final project idea

Based on my previous experience and interest I chose my final project to design a Collaborative 6- Axis Robotic arm KRAB. As an extensive user of Rhino - Grasshopper platform, my proposal is to control KRAB  from Rhino Grasshopper itself using a Inverse Kinematics solver based on the source plane and user defined target plane.


working principle

weekly work

final project

The joint configuration of the robotic arm will follow the standard 6-Axis configuration available in the market :




final project

The robotic arm project started as a basic sketch in which the shape, size and dimensions are fixed.

final slide

final video

bill of materials

The total price of the project has come up to 5200 INR or about 80 USD. The bill of materials can be accessed by clicking on the image or it can be downloaded here.

work of previous weeks

A few of my previous week project are connected with my final Project.

01. electronics design

The Krab Board that sits in the heart of the robot, the control board was designed in the electronics design week.

02. embedded programming

In this week I have started the coding with the board through Grasshopper. So it s a very important week for this project.

03. input devices

The clash detection circuit of the Robot was made in the input device using ultrasonic distance sensor.

04. interface and application programming

The way Krab moves, works, and helps user to interact with it was designed in this week.

3d & cnc design

In the final project development weeks i had printed the 3D printed parts and CNC milled base to hold the bearing the base motor.

This photo shows the Finished and unfinished 3D printed parts. LASER cut pieces of acrylic, motors, bearings and CNC cut base.

CNC Machining in ShopBot. Now the pars of the robot will be showed in detail with their motor fixture, bearing fixture and connection to each other.

J5 with MG90S attached and Bearing

J5 with MG90S attached and Bearing (Side view). The bearing was press fit in an ABS shaft which will into anothe ABS case.

J4 with MG90S attached. The four black screws in the center hold the servo for for connecting in J3

bearing fixture

mini servo horn

J5 and J4 getting fixed.

Servo Horn fixed on J3

Servo and horn fixed on J3

J3 Connecting with rest of the assembly of J4 and J5


J2 connected with servo and horn

J2 getting connected with rest of the assembly

J1 Bearing are fixed o the CNC Base and Motor is being attached with the holding plate.

Base Connection

Connection Diagram

comment integration

I have tried to incorporate Neils comment as much as possible in this iteration of the Robot.

Wire Passage

All the wires are passing through the slit in the J2. only clutter I could not solve was the place where the wires are coming to connect at board. Its 6 wires thats bundled in the .

design files

Original Design Files can be obtained from here:

3d printed parts :

laser cut :

cnc milling:


png for milling:

model, control, interface:  Requires, Rhino-Grasshopper, Human, Firefly installed on system.



There has been some projects in this regard which has inspired me to develop my on robotic arm.


  • Daniel Piker's lobster sits in the core of the code I have made and added to. Without this the project would not have taken shape.
  • Ryan Hughes of ARC, Arkitektskolen Aarhus, has done beautiful work to integrate Lobster to control industrial robots from which this project has rooted.
  • And, finally of course, Rudrapal, whose robotic arm actually made me think take up this project.


project development  >>

Avishek Das   |   2017   |   FabLab CEPT