At Andrew Tool & Machining Inc., coordinate measuring machines (CMMs) are a key element of the manufacturing process, but they had never faced a project with such intricate measurements, tight tolerances, heat treatments and a very short time frame requirement. Their objective was to land an order for an MSL project (Mars Science Lab). A CMM from Carl Zeiss should make it happen.
Carl Zeiss had already demonstrated its capabilities at Superior Tool, a sister company to Andrew Tool. "Our PRISMO CMM at Superior Tool is the backbone of our quality department and my goal was to replicate and build on this capability at Andrew," says President Bruce Hanson. Andrew Tool is a unique machine shop with over 30 years of experience handling everything from very simple to the most complex geometries. The majority of Andrew Tool’s customers are found in the aerospace, defense, medical and microelectronic industries, all having parts that often require extremely tight tolerances.
This new, complex project from MSL required Andrew Tool to manufacture actuators (gearboxes) for the next Mars rover, Curiosity. This new rover will weigh over 10,000 lbs, five times the weight of the current rovers, and carry more than 10 times the weight in scientific instruments compared to the current Spirit or Opportunity rovers. Therefore, the propulsion system’s power and torque will be more robust, and the unit’s wheels considerably larger than previous designs. NASA engineers believe these changes will help prevent the problem that Spirit is encountering now: it’s stuck in a sand pile.
There were many parameters that Andrew Tool had to adhere to in order to help NASA make their new actuator design a success. Many of the parts had very deep pockets, small radii added to the challenge, along with extremely tight tolerances, many of which are tied to different gear pitch diameters. Additionally, position tolerances of .0005 millimeters, control of .002 millimeters, and size control within .0025 millimeters, even on relatively large dimensions added to the challenge. All of these factors coupled with a demanding 18-month timeline and AS9100 certification requirements made it critical for Andrew Tool to bolster its CMM capabilities for precision and speed. Andrew Tool decided to purchase the ZEISS ACCURA with the VAST XT gold active scanning sensor.
With any new machine being added to the production process, there’s always a learning curve. “The ZEISS ACCURA helped us orchestrate the project by providing timely, accurate, and understandable in-process reporting. It can’t be overstated how critical good inspection is for process development and setup,” says Bryant Broderick, Quality Control Engineer at Andrew Tool. The project included 14 different part numbers with quantities ranging from four to 12 plus setup parts. The temperature compensation feature was especially helpful because they were able to check parts right off the machine tool and relay the results to the toolmaker. With a coefficient of expansion of 0.14 µm per degree, a few degrees could mean the difference between pass or fail. “We were amazed by how effortless the ACCURA made this whole process.”
The robust reporting capability in CALYPSO is a great asset for the AS9100 certification process required by NASA. This certification involved a lot of time on the program management side of things, ensuring there was documentation for all of the critical paths of each part throughout the manufacturing process. All of this information was contained in a spreadsheet with all of the serialized parts to clarify where each part was at any point. CALYPSO software easily documented the information electronically each time the part was measured. “Verbal information of part details means nothing; documented data is everything,” states Don Felix, Director of Sales and Marketing.
“We couldn’t have been successful without Carl Zeiss,” says Felix. “The benefits Zeiss brings have been enormous and we see positive results every time we use the CMM.” Andrew Tool even acquired a new customer after another NASA supplier saw several of the MSL actuator parts. They were so impressed with the precision and complexity of the parts that they were instantly sold on Andrew Tool’s capabilities. Andrew Tool was ready to accept this new challenge with enhanced confidence in the data from its ZEISS CMM.
Headquartered in Minneapolis, Minnesota, USA, Andrew Tool & Machining focuses on the product development process.