Picking orders with high efficiency is great. Efficient manufacturing is also desirable. But what do you do when all those cases and cartons and bags arrive at the shipping dock and you need to build pallets as fast as you picked and produced? That's where palletizers come into the picture.

If volumes are low, manual palletizing might be an option. Workers can hand stack cartons or bags on any size pallet in any pattern. While it's affordable and flexible, manual palletizing is also slow, hard work dominated by repetitive lifting motions. It's also limited by the weight of the individual bags and cartons. Mechanically assisted manual palletizers are typically used for heavy items.

And then there are automated palletizers. Compared to manual systems, automated ones are more costly and less flexible, requiring certain sizes of loads and pallets and pre-set stacking patterns. On the other hand, automated palletizers are faster, more reliable and solve the ergonomic issues associated with manual operations. Suppliers say the elimination of one back injury alone can pay for the cost of an automated palletizer.

There are two general categories of automated palletizers—in-line and robotic.

In-line systems move an entire layer of cartons or bags at one time. These include vacuum-head models that use pneumatically powered suction cups to grip and place products onto pallets. The other type is known as a row stripping palletizer. It first forms a row, then pushes it aside while the machine makes another row that is placed on top of the first. This continues until the full pallet load is built.

Robotic palletizers build pallets several cartons at a time, and come in three designs—SCARA, articulated arm, and gantry. SCARA (selective compliant articulated robot arm) palletizers use a mast and cross arm to maneuver products through four axes of motion. Articulated arm designs also offer four-axis motion, but the arm is jointed, offering greater range of motion and flexibility than SCARA types. Gantry palletizers mate a robotic arm to an overhead crane or I-beam.

The design of in-line and robotic palletizers directly affects three attributes—speed, flexibility and cost.

Speed costs money, says Pat O'Connor, product manager of palletizing systems for Alvey Systems (877-935-4564), a unit of FKI Logistex. Speed also sacrifices flexibility. As the table shows, automated palletizers handle as few as 10 or as many as 200 items a minute. But to achieve such high speeds, these palletizers must handle multiple items at a time, minimizing flexibility.

The fastest models are high-feed row strippers that handle 160 or more cartons a minute. These build a pallet load several feet above floor level and do it from the top down. Product comes in on high conveyors above head level, where each layer of cartons is swept off the conveyor by a rake, framed into a pattern, then set down onto a waiting pallet below. This design gains speed by moving both the pallet and the product layer at once.

Low-feed row strippers build pallets at floor level from the bottom up, but at rates closer to 140 cartons a minute. The slowest of the in-line models is the vacuum-head, which handles less than 25 cartons a minute.

Robotic palletizers, on the other hand, typically operate in the 10 to 30 carton per minute range but do it with maximum flexibility. While row strippers are busily sweeping large quantities of cartons at a time onto a single pallet, a gantry unit can slowly palletize the output of 10-20 conveyor lines. All robotic palletizers are sufficiently flexible to easily build loads of mixed stock keeping units, even if the size of the items differs radically.

Another aspect to palletizer flexibility is the ability to handle different sized pallets. While many pallets are 48 x 40 inches, some companies use 10 or 15 different pallet sizes, O'Connor says. For instance, the construction industry uses a different pallet size for paint cans, ceiling tiles, and many other types of equipment. So a standard palletizer is built to be flexible, handling pallets as big as 56 inches in either dimension, and as small as the 36 x 30-inch pallets used in the food and beverage industry to stock route trucks.

When moving up from manual to automated palletizing, most people start with the lowest-end robotic, the articulated arm, says Bobby Edmond, director of sales for HK Systems' von Gal palletizer line (800-457-9783). Depending on their needs, the next most common step is to the gantry. And for the highest volume and speed operations, row strippers are the choice.

So what's best for you? Alvey's O'Connor says it comes down to five questions:

• Are you handling more than one line?
• Do your conveyors feed in at floor-level or elevated?
• How do you build your pallets; according to case sizes, stacking patterns, or type of packaging?
• What type and size of pallet do you use?
• What is the speed of your conveyor line?
• The web site at Columbia Machine (360-694-1501) boils it down to four criteria:
• Products: are you stacking cases, bags, pails, bales, drums, totes, display packs, or bundles?
• Layout: save space in your facility by using modular designs and double stacking
• Budget: more options means more value
• Future: upgrade your palletizer as your warehouse grows

So, what's next for the industry? Today's machines have a sophisticated human interface module (HIM), a graphical layout similar to high-end copier machines in offices, says Paul Probst, vice president and general manager at HK.

Another trend is retailers increasingly pressuring warehouses to deliver product that's ready to place directly on a store shelf, O'Connor says. So today's pallets often ship with a larger number of small cases, held together merely with shrink film, not large boxes. That means palletizers have to run faster than ever to handle the greater number of individual cartons.

And of course, there are specialized designs tailored for specific industries as diverse as pet foot in bags and beer in cases. In the end, palletizers today must deliver maximum performance on multiple levels to meet demanding end user requirements.

Click on this icon to read more about the best way to pick a palletizer.