I am making a strong commitment to printing all of the PLA drive assembly parts now that I have the filament. So I drove ahead with first setting up multiple part builds. The build plate was packed.
The other thing I needed was some minored versions of the parts . To have right and left sides, I used Fusion360 to copy and mirror the selected bodies along the there x-axis. I Re-exported the new shape and it was ready to print.
There is a lot of parts! The wheel has two sides connected by a center hub and It has six separators. That slides on to the 8 mm shaft connected to the pulley and it’s adapter. The shaft rides on the two pillow block bearings and is locked together with two collars. That assembly has a total of 15 printed part not including tires and rims.
Each wheel has a motor,so it has a mount and tensioner and slide base, three more pieces. Which is 18 x 4 = 34. Some parts take 5 hours and others 15 minutes, I wish I would have tracked the time better and could tell the grand total, but I would guess about 55 hours. I print slow and steady. There have been quick restarts but no failed prints. That is a very good improving average from a failed part every other start.
I hope as you go through your hard beginnings to not get discouraged, lose hope and quit learning. It’s all about watching and seeing what happens as it tries to print the part. After a good first layer I can now let it go and let it do it’s thing.
Make sure to clean up dust, oil your carriage rods and watch for printer temperature malfunctions.
Large parts like the wheel sides have to be printed on the seahorse and the smaller ones can fit the Makerbot Mini. I only have one roll of filament so only one can run at a time.
Saturdays are my most productive because when one finishes I can start another and try to mow at the same time.
Parts I can’t print that I still need…
2 – 8mm x 150mm drive rods
1 – 8mm x 300mm rocker shaft
6 – 8mm skate bearings
4 – T5 10mm x 350mm drive belts
3 – Nema17 stepper motors
3 – stepper drivers
4 – stepper wire connectors
Misc screws and nuts
Making progress!
One part I added was the motor mount slide base. I think it will make the tensioning operate much smoother. It has edges for the mount to ride against and slots for the locking screws. It came out a little tight but that is fixable.
Let’s think a little about software.
The base is looking great, this means that after this build section, programming is next. I have thrown together some preliminary python functions. But without real hardware it’s hard to see what it is really doing. My goal is to give the program a very simple top level command so it could be operated with robot control or hand remote control.
With this type of drive any direction is possible or rotation. Running normally forward and pretending there is a steering wheels is possible or making a rotated turn is fine too.
The other important function of movement is accelerating and deceleration. No brakes are there but you can simulate that effect. The calculation is actually inside the Rip software for a 3d printer. Because speed and motion steps is computed for the head. The other benefits of speeding up a motor are the amperage is lower and that saves battery life.
Let us say you want to travel two meters and the current angle is 20 degrees but you need to end up at 30 degrees. The motion could have it rotate first. So two commands on movement need to be sent. Move(0,0,10) Move(1,2,0) in this simple function it needs the move type, the distance and rotation. Once this function is called a flag is set to true that will check if it has completed the task.
We also need to make a request of the speed and progress data that it holds. We really need to be able to send multiple commands at a time and let them finish in a queue. As one is being worked on the others are in a buffer then it could be cancelled or paused / continued as our needs might change.
The outlining of the program really helps build in simplicity into a very complex process.
Now I need 56 tires, but that will be for another day. I am happy with this much done.
Dream it… Print it.
Thanks for stopping by, Ron
Seahorse 3D Printing 