Design and test of flexible packing line for egg color box

Abstract: Different varieties of gift boxes are commonly used to pack eggs, in order to satisfy the demands of consumers. It has brought great difficulties for the automatic packing of eggs. At present, manual packing is often used in egg processing industry in China, considering the variable size of color box, the different quantity of each box, and the fragile physical characteristics of eggs. In this study, a flexible cartoning, and handling mechanism was developed for the color boxes to realize the automatic packing of eggs. The movement trajectory in a Cartesian coordinate manipulator was planned, using the trajectory planning algorithm, thereby to industrialize the flexible packing production line for an egg color box. Besides, the basic physical properties and the packing protection performance of the color box were tested, including drop test, pressure test, frequency sweep test and random vibration test, in order to ensure the stability and reliability for the manipulator holding the color box and avoid the damage of the eggs in the box that caused by the resonance of the production line. The protective performance parameters for the color box were detected, including the critical drop height, the non-damaged clamping force, the resonance frequency, and the non-damaged egg transport system excitation. In the drop test of color box, the results showed that the critical drop height of eggs in the box was 290 mm, while, in the pressure test, the eggs in the box cannot damaged when the clamping force of the color box was less than 870 N. In addition, the frequency test of the color box proved that the resonance frequency of the color box package was 10-15 Hz, and the random vibration test determined that the excitation of the system can meet Grms≤0.52 g2/Hz. The splint and the guide frame can be quickly disassembled under the constraints of the physical parameters for the color box. The egg box can be boxed with flexibility, high efficiency, and low damage using the central controller (Siemens PLC S7-200 Smart) and the touch screen (MCGS) according to the size, specification and quantity of the color box. The maximum effective strokes of the X and Z axial were 750 and 380 mm in the Cartesian coordinate manipulator in the production line. The X-axial velocity of robotic arm was adjustable from 0 to 199 mm/s, while the Z-axial velocity was from 0 to 149 mm/s. The maximum stroke of the Y-axial gripper plate movement was 200 mm, and the maximum linear velocity was 50 mm/s. The rated power of the machine was 1.5 kW. So far, the production line has been running for 11 months on the packaging line, where the mechanical equipment, software and hardware of control system were stable and reliable. An on-site test was performed on the production line for 10 days, showing that the packing efficiency with 6 boxes and 4 boxes in a color box were 96.2 and 120.4 boxes/h, respectively. Compared with manual packing, the efficiency can be enhanced by 4-6 times, indicating that 3-6 assistant workers can be saved, while the damage rate of egg was reach zero in the whole test process. The findings can provide a sound reference to the design and application of the automatic production line of color box for egg packing in food industry.