3D-Printed Egg Gripper Prototype
Background
Robotic grippers are essential components in modern automation and robotics, used for handling objects of varying size, shape, and fragility. Among various types, impactive (pinch-type) grippers are widely used due to their simple design, easy control, and ability to handle objects by applying frictional force.
This project was initially developed as part of a Master of Engineering course to understand gripper mechanics, gear transmission, and actuation control. The earlier phase involved theoretical design, 3D modelling, and motion analysis of a two-finger gripper. Building upon that foundation, the current phase focused on physical prototyping, 3D printing, and experimental validation of the design.
Motivation
To extend the previous conceptual design into a working prototype and verify the mechanical performance through experimentation.
To apply mechanical design principles such as torque transmission, gear ratio selection, and force analysis to a real 3D-printed mechanism.
To gain practical experience in integrating CAD design, fabrication, assembly, and functional testing using DC motor actuation.
To demonstrate a compact, low-cost robotic gripper capable of holding fragile objects, such as an egg, without breaking it.
Objective
The objective was to design, fabricate, and test a two-finger robotic gripper that can securely hold an egg using a 6 V DC motor and a worm-gear transmission.
The design was required to provide sufficient gripping torque, prevent back-driving (self-locking), and maintain smooth and symmetric motion of both fingers.
Design Framework
The gripper follows a two-finger impactive mechanism, where both fingers close symmetrically to grip the object.
The mechanism was modelled in SolidWorks, and motion analysis was performed to evaluate torque transfer, angular displacement, and closing motion.
The gripper components were designed to be 3D printed in PLA, suitable for lightweight and accurate prototypes.
A 6 V DC motor was selected for actuation, coupled through a worm-gear mechanism to multiply torque and prevent reverse motion.
The gear ratio of 25:1 was chosen to achieve high torque output and self-locking behaviour.
The entire assembly was sized to fit within a 180 × 180 × 180 mm print area, with 5 mm steel shafts, miniature bearings, and M3 bolts for assembly.
Fabrication and Testing
All parts were printed using 100 % infill and 0.2 mm layer height for maximum rigidity and accuracy.
Bearings and steel pins were used at pivots to reduce friction and improve durability.
The assembly was tested using a 6 V DC supply, achieving smooth operation at around 60 rpm motor speed.
The gripper successfully gripped and lifted an egg multiple times without any surface damage or slip.
Performance remained consistent over several open-close cycles, demonstrating structural stability and mechanical reliability.
Validation Summary
Required gripping force achieved with high safety margin.
Output torque more than adequate for intended load.
Worm gear ensured self-locking and smooth torque transfer.
No visible deformation or cracking of printed parts after repeated operation.
The prototype successfully validated the design calculations and mechanical concept.
