System builder and integrator Demco Automation recently was asked by a major manufacturer of ophthalmic surgical instruments to automate a manual assembly process for retinal needles that relied on visual inspection by the operator. Demco saw the application as a perfect fit for its patented Wedge rotary dial machine for automated small parts assembly and inspection. For quality control, the Demco solution added a DVT machine vision camera. Today, at lower cost and with greater efficiency than the manual process, the Wedge produces retinal needles that are 100% inspected and have zero defects.
At the medical device company in Sinking Spring, PA, only a limited number of operations have been automated; most are performed manually, as was the case with the retinal needles, which were bent and flared by hand and then hand inspected under a microscope. Consequently, each was manipulated by 4 or 5 workers in a tedious process that created a lot of scrap.
Demco was charged with building a system that would produce a 1.2 degree bend in the needle, ±0.1 degree, and then inspect the needle to confirm the bend was within spec. To tackle the job, they built a 10-station Wedge with a DVT inspection camera installed at the bending station. A complete machine vision system in a single palm-size unit, Model 544 smart camera with 1,280 x 1,024 pixel resolution does not require a separate processor, cables, cord, or remote heads. It also has plug-and-play capability with all Logix controllers, including MicroLogix.
A scalable automation platform, the Wedge allows the customer to prove out processes at a station level in a manual mode and then move those same stations to an automation chassis to fully integrate the process. Assembly stations can be reconfigured in minutes through the use of quick-connects/disconnects, modular controls, and easily removable mechanical systems. The design eliminates the need for drilling or modifying tabletops, motion control software, and station wiring when reconfiguring the base machine. "We save our customers time, money, and the frustration of building automation from scratch," says Demco President Tom Garrity.
Built in less than 12 weeks and installed in only 8 hours, the 10-station Wedge moves the surgical needle through a series of stations where the needle stock is loaded into the dial nest; clamped and located, and flared at the ground end; and bent by a pneumatic press with integrated tooling. A pressure transducer/switch is used to ensure the bending force is met during each cycle. After bending, a mark is placed on the large tube to aid the downstream operator in determining proper orientation. Before the end of the cycle, the DVT vision system inspects the bend. If a rejected assembly is present, it is flagged to be removed from the system by a pick-and-place unit, equipped with gripper, that drops it into a rejected parts tote. Needle assemblies passing inspection are manually removed from the dial nest and placed into a tray for downstream processing.
Designed for dial assembly and rotary table applications, a 16-position Camco roller drive indexer enables precise station-to-station positioning at very high speeds. The low-profile, large-output surface unit has hardened cams, precision cam followers, and oversized bearings on all shafts. A 4-point contact bearing, with a large through hole, supports the output shaft.
One of the unanticipated benefits derived from installing the Wedge has been the addition of midstream inspection. The DVT camera can "see" contamination in a needle and reject it in midprocess. As a result, the company has been able to go upstream and improve the grinding/stage, cutting costs dramatically. Previously, a faulty needle would have made it to the end of the line as part of the entire reject batch, with no information as to why it was rejected.
According to Garrity, the compact DVT camera has played a critical role in the success of the system. Integration with Allen Bradley controls was seamless; the intuitive software speeds programming. "We think the DVT camera is an excellent value and highly recommend it to all of our customers," he concludes.