Guide Used in Leak-Testing System or Plastic Bottles
- Friday, 01 December 2006
Container leaks can range from mildly annoying to potentially dangerous. To avoid faulty containers from ever leaving the production line, producers have installed testing devices as part of the bottle production process to ensure integrity. As many bottle/container manufacturing systems were pre-existing, a unit able to integrate itself into the existing production line without necessitating a long shutdown or costly re-design was seen as ideal. When Air Logic Power Systems Inc, (ALPS, Milwaukee, MI) developed such a unit, the RS-100 Plastic Container Integrity Tester, it chose the PDU2 linear transmission unit from HepcoMotion (Tiverton, UK) and distributed by Bishop-Wisecarver (Pittsburg, CA). Using the PDU2 eliminated many of the bottle handling issues that could potentially slow production by its ability to move in synch with an existing production line.
Made of aluminum and belt-driven, HepcoMotion’s low-maintenance PDU2 profile driven unit forms one part of the APLS’s RS-100. The linear motion PDU2 drives the probe head that conducts the integrity test swiftly back and forth so that it moves with each bottle without disrupting the product flow. The device integrates into existing conveyor systems and works “on demand,” testing a bottle when it is sensed by means of a photoeye when it enters the testing chamber (a see-through guard encloses the slide and probe head, keeping hands and fingers out and away from the moving parts). The herculane wheel technology employed by the guide provides motion, speeds, and acceleration. While its length is manufactured to a customer’s specifications, the PDU2’s width and height already fit ALPS’s configuration for the RS-100, so no redesign of the testing system was required. The carriage plate is designed to accommodate the mounting of a second unit; with the RS-100, a probe head that tests each bottle is attached to the plate (in this application, the PDU2 is installed in a upside-down configuration). Since ALPS began testing its first PDU2/RS-100 unit (which stands 103" tall and is 53" wide), it has logged more than 50 million cycles. The machine is controlled by a touch screen interface to allow ease of use.
Specifically designed for the for the PET (polyethylene terephthalate) bottle manufacturing industry, pharmaceutical bottles, health and beauty containers, containers for consumables (soda, juice, and water), and chemical containers can all be tested via the RS-100. PET can be semi-rigid to rigid (depending on its thickness) and is lightweight, and is one of the most commonly used plastics, being biologically inert, resistant to impacts, lightweight, transparent, a reliable gas/moisture barrier, and able to keep its shape. In bottle manufacturing, raw PET pellets or test tube-like preforms are first are heated and blown into the intended shape (including the threads for the cap) by means of a blow/injection molder, then conveyed away to cool. The RS-100 tester serves as the second stage of the production line, fitting into the line where the bottles are cool enough to be pressure-tested without their shape being permanently warped by the test. Bottle production accounts for approximately 30% of the global PET demand.
The RS-100 fastens onto each bottle/container by means of the guide-mounted probe head. The probe head extends and comes down, sealing itself onto the bottle, and as probe and bottle run the length of the guide (38.5 inches), the pressure-decay leak test is performed, although with customization, the test can be performed in 150 microseconds. Monitored by computer, the pressure test involves air that is injected into the container and a pressure test is then performed to verify the integrity of individual bottles. The RS-100 typically tests in the range of 40 to 120 bottles/containers per minute, depending on the container size (up to 160 for small containers). Bottles found to have leaks are automatically ejected from the conveyor with an air jet into an adjacent bin and eventually reenter the bottle-forming process. After a successful test, bottles move on to the packaging process. The machine can stop bottle flow if necessary, and prevent untested bottles passing through it. Additionally, the RS-100 features a control downstream diverter for bulk packing of containers. An additional photo-eye can monitor downstream bottles for jams as part of a larger system-wide efficiency check.