Designing Systems (CONT’D FROM PAGE 26)
ual, though the industry is working on practical solutions to automate this task. Placing tags at the converting machine is a non-productive task that can require additional labor or reduce throughput. On the other hand, placing at the unitizer adds to the burden of the operator – again by in- creasing labor or reducing throughput. Some unitizers can print load tag information directly on top sheets; however, the size and amount of informa- tion is limited. Additional equipment such as stretch wrappers: Do you have enough volume of stretch-wrapped product that an off-line semi-automatic wrapper won’t suffice? If so, is the material requiring wrapping almost all produced by a single machine (e.g. a rotary die cutter)? High speed auto- mated stretch wrappers can be integrated into machine or unitizer discharges. Because they are slower than unitiz- ers but are generally capable of keeping up with produc- tion equipment, they should ideally be placed at machine discharges prior to the main line. However, if required on multiple machines, this may be impractical due to cost and space constraints. In this case perhaps the best solution is to install a single wrapper in a separate unitizer discharge line so that it does not restrict unitizer throughput. Be sure the frame of the unit you select does not restrict large un- wrapped material from passing through. Keep in mind that it is possible to build wrappers whose clearance between frames is larger than the wrapping mechanism.
lets, handling pallets and placing material on them slows the process. If this is a significant part of your mix, consider automatic pallet handlers and inserters. Imagine the sav- ings of an automatic system that is capable of discharging two units on a pallet to the forklift without the operator’s intervention. Try to minimize the types of pallets required, as handling many pallet configurations complicates mat- ters significantly. Bottlenecks Assuming unitizer capacity is adequate and material handling at the unitizer discharge does not create a bot- tleneck, can your conveyors transport the material fast enough? Are they running at 40 or 60 feet per minute? How many right-angle transfers are in the system, and what type are they? Old style pushers, aside from safety concerns, require the pusher bars to return to their original positions, thus essentially doubling the cycle time. Chain transfers are much quicker as they only have to raise and lower. Ball belt devices are even faster. Regard- less, the combined cycle time of each transfer and load separation is slower than that of the conveyor, and delays due to multiple transfers have a cumulative effect. Clever design can mitigate this: a single device may be utilized to transfer two units simultaneously to parallel lines. Miscellaneous Factors Load tags: Placement of load tags is almost always man-
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• Machinery selection • Plant layout • Project Management • Consulting
A true corrugated industry veteran with nearly 50 years’ experience, Richard Etra can help you with every aspect of box plant operation. Contact Richard today for a no-cost consultation: email: richard_etra@etracorrugatedsolutions.com ph: 917-647-9520
28 July 25, 2022
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