Pursuing the Perfect Palletizer
February 13, 2003
Automated palletizers can make your operation faster, but speed comes at a price. Find out the trade-offs and how to get the best system for your operation.
Sounds daunting? It most probably is if you're still relying on manual palletizing, which only works if volumes are low. It may be inexpensive and flexibleworkers load cartons or bags on any size pallet in any patternbut it's slow, difficult work that demands repetitive lifting motions. Moreover, it's constrained by the weight of individual bags and cartons. For heavy items, mechanically assisted manual palletizers typically lend a hand.
Automated palletizers, on the other hand, can fulfill your operation's need for speed. Compared to manual palletizers, automated systems may be more expensive and less flexible, since they only work with certain size loads, pallets and pre-established stacking patterns, but they offer greater reliability and silence ergonomic complaints. In fact, suppliers claim that you can purchase an automated palletizer just from the money you'll save from avoiding one back injury.
The two main categories of automated palletizers are in-line and robotic.
In-line systems stack whole layers of cartons or bags at a time. Representing one type of in-line system are vacuum-head units, which clutch products with pneumatically powered suction cups and place them onto pallets. The other type, the row stripping palletizer, first organizes a row, then pushes it aside while the machine forms another row that is put atop the previous row. This goes on until the full pallet load is assembled.
Robotic palletizers, meanwhile, build pallets a few cartons at a time. They are available in three designsSCARA, articulated arm and gantry. SCARA (selective compliant articulated robot arm) palletizers utilize a mast and a cross arm to position products through four axes of motion. Articulated arm designs also feature four-axis motion, and even one-up SCARA counterparts in range of motion and flexibility because of their jointed arms. The third kind, the gantry palletizer, combines a robotic arm with an overhead crane or I-beam.
The speed, flexibility and cost of all automated palletizers depend on their design. And there are trade-offs. For example, not only does high speed cost money, it also compromises flexibility. To be on the high end of the automated palletizer speed range (which is from a modest 10 to a blazing 200 items a minute), the palletizer must be able to move multiple items at a time, and that means less flexibility.
The fastest palletizers are high-feed row strippers, which can move 160 or more cartons a minute. They build pallets from the top down, several feet from the floor, and attain such high speeds because they simultaneously move the pallet and the product layer. In comparison, low-feed row strippers assemble pallets at floor level from the bottom up and only manage rates approaching 140 cartons a minute. The most sluggish of the in-line bunch is the vacuum-head, which moves less than 25 cartons a minute.
Robotic palletizers, in comparison, excel more at flexibility than at speed, handling only 10-30 cartons per minute. While row strippers are ideal for placing huge quantities of cartons at a time onto a single pallet, a gantry unit can slowly build pallets from the output of 10-20 conveyor lines. In fact, all robotic palletizers are flexible enough to put together loads of various stock keeping unitseven if the items are of dramatically different sizes.
When upgrading from manual to automated palletizing, most companies first opt for the lowest-end robotic type, the articulated arm, says Bobby Edmond, director of sales for HK Systems' von Gal palletizer line. After that, depending on requirements, people tend to move up to the gantry. Meanwhile, for operations that have to palletize the highest volumes at great speeds, row strippers top the list of options.
How do you figure out what palletizer is best for your operation? According to Pat O'Connor, product manager of palletizing systems for Alvey Systems, a unit of FKI Logistex, you have to ask yourself the following five questions:
Also keep in mind that today's automated palletizers are getting better than evereasier to use and faster. For example, they offer a sophisticated human interface module (HIM), a graphical layout similar to advanced copier machines in offices, says Paul Probst, vice president and general manager at HK.
Today's machines are faster since they have to stack many more individual cartons. This is because many of today's pallets are comprised of scores of small cases that are shrink-filmed, not boxed together, since retailers are increasingly demanding products that can go straight to the store's shelf, says O'Connor.
And aside from standard palletizers, specialized ones geared for certain items ranging from pet food to beer, are also available. In short, automated palletizers are stacking up to meet users' escalating demands.
Source: Automated Palletizers Stack It Up
Benjamin B. Ames
Modern Materials Handling, Feb. 1, 2003