Bourn & Koch, Inc., has been on a growth path for the past number of years. The growth has been accomplished by acquisitions and new product development, both during times when the market has been shrinking. One of our latest acquisitions was the Fellows Corporation, in July 2002. The product line was well respected in the industry as a leader in its day, so much so that some of the competition has copied some of the strengths of the Fellows design. The Fellows product line had not made any major impact in the industry with new technology in recent years — until now, with the introduction of the HS650 Gear Shaper.
The Gearless Gear shaper is a truly electro-mechanical machine taking advantage of the heart of the Hydrostroke integrated with state-of-the-art CNC control, true digital motors and drives, control system theory and structural dynamics, clever mechanical design, and strategic use of materials. This value engineering approach resulted in more than a 50-percent reduction in the number of piece parts used to construct this machine. (Table 1)
The new-generation HS650 Vertical Shaper integrates state-of-the-art CNC hardware, integrated digital drives and motors, and unique mechanical designs to provide a more-robust solution for shaping gears then ever before.
A physical description and verbal layout of the machine is shown on Figure 1.
Mechanical Design Highlights
The machine is reviewed here from the workpiece to cutting point interface and out through the remaining structure.
Stroke Axis: The Hydrostroke Edge
Key Hydrostroke technology has been integrated into this new-generation shaper. The Hydrostroke is the heart of a productive shaping system. The system has the continued advantage of quick return action that has made the Hydrostroke the most productive gear shaping system available, setting the industry standard for performance. The new arrangement integrates positioning, stroke, and return ratio setting into a single axis. This allows for simplified end user set-up and increased programming flexibility.
Previous generations of the Hydrostroke spindle were led by a rotary motor on the end of a rotating shaft. This arrangement made it quite difficult to estimate true cutting performance. The new arrangement allows the Hydrostroke to be led by a truly linear actuator. This linear actuator is a digital high-force linear motor provided as a complete package from the CNC provider selected.
Other benefits of the Hydrostroke include concentric force loading on the spindle, thus providing less wear and damage to spindle support bushings. The Hydrostroke also allows for direct measurement of the cutting pressure by reading the load sensor. The load sensor is used to adaptively control the supply pressure for energy efficiency. As with any new machine-tool investment, tooling is an expense. Great care has been taken to ensure that the new design is compatible with previous tooling for this class of machine: 50-8, FS630-200, etc.
Optional CNC Guide
The CNC guide of the Gearless Gear Shaper has been designed in a manner to match the high-stroking speed of the Hydrostroke with a high performance rotary action to allow no lost performance.
The Gearless Gear Shaper has CNC guide capabilities for job shop activities and early riser production while meeting high production demands with dedicated guides that can be integrated to get maximum utilization for full production requirements. Having the capability to utilize both the CNC guide and rigid guides allows the high-production end user to do “proof of concept” work on new gears and early production requirements while specifying the final helix requirements in the design cycle. This allows a strategic overlap from the end of previous production and the ramp-up of a new product.
The Hydrostroke cutter spindle has been carefully supported by a high-precision, high-stiffness bearing allowing the high torque digital integral motor to rotate the spindle to perform high-speed helical motions. The arrangement takes advantage of common components on previous generation Fellows machines, making spare parts more readily available and minimizing the customers’ inventory and spares costs.
Oriented Stiffness Back-Off, CNC Roll-Over
Back-off cams, bearings, and spring tension required substantial maintenance, manufacturing costs, and set-up difficulties. The design intent of this axis was to simplify the operation, maintenance, assembly, and manufacture while providing increased capability. The new arrangement eliminates cams, rotary bearings, and spring tension. It provides stiffness in the proper orientation to allow the required rotations without the use of bearings or expensive hard to maintain cams. Additionally, the orthogonal directions provide increased stiffness in the direction required to oppose the cutting forces.
When switching from an internal to external gear, there is no need to reverse, or “Roll-Over” the cam. This is handled entirely by a CNC program: simply program a negative motion and add a minus sign. How much simpler could it be?
The axis is constructed of a clever oriented stiffness design attached to a high-force linear actuator. This creative design allows for a 15:1 force ratio amplifier, enabling extremely high force to oppose the potential 8,000 lb cutting load. This axis has a linear scale feedback, providing precise motion location.
C-Axis Table Construction
In the same philosophy of creating a truly electro-mechanical system, the table of this machine was redesigned to accommodate a high-torque integral digital motor assembly. This is integrated with a high precision rotary encoder, providing up to 250 times the rotational accuracy over traditional worm and worm wheels. Combined with the CNC guide axis, this will provide a more precise location of the cutting edge. Other advantages of the new design include no backlash and no worms or worm wheels while maintaining previous features such as spindle chip evacuation and an internal work clamp cylinder.
Vertical Elevate Positioning Axis
The HS650 has been designed with a gantry twin ball screw arrangement to allow the user the ability to reposition the cutter spindle via a CNC part program. This motion is 300mm long and allows the user to move the cutter spindle up and down to accommodate different gear locations along a shaft, or perhaps multiple gears on the same shaft when integrated with a tool change.
The in-feed axis has been constructed to allow quick access to parts. This is performed through a standard ball screw transmission with a direct-coupled servo motor. The axis has been constructed in a manner to allow the addition of an extension riser, and also for manual introduction of cutter rub movement.