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Final packaging and handling: palletization by robots.

Final packaging and handling: Palletization by robots

The following article is the second of a series of two articles prepared for the February and March editions of Tea & Coffee Trade Journal. It is intended to give aid to managers, project people and technical teams in the planning of final packaging and handling systems, comprised of case packing, palletizing and pallet securing.

Traditionally end of line packing equipment has not been considered as part of the production line because the individual pack is the final product the customer would see. Everything after the primary packaging was considered as part of the distribution and warehousing. In some cases even the responsibility has been separated.

Modern PLC control systems, management information systems and data acquisition systems have changed production lines comprised of individual controlled machines to integrated production manufacturing centers. These centers encompass all machines and equipment from raw material to the secured pallet. What is most important is that these integrated centers give control and responsibility to the operators who make the secured pallet, the "selling unit."

What effect does this have on palletization? The insurance liability should be considered when specifying production centers, and every effort made to automate this specific area. Back injuries are the number one avoidable ailment associated with manual palletization.

In earlier days the layer palletizer was the only equipment available. As the word states, a complete pallet layer has to be accumulated before it can be palletized and this of course requires a lot of space. Consequently this equipment was located outside the production area. Because the speed often exceeded the actual line speed these single layer palletizers were extended to become centralized multibrand layer palletizing systems.

This produced a complex infeed system and long accumulating conveyors for each product. It goes without saying that enormous space was required for this type of system. In the event of a jam, all production could be stopped. In addition, the layer forming equipment was of mechanical design with complex change parts for additional product sizes.

The inefficiency of production lines with split responsibility between up-stream equipment and end packaging has led to new layout designs with a dedicated palletizer to the end of each production line, the so-called 1 : 1 solution.

Robotic Palletizers

A term so often misused is the work robot. The work robot can be described as a freely programmable manipulator with several degrees of freedom to each axis which work independently allowing several mechanical movements to take place simultaneously at different speeds.

Industries such as tea, coffee, biscuits, tobacco, paper products and pharmaceuticals operate line speeds less than eight cases (bundles) per minute and seldom ever exceed 16 cases (bundles) per minute. These line speeds are ideal for the robotic palletizer system. A modern robotic palletizer can reach up to 10 cycles/min. and with combined single or twin pick-up heads this substantially increases the number of applications for robotic palletizers.

There are various types of robots on the market. The linear axis robot, the gantry robot and the articulated robot are primarily used for palletizing. The major differences between these three types are that the linear axis and articulated robot are more accurate and faster than the gantry type. The gantry type tends to be a bigger machine complex, running at a slower rate, and also requiring the product accumulation, similar to layer palletizing.

The main design criteria of robot palletizers are: sturdy design to allow 24 hours operation, few mechanical movements, high availability, quick size changes, speed, minimum space requirement, easy to operate, intelligent controls, hygienic standards, gentle product pick-up, high safety standards, and low noise levels.

The pick-up heads play an important roll. These pick-up heads and systems have been developed over the past years and are now available for any product.

For RSC and wrap-around cases, vacuum heads are used. Low board trays and open cartons can be picked up by dome-shaped suction heads. Combined mechanical/suction pick-up systems or pure mechanical (size-independent) pick-up heads are used for shrink trays or shrink packs. Bayonet-sockets allow quick head changes for different products.

The pick-up heads are programmable to produce the most complex pallet pattern such as column stack, interlinked patterns or rolled cases (bundles) to fill a center gap. An interlinked pallet pattern possibly used with slip sheets provides a greater stability and more product on the pallet. It can also offer bar code or case label presentation to be facing out, for ease of reading.

There is software for standard PC's on the market which provides a detailed calculation of the best utilization of pallet space and this often suggests rolled cases as center pieces, or top layers. These are all produced more easily on the "robotic system." The cost saving in good pallet utilization can, in some cases, be equal to the transport costs.

The latest robot design features service-free, AC-servo-drives with rotary encoders. This together with appropriate controls, avoids the blackout situation after emergency stops found in the more simple systems. This ensures that in the event of an emergency stop there are no half completed pallets which have to be unpacked, or completed manually. Preferably the PLC control system should separate the control for the robotic drives and auxiliary functions. The processor should have the capacity to store several programs in the memory. A 128 K-byte processor can store 10 different pallet patterns. Eproms can be used to expand the memory capacity.

Pallet Conveying

To further automate your palletizing operation, the market offers empty pallet conveying equipment. This equipment should also be of modular design. Empty pallet magazines, lifting, turn tables, roller conveyors, slip-sheet placers and interleave placers, are often done by the robot. Chain conveyors have to meet the specific factory requirements and space available. A new development for users of pool-pallets is the empty pallet control system. Such a system checks the incoming empty pallets for faulty wooden boards, sticking out nails, size and height. The unit can be provided with a pallet stacking unit, thus all arrival faulty pallets can be rejected and returned with the carrier on arrival.

If space restrictions do not allow the dedicated 1 : 1 solution at the end of each production line a centralized robotic palletizing system could be the answer. For such an application each palletizer remains dedicated to one production line. Such a system is generally comprised of a centralized infeed conveyor and executed as a loop conveyor, where products travel randomly. Bar code readers/scanners identify the products and feed them to the corresponding palletizing unit. This robotic system is quite simple and can be expanded by adding more robotic palletizers.

As mentioned earlier, systems like this with intelligent controls can be executed with data collection systems. The collection of all required data from production for the production manager to access not only what raw materials have been used but also what has been shipped.

There are various options available for downstream equipment from the robotic palletizer. One of the most popular is a direct link to Automatic Guided Vehicles (AGV system). These systems can work as a full pallet carrier only, or as a combined system which also provides empty pallets. These AGV-systems are particularly advantageous when dedicated robotic palletizers are sited far away from the warehouse facility.

The full pallet securing system is normally a film wrap. These units offer a high capacity, more than 50 pallets/h. Whether stretch wrap, shrink wrap, banding or hot melt (between layers) is used depends on the product, the means of transport, the distance, the pallet weight and pallet protection. However, a pallet should not only be secured for the warehouse but also to reach the point of sale (POS) in perfect, undamaged condition.

The use of palletizers offers many advantages, however before choosing, a detailed analysis must take place. The choice is not a machine, but rather a system. The use of robotics is a sign of quality for the company and shows the capability of the engineering team concerned in the design.

PHOTO : Combined suction/gripper head

PHOTO : Size independent mechanical gripper

PHOTO : Articulated robotic palletizer with 1 vertical axis and 3 horizontal axis

PHOTO : Dome-shaped suction head for low-board trays
COPYRIGHT 1990 Lockwood Trade Journal Co., Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Title Annotation:part 2; coffee industry
Author:Mathews, Alois; Gauthier, Darrell
Publication:Tea & Coffee Trade Journal
Date:Mar 1, 1990
Previous Article:Italy: trends run to exports decaf and concentration.
Next Article:Gillies: looking into the 90s and back to our roots.

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