Molded Parts: Stamp, Place, Remove, Inspect
Filtertek, Inc. is a world innovator in filter technology. The Hebron, IL, manufacturer makes custom filtration products and fluid control devices for automotive, healthcare and consumer product applications. The company’s ingenuity is reflected in a portfolio of more than 340 issued patents and pending patent applications for novel designs of fuel filters, transmission sump filters, semi-solid product dispensers, check valves, IV filters, and more. But it had a problem. Said John Leahey, Filtertek’s director of domestic medical products, “We needed to increase the output of injected molded parts to meet our customers’ demand.”
HiTech Manufacturing Solutions, Inc. in Green Bay, WI, specializes in designing and building custom automation machinery. Project Manager Larry DeGroot worked on a concept for Filtertek and HiTech was consequently contracted to build and integrate automation machinery with a molding machine. As a result of HiTech’s integrated approach, Filtertek doubled its production volume while significantly lowering and/or eliminating labor and material usage.
What Filtertek had before
“The biggest challenge in designing this machine,” DeGroot said, “was thought to be the punching and handling of the membrane. As it turned out, this was easier than expected.”
However, unexpected challenges occurred in the speed and handling of parts during the unload and inspection stages, said DeGroot. “But with our strong engineering skill set and communication with the customer, we were able to come up with robust solutions,” he said.
Previously, for example, the screen inserts in one of Filtertek’s products were produced in a manual, sheet-fed operation. In the new, automated machine, the screen insert is made from a ribbon feed and the inserts are loaded directly into the part cavities. Also, the parts used to be inspected as a separate process. In the new line, DeGroot says, 100% inspection is done in-line, at twice the production rate.
HiTech designed, built and integrated the automated machinery to:
Punch and place a hydrophilic membrane;
Remove finished filters;
Vision inspect 100% of filters for the presence and placement of the membrane; and
Test air flow rate in process on a statistically significant sampling of finished filters.
The system is designed to produce 48 parts every 15 seconds. Parts are sorted and retained by mold base (four mold bases) from the molding machine. A Rockwell Automation Allen-Bradley MicroLogix 1500 PLC is used with DeviceNet I/O. A Pro-face Xycom touchscreen industrial PC running Windows XP is the HMI hardware. Rockwell RSView Machine Edition software is used for the operator interface, employing embedded ActiveX controls to connect two Cognex DVT machine vision cameras. Through the interface, the operator can view batch controls, machine status, machine position, alarming, the vision system interface with real-time images, and production data/statistics.
After the first molding station completes a set of parts, the runners are ejected and captured for recycling. Sensors and fault logic ensure runners are not left in the mold.
Next, a punch press cycles on demand and cuts 48 pieces of membrane as the molding press table indexes. A vacuum fixture picks up these membrane discs, retracts, and lowers them into molded component halves. MAC pneumatic controls ensure that all filters are inserted into the parts.
At the filter ribbon handling stage, six 3-in. reel hubs are mounted on the punch press stand. A servo drive advances the filter ribbons to minimize waste in the ribbon and ensure that no splices are punched. Reel sensors alert operators when the reel is getting low on material.
Handling finished parts
To remove the molded parts, a servo-driven carriage is used to move grippers over finished parts. Finished parts are positioned by the mold where they can be gripped and taken from the mold/molding machine by an end-of-arm removal system. While transferring from the mold, runners are automatically removed from the end-of-arm grippers. The carriage has a servo-driven slide to allow the parts to be unloaded into zones on an inspection conveyor. Loading into zones optimizes unloading speed.
A servo-driven conveyor with fixtures is used to sequence parts for inspection and testing. Parts are tracked along the conveyor using a known, repeatable unloading sequence and data shifting to follow the conveyor. This allows the parts to be sorted into appropriate individual bins matching mold bases. Parts are sampled off the inspection conveyor by the flow testing equipment. The sampling cycle rate is user selectable, up to three times per hour. Sampling allows each mold cavity to be tested during a test cycle.
Each part that is not flow tested is inspected by a Cognex Model DVT 515 vision system. “The vision system uses telecentric lenses and on-axis lighting to allow internal and external inspection of filters,” says DeGroot. “This is needed because the filter is half way down the inside of a cylindrical part. A telecentric lens allows simultaneous inspection of the inside and outside of the filter.”
Filter media is tested for presence and correct placement. Good parts are removed using pneumatically operated suction and guided into a servo-driven parts diverter. Bins for each mold allow the diverter to segregate good parts, which allows the user to monitor product quality for each mold separately.
This new concept in molding automation provided the customer with a reliable machine that produces a quality product, including 100% visual and in-process air flow rate sampling inspection. As a result of HiTech’s integrated approach, Filtertek greatly increased its production while significantly lowering and/or eliminating labor and material usage.
|Renee Robbins is senior editor of Control Engineering. She can be reached at email@example.com|