EQUIPMENT NEWS
Slot dies apply optically clear coatings while maintaining accurate coat weights
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A fixed-lip slot-die coating system enables converters to produce very thin and optically clear coatings and maintain coat weights within close tolerances. The Liberty dies can be incorporated into a coating system from Extrusion Dies Industries (Reichshof-Wehnrath, Germany) and can be adapted for a wide range of single- and multilayer applications and for such specialized techniques as stripe and discontinuous patch coating. The fixed-lip configuration is said to be more precise and productive than the roll-coating alternative: unlike systems that wipe coating fluid onto the substrate, this system uses coating heads with lip gaps up to 3 mil from which fluids are drawn to coatings as thin as 1 µm. The slot dies have maintained cross-web coat-weight tolerances within 3–5% in commercial applications involving many fluids and substrates, even at a coating thickness of 2 µm.
While the lip of the die is fixed, coating thickness and width can be varied by means of interchangeable shims. Coatings of more than one layer can be applied through dual- and triple-slot dies or through slide-type, or cascade, dies made up of an array of die bodies set at an angle to the web and capable of dispensing 10 layers of coating or more. Single-slot dies can be supplied for coating web widths up to 3 m and for wet coat weights of less than 1 µm to 254 µm. The dies are typically shipped as part of a system including a positioner, vacuum box, and fluid-delivery equipment.
Wall-thickness scanner installs in extruder cooling trough
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A pair of ultrasonic wall-thickness scanners feature transducers that can be synchronously adjusted to have the optimal measuring position within seconds. The UMAC Z50 and UMAC Z100 scanners, available from Zumbach Electronics AG (Orpund, Switzerland), together cover an extrusion size range of 5–100-mm OD. They provide fully noncontacting in-line wall-thickness measurement of tubing, hose, and cable jackets. Full process control becomes possible when a scanner is used in conjunction with the manufacturer’s Wallmaster data acquisition, processing, and display system.
The compact scanners can be installed in the cooling trough directly after the extruder in the processing line. They provide automatic control and easy centring, though exact centring is not critical. Available configured for four or six points of measurement around the circumference of the extrusion, the devices allow quick positioning of all transducers through a central adjustment, while an easily removed segment facilitates product change. A single scanner offers a large measuring range. The scanners are constructed entirely of noncorrosive materials and thus can operate underwater for a long time without maintenance.
Automatic tube cutter matches speed of extrusion line
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Using a rotating cutting unit, an automatic tube-processing machine for integration into extrusion lines cuts extruded tubing into consistent preselected lengths and collects the tube segments into neat bundles. The Rotocut machine from Tecnoideal S.r.l. (Mirandola, MO, Italy) operates at a high speed relative to the speed of the extrusion machine, enabling cut quality to be very good. The microprocessor-controlled cutter is particularly suitable for cutting plasticized PVC and other types of tubing for demanding biomedical applications. It can produce optimal results when cutting tubes of various types and profiles from a range of elastomers.
The machine is supplied with a discharge conveyor to collect the cut tubes in an orderly fashion. An optional tranverse discharge conveyor is available to collect the tubing into bundles of programmable size. Preinstalled control software for both of these conveyors allows operational parameters to be set easily from the machine control panel. Appropriate for cleanroom use, the cutting unit can be supplied with two types of cutting blade and six series of cutting bushes in order to accommodate tubing of various diameters and materials.
Tubing line speed is adjustable between 5 and 150 m/min, and maximum cutting speed is 850 cuts per minute with one blade and 1700 cuts per minute with two. Tubes with 2.5- to 17-mm ODs can be cut into programmable lengths of 10 to 1999 mm with repeatability of ±2% for tubes shorter than 200 mm and ±1% for longer tubes.
The company also offers a benchtop cutting machine suitable for medical-grade tubing. Known as the Readycut, the machine features an integrated system to dispense solvent on the tube end. Up to 50 different production cycles can be stored in the machine’s memory, offering flexibility when planning production cycles.
Extruder line includes high-performance multilayer system
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Complete extrusion systems for medical device manufacturing are the specialty of an industry supplier that offers process support as well. Systems provided by Davis-Standard GmbH (Erkrath, Germany) include extruders, feed screws, integrated control systems, and such associated downstream components as dies, melt pumps, vacuum tanks, cooling tanks, puller-cutters, and auxiliary equipment. The equipment can be built with upgraded components to handle the processing of corrosive polymers and high-temperature materials. The product line includes the HPE high-performance system for coextrusion and multilayer applications. The small-footprint unit is available in an adjustable vertical or horizontal configuration.
Chemical grinding equipment produces no burrs when cutting metallic tubing
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Electrochemical grinding of stainless steels and other metals is a chemical rather than abrasive method of grinding and cutting off metallic tubing for medical devices, and thus does not produce burrs or generate grinding stress as abrasive wheels do. Grinding equipment based on this electrolytic process that dissolves metal at the work zone has been made by Everite Machine Products Company, Inc. (Philadelphia, PA, USA) for more than 50 years. The UG618 Ultra-Grind CNC electrochemical surface grinder is a recent addition to the company’s product line. This burr-free cutoff and surface grinder features a fixed-table design that facilitates the integration of automated loading and robotics.
The machine is well suited to applications requiring machine automation because it makes access to the work area convenient. Its rigid cast-iron construction and conversational computer numerical control together ensure that the grinding process will generate no metallurgical damage. Tubing, catheters, cannulae, trocars, surgical tools, and implants made of stainless steel, Inconel, titanium, carbide, copper, nitinol, tool steel, and aluminium can be cut, as can a variety of other medical device components. The machine is able to grind accurately very tough materials of any hardness or strength, and parts with complex geometry. It can cut fragile and thin-walled workpieces and thermally sensitive materials.
