|IDCs are reel fed into the PC board sub-assembly module. |
Manufacturers of high-density telecommunication connectors have, for the last several years, been constantly redesigning their products in a race to satisfy ever higher demand for increased data transmission capabilities (baud rates). When one major manufacturer was ready to design a category 6 (industry rating) connector, a step up from its category 5A connector, the company recognized the wisdom of teaming up early with an automation expert experienced with the challenges specific to this type of product.
One of the most important contributions an assembly automation supplier can make is that of consultant during the product design process — not as an expert in the product functionality, but as an expert in DFA (design for assembly) and DFM (design for manufacturability). This expertise must be taken advantage of before the design starts to take solid form.
These methodologies, DFA and DFM, result in products that require fewer parts, parts that are easier to feed and handle automatically, and a more reliable assembly process (higher efficiencies).
|Overall view of entire assembly system. |
Developing a process that can be broken down into simple individual steps, as much as possible, is critical to this effort. This manufacturer invited ATW to participate very early on. The challenge was to design a cost-effective CAT 6 connector that would meet exacting "BICSI" (industry association) standards. The job ultimately was to make sure the product could be mass produced reliably at the lowest cost.
The platform selected was a Bodine Model 64 high speed indexing carousel machine. One would be used to sub-assemble the PC board and one would be used for final product assembly operations.
The product in this case was a PC board-based telecom connector. The PC board is produced with pre-soldered, zero clearance holes. Once loaded onto the high speed indexing machine, one side of the PC board is populated with IDCs (Insulation Displacement Connectors), a common electronic component in a relatively straightforward process. Vision cameras are used to verify IDC placement and position. The board is then inverted in the fixture for population with the critical Contact Wires. These wires are presented on a coiled lead form. They are flattened, die cut, transferred and pressed into the zero clearance holes. The die set also pre-forms the wires and the resulting shape is critical to the ultimate functionality of the product. ATW's expert team was instrumental in assisting the product designers in the wire lead form geometry and its presentation the production line.
Once the populated PC board is again vision verified, it is ejected to a carrier puck and run through a reflow oven to complete the PC board sub-assembly process. A second assembly module performs the final assembly and testing operations.
PC boards and carrier pucks exit the re-flow oven on a conveyor and arrive at the final assembly module. Like the PC board assembly module, this is a highly mechanized, high-speed, indexing assembly platform. Operating at 50 cycles per minute it yields a gross production rate of 3,000 assemblies per hour.
PC board sub-assemblies are transferred from the carrier puck into the assembly machine fixture. Carrier pucks are shuttled onto a return conveyor for the ride back to the PC board module. All part transfer operations are followed by an inspection station to verify part presence and position in the fixture or the assembly. Next, the machine vision re-verifies the contact wire positions that are so critical. A vibratory feeder bowl is used to present an insulator which is transferred and then inspected in the subsequent station. A label is placed on the insulator and its presence and position are verified at a vision check station.
Inverting the Sub-Assembly
At this point the sub-assembly is inverted 180° in the fixture. It is inspected and indexes to the next station. A nose housing is fed vibratorily and transferred onto the PC board, capturing the contact wires in position. The nose housing is inspected for presence and position. Vibratory feeder bowls are a very common method for feeding component parts automatically to high speed assembly systems.
|Populated PC boards in carrier pucks are shuttled into the reflow oven. |
The nose housing is ultrasonically welded to the insulator. This process is verified by electronically monitoring the ultrasonic welder itself; power output, horn pressure, displacement after firing, etc. Two labels are then fed from reels and automatically transferred to the nose housing. Vision is again used to verify presence and position.
The assembly is now laser-marked with a product identification number and a date code for production tracking purposes. Next, the product is tested electrically for functionality. Two separate continuity checks verify contact wire, PC board, and IDC connectivity. This is followed by a Hi-Pot test which insures that no shorts or arcing occur, even with exposure to relatively high voltage.
Once the product is assured "good", a stuffer cap (acts as a cover) is fed, transferred, and snapped onto the assembly. And this too is inspected for presence and position. Good assemblies are ejected to a take-away conveyor for pack-out. Faulty or incomplete assemblies are ejected categorically to various reject chutes, depending on the reason for rejection. The electronic controls which monitor the assembly system (normally a programmable logic controller) use a shift register memory to lock out downstream operations once a specific assembly is determined to be faulty.
This highly automated system has proven to be extremely productive and reliable — in large part because of the early-on
collaboration of the product design team, the customer's manufacturing engineering team, and the automation experts at Bodine, the system designer and builder, now available through ATW. Contact: ATW, Assembly & Test Worldwide, 230 Long Hill Cross Road, Shelton, CT 06484 203-712-1929 fax: 203-712-1907 E-mail: firstname.lastname@example.org Web: http://www.assembly-testww.com