more robust solutions that can add many highly desirable processing stations either pre- or post-hobbing. Among the most versatile are those built by Gleason Automation Systems. Automated load/unload is performed from stackable tray systems that prevent part-to-part contact, which is common in free-flow conveyor systems. Secondary operations such as coolant spin-off, laser marking, in-process gauging, pin stamping, and others can be easily added to meet many customer objectives.
These new Gleason machines — built on a globally proven platform and supported with the latest cutting tool, workholding, and automation solutions all from a single source — represent a significant step forward for manufacturers of automotive transmissions seeking to achieve that delicate balance of high quality with reduced cost per workpiece.