Layout and function of a film stretching machine
Layout and function of a film stretching machine
DORNIER extrusion systems are available as single extruder with melt pump or as cascade extrusion system and all of those extruders are very constant with respect to output and temperature uniformity. The extruders can be combined with filters, melt pumps, melt lines as well as die and controls etc. to form an extrusion system. The extruded hot melt is cast on the chill roll and cooled. In case of polypropylene production the casting drum normally is arranged in a water bath. This is however not the case for polyester film production. Longitudinal stretching machine After controlled cooling the primary film passes through the longitudinal stretching machine (MDO), where the film is stretched in machine direction by several groups of driven rollers, which are running at different speeds. Transverse stretching machine with patented clip In the following transverse stretching machine (TDO), the film is gripped with clips on both sides and stretched in width with heat applied. Cross loads up to 3,500 N per clip can occur. Material and mechanism have to withstand temperatures in the range of 100 to 280°C at production speeds between 100 and 500m/min according to output and film thickness. | Up to 2,400 clips are incorporated in a transverse stretching and heat setting machine. One of the advantages of the DORNIER TDO is the special monorail clip guiding system where the clips are guided without any interruption from the inlet up to the exit of the machine. In polyester film production, the returning rails on a DORNIER TDO are also located outside the oven. After the film has been oriented in both directions, the stretched film is guided by a take-up system from the TDO to the winder. Film cooling and edge trimming are done in this section. The thickness is also checked at the same time. The results of this thickness check serve to control the nozzles before the casting unit. The film is wound on cores with a length of up to 50 km and then sized using re-rolling and cutting machines to meet customer requirements. |
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