Design Automation of a Two Scissors Lift

Abstract

In this study, the design of a two scissors greenhouse lift trolley is considered. The maximum height of the platform from the ground is 3500 mm. A program developed in Visual BASIC to automate the design is introduced. The lift is modeled in SolidWorks (SW) and the finite element (FE) modal and static analyses are performed as an initial design first by using graphical user interface (GUI). The lift contains revolute joints and slider joints. A simply supported beam which has two revolute joints and a slider joint is studied to verify how to model the joints. Pim connectors are defined for revolute joints in SW-FE analysis. Spring connectors with very large values are defined between sliding faces in the normal direction for translational joints. The results obtained with solid finite elements in SW are compared with analytical results for the natural frequency and static analyses and it was observed that the results are in good agreement for the simply supported beam. 
 An Excel file where a main sheet contains the list of the bodies and all the geometric values is created after the initial design. The Excel file also contains sheets for each body. Body sheets have all the dimensions in the sketches and features. The dimension values in the cells of the body sheets are defined by formulas related to the geometric values given in the main sheet. Kinematic, kinetic, and revision of the SW model are performed by the design automation program. The FE analyses are done by GUI and the results are evaluated. If the results are not satisfactory, the geometric values are changed in Excel file and the analyses are repeated. The final design is obtained by the iteration easily. The automation program and the procedure developed in this work can be extended other scissors lifts.