Moving to the Fully Flexible Assembly Line

The traditional assembly line moves products from station to station on conveyor lines or overhead cranes. As the work in process moves to a new station, workers, and increasingly robots and cobots – robots that can work safely in proximity to humans – do their work before the product is moved to the next station.

Traditional Assembly Line Using an Overhead Crane

But Rob Keij, the Commercial Director at Kivnon, says that is the old way of doing business. Kivnon is a Spanish provider of Automated Guided Vehicles (AGVs). “AGVs have traditionally been used to move products from point “A” to “B”.  They are still used that way.” But AGVs can also be used as “flexible fabrication platforms” to replace conveyors, overhead cranes, and other forms of bolted down conveyance.

AGVs support a flexible assembly line

Using AGVs to Transition to a Flexible Assembly Line

For example, one of Kivnon’s customers manufactures automotive engines. They replaced a monorail with 35 AGVs. This makes it easier to produce products flexibly. If there is a model change, the manufacturer can add two more steps and four more meters to the production line. Or if maintenance is being done machinery in one section of a factory, AGVs can be routed around workers in that area of the factory. This is something a traditional bolted down line can’t accommodate without costly and time-consuming modifications to the material handling equipment.

Kivnon offers a couple different types of AGVs. One of their AGVs follows a path that senses magnetic tape that has been laid down on the floor. Another type of AGV sold by the company uses simultaneous location and mapping (SLAM); basically, the AGV has an internal map of the facility embedded in its controls and sensors triangulate on “targets” such as mapped walls and racks so that the AGV can stay on its path.

Operators can click on the AGV application and quickly design a new path or make modifications to an existing path. According to Bob Trebilcock, Editorial Director at Supply Chain Management Review, and the go to guy on all things related to material handling, “years ago these kinds of path changes required custom coding. Today, many AGV suppliers have software where these kinds of changes can be made by users fairly easily.”

In comparing AGVs that run on magnetic tape versus SLAM, Mr. Keij said that magnetic tape is cheaper, but that it takes longer to put down or pull up tape when a line change is needed. With SLAM, the facility needs to be mapped initially, and then is a more time-consuming process than putting down tape, so startups takes longer. “But if you want full flexibility, you need mapping (SLAM).”

Mr. Keij asserts that their are other advantages that AGVs have over bolted down material handling systems: they can be implemented more quickly, are less expensive to maintain, and they free up more space in a factory.

In doing research on flexible automation, I’ve noted some acrimony between suppliers of autonomous mobile robots (AMRs) and suppliers of automatic guided vehicles. AMRs can autonomously redefine their route to avoid an obstacle.

But from Mr. Keij’s perspective, much of this is just marketing hype. The Kivnon AGVs can be programmed to connect with manufacturing execution systems, robotic cells, and automatic doors to allow for more efficient product handoffs, production, and travel. Having one of their AGVs order an automatic door to open is, after all, also a form of autonomy.

Further, having a mobile robot autonomously redefine its path “does not work in an automotive factory.”  Mr. Keij explained, “manufacturers have a specific time frame they are looking for material to be delivered to the line.” If a robot picks a new path to avoid an obstacle, the desired sequence of material delivery to the line can be disrupted. Kivnon takes a lean approach to line deliveries. If obstacles arise, and it necessary to deliver material to the line within tight time windows, Kivnon has monitoring software that detects that an AGV has stopped. This software sends proactive alerts on phones or via email or even causes a light or sound alarm to switch on. For example, if a person has put a box in the path of an AGV, the alert might be programmed to go off after two minutes if that AGV has stopped on a location on the loop where it would not normally stop. “We think it is smarter to move the box and maintain the sequence, then it is to navigate a different path.”

In conclusion, as I’ve talked to suppliers in the AGV/AMR industry, I’ve come to realize that this is not just a situation where AMRs are “smart” and AGVs are “dumb.” There are a range of different types of intelligence that these machines can possess; it can be counterproductive to pay extra for a form of intelligence or autonomy not needed to complete a particular kind of task.

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