Pallet changers help VMCs hold their own in production environments

Vertical machining centers are machine shop mainstays, owing in no small part to their versatility, small footprint and relatively low cost. However, in high-volume environments, they tend to lag behind their horizontal counterparts.

Fortunately, a pallet system provides a fairly simple fix.

“One way to measure the output of a machine is spindle utilization,” said Mike Munao, sales manager at pallet changer manufacturer Midaco Corp., Elk Grove Village, Ill. “How many hours of your 10-hour shift is the spindle running? I’ve heard the national average of a VMC’s spindle utilization is only 34 percent without a pallet changer.”

Manual pallet changers allow operators to load parts onto one pallet while another is being machined, then simply load the new one when the process is completed. Image courtesy Midaco.

With a pallet changer, he continued, average utilization rises to 60 to 90 percent by allowing the operator to perform tasks outside the machine tool while it is running.

There are three main types of pallet changers—manual, automated and robotic—but the underlying principle is the same: As soon as one pallet full of finished parts is unloaded from the machine, a new pallet of parts to be machined is put in.

With manual pallet changers, the operator physically loads and unloads pallets via a receiving bay on the front of the machine. Automated systems can be loaded with pallets, but the load/unload process is handled by the machine itself. Robotic systems utilize a arm to load and unload pallets, with each arm able to serve multiple machines.

Manual Methods

Several types of pallet systems are available, with manual styles being the most basic. These systems involve installing a receiver bay on the front of the machine into which an operator loads a pallet of parts to be machined. The pallet is then brought inside the machine tool. This allows the operator to load new blanks onto the next pallet. When the part or parts on the pallet in the machine are done, it can simply be swapped for a different pallet loaded with blanks for machining.

“By dedicating pallets for different jobs, you can eliminate a lot of redundancies,” Midaco’s Munao said. “Whether it’s vises, table work or whatever the customer is doing on a daily basis, they can have pallets dedicated to that type of work ready to go, so there’s a lot less setup time getting the parts into the
machine.”

In addition to a manual system’s relatively low cost—Midaco offers manual pallet changers that start at around $20,000—it also occupies little floor space.

A Fastems 6-axis robot arm can move pallets among multiple machines. Image courtesy Fastems.

While an automatic system is mounted to the side of a VMC, Munao added, a manual system sits in front of the machine, where a human is able to physically load pallets into the pallet changer. “People put their machines very close together, so there might not be much room side-to-side, but there’s always room in front of the machine.”

Automatic Advantage

Some hesitate to call manual systems “pallet changers,” because the operator has to physically swap out pallets.

“A pallet changer, as we define it, is an integrated system that is mounted to the front or the side of the machine with the express purpose of loading pallets,” said Stephen Bond, national sales manager for FANUC products at Methods Machine Tools Inc., which sells manual and automatic pallet
systems.

“Most of the shops that are buying VMCs are job shops, and they want to have at least some form of rudimentary automation,” said Richard Ware, vice president of sales and marketing at machine tool builder Mazak Corp., Florence, Ky. “A pallet changer lets them do more than just man one machine with one person. In addition, the most active sectors in the industry are aerospace and automotive, which are high-volume producers, so pallet changers let them hit those high volumes.

An automatic pallet changer provides all the benefits of a manual changer, explained Midaco’s Munao, but it changes automatically through the machine control, making the changer machine-driven rather than operator-driven.