A Line-us Clone 2.0: The Arms and 3d Printing Misfortunes

I spent the weekend starting on designing the robot. A few things have changed since I started the project. I’ve been trying to figure out how to feed the robot the images and finally decided on an idea. I’m going to write a python program that works as paint whilst remembering how the paths/drawing is drawn by logging the x-y coordinates of the lines. It’ll be a simple program that will output the x-y coordinates to an output file of some sort that will then be loaded onto the MCU.

I then went back and deliberated whether I needed the PSOC to be the MCU as it is probably overkill. I think I may switch to a teensy, but I haven’t quite decided yet.

I also started designing the physical robot itself. I started with the arms as it was one of the more crucial parts of the project. I started by trying to print the gearheads of the servo into the arm with poor success. My 3D printer has a 0.4mm nozzle so getting the definition of the micro servo’s gears were difficult. I then decided to switch back to my original idea of using the servo arms and incorporating them as part of the robot arms. That worked out much better. I had real struggles with the tolerance on my 3d printer as I wanted the bearings to all have a press fit. I managed to get some and not on others. It was a real hit-or-miss for a while until I managed to calibrate my printer. Just shows that I need to be using that printer more often.

I had particular issues trying to get the pin for the middle of the bearing made. Because the bearing I’m using was so small (3mm x 3mm x 7mm – requiring a 3mm pin), the printer tended to overheat the print causing it to melt sadly as it grew. 

You can see the deformation at the base. This caused the bearings not to sit well on the arms. I tried reducing the size of the pin to compensate for that. Finally, by a stroke of luck, when I printed one of the prints at ulti-quality (printing it slower) it came out perfectly. I then figured that the nozzle was probably applying too much heat on that small surface area. I then decided to print a smaller test print of the same height a little away from that print so that the pin had time to cool after each layer.

Prior to figuring that out, I decided to heat one of the pieces with a lighter and smoosh a bearing on top in hopes that it would form to the bearing. It didn’t. I would not recommend this. Lessons were learnt

I also tried using glues and toothpicks to adhere the bearings to the plastic. Turns out hot glue does not stick to metal bearings well and elmer’s glue… well doesn’t work. It probably would have been easier to just screw everything together, but I was really aiming for that sleek look.

I finally figured out how to get the perfect prints after many many iterations. Here are some of the scraps with the 2 arms on the right actually being useable. There were more scraps that were lost during the prototyping process that aren’t in these pictures.

3D printing lessons were learnt this weekend, but overall I managed to get the arms all designed and mostly printed. I’m still tweaking the dimensions slightly to get an oh so much better fit. Unfortunately 3D printing is not like machining. I think I need to build more often as this tweaking took longer than it usually would have took me.

A Line-us Clone 2.0: The beginnings

I love robots. In fact, I studied them as a college student and have done some real-world work with robots from self driving cars to smart automation in production. If you want to know more about those applications, you should take a look at my resume. My depth in University was in Robotics, specifically in embedded controls and kinematics and dynamics. Which is why this Kickstarter project spoke to me so clearly. Unfortunately, by the time I had found out about the project, the 1000 available units had already been spoken for. So instead, I’m going to build my own.

In full disclosure, one clone has already been made by Barton Dring. You can see his very comprehensive build logs here: http://www.buildlog.net/blog/2017/02/a-line-us-clone/

I plan to build on the knowledge he has published and build my own.

To that end, I started gathering materials:

10 x longrunner metal-geared micro servos (Should only need 3 for the project)
1 x PSOC 4 kit (This will be a new MCU/FPGA for me)
10 x magnets (For having the base stick between a window wall) (should only need 2?)
Lots x Assortment of bearings (wanted to try a few to see what works best. I’ll update the next logs with which I use)

Most of the items listed I got from Amazon. The PSOC kit I got for free from Seattle’s makerfaire in 2016, but you can get it from the cypress store for 10 bucks. It’s a good deal for what it supports.

I’ve also started modelling the servos for the system so I can build the rest of the robot around it. These tiny motors pack a punch in torque for how small they are – I’m impressed. Instead of finding the gear head cad drawings, I’ve decided to incorporate the one sided servo arm into the arm of line-us. This way there is more structure to the arm (I think) and I don’t have to find the gear head drawings and make them – because they are tiny on the micro servos and I don’t know if my 3D printer (ultimaker plus) can handle that.

I’ll start working on modeling the servo arms next and then designing a robot arm to fit around it right after. This weekend should be fun. 🙂 Also, look at how cute that robot is.

 

First blog post

Using a simple template for this website blog. It comes with minimalistic photos for your enjoyment. This project log will be about the projects I take on as a graduated engineering students. My passions are in Robotics and Technology, with a need to create so please come along on my journey.