Internship Report #64031

Duivenvoorden, Aard (2011) Item availability restricted.

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Abstract:A slitter rewinder is a machine that slits and rewinds (printed) paper or plastic film before it can go to conversion or to customers. The slitter rewinder S6 has been purchased at a bargain price and has been running for over a year. However, there are a lot of improvements possible on S6. The initial motivator for this re-engineering project is to make it more suitable for slitting paper, since there are only two (of the six) slitters on which this is possible. This is achieved by using two ball quick lock shafts for rewinding the film instead of regular shafts. The end result of the re-engineered machine is a more versatile, more user-friendly and more time efficient machine. How do ball quick lock shafts improve the machine? On S6 polyethylene and paper film is slit. When it is rewound, it is important that the tension of the film is constant to prevent both slack/wrinkles and tearing under stress. When for whatever reason the diameter of two reels on a single shaft slightly differs, the tension will be different for the both, since the torque is homogeneous along the shaft. In the worst case this causes fracture The ball quick lock shaft is made up of segments which can have different velocities with respect to each other. This system balances out any differences in diameter that might occur. The machine will also become suitable for slitting narrow film widths which currently is a time-consuming job to set up on another machine. On S6 it will become easier due to the locking mechanism that the shaft exhibits. Also, because the difference in diameter is balanced out, a single lay-on roller will suffice as an opposed to one lay-on per reel. Change-over is simplified on both unwind – and rewind shafts. The balls in the ball quick lock shaft also allow to slide of heavy rewound reels where previously the shaft and rewind reel would have to be taken off as a whole. A conceptual design of a ‘change-over system’ is also presented. This will further ease the taking off the reels. The unwind system has been enhanced in such a way that the change-over time has decreased from 15 to 3 minutes. To reduce operator handling, the application of tension on the unwind and rewind shafts is automated. This is realized using a proven closed loop control system with a so-called ‘dancer roller’. This system ensures that the torque on the shaft is increased when the material slacks and vice versa, thus keeping the film at constant tension. Because the rewind tension determines the rewind quality, a sophisticated controller and pressure regulator are used. The unwind tension only serves to prevent the machine from overrunning; hence a simple circuit print suffices. With these improvements the re-engineering of S6 will result in an effective machine that will enable a higher efficiency on a wide range of slitting jobs. The cost of re-engineering of S6 is estimated to be SAR210.000. Together with the purchasing price of SAR30.000, this is roughly six times cheaper than buying a new equivalent machine. The ball quick lock shafts where ordered end of 2010 and the re-engineering project started in February 2011. Unfortunately, the ball quick lock shaft did not arrive in time, making it impossible to commission most of the re-design. The unwind shaft and the automatic tensioning on the unwind have been commissioned. The production of all other parts necessary will take roughly 2 weeks; assembling and commissioning the rest of the re-design will take 1 to 2 weeks. The fully re-designed machine will be operational in 1 to 3 months from now
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Link to this item:http://purl.utwente.nl/essays/64031
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