Showroom Another 6DOF with DC motors and encoders inspired by Fly PT

Hello again!
About a year after completing my first project related to the 3DOF motion platform, I am back on the forum. It is time for the next step in creating a sim racing setup. While driving on the 3DOF platform, I could feel the lack of the additional motion axes that are present in 6DOF platforms, so I decided to build another motion platform, this time a 6DOF one.

After many weeks of reflection and browsing the xsimulator forum, I found the 6DOF platform project by pmvcda aka Fly PT from a few years ago to be the most appealing, mainly due to the compact size of the platform and the well-documented and ready-made construction plan with a list of necessary materials.

I also drew many ideas from various 6DOF projects presented on the xsimulator forum, and it is impossible to list them all. I admired these projects for weeks, and many hours spent browsing the forum provided me with a lot of insight into the problems and solutions related to building this type of platform.

Special thanks to noorbeast for the tireless work put into running the forum and the very active help in solving problems, and congratulations to all the builders who are working toward the successful completion of this fantastic journey called DIY motion platform building.

So, let's begin:

My construction plan consists of several points:

1. Design and Planning (a great job done by pmvcda aka Fly PT) – I refer to the thread:
   https://www.xsimulator.net/community/threads/flypt-6dof-brushless-diy-actuators.10799/
   • Schematics and technical documentation
   • Selection of components: motors, controllers, sensors
   • Selection of materials for the mechanical construction (steel, aluminum, etc.)
     
2. Mechanical Construction:
   • Cutting and welding metal parts
   • Assembling the base and upper frame
   • Installing the joints
   • Mounting the electric actuators
     
3. Electrical Installation:
   • Mounting the motor controllers and power supplies
   • Connecting the motors, sensors, and controller (e.g., Arduino)
   • Electrical safety tips
     
4. Testing and Adjustments:
   • Testing motion in the XYZ axes and rotations
   • Troubleshooting technical issues (e.g., vibrations, inaccuracies)
   • Settings for different applications (racing simulations, aviation simulations, etc.)

1. Design and Planning:
After my first platform build, I had a few leftover parts that I wanted to reuse, which is why I made changes to some elements that deviate from the original plan. These are: DC 300W electric motors. Due to the size of these motors, the entire lower construction of the electric actuators was altered. The control method for these motors also changed, as they are not BLDC motors like in the FlyPT project. Instead of Hall sensors for position feedback, I will use incremental encoders. This means that the electronics and software for controlling DC motors will also change. At this point, I don't have an exact connection diagram for the control elements, but I hope it will be in the near future. For the construction of the lower and upper frame, I will use aluminum profiles according to the Fly PT project.
I placed my first orders for the necessary parts about a month and a half ago. Some of the components I had left over from my previous platform build. Today, nearly all of the ordered items have arrived, allowing me to begin building my new 6DOF motion platform. I mainly ordered from Amazon, AliExpress, and Allegro in Poland, and some items were bought locally from stores in the town where I currently live.

2 Mechanical Construction:
Thanks to a few days off work during the holiday period, I was able to dedicate the entire time to this project.
I started the build about two weeks ago by purchasing aluminum profiles from a local supplier. Since I had the opportunity to weld the aluminum profiles myself, I decided to give it a try. Unfortunately, after several hours of attempts, I was not satisfied with the results. I could not achieve a good weld fusion at the joints. Below are a few photos of this "tragedy."
Welding aluminum with a coated electrode is not an easy process. After several hours of trial and error, the key to success turned out to be heating the material to around 150°C. This allowed for a good fusion of the material at the joining points.

But for now, I skipped the part with welding aluminum because I already had parts for building the electric actuators, and this work gave me a lot of satisfaction.

In the meantime, the 3D printer worked several hours a day for about two weeks to deliver the needed parts.


So, the actuator construction has begun:
I had to disassemble the gearboxes from the motors I had and prepare the motors for assembly.


And I started by welding the actuator bases,


measuring, and drilling numerous holes in the plates for motor mounting. To the upper plate, I welded threaded rods for mounting the SFU 1605 screw.

Stick welding aluminium? Wow, I didn't know that this was possible at all. We tried MIG welding last week but it didn't work at all. The wire buckled up several times inside the tube and although both workpieces melted the two puddles never joined. The DC arc couldn't break the oxide layer. So we had to give up and ordered an AC TIG welding machine. With the professional welding machine of another friend the results looked pretty well. I hope we'll get at least somehow acceptable results with the cheaper hobby machine we ordered...

It's possible, but not easy as it turned out. Heating the material helped to break through the oxides. I managed to weld the lower frame, but I have concerns about the upper frame, as the weld might be too shallow, so I'll probably take it to someone with a TIG welder to ensure the best possible quality of the joint. I estimate that the strength of the welds on the lower frame is at most 30-40% compared to aluminum of the same thickness. I also considered trying MIG welding, but I didn't have aluminum wire for that welder at the workshop. The lower frame welds don't experience any significant forces, so I'm not worried about their strength, but the upper frame needs to be welded properly.

Construction continued...
The next step is to attach the upper joints to the 24mm inner diameter aluminum tube of the linear actuator. It turned out that 17mm socket wrenches fit perfectly, and I placed a washer as a movement limiter between the socket and the cross joint and then I welded the socket and the cross joint together . I also welded a 12mm bolt into the cross joint.
The next step is to attach the upper joints to the 24mm inner diameter aluminum tube of the linear actuator. It turned out that 17mm socket wrenches fit perfectly, and I placed a washer as a movement limiter between the socket and the cross joint. I also welded a 12mm bolt into the cross joint.
Through the aluminum tube and the socket pressed into it, I drilled a hole and installed a spring pin. So, everything looks solid and strong.

Next, I cut the threaded rods and aluminum tubes to the appropriate lengths to serve as mounting bolts for the motors. Unfortunately, I don't have any photos from this process.
It has come time to make thread to aluminium profiles too.

It went fast with 5mm tap and screwdriver.

So, everything was ready for mounting my very first linear actuator.

Finally time to mount Actuators together!!!
Part 1


And Part 2.

Here is the video from first test of movement. I used two Arduinos, one is changing encoder digital signal through DAC converter to analog 0-5 V output. So, another Arduino see the signal exactly like from potentiometer. So, no changes in software smc3 for testing made. Finally version i think will work on one ESP32 for encoders signal conversion and 3 arduinos or maybe 2 ESP32 , not decided yet.

The project is worth looking forward to.

In the meantime, an update regarding the lower supporting frame,

and I managed to assemble all the linear actuators.

The second stage of my project has to wait a bit for the upper frame, but I can now move on to stage 3 and focus on assembling the electronics.