The XY System

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 system.

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.