The MX-Phoenix hexapod robot project
Posted on November 29, 2016 in MX-Phoenix
It’s been a while.. Well, time just seem to disappear when kids, family and work require the most of you.
Not so creative title.. and what to call my current project isn’t that important really. I did start on a simple hexapod design a couple of years ago, that ended due to some distractions and suddenly my Autodesk 123D files disappeared from the “sky”.
Meanwhile I’ve been working on a new gait-algorithm for hexapod robots (codename DynaZgait). I did post some short vids on my Instagram. Earlier this year I decided to learn 3D printing and bought a very cheap Wanhao Duplicator i3. I’ve done all of the most common modifications and upgrades. So far I’m satisfied with the result and print quality.
I’ve to mention that I bought this printer from a Norwegian company called 3DNet. So far I’m very pleased with their excellent service and fast delivery. Since the Wanhao Di3 is a low-cost printer some of the parts used suffer from that.. But 3DNet has been very helpful and sent me replacement parts every time I complained..
As you can see I’ve even added an extra heater in the cabinet, useful when printing ABS during the cold winter.
Another project was a new remote controller based on the code used on the Arbotix Commander 2.
My next plan for a remote is to make a much smaller one using some other very nice 3-axis gimbals from Turnigy.
When it comes to CAD I’m a bit noob. At first I tried Autodesk 123D, but I found a bit to limiting. Then I moved over to Inventor and found that OK, but a bit cumbersome.. After that I tried Fusion 360 and found it to be a really awesome tool and easy to use/learn.
Making of the MX-Phoenix hexapod.
Anyway, I decided to make a new hexapod robot again. This time using the much larger and powerful Dynamixel servos from Robotis. I’ll use 6 MX-64T as coxa servos and 12 MX-106T for the femur and tibia sections. I’m calling the robot MX-Phoenix simply because it’s a little inspired by my first hexapod robot I made 10 years ago. It’s kinda “back to the basics”, but this time I’ll have more focus on my primary goals that I didn’t achieve on my first robots: A more dynamic gait engine and terrain adaptation. I also want a hexapod robot with a relative small body and large leg section, I’m also trying to keep the total weight as low as possible.
All my previous robots has been made using mostly custom hand-made parts. We all know that making several equal and precise parts is very hard without using a CNC, laser cutter or other computer assisted tools. For a very long time I thought using a laser CNC cutter to make the parts would be the solution. But after getting familiar with 3D design and 3D printing I realized that the optimal way to create unique 3 dimensional curved parts was to use 3D printed parts. At first I thought the plastic would never hold or be strong enough for a large robot. As many others I started printing PLA “things”, but I soon realized that ABS was the best material. Of course there are many other more sophisticated materials that I’ll try later.
I started designing a small and simple hexapod body containing a 3S 5000mAh LiPo, Teensy3.6 + Kurt’s T3.1 breakoutboard and the coxa servos (MX-64T).
The CAD images is a bit easier to see than the photos (poor light). The battery simply slide inside the body between the body sections:
A couple of photos of the final result:
The body sections are printed in ABS and “Acetone vapor-treated”. The final result is very strong and solid.
Next step is the leg design. I’m planning to first use the Interbotix Tibia’s as a Femur, lol.
In the future I’ll move over to a more advanced hexapod design. With limited free time available I just have to learn CAD a lot more and this project is a good start.
About 13 days ago I designed a tibia using Fusion 360. I’m pretty sure there are more effective ways to do it, but at least I ended up with something I would like to try:
In the future I might try to design some shell/covers that are more curved for the femur part (Interbotix Tibia bracket). I did an attempt to add a simple foot sensor/switch made of some few parts:
After designing the tibia I couldn’t wait to try printing it. I was very curious and excited to see how the final result would be. I’m still using the Cura slicer that came with the printer and my earlier experience with the support construction was very mixed, especially when printing ABS. Luckily the result came out very good, no warping at all. FYI I’m printing at 250C/100C and using a cabin with a heater set to 35C:
I was a bit unsure if I should go for a Aceton Vapor treatment again or not. This method sure has some con and pros, but at the end the part will become stronger. So, after about 3 days of printing all parts was ready for the next step. For Aceton Vapor treatment I’m using a big pot where the sides are covered with some cloths. This is some really nasty stuff that require good ventilation and personal protection (mask and gloves). I’m doing this process outdoor in my garage. A picture of my pot..:
If you want to know more about this process there are tons of information about this on different forums/blogs/youtube. I was not 100% pleased with the result though (still learning). But its gonna work I think. A picture of the result:
When I connected the servo-wire from the femur to the coxa servo I decided to make a simple wire guide/protector under the C-bracket:
I’m still not finished with all the mounting stuff since I’ll probably have the femur and servos free with no brackets attached at first. I need to do several changes to the code first and I don’t want to break anything when testing the code for the first time. Safety first..
I’ve mounted the legs just temporarily with a couple of screws just to see how it would look like. Here are some better pics:
A close-up of the foot-switch, I’m using an anodized aluminium rod, a micro-switch, 3D-printed washer and stopper, and a rubber 3M knob:
MX-Phoenix vs. the original Phoenix hexapod:
And versus PhantomX MKI:
Maybe not that big difference?.. The total weight is 4,72kg. My goal was under 5,5kg so I’m pretty satisfied with that.
The next step is to make the first step..
When I’m satisfied I’ll post a new video on my youtube channel. (Finally!)