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The most striking feature of SML’s current generation of MDOs is the design consisting of two independent frames. While the line’s overall setup guarantees high production speeds, the dual-frame system allows maximum service-friendliness.
The first frame with ascending rollers houses all the rollers of the preheating zone and the rollers of the stretching zone which run at low speed and operate the hold back function of the stretching process. The stretching rollers which operate the pulling function and go high speed, as well all the other rollers of the stabilising and cooling zone, are located in the second descending frame.
The two frames are relocatable to each other. The variable distance between the two frames precisely defines the length of the stretching gap, which is adjustable during production. Thus the MDO process is adapted to the polymer and to the relevant production line speed. “Ultimately, all the essential mechanical properties of the film in the machine and cross direction are determined by the length of the stretching gap and the stretching speed. Our system guarantees both maximum control of the film properties and very high production speeds,” Robert Preuner, Head of R&D at SML, explains.
Vibration resistant design / High production speeds
The frames are moved along strong linear guiding profiles, driven by robust jack screws, which strongly resist vibration. The positioning of the frames is done by highly precise servo positioning drives. The dual-frame layout is the ultimate space-saver. It takes into account the increased number of rollers necessary for elevated line speeds. At the same time an excessive height of the stretching unit is avoided.
Fast cleaning, shorter downtimes
Significantly shorter cleaning and service times, and with it more cost-efficient operation, are further key advantages of SML’s current generation of MDOs. In the service position, the two frames of the MDO can be moved apart as far as 0.8 meters. There is optimum access to rollers, also on the inner side of the frames, for fast, comfortable and safe cleaning. Additionally, all of the rollers of the MDO, including the pressing rollers, have a quick-change mechanism. If necessary, the rollers can be changed fast and comfortably via integrated hoists.
Versatility both for polyolefins and PET
The SML “dual-frame design” offers stretching both according to the short gap and the long gap procedure. Thus SML’s new MDO generation is not limited to process polyolefins but is also perfectly suited to PET applications like twist film for candy wrapping, adhesive tapes and shrink labels for bottles, which need to be stretched with a long stretching gap.
Potential for new products
Newly developed formulations provide tremendous potential for stand-up pouches (MOPE) and tear-open packages (MOPP). Established polyolefin applications using the short gap process are technical films for cable insulation, tear tapes and tape carrier handles. Hygiene breathable films for diapers and incontinence products are produced at an amazing production speed of 500 m/min.
