AGVs Stretch Manufacturing Cells' Flexibility

Those of us who have designed a lot of manufacturing cells are often frustrated by operations that just don't want to live in a cell. Heat treatment, cleaning, painting, plating, and a few more exotic operations do best in dedicated areas. Sometimes we can design the problem operations out of products, but sometimes we can't. A couple of manufacturing trends came to my attention in recent weeks that I think may help with this dilemma. Here they are.

The first trend came up when our Chief Editor returned from the ProMat 2013 material handling show last week. He had shot interview videos of implementers from about a dozen AGV manufacturers. The clips are available on the Plant Services website (http://www.plantservices.com/multimedia/2013/AGV.html). He had interviewed them for next month’s cover article on AGVs. Many were excited about new lighter, less costly, more flexible units that are designed for material handling between departments. New guidance systems are reducing the need for guidance hardware in the plants. The smartest units use GPS to locate themselves and their destinations on a memorized map of the facility, and they carry sensors to let them operate in traffic. Others are guided by lasers reading targets that are cheap to install. Most have wireless connections to computers with simple interfaces. Wires buried in floors are pretty much a thing of the past, and tapes, which must be maintained, are also on the way out.

Some of the units are lighter and much less costly than their predecessors. Combined with the almost total lack of factory infrastructure to make the AGVs work, these units are beginning to put automated material handling within the reach of warehouses and smaller manufacturers.

A second trend, focused or "spot" automation, combines nicely with the new direction in AGVs. Focused automation breaks with the tradition of setting a single level of automation for an entire cell or manufacturing system. Relatively automated operations are placed adjacent to more manual stations, creating a couple of interesting advantages: Humans are available to supervise the automation without being dedicated to it. This means that system changeovers and daily maintenance don’t require specialists to come into the line. The operators handle the work.

The automation can be simple, performing operations that don't require much flexibility, while humans do the work requiring more versatility. This leads to less expensive automation, focused on the operations that can profit the most from it. Operators are always nearby to supervise the automation and change it over as needed.

When AGCs (automatic guided carts) and ALTs (automatic lift trucks) are added into the focused automation approach, it becomes economical to make virtual connections between cells and dedicated process areas, effectively pulling paint, plating, and heat treatment operations into the cells’ kanban systems. Orders for material can be sent wirelessly to the low-cost automated vehicles and stock can be replaced without human intervention. Similarly, when there is a need to move parts from the cell to the remote processes, the automation can pick up the loads and bring them to the next operation. By requiring a back-haul, the automation can balance the flow into and out of the cell.

Depending on the mix of products and the nature of the off-line operations, it may be necessary to install limited storage queues between the remote operations and the cells. These must be designed into the system. But the storage and movement equipment is likely to cost half what the same capabilities would have five or ten years ago. The queues won't spoil the financial picture.

Focused automation of material handling can be accomplished without redesigning the plant around the new equipment. The amount of training and engineering required is consistent with a warehousing or light assembly operations. Rocket scientists need not apply.

A look around most factories will reveal some departments that would lend themselves to cellular manufacturing, except for one or two problem operations that have prevented integration. Perhaps the combination of focused automation and some of the new AGV-lite applications might make the savings attainable. Thanks, ProMat.