Automated process for modular bulb packaging
ISO, Horti Innovators, revolutionises agriculture and horticulture automation using robotics, vision technology, AI, and machine learning. Tulip bulb growers are among their key focal points. ISO developed a wireless communication solution, provided by SMC, that enables growers to efficiently sort and pack an unprecedented number of tulip bulbs while addressing complex design challenges.
Packing tulip bulbs is a multifaceted process. It involves handling large quantities of bulbs which need to be arranged in rows with specific spacing. Additionally, each bulb must be positioned with its sprout (the first signs of the tulip stem) facing upward. Ensuring bulbs remain intact during transportation, and maintaining their correct position within the packaging, is an additional complexity. This is crucial to prevent any damage to the sprouts.
ISO has developed a modular packaging line that automates the entire process. Robots and vision technology are used to handle most tasks. "These machines are standardised and can be customised based on the customer's requirements and layout. They can process various types and sizes of tulip bulbs used for cut flowers," explains Bastiaan Ophorst, mechanical engineer at ISO.
Smart packaging requires a wireless vision system
A brief explanation of the process: a forklift transports pre-sorted tulip bulbs in cubic containers, which are determined by bulb size. The cubic containers are emptied into a collection container at the start of the packaging line, forming several layers of bulbs. Vibrating plates are used to transport the bulbs toward a loading station, ensuring they are arranged in a single row and creating appropriate spacing between each bulb, based on the desired packaging quantity.
Six cameras are used for monitoring and capture images of each bulb. Combined images are used to generate a 3D representation, providing detailed information about the bulb's position, 3D geometry, and sprout location. This data is crucial for grippers on the robot arms to handle each bulb correctly. Additionally, a 3D camera performs an optical health check on each bulb to prevent unhealthy bulbs from being packed. These defective bulbs, known as "sour bulbs," are marked by the packaging line's control system and removed from the belt. Bulb spacing is controlled by adjusting belt speed thereby preventing congestion during the process.
Once the vision system determines the position and orientation of bulbs on the belt, they are fed into the packaging machine with the required spacing, forming a perfect row. The packaging line typically consists of multiple modules (called "planting units"), usually four units, each equipped with one robot. The gathered information on the individual bulb's position and orientation guides the grippers to pick up a series of bulbs and place them onto a bridge. The number of positions on the bridge depends on the number of bulbs to be placed in each row of the packaging container. The robot arm accurately positions bulbs on the bridge, ensuring that each bulb is securely held by a gripper. Each bridge can accommodate up to two times seven grippers arranged in two parallel rows at 180 degrees opposite each other. Once all seven grippers are filled, the bridge rotates, and the rows of bulbs are transferred into the packaging. Depending on the bulb type, each position in the packaging contains a small pin for securing the tulip bulbs or a layer of moist soil for bulb stability. The bridge gently presses the bulbs onto the pins or into the soil, thus securing their position. This guarantees that the bulbs remain upright during transport to the growing area. Once the packaging is filled, it is replaced by empty packaging. The packaging, filled with bulbs, is then transported to a final station, where a grower's employee performs a visual inspection before shipping.
Positioning of the bulbs onto the bridge
Reliable wireless communication achieved
Wireless communication played a vital role in overcoming a technical challenge in the design of this packaging line, specifically the rotating movement of the bridges. Given that the rotation always occurs clockwise, wired communication solutions were impractical. Ophorst explains, "We explored the possibility of using slip rings, but they would have required numerous conductors. With over thirty functions/detections in each plug-in bridge, wiring was not feasible. That's when we realised that wireless communication was the way forward. But how could we ensure reliability?”
"The solution came from SMC," says Bert Evertse, PLC programmer at ISO Horti responsible for controlling the packaging line: "We had previously tested a Bluetooth-based product from another brand, but it proved to be susceptible to interference, which is highly undesirable for a high-speed application like this. Fortunately, SMC provided the right solution at the right time. They proposed an industrial wireless network within the packaging line. We installed a base (transmitters) module on the non-rotating part of the line and a remote (receivers) module on the plug-in bridge. The control data for the plug-in bridge is transmitted via SMC industrial wireless communication from the base to the remotes. The control data, which includes approximately 60 bits per module, along with diagnostic information, is delivered to the base via Ethernet/IPTM. The configuration of the base and remotes is addressed once during installation via Near Field Communication (NFC).”
The distances between the base and the remote can vary, in this configuration it is 5 to 6 metres. A maximum radius of 10 metres is possible. Surprisingly, the moving parts within each module, such as the servo motors of the robot arms, do not affect data transmission. Evertse affirms, "There have been no malfunctions whatsoever. In fact, the communication is extremely reliable."
Wireless remote module on the plug-in bridge
