June 2003

The XY System By Mike Porter

Can you imagine a 17-acre greenhouse range that producesmultiple varieties of bedding plants and has all-material movement into and outof the greenhouse done by one person? Can you imagine having transplantingintegrated with material movement? Can you imagine growing containers being anintegral part of the shipping system? The technology to do this does exist andis being used. The key element in making this possible is a state-of-the-art XYsystem.

Why XY?

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

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

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

XY Basics

To move the plant material in the X direction, some form ofcarrier is needed to hold the flats. Transport carts become these carriers inmany 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 designedfor handling by the other parts of the system and to be stacked on atraditional cart base to form a shipping cart. The carriers are also placed onthe floor of the greenhouse with the plants on them for the entire growthcycle. The concept of using cart shelves as carriers and growing container is abrilliant example of an integrated greenhouse operation system.

The second device necessary to move material in the Xdirection is some form of a shuttle to actually move the carriers to theappropriate bay. In a manual system, the shuttle is normally a tractor to movethe train of carts. In a palletized benching system, the shuttle device is atransport line. These transport lines can be powered or manually operated. Inthe new XY system, the shuttle ç device is a large robotic shuttle carthat moves up and down the transport aisle on a track. The car is approximately30 x 15 feet and is designed to hold 48 carriers in three rows of 16. Inanother example of integration, the greenhouse bays are 30 feet wide toaccommodate the automation equipment.

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

In the above example, two shuttles should be used to keep upwith the capacity of the pick and place. Each of the three rows of carriers canbe selected independently. Consequently, the quantity selected can be inminimum quantities of 16 shelves. To get an idea of the amount of material thatcan 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. Asanother example of system integration, the pictured greenhouse has beendesigned with the transport aisle in the middle. This placement minimizes thedistance the pick and place unit must travel, thereby increasing the capacity.

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

More Integration

Movement of goods in and out of the headhouse is alsointegrated with the XY system. Material can move directly from transplant linesonto conveyors that automatically load the shuttle. When product is beingremoved 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 onthe system and its capacity, as well as present thoughts on how the involvedconcepts can be used to develop variations for a range of growers.