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Machine No. 5370
This machine automatically assembles and tests the tip of a Disposable Biopsy Forcep that is made up of 8 components. The parts are very small as illustrated above. The Cups, Links and W. Connectors are loaded into a pallet tilled by a shaker table. The operator then loads the entire pallet onto the machine. The machine then assembles the parts into fixtures on a precision link index conveyor. Even though the accuracy of the indexer is quite good, the small size and tight tolerances of the parts requires an extreme amount of precision that is not attainable mechanically. Each part is visually located with a CCD camera connected to a PPT vision system prior to being picked and placed. The location is also verified visually before the part is put down. The two Cup and Link assemblies are built separately in two cavities in the fixture and are later combined into a third cavity with the W. Connector. One of the Cup/Link sub-assemblies gets tipped over before it is placed in the final assembly cavity. The parts placers are built using precision THK Linear Guides and ground ball screws to give a repeatability of 0.0005″.
MACHINE CONTROL – The machine is controlled by a pair of Intel 486 based PC’s. The main control computer is a 20 slot passive backplane computer with a 486SX-33 processor. It has four 8 axis DSP based motion control boards that control the motion ot the 28 servo and stepper axes on the machine. Two TMS 34010 based vision system boards and a GE PCIP card used to communicate with up to 4 racks of GE 90/30 Input Output modules. This computer actually controls the real-time operation of the machine using a custom C++ program running on DOS 6.2 The other computer is a Compaq 486/33 that provides the Man Machine Interface and Data Collection. This computer has a touch screen monitor and runs a custom Microsoft Visual Basic program to interact with the operator. The two computers communicate over an Ethernet network cable.
CYCLE RATE – The machine produces 1 complete assembly every 30 seconds.
ROBOTS – The 5 part loading stations use tour axis Cartesian coordinate robots made up ot Intelligent Actuator servo driven ball screw slide modules. Each axis module is repeatable to +A 0.0004″. All modules are heavy duty and are dowelled or keyed together to preserve alignment if they are disassembled for repair.
WELDER – Two Aidlin Automation capacitive discharge resistance welders are used in combination with a controlled force to form the ends of the rivets during assembly. Miyachi weld monitors are used to measure the current and pulse duration of the weld to ensure repeatability and quality.
BASE – The base ot the machine is composed ot a welded heavy wall steel tube frame with a 1 1/2″ thick steel table top. The entire assembly is blanchard ground flat after stress relieving The entire base and electrical enclosures are powder coated to clean room standards.