Heavy duty draw-force tester for fibre tows and coarse filament yarns
 DYNAFIL HD
The high variation in force and elongation measurements on fibre tows is a well-known phenomenon in the quality control of staple fibre productions. Histograms of breaking elongation obtained from large numbers of single fibre tests often show several clusters instead of a Gaussian distribution. In general these clusters are caused by differences between the individual spinning positions.
Therefore, it makes sense to analyze the drawing properties of undrawn fibre tows from individual spinning positions. These measurements also help to find the optimum drawing conditions in later processing of the fibre tow. The DYNAFIL HD has been designed for draw-force tests on fibre tows up to 30.000 dtex, but has already been used for testing tows up to 70,000 dtex, too. Filament yarn: Draw-force testing of LOY and POY filament yarn as well as shrinkage-force testing of industrial filament yarn on Textechno's dynamic thermal stress testers DYNAFIL M, C, and ME are widely used in production control of filament yarn. However, the mentioned testers are limited to a maximum count of about 2,000 dtex. As the DYNAFIL HD is suitable for sample counts of at least 30,000 dtex, even the coarsest filament yarns in production nowadays can be tested. Test methods:Draw-force or shrinkage-force test at constant speed and draw ratio This is the commonly used test in production control. Draw-force level is evaluated with respect to mean value and coefficient of variation (CV%), as well as minimum and maximum values. Hence variability can be determined both from spinning position to spinning position and within each position. Draw-force test with constant draw ratio but rising speed The results of the test indicate at which speed the yarn temperature while passing the contact heater drops below the glass transition temperature. This allows to establish the optimum test speed. In case of shrinkage-force testing (draw ratio = 0 %) this test will show at which speed the maximum shrinkage-force is achieved. Draw-force test with constant speed but rising draw ratio This test is interesting especially in combination with the optional broken filament sensor. It shows at which draw ratio the yarn or fibre cable can be drawn in one process without generating too many filament breaks.
Technical dataThe heated intake godet increases the temperature of the yarn to a point several degrees below the glass transition temperature (in case of polyester), while the contact heater adds the additional energy to transform the polymer from the glassy to the rubbery state. The drawing point is located on the heater. A compensating tensioner together with a hysteresis brake applies a controlled and stable pretension to the yarn or cable. The finish applicator is used to apply an additional finish similar to production (optional, especially used for fibre tow). The force measuring rollers are arranged in such a way that the yarn path is guided back towards the front panel. The broken filament sensor can detect broken individual filaments, e.g. as a function of draw ratio, while the speed of the draw-off godet in relation to the speed of the intake godet determines the draw ratio. A suction nozzle is used to feed the yarn into a waste container but can also be taken out of its mounting and used as a threading aid. Godet speed: 0.1 ... 100 m/min (intake and draw-off godet)
Surface temperature of intake godet: ambient to 100°C (can be extended to 250°C)
Temperature of contact heater: ambient to 200°C (can be extended to 240°C)
Draw ratio: 0.1 ... 6 (can be extended)
Subject to technical changes |
