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Conair and partners to demonstrate medical swab tube manufacturing 
Source:Adsale Plastics Network    Editor:JK    Date:27.Jul.2021

At Plastec/MD&M West 2021, Conair Group is once again partnering with Davis-Standard and Zumbach Electronics, this time to demonstrate high-volume production of medical swab tubes used in COVID-19 test kits.


After extrusion and cutting, these extruded polypropylene tubes are tipped with a flocked nylon swab head and used for collecting nasopharyngeal samples for COVID testing and other medical applications.


The long, very thin swab tubes (0.09 in. x 5.58 in.) begin as a continuous plastic tube produced from a ¾” Davis-Standard Medical Extruder. As the hot tube exits the extruder die, it passes through a water-filled pre-skinning tool, developed by Conair, which rapidly hardens the fragile extrudate before it enters a 5-ft-long Conair MedLine Model 235 vacuum cooling tank.


The tank’s water temperature and vacuum level, managed by a PAVC+ vacuum control through a touchscreen HMI, create gentle pressure inside the warm extrudate, stabilizing tube dimensions as final cooling takes place. A ceramic air wipe assembly dries the product as it exits from the tank.


Like all Conair MedLine products, the Model 235 vacuum tank is based on a proven Conair design, but is specially sized, configured, documented and supported for use in cleanrooms and other controlled environments.


Just inches inside the vacuum cooling tank, QC measurements begin as the “hot” tube passes through an immersed ultrasonic gauge supplied by Zumbach Electronics, which takes continuous wall-thickness measurements.


At Plastec/MD&M West 2021, Conair, Davis-Standard, and Zumbach Electronics partner to demonstrate medical swab tube manufacturing.

Some six feet later, after the tube has exited the tank, a second Zumbach instrument – this time, a three-axis laser gauge – continuously measures and displays the OD, ID, and ovality of the now-cooled tube on a display screen. The data from these two instruments are used for two purposes. 


First, they provide closed-loop control of critical tube dimensions throughout the production run by regulating puller speed and cooling tank vacuum. Second, they feed QC and length data that is used by downstream equipment to identify and eliminate any out-of-spec product before it reaches the final collection point. 


After laser measurement, the extruded tube continues through a Conair MedLine MD-L1-12-D puller/cutter unit, where dual belts (top and bottom) powered by a dual-servo, planetary-gear drive gently pull it forward at speeds precise to ±1/100% of setpoints.


Upon entering the cutter section, the tube passes through specially-lined stainless-steel bushings where a high-speed rotary knife automatically cuts it into finished swab lengths that fall onto a Conair MedLine 403 takeaway conveyor.


A final product sort is made on the conveyor, using a QC mode available in the MedLine cutter control. This mode receives dimensional and length data from upstream instruments, then digitally “marks” any out-of-spec tube sections using a length offset that enables the cutter to track their position on the line. Then, the cutter can be programmed to cut those sections differently or not at all, or to instruct downstream equipment to handle those sections differently.


In this demonstration, the cutter control removes good tubes from the takeaway conveyor with a puff of compressed air, blowing them into a bin for collection. Out-of-spec parts are left to flow to the end of the conveyor for reprocessing.


The tubing line is controlled by the Davis-Standard eVue Control System. This is a PLC-based controller with a touch screen HMI that communicates with the Conair and Zumbach equipment to control the entire line from one location.


Moreover, the demonstration of the cleanroom-ready MedLine vacuum tank, tooling, and puller/cutter unit is supported by several additional Conair auxiliaries:


The polypropylene resin for the swab tubes is drawn directly from machine-side storage and fed to the extruder feed hopper by a Conair AL-2 Access Loader. This self-contained unit is equipped with an angled stainless-steel canister and its own vacuum motor, which can deliver up to 100 lbs/hr to the extruder’s feed hopper. The loader’s straight-through tubular body ensures smooth resin flow, even in low quantities.


Tempered water used in the pre-skinning tooling and vacuum cooling tank is provided by a single Conair TW-P temperature control unit. This TCU, representing the top end of Conair’s Thermolator product line, is equipped with a premium digital HMI, solid-state relays, and a modulating cooling valve.


When the TCU requires chilled water to maintain a precise cooling temperature, it is provided by a two-ton Conair EP2A portable chiller, which features nonferrous internal components (evaporator, pump, reservoir and piping) for long-lasting corrosion resistance. This chiller has a compact footprint with an easy-to-access interior, and a touchscreen HMI control that provides precise temperature control along with extensive diagnostics.



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