Machine control: Robotic palletizing helps Hershey's plan for change
Conventional palletizing, while fast and cost-effective, would not work with Hershey's space restrictions and eight production lines. Working with Hershey packaging system engineers, FKI Logistex and Motoman Inc. created and commissioned a robotic palletizing system that adapts to changing needs.
The plant that manufactures Hershey products for brands including Hershey's, Kit Kat and Cadbury, has a wide variety of low- to mid-velocity products (called stock keeping unit, or SKUs) that can change seasonally, weekly, and even daily based on demand. When this increasingly wide variety of product SKUs and packaging configurations started to require faster and more flexible palletizing, Hershey engineers knew it was time to make the switch to an automated system.
Hershey packaging systems engineer Alex Diaz (left) and project manager Dennis Empson (right) turned to a hybrid solution to adapt to a diverse and constantly changing product line. Source: FKI Logistex
Packaging systems engineer Alex Diaz, along with project manager Dennis Empson and staff engineer Matt Eroh, teamed up with long-time material handling partner FKI Logistex to design an automated palletizing system that could handle Hershey's low- to mid-velocity SKUs. Almost immediately, it became clear that conventional palletizing, while fast and cost-effective, would not work with Hershey's space restrictions and eight production lines. Robotic palletizing offered a more versatile option by enabling Hershey to send three different lines to one robot and palletize in three different positions at once. This greatly reduced the amount of conveyor required, but posed a problem of its own: The robots could not keep up with the production rates of Hershey's higher velocity SKUs.
A partnership between FKI Logistex and Motoman Inc. facilitated Hershey's transition to robotic palletizing. The team worked together to design a system that sends mid- to high-velocity SKUs to an FKI Logistex A-780 case palletizer, and low-velocity SKUs to one of three Motoman EPL 160 jointed-arm robots.
An overhead system of FKI Logistex conveyors and merges bring cartons of finished Hershey products to the palletizing room from various production operations around the plant. SKUs with high production rates enter on the high-speed line, which leads directly to the FKI Logistex A-780 case palletizer. A bar code scanner identifies each SKU and its associated pattern, letting the A-780 immediately palletize up to 37 cartons per minute. Positively driven, heavy-duty FKI Logistex chain-driven live roller (CDLR) conveyors and a motor-operated turntable direct each complete load to a stretchwrapper capable of handling up to 60 loads per hour.
Lower-velocity SKUs enter the palletizing room via three lines of case conveyor. Cartons are scanned and sorted at up to 25 cartons per minute by FKI Logistex Sortrac air-operated right-angle pushers into seven lines feeding three Motoman EPL 160 jointed-arm robots (Or, they bypass the robots to go to an optional hand-palletizing lane.) The robotic portion of the system uses an FKI Logistex laser-positioned rail-running transfer car to transfer the palletized loads to the turntable with high speed and accuracy. The turntable then directs the palletized loads to the stretchwrapper.
Flexibility for future change
The new palletizing system gives Hershey the capability to easily integrate the remaining hand-palletized lines into the automated system by adding a spur conveyor and possibly a fourth robot based on future demand. This built-in flexibility is something that Diaz agrees should be standard on all material handling systems.
"Most of the SKUs that we started the project with were not being produced by the time we got the system running," says Diaz. Three new patterns were added to the A-780 palletizer before FKI Logistex even arrived on-site, and up to 50 percent of product sizes and patterns were changed before installation was complete. Because of these packaging changes, Hershey commissioned FKI Logistex to install pattern generation software for the A-780, which Hershey had chosen not to include in the original system design.
"At first, when our packaging department came to us with a new pattern we had to e-mail it to FKI Logistex to make changes to the PLC code," explains Diaz. "This process required an engineer to analyze the new pattern requirements, ensure that existing patterns would not be adversely affected, program the changes, and then upload the code back to us. With the FKI Logistex pattern generation software, the Hershey plant operator can directly program the new pattern into the palletizer, test it, and have it operational in a matter of hours."
The FKI Logistex pattern generation software is controlled by an easy-to- use touch screen display directly connected to the A-780. After entering a password-protected "utility" mode, Hershey plant operators can add new patterns and make changes in real time. "The pattern generation software is a recommendation I would give anyone for this type of system," continues Diaz. "It gives us the flexibility to make changes ourselves and get the new packaging configurations up and running quickly. With six new SKUs, it pays for itself."
One of the biggest challenges of the project was finding an end-of-arm tool for the robots that could handle Hershey's wide variety of SKU sizes and weights. Although FKI Logistex typically designs and manufactures the tooling for the robots they integrate, the team decided to outsource the end-of-arm tool. They chose to use a UniGripper flexible vacuum tool from a Swedish company Tepro Machine & Pac System. It activates specific vacuum areas to create the necessary lifting forces for each package, based on the shape and location of cases programmed into the system. UniGripper uses a patented technology that automatically senses the product position and creates the necessary lifting force. (Integrators receive an integrated system of pneumatics, sensors and electrical components for connecting to robots.) "I've installed some other robots, and this was by far the easiest-to-use and most versatile end-of-arm tool I have ever worked with," says Empson.
Hershey engineers beat the clock
Hershey and FKI Logistex faced an aggressive timeline for installation of the new palletizing system. Once the installation process began, the Hershey team tore out conveyors, vacuum lifts, and other hand-palletizing equipment and employed hand palletizing in other areas throughout the plant. Crews worked multiple shifts and overtime in a very tight space, but their hard work paid off. "We installed the entire system in five weeks and had it commissioned in three and a half weeks," says Diaz. Working long hours, Hershey engineers checked the wiring of the entire system in less than three days.
As part of the contract, FKI Logistex provided on-site training on the new system to Hershey personnel. Select Hershey mechanics also visited Motoman for additional training on the robotic palletizers. More than 30 Hershey employees received training, including all of the plant's forklift operators and electrical technicians. "Once we reached the point where the operators were comfortable with the system, we've been running efficiently," says Diaz. "And the fact that Hershey has yet to call FKI Logistex to make adjustments to the system is a testament to just how well the training worked," adds Empson.
Since the completion of the project in June 2006, Hershey has seen increases in palletizing speed and efficiency, and has had no major problems with the equipment or the system itself to report. The equipment, which has proven to be reliable, is saving Hershey a great deal of money on manual labor costs, as well as greater potential savings from reducing ergonomic complaints, says Diaz.
Hershey engineers are happy with the system's performance, and Empson has called the palletizing solution the "latest and greatest" in Hershey material handling systems. Throughout the course of his first major material handling project, Diaz says he learned a lot about adapting to new technologies and being prepared for future change. "Basically, nearly everything you plan has changed by the time you implement it," notes Diaz, referring to the constant packaging changes he faced during the project. "Change comes quickly," he continues, "and you have to adapt to it as quickly as possible to be successful."
- Edited by Renee Robbins, senior editor
Control Engineering News Desk