New High-Speed ‘Micro’ Planetary Cutter from Conair Delivers Precision Solution for Rigid Medical Tubing

A new micro-scale planetary cutter is able to precision cut rigid and semi-rigid medical tubing as small as 0.080-inch (2.03 mm) in outside diameter (OD) automatically at line speeds of up to 100 ft/minute (30.5 m/minute). The new cutter – part of a family of downstream extrusion equipment for medical applications from The Conair Group – can make distortion-free and particulate-free cuts at rates up to 100 per minute while holding cut-to-length tolerances of ±0.005 inch (±0.127 mm). Even tighter tolerances are possible with a dual-head model, which cuts both ends of the tubing at once, leaving only a short scrap piece.

“Most rigid medical tubing today is cut-to-length using rotary or fly-knife cutters,” explains Bob Bessemer, Medical Downstream Extrusion Sales Manager for Conair, “and the results have been mixed. Even with close-fitting cutter bushings and good blade technology, it is sometimes difficult to obtain a distortion-free/particulate-free cut on the extrusion line. When a rotary knife impacts a rigid tube, the tube is slightly flattened until the blade actually penetrates the tubing and this can affect ovality at the cut site. There are other undesirable effects, too, including scratching, angel hair or agglomeration. Depending on the fit and function required for the application these flaws may be unacceptable, in which case tubes are cut oversized on-line and then re-cut off-line, by hand, to finish the part.”

The Conair micro planetary cutter was developed to fill this need in the production of precision medical tubing. This unit has a cut capacity from 0.080 to 0.5 inch (2.03 to 12.7 mm) OD and will allow cutting up to 100 cuts per minute with cut to length tolerances of ±0.005 inch (±0.127 mm) or less on tubing from 1 to 18 inches (25.4 to 457 mm) in length. Operator friendly touch screen controls make this unit simple to use. To obtain the extreme cut-to-length tolerances required by many of these applications, a dual head has been developed, which cuts the part between the adjustable heads with a short scrap piece per cut. Typically this scrap piece is no longer than 1.5 to 2 times the tube diameter. The tubing is totally supported between the cutter heads to insure length repeatability. A pre-feed unit, which is integral to the cutter, supports the tube as it feeds it to the cutting mechanism, while also ensuring that no cutting effects are reflected back to the die. In this way, even the most transparent tubing is cut without unwanted annular die marks due to part stoppage.

Planetary cutters have long been associated with large pipe extrusion where dust-free cutting was desired. Most planetary cutters are similar to rotary knife cutters in that they displace material rather than remove (saw) material. The major difference, however, is that instead of chopping through the pipe, the planetary cutter has a blade that rotates around the pipe (or tube) cutting it the way a lathe would. Depending on the material and wall thickness, the cutting blade may be either a rectangular razor blade or a rolling round blade.

However, since pipe lines operate relatively slowly and the pipe is cut in 10 to 20 foot lengths, these cutters are often very large and slow. More recently, the technology has been evolving to allow higher line speeds and cutting of smaller diameter tubing, especially were the quality of cut is critical and where particulate-free cutting is desired.
Until now, the smallest planetary model had a cutting range between 0.75 and to 2.5 inches (19 to 63.5 mm) OD, with a maximum cut rate of 50 depending on material and wall thickness. Servo table travel and dead-stop technology have allowed cut tolerances of less than 0.010 inch (0.254 mm), which is good enough to eliminate the need for secondary operations. The medical industry has started to take notice of this evolving technology and there is increasing demand for a “micro” planetary cutter that can deliver in-line distortion-free and particulate-free cutting of small diameter rigid medical tubing.

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