I am currently in the process of designing and building a five-axis robot from scratch. I, therefore, also need a gripper to be able to manipulate objects. The drive for the gripper should be a commercially available micro servo, as shown in the following picture. In addition, the gripper should have parallel closing fingers to be able to grip objects securely. While searching for existing 3D models for grippers on well-known websites such as GrabCAD and Thingiverse, I unfortunately did not find any suitable ones. Therefore, in this post, I would like to present my own design of a 3D printed parallel gripper for a micro servo. There will be a separate post about the whole robot soon.
Design
The servo can perform a rotation of about 180°. This rotational movement must, therefore, be transformed into a linear movement of the fingers. On the one hand, this can be achieved using linkages. The problem here, however, is the non-linearity of the transformation and the design effort required to make this system stable and efficient. For this reason, I opted for the rack and pinion gearbox variant. The following picture shows the rack and pinion gear consisting of the two gripper fingers and the central gear wheel. The gearwheel is attached to the servo shaft. I adjusted the size of the gearwheel so that after one 180° rotation of the gearwheel, the fingers moved apart at their maximum distance of 47 mm. Furthermore, the teeth of the gearwheel are so large that an FDM 3D printer with a 0.4 mm wide nozzle can print them comfortably.
I initially provided two T-slots for the finger slide track. Combined with the rack and pinion gear, I get the following profile for the gripper. The flanks of the slots and the gearwheel partly support the fingers. The tests carried out show that this works flawlessly. I placed the servo itself completely inside the housing of the gripper.
The flange to the robot’s wrist consists of four M3 internal threads. You can see it in the following image. The white circuit board contains an angle sensor that detects the current configuration of the robot’s last axis. I adapted the housing of the gripper to the flange so that it also completely encloses the angle sensor. Four M3x35mm countersunk screws attach the gripper to the wrist.
3D Printed Result
I printed the gripper with PLA+ on my 3D printer Artillery Sidewinder X2* with 20% infill and a layer height of 0.2mm. Below are some photos of the gripper and a video of the gripper in action.
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CAD Files
You can download all CAD files as STEP and STL files from GrabCAD: Micro Servo Parallel Gripper | 3D CAD Model Library | GrabCAD
* The links are affiliate links. The offers do not come from me. However, I receive a commission through the reference if a purchase takes place, but without you incurring additional costs.
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