This is a fun little 3D print that might be interesting for newcomers to the 3D printing game. The design is based on the mechanical principle of a traditional wooden toy that lets the robot climb up the string if you pull on it.
Parts List
The STL files are available for download here on github.
Besides the printed parts you will need an elastic band and the robots “rope”.
The elastic band is one as used in textile work. A normal rubber band might work too but is not as long lasting. The band can’t be wider than 5mm (0.19 in) and thicker than 1mm (0.04 in).
For the rope not everything will work as the correct amount of friction in the robots “hand” is crucial for the climbing action to work. The model is optimised for a ca. 3mm (0.1 in) string. There are two versions of the clamp the tighter one should work with a ca. 2mm string. From my experience a braided string works best.
Printing
The model is optimised for printing with a 0.4mm nozzle. The sloped surfaces look best with a 0.2 layer height but larger layer height wont be a problem. Most of the models parts are optimised for printing without support and all are oriented correctly in the STL files for optimal printing.
The following parts need extended settings.
| STL | support | brim |
|---|---|---|
| body-l | x | – |
| body-r | x | – |
| arm-l | x | – |
| arm-r | x | – |
| head | – | x |
Assembly
The video above contains step by step assembly instructions.
If you printer is tuned to produce precise dimensioned part the robot should friction fit together without glue. Otherwise just use glue or tune up the fit with a file or sanding paper if the parts are too large.
- Clean out all supports.
- Feed the elastic band through the slot in the axis. Tie a knot and let it slip into the hole in the center.
- Break apart the three dowel pins and push them into the holes in the left body half.
- Press the shoe into the left leg.
- Place the left body over the left leg. Press the axis into the leg leaving the hole along the center of the axis pointing outwards. The slot that excepts the elastic band should point exactly upwards away from the foot.
- Press the right body onto the left. Make sure to wrap the the elastic band around the axis and place it in the slot so that it is not clamped between the two body halves. Check also the explosion diagram in the video for reference. The axis should be able to rotate freely in the body.
- Press the leg connector into the left leg.
- Press the right leg onto the axis and the parts connected to the left leg.
- Feed the elastic band through the head and secure it with a knot. Make sure to stretch the band far enough so that the legs springs back completely when you let it go.
- Press the left arm into the body.
- Assemble the clamp. Feed the string through it and plug it into the left arm. Make sure that it aligns as shown in the explosion diagram.
- Attach the right arm to the body and clamp.
- Close the hole in the head with the cap.
Tuning the clamping mechanism
In general the clamp should clamp just hard enough to hold up the robots own weight. Use a round file to smooth the bottom of the groove the rope runs through in clamp-p1.stl’ to remove all the printing striations. Apart from that it’s important that the hole through the “shoe” is large and smooth enough to let the rope slide through without friction. A good way to achieve this is to bore out the hole with a fitting drill. I chose a 3.5mm drill for the 3mm rope I used.
You’re done. Have fun
