The XY System

June 12, 2003 - 10:33

The ultimate piece of automation for labor savings and system integration.

Can you imagine a 17-acre greenhouse range that produces
multiple varieties of bedding plants and has all-material movement into and out
of the greenhouse done by one person? Can you imagine having transplanting
integrated with material movement? Can you imagine growing containers being an
integral part of the shipping system? The technology to do this does exist and
is being used. The key element in making this possible is a state-of-the-art XY

Why XY?

While XY systems may sound exotic, the basic concept is
simple. In fact, almost every greenhouse uses some form of an XY system.
Visualize a greenhouse layout overlaid with a set of graph coordinates. For
consistency, let's call the direction of the main transport aisle the X axis of
the graph. Conversely, let's call the direction of the greenhouse bays the Y
axis. The X direction is used for transporting plant material to and from the
headhouse and shipping area. The Y direction is used to place and space product
in the actual growing areas and to remove product for shipment or other work in
the headhouse.

In some ways, all methods used to transport material are XY
systems. Using a train of carts to move plants to the appropriate bay takes
care of the X. Manually unloading the carts and moving material into the bays
takes care of the Y. Obviously, this is not the most efficient or high-tech XY
system, but flexibility and capacity are restricted only by the amount of
manpower. Similarly, monorail systems, palletized benching systems and
forklifts described in previous articles (See April 2003 GPN) are all XY
systems. Each of the above systems works well in the right circumstances.

What makes the new system different? Many bedding plant
growers express two major concerns when considering systems for material
movement. The first is the large amount of material that must be moved in a
short time due to the compressed selling season. The second is how to deal with
the large number of varieties typically grown in a bedding operation. The
ability to selectively pick from anywhere in the greenhouse bay is critical.
The new XY systems address these two concerns better than any other system on
the market. Variations are also available that allow the same concept to be
used by medium-size growers.

XY Basics

To move the plant material in the X direction, some form of
carrier is needed to hold the flats. Transport carts become these carriers in
many manual systems. A bench is the carrier in a palletized container system.
In the XY system, the carrier is a specially designed carrier or cart shelf.
Cart shelves are available in a standard 60- x 22-inch size and are designed
for handling by the other parts of the system and to be stacked on a
traditional cart base to form a shipping cart. The carriers are also placed on
the floor of the greenhouse with the plants on them for the entire growth
cycle. The concept of using cart shelves as carriers and growing container is a
brilliant example of an integrated greenhouse operation system.

The second device necessary to move material in the X
direction is some form of a shuttle to actually move the carriers to the
appropriate bay. In a manual system, the shuttle is normally a tractor to move
the train of carts. In a palletized benching system, the shuttle device is a
transport line. These transport lines can be powered or manually operated. In
the new XY system, the shuttle Á device is a large robotic shuttle car
that moves up and down the transport aisle on a track. The car is approximately
30 x 15 feet and is designed to hold 48 carriers in three rows of 16. In
another example of integration, the greenhouse bays are 30 feet wide to
accommodate the automation equipment.

Moving material in and out of the bays requires some sort of
pick and place device. In manual systems, this is normally people. In
palletized benching systems, the benches are rotated in and out of the bays on
rail systems. In the XY system, the pick and place unit is a diesel-powered
device with one operator -- the only person in the entire greenhouse range. The
pick and place unit is sized to match up with the shuttle. It will pick all 48
racks off the shuttle and can place them anywhere in the greenhouse bay. While
the placing is being done, the shuttle returns to the headhouse for another
load of plants. The reverse process is used to empty the greenhouse.

In the above example, two shuttles should be used to keep up
with the capacity of the pick and place. Each of the three rows of carriers can
be selected independently. Consequently, the quantity selected can be in
minimum quantities of 16 shelves. To get an idea of the amount of material that
can be moved, each cycle will clear 440 sq.ft. of greenhouse space. Therefore,
100 cycles will clear an acre of space. This is a high-capacity system. As
another example of system integration, the pictured greenhouse has been
designed with the transport aisle in the middle. This placement minimizes the
distance the pick and place unit must travel, thereby increasing the capacity.

The pick and place unit is designed to place itself on a
shuttle car for transport to another bay and can also be fitted with a boom
that can be used for tasks such as pesticide application and irrigation.

More Integration

Movement of goods in and out of the headhouse is also
integrated with the XY system. Material can move directly from transplant lines
onto conveyors that automatically load the shuttle. When product is being
removed from the greenhouse, the same conveyor system is used. In addition,
other equipment will automatically stack the carriers to form a shipping cart.
The grower in the pictured greenhouse uses the cart shelves for shipment.

Look for August's column, which will go into more detail on
the system and its capacity, as well as present thoughts on how the involved
concepts can be used to develop variations for a range of growers. style="mso-spacerun: yes">

About The Author

Mike Porter is president of Nexus Corporation, Northglenn, Colo. For advice about automation implementation, he can be reached by phone (303) 457-9199 or E-mail at

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