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This project was completed with the invaluable collaboration of

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Project Outline

The SCARA Robot project was a final year Mechatronic Engineering project conceived, designed and manufactured from scratch by Charl Rossouw, and done in collaboration with RAPID3D.

 

 

This was an awesome cross-disciplinary project which features aspects of 3D printing, Topology Optimization, integrated Electronics, Robotics, Vision System Capability as well as IoT in a neat packaged solution.

The robot features state-of-the-art electronics, controlling arms that were topology optimized and printed in nylon, whilst also having a unique compliant gripper which was printed in one piece. As such, it represented a unique fully integrated application of Industry 4.0 ideals.

The objective was to create a fully functional SCARA Robot with Vision Capability and Online Control at a fraction of the cost of standard SCARA Robots. Specifically, the project outcome was to develop a 4-DoF SCARA Robot to be integrated with a CNC milling machine to handle material in and out of a designated workspace. The SCARA Robot needed to locate a part through Machine Vision, and be monitored through a web-based IoT platform. The web-based platform would also have provided user interaction to provide the SCARA Robot with reconfigurable stopping points. 

Additional outcomes defined by the student were to design a mechanical structure that was Topologically Optimized and could be Additively Manufactured, and, as a bonus item, to design a one-piece Compliant Mechanical Gripper for the end effector of the SCARA Robot.

 

 

Design Process

A non-traditional Simulation Driven design approach was undertaken using freeform topology optimization as the primary mechanical design tool. This kinematic model was first developed based off the mechanical functionality and the special relation of the robots elements. This process yielded the forward and inverse kinematic equations that were used to specify the mechanical, electrical, and control requirements.

The mechanical functionality and electrical control system were designed simultaneously. From the kinematic model the constraints were developed into joint designs based off the loading and motion requirements. The torque and acceleration requirements were obtained through simulation of the kinematic model and motion analysis techniques.

 

 

The electrical control system was designed such that it mimicked an industrial environment where a PLC or IPC controls a process through motor drives. The IPC was represented by a combination of an Arduino Uno and an ESP32 development board.

The motor drives were represented by STM32 Blue Pill microcontrollers and DRV8825 stepper motor driver. Stepper motors were used to actuate the mechanical structure. A PCB was designed to mount and house the electrical control system.

 

 

As previously indicated, the mechanical structure was developed using freeform topology optimization. The constraints and loadings from the kinematic model, and the mechanical and electrical control systems were defined in the software. PolyNURB structures were created using the graphics output of the topology optimization.

This polyNURB structure was converted into a solid body which was then structurally analyzed. Adjustments were made to the loadings and polyNURBS until a satisfactory result was achieved. There was also partial latticework design on the main body surround but it was restricted to this due to time constaints.

 

 

A unique aspect to the project was the design of a one-piece compliant mechanical gripper that could be additively manufactured as a single part whilst still maintaining its full functionality, as it was driven by a servo motor.

The development of this complex device was a challenge as it was originally 12x different components that we wanted to additively manufacture as a one-piece print, yet maintain the same functionality as the multi-part component. This was ultimately achieved in an elegant solution as shown below using reference to compliant mechanisms.

 

 

A Vision Module with an on-board processor was also integrated into the design and the module was coded to locate a part based off a colour differential. The coordinates of the parts corners and centroid with reference to its reference frame were sent to the Arduino to calculate the actuating angles.

A webpage was created that was hosted on the ESP32, which was set up as a webserver. The webpage displayed information about the robot’s actuation, and allowed the user to enter reconfigurable stopping points.

 

The ultimate solution was a huge win for us all round, and was quite an astonishing piece of work, attracting attention world-wide, with a request from Altair to display it at HannoverMesse this year. A paper will also be completed in the first 6 months of the year for publication.

The student as a result of his outstanding work acquired an R&D position at one of our leading leading companies, where he will specialize in virtual commissioning, digital twinning and 4IR IoT capabilities of industrial assembly lines.

 

 

The fully functioning robot was also displayed at three events:

  • the RAPDASA Industry Open Day at the NMU,
  • the RAPDASA AM Conference in Bloemfontein, and
  • the African Manufacturing & Composites Expo

A presentation on the Design Process was also given at the RAPDASA AM Conference as part of the Biomimetic stream of the event.