Design and Development of Pruning Shear Using Compliant Mechanism

Chong, Chen Hooi (2020) Design and Development of Pruning Shear Using Compliant Mechanism. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

Text CHONGCHENHOOI_Full Text.pdf Restricted to Registered users only Download (4MB)

Abstract

The studies have been carried out on the designing and development a compliant pruning shear under fatigue strength control. From the literature review, it is well known that compliant mechanisms have seen increasing use in several industries including automotive, aerospace, medical and construction. Besides, Compliant mechanisms can achieve a wide range of mechanical behaviours through their monolithic structures that elastically deforms without any joint and link to produce a desired force or displacement. The flexibility of compliant mechanisms allows for energy transform through straining of the members. To aid with this study, the Quality Function Deployment (QFD) is performed by using the House of Quality (HOQ) and Value Analysis and Value Engineering (VAVE) to evaluate and select the ideal conceptual design. Moreover, SolidWorks and Autodesk Fusion 360 is introduced for the simulation analysis purpose. The simulation type is based on the non-linear elastic plastic deformation. Throughout the simulation, various forces have been applied on the pruner to analyse the stress and strain distribution, displacement and safety factor. The maximum stress and strain distribution on the pruner are 44.25MPa and 0.02121 respectively when a 350N force is applied. The minimum safety factor is 1.293 and the displacement ratio for handle and head of pruner is 1:0.5 when a 350N force is applied. Consequently, the pruner is potentially able to withstand a force up to 500N. Moreover, the theoretically calculation shows that the pruner is able to produce a desired output force of 560N when a 350N force is applied. Next, the final results will be used for prototype fabrication on a 3D printer by using a material called Thermoplastic Polyurethane (TPU). The designed pruning shear is used to evaluate the capabilities of the proposed compliant mechanism. Lastly, the performance of the prototype might have slightly different compared to simulation result due to the infill density and infill pattern by the 3D printing. Further improvement has been discussed such as replacing the material by Polypropylene (PP) due to it is highly resistant to fatigue.