Home > CAD Parts

• Materials and Tech
• Robotic Arm
• Freenove Smart Car Rear- and Front-Mounts
• Elevator
• DC Motors
• Tips and Tricks

This page documents parts I have designed for 3D printing.

Materials and Tech

• CAD software: I started out with FreeCAD. I was impressed by the range of capabilities that comes with the software and the quality with which they are delivered—at least initially. Everything worked well for small parts and the initial phases of the larger arm project. However, as the design grew, the tree-structure representation of design elements became unwieldy. It was difficult to predict how the tree would rearrange following an operation. Ultimately, a bug surfaced in the FreeCAD software, and I was unable to undo and recover my design. I started looking elsewhere and found Autodesk Fusion 360, which can be obtained free of charge for personal use. I was, and still am, quite new to CAD; however, Fusion 360 is obviously a top-notch product. Everything just works. The operations are stunningly intuitive and well-crafted. It is difficult to imagine a reason for looking elsewhere except, of course, for the facts that the free version cannot be used commercially and the commercial version is quite expensive.
• Mesh slicer: UltiMaker Cura is a simple tool with a single purpose: slice the mesh outputs of CAD into horizontal layers that can be 3D printed. The settings are endlessly configurable, but the defaults work quite well. Support structures are effective and efficient, and I haven’t had a problem yet.
• 3D printer: This is the only item in the list that is not free. With endless options on the market it can be difficult to choose; however, at under $200 with generally quite positive reviews, it is difficult to get past the Creality Ender-3. It was simple to assemble and has been cranking out high-quality pieces since the start.

• Automatic bed leveling: I added the CR Touch Automatic Leveling Kit to my Ender 3. The sensor comes with a mounting bracket for the Ender 3; however, it isn’t truly designed for this model, and I had previously replaced the hot end with something different. As a result, the sensor was mounted too far above the bed, which caused the hot end to drop down into the bed. After much experimenting and searching, I found that the sensor needed to be offset down toward the bed in order for everything to work. I did this by adding spacers as shown below:

  

  The steps for calibrating the leveling probe’s z-offset are as follows:

  1. Auto-home the printer and disable the steppers.
  2. Move the z-axis to identify appropriate z-offset, using a sheet of A4 paper for thickness. Note this value.
  3. Auto-home the printer and disable the steppers.
  4. Set the leveling probe’s z-offset to the value noted in (2) and save the configuration settings.
  5. Level the bed. The hot end should be in the correct position above the bed, with the z-value showing 0.0 on the printer display. Octoprint has a bed leveling visualizer plugin, which displays the bed mesh as shown below:
  6. Add G28 G29 to your slicer’s g-code preamble. The G28 (home) command is probably already present, in which case you just tack on G29 (level bed).
• 3D printer web interface: I use OctoPrint with my Raspberry Pi as an efficient and easy way to manage print jobs. See here for tips on configuring OctoPrint on the Pi.

Robotic Arm

This was the first real project that I pursued with 3D printing. The concept is basic, including five degrees of freedom driven by SG90 servo motors. The design poses several good challenges for anyone starting out with CAD or—like me—returning to CAD after a very long time (9th grade high school, if my memory serves):

• Mobility: A little practice goes a long way toward designing solid objects from 2D sketches (points, lines, circles, planes, etc.) and 3D operations (extrusions, joins, cuts, holes, etc.). I found the learning curve to be quite gentle in this regard, particularly with the right CAD system (more on this later). It was much more difficult to build constrained movement into the design. Think hinges and keyed rotation shafts. These were tricky at first, but effective patterns became evident after a few attempts.
• Motor-part integration: This is where the magic happens, where the design comes to life. In the case of the robotic arm it was a matter of connecting the rotating shaft of the SG90 servo with a mobile part of the arm design.
• Build tolerance: Mobility requires parts to be in contact but not be too tight. CAD provides exact precision, and although entry-level 3D printers provide surprising fidelity, they are not exact. However, the inexactness is systematic in my experience, and small tolerances seem to be quite achievable.

All of this adds up to a good bit of time, failure, iteration, and fun. Full details can be found here.

Related projects:

• Smart car

Freenove Smart Car Rear- and Front-Mounts

The smart car comes out of the box with a front-mounted camera. I designed this bracket to move the camera to the back and provide room for front-mounted parts like the robotic arm described above.

The files for this design can be downloaded from Thingiverse here.

Related projects:

• Smart car

Elevator

This is an elevator designed for the stepper motors found here.

Full details can be found here.

Related projects:

• Smart car

DC Motors

The following is a four-coil brushed direct-current (DC) motor:

Full details can be found here.

Tips and Tricks

1. The small deboss labels on various components contain the Fusion 360 version numbers of the design file. This is a handy way to keep track of the design file version used to print each component, particularly when diagnosing issues, updating the design, and printing new versions. I use the ParametricText add-in to automatically update the version numbers when saving the design file.