Higher accuracy, increased inspection throughput, reduced part failure rate
As Rochester Precision Optics (RPO) knows all too well, optical component manufacturing requires high accuracy inspection with a delicate touch. A recent expansion in production and an increasing demand for faster throughput and improved part quality made the search for the right quality inspection equipment much more important.
RPO, located in West Henrietta, New York, recently added 43,000 square feet of space to their existing 64,500 square foot headquarters building in February 2012. This expansion facilitates the increased demand of their comprehensive design and manufacturing capabilities for rapid prototyping and high volume production of lenses, assemblies and sub-assemblies. For quality inspection, RPO had been using various gages, optical systems and various manual tools. They now needed a CMM (coordinate measuring machine) to give them the higher accuracy and increased measuring throughput to meet new customer requirements.
RPO chose the MICURA bridge-type CMM from Carl Zeiss Industrial Metrology. “Accuracy was our main concern, but the MICURA was also the right fit for measuring our small, intricate parts,” states Nick Gennarino, manager of Quality at Rochester Precision Optics. The compact MICURA 5/5/5 with VAST XT gold active scanning sensor is designed to provide submicron accuracy and low probing force with high-speed scanning rates of up to 200 points per second.
In addition to incoming, in-process, and final inspection, RPO uses the ZEISS CMM for first article inspection and design research. The most common components they measure are the metal or plastic barrels which will contain the lenses and are about 2 to 4 inches long. First, the material is machined to the required tolerances for various diameters, undercuts, grooves and threads. That is followed by the initial inspection on the CMM. Once the part is accepted, the lot will move through production, with machinists performing in-process checks with hand tools and carrying out periodic checks on the CMM. After the lot is completed, final inspections are done on the MICURA before and after the parts have been plated by a 3rd party. It’s critical to monitor part dimensions closely before and after the plating process because of the inherent risks of dimensional changes resulting from the plating process. Pre-plate dimensions are correlated with post-plate dimensions to better control the final product, improve efficiency and reduce waste. “You have to know what you’re putting into the plating process so you can expect good parts out of it,” states Nick. Once all of that is complete, they move to the assembly department. Targeted tolerances range from 3 to 10 microns and they currently measure about 40 barrels per week.
After a few short months, RPO noticed increased throughput along with a significant part failure rate reduction. A big challenge with the aluminum barrel inspection was meeting the required tight tolerance dimensions before the parts went out for plating. With the ability to check the barrels on the MICURA before and after plating, the part failure rate has been reduced from 30 percent to zero. “For us, that was huge,” says Nick. And on one particular barrel, a 13-piece inspection period was reduced from 8 hours to 2 hours. This increased throughput allows RPO to inspect even more part types now.
In addition to increased accuracy and speed, the MICURA has brought new inspection opportunities to RPO. Molds for glass lenses, from another department within RPO, can now be measured in house. Mold profiles can now be checked for the accuracy and precision needed to provide meaningful information to discover mold issues that they can now correct. “We can drill down to the micron, and see everything if we need to,” remarks James Keene, mechanical inspector / programmer at RPO. They have also been able to understand their parts and processes better, and see how part material is changing. “It’s amazing to see how much material can grow, shrink, or warp,” states Joe Hennigan, mechanical inspector / programmer at RPO.
Rochester Precision Optics (RPO) was formed in 2005 when it acquired the manufacturing technology, intellectual property and assets from Kodak Optical Imaging Systems. Starting production in 2006 and building on its core technology of precision molded glass aspheres, RPO has grown from 27 employees to over 190 today.