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3D printing my balancing robot

April 28th, 2013 No comments

3D Printing Fever!

Hello everyone. Did I tell you I am having a blast with the 3D printer? My god, this thing is wonderful. Is every engineer’s dream come true. Seriously. Anyway, in my last post I told you about putting together a Mendel90 reprap. Since then, I devoted some weekend time to calibrate the machine and I am really satisfied with the results.

As an engineer, my 3D printing time is focused on creating useful and functional parts, rather than something artistic like a complex shape or a small Yoda (even though I would like to print one some day). Anyway, its been some time since I decided to create a balancing robot, a project unfortunately I neglected for too long. So, this will be a nice opportunity to design my own parts and progress on the balancing robot project!

To do that, first I needed a CAD program to design my parts in. I never used a 3D CAD software before, so I went into the wild to see what is available. The features I was interested in are:

  • Run on Linux (Ubuntu)
  • Easy learning curve
  • Price below 50 Euros (or free!)

Let me tell you, there are not that many choices fulfilling the above. I ended up using FreeCAD and I really like it. Until now, it suits my needs, its free and works just fine on my Ubuntu. OK it is a little buggy sometimes but I don’t mind. At the beginning it was a bit difficult to understand how it works, but after I read about the Part Design and Constraints I quickly got the point. I have to admit, Constraints is something I didn’t know it existed in CAD software and after I discovered that I immediately loved it! When I get more experience with FreeCAD I will make a tutorial on the basics. I think it really deserves more visibility.

Designing the parts

When designing parts to be 3D printed on my machine, there are a few things that govern my design. First, the design must be compatible with the 3D extruding printing constraints. You must be careful of steep overhangs. Another thing are the holes. Most of the slicer software has some problem printing small holes accurate. My current calibration gives me hole accuracy 0.4mm(+/-) which is not that good but it hasn’t caused much trouble yet. However, my main concern when designing is the use of filament, for a few reasons. The most obvious one is cost. If you make a really big and heavy part, you could raise the cost to a level which 3D printing it out doesn’t make sense, if you can buy a similar part (robot chassis for example) much cheaper from the web. And keep in mind that you may make mistakes and need to reprint a part 2 or 3 times (even more?) before deciding its the one! What is more important for me though, is printing time. You see, more filament = more printing time! Most of the times I am anxious to try out my latest design and I hate to wait more than 10-15 minutes. So I tend to design, quick-to-print parts. At least for now.

Today’s print: Motor mount

Today, I designed a part used to mount the motors on the chassis. Took some specs from the motor datasheet, and designed the part so it can be screwed on the motor and hold it firmly. So I fired up FreeCAD and some time after, the result is this:

Freecad design

Freecad design

After exporting the .stl file and slicing it with Cura it was ready for printing. The pictures show the result.

Fresh out of the oven!

Fresh out of the oven!

Good alignment of the holes

Good alignment of the holes

Motor screwed on the mount

Motor screwed on the mount

Attached on the chassis

Attached on the chassis

 

Hopefully sometime within next month I will find some time to attach the motor controller and start working on the electronics of the robot.

Until next time…