Building a Robotic Arm — Part 2

Building the mechanical assembly

In the first part of this series I listed the parts required to build the mechanical assembly for a robotic arm. You might remember my delight is discovering that no instructions were included! Yes, I’m one of those silly people who assemble IKEA furniture and then look at the instructions to see if I did it correctly. (Surely having parts left over just means I have assembled it more efficiently, right…) Realising that most people won’t want to spend an hour staring at a pixelated image of the assembled arm on the amazon product page to determine the best order in which to assemble it I decided to create some instructions.

Assembled robotic arm

There’s a few ways you can put these arms together. I opted to copy how the arm was assembled according to the pictures on the amazon product page.

A quick note on fasteners

Before we begin there are 4 types of fasteners used in this robot arm kit. To avoid any confusion in this guide I will refer to them by a number as shown in the image below.

Nuts and bolts
  • Machine screw #1 is used to attach the metal servo horn to the servo and also to attach the servo horn to the metal parts of the robotic arm. These screws came with the metal servo horns and were not part of the robotic arm kit. Some equivalent screws were included with the arm kit but I decided not to use them as they were shorter.
  • Bolt and nut #2 are used to connect all the non-moving metal parts together.
  • Bolt and nut #3 are used with a bearing (not pictured) to connect the 4 main moving joints of the robotic arm.
  • Bolt and nut #4 are used to attach the body of the servos to the robotic arm.

#1, #2, and #3 all have the same thread which I believe is an M2 thread. #4 appears to have an M4 thread.

Right, with that out of the way let’s get going! Read More

Building a Robotic Arm — Part 1

Introduction

Apparently a quarter life crisis is a real thing. Not wanting to miss out on this phenomenon I decided to build myself a robotic arm. Not the sort of arm that replaces a missing limb, but the sort that are used in factories around the world to pick, place, and construct products.

Unfortunately living in an city quickly shrunk my dream of building a giant robot to a more apartment friendly size. Probably for the best!

I have absolutely no idea what I will use a robotic arm for. I suspect the desire to make one came from watching Simone Giertz and her “Shitty Robots”. These robots are designed to complete a single task, but instead fail spectacularly often resulting is a huge mess.

Since I am mainly interested in electronics and software I opted to buy a kit for the mechanical parts. There are several options out there; searching ebay, amazon, and Alibaba for “robot arm” yields 1000’s of sensible results. Most variants are built around standard hobby servo motors that are typically used in remote control cars and planes. While these motors are not exactly known for their repeatability, smoothness, or accuracy they are very cheap!

I opted for a “Mirocle Aluminium Robot 6 DOF Arm” from amazon which was £22.50. Unfortunately it has subsequently gone out of stock, but searching ebay for “6 DOF robot arm” gives many identical kits.

My kit, like most of the ones I saw, did not come with servos. I ended up buying six super cheap “Tower Pro MG996R” clone servos off ebay for £21.50 delivered. Given the price the servos are actually of reasonable quality, and have metal gears. However, if you are not a cheapskate like me, buy better servos!

Tower Pro MG996R servo with top removed

The servo horns supplied with the servos were plastic. I believe my robot arm kit was supposed to come with some replacement metal ones, but they weren’t in the box. Instead, I purchased some metal ones off ebay relatively inexpensively.

Now I had everything I needed to build the mechanical assembly of the arm. I was very happy to find that no instructions were included with kit. Figuring it out myself is much more fun 🙂

All the parts ready for assembly (Knolling)

Click below to read the next post:

Part 1 — Introduction (You are here)
Part 2 — Building the Mechanical Assembly
Part 3 — Designing the Electronics System (Pending)
Part 4 — Developing the Microcontroller Software (Pending)
Part 5 — Developing the PC control software (Pending)