Forest City Gear Products on Actuators of New Generation Mars Rover
Forest City Gear Oct 30, 2009
Roscoe, IL - Forest City Gear announced today it has successfully completed its supply of approximately 60 space-qualified gear components, housings and carriers to Aeroflex (Hauppauge, NY), a major contractor on the newest Mars Rover vehicle for the Jet Propulsion Lab (JPL). The Mars Science Laboratory mission is scheduled for launch in late 2011 and will determine whether Mars was or still might be an environment capable of sustaining microbial life and thus be inhabitable. On this vehicle, Forest City Gear products execute mechanical motions on the actuators onboard, including drive gears, gearboxes, planetary gears and wheel assemblies. Various spur, helical and spline gear types were furnished on this project.
Forest City Gear, owing to its unique arsenal of gearmaking machines and inspection equipment, was chosen to finish, hob and shape various gear designs for Aeroflex and also to form gear grind, using dozens of CBN wheels made specifically for this project. Gears for the Rover project typically had diameters ranging from under 1/4" up to 4-1/2" and featured fine surface finishes on gears to 96 pitch. Per part, the production required ranged from several pieces to a "large" run of 100 pieces. For a number of the components, Aeroflex outsourced the blanking to its vendors, some of the top machine shops and metal fabricators in the country, with Forest City Gear then cutting the gears and/or grinding into the blanks. Forest City Gear also made many of the gears complete, per prints supplied by Aeroflex.
On many of the parts, noted the Production Manager at Forest City Gear, Jared Lyford, the profile cornering and tip relief were particularly challenging, especially on some of the various alloy materials used for this project, where performance and weight factors also held top priority.
Of particular note is a three-tiered internally geared carrier, machined from bar stock of an advanced engineered alloy with properties similar to titanium, but better able to hold the fine pitch and undercut gear design (as shown in the attached photo). This material also remained more stable during heat treating and predictable in the precise machining and undercutting required. It actually shrinks, not expands, during heat treating, but in a statistically predictable manner. This particular component is used in a drive assembly on the Rover.
Another of the unique gears used on the previous generation of Rover vehicles was a heat-treated 17-4 stainless steel tether line ring gear with a wall thickness only 0.150".
Fred Young, CEO of Forest City Gear, commented on the successes his company achieved on this project. "Our relationship with this project began with a modest order from another vendor for some small gears on the first generation Rover wheel drives. The shaping of the high crown design was a problem for the customer's previous suppliers, who couldn't get a cutter with enough back-off to successfully cut the crown shape. The crown hobbing had a shorter relief and a different cycle was needed at the back edge."
Confronted with this issue, Young suggested a design modification to accommodate the crown hobbing by shortening the spline face width, widening the relief groove voids and making the acquisition of a smaller diameter hob than could be typically manufactured. These suggestions were quickly accepted by the customer and parts were delivered in short order, with the added benefit of a weight reduction that translated into thousands of dollars per ounce on the final payload.
A similar situation arose on the second Rover's gears. The customer, Aeroflex, came to Forest City Gear for a spec check on their gear supplier's work and, upon seeing the out-of-tolerance data provided by Fred Young's quality department, gave them the order on the spot.
Since the manufacturing protocol mandated by Aeroflex for this project at Forest City Gear required 100% inspection on every dimension of every part made, the supplier devised its own software programs to facilitate easier processing of the massive data files. Aeroflex has found this documentation to be very helpful in its own quality assurance programs at its customer, JPL.
Forest City Gear provided assorted components for the previous generations of Mars Rover vehicles and, on this newest project, worked closely with an Aeroflex team led by Boz Sharif, chief engineer, Doug Ward, materials expediter and Rich Finucane, program manager. Additionally, during the manufacturing stages, JPL engineer David Rooney visited Forest City Gear several times to work with this supplier on the various products being supplied to Aeroflex.
For more information on this announcement, please contact:
FOREST CITY GEAR CO., INC.
Roscoe, IL 61073-0080
Web: www.forestcitygear.com
Email: ehawkins@forestcitygear.com
Attention: Everett Hawkins, Director of Sales
Mars Rover vehicles have been on the Red Planet since January, 2004, sending back a non-stop data stream. Forest City Gear products are used on the Rover wheel drives and deployment actuators.
Forest City Gear produced this three-tiered actuator mechanism, featuring layers of internal gears made from an advanced engineered alloy material that was found to perform more predictably after heat treating, especially in gearcutting and gear grinding operations.
The newest generation Rover, the Mars Science Laboratory, will be twice as long, four times the overall size and ten times the weight of the previous Rovers. It will be lowered to the surface of the Red Planet by a tether mechanism, similar to a sky crane. The use life on that device will be approximately seven seconds.
Isometric wheel assemblies on the Rover, including gear sections produced by Forest City Gear to its customer's design specifications.