Plastic handling to make DIY robotic parts
Even with 3D printers and milling machines accessible nowadays, I guess this post will interest some people. From time to time, I am asked how I produce my parts, so this post is dedicated for this people, for guys who don't have a 3D printer or a milling machine, and/or for guys who simply appreciate the old school method.
In fact, even I am working on a low cost milling machine project.
I would like to clarify that this method does not have the precision of a milling machine and does not have the same versatility of a 3D printer (obviously), but it's a low cost alternative to make nice parts and may be combined with PVC pipes to make more complex shapes.
Well, in this post I'll show how to make robotic parts, using only simple tools and polystyrene sheets.
This post and the videos complement each other. The videos shows in detail the techniques used and this page contains callouts.
This technique can be easily used in many types of parts.
Below you see listed every material and tool used.
- 2mm white polystyrene (HIPS - High Impact Polystyrene) sheet;
- masking tape;
- sandpaper (thin and thick);
- instant adhesive (cyanoacrylate ester);
- A4 paper.
- sharp blade;
- metal ruler;
- drill (1.5, 2.5 and 8 mm);
- vacuum cleaner;
- laser printer;
I would like to draw attention once again (already mentioned in the first video, from 9 till 24 secs.) to the personal safety. Personal protective equipment are relatively inexpensive. Work safely... and just have fun!
OK... let's get working!
What we want to reproduce is the part that you see below, which have a housing for a Hitec HS-225/5245 servo motor. It will consist in a 4 mm thick part (i.e., 2 X 2 mm pieces).
The software that I use to design the 2D templates perhaps is the most unlikely. But if you intend to use the technique can use any design software.
With the template done, I export the image (printing directly, depending on the software, may lose the actual size of the drawing). Then I paste the image in a text editor and adjust the document to be borderless and expand the image till the edges (for A4, 210 X 297 mm).
Then print it in A4 paper with laser printer. (If someone want to reproduce this part, here https://drive.google.com/file/d/0B2gOXfxaf2xjWmhKLVhGWEZiTVk/edit?usp=sharing is available the template with higher resolution).
With the template printed, adjust it to have just a small tab beyond the drawing. Cut a rectangle of polystyrene for each piece, a slightly larger than the drawing.
With the drawing (the printed side of the template) in contact with the polystyrene, bend the tabs and pin them in place with masking tape.
This technique utilizes the toner transfer method, commonly utilized to make DIY PCBs. Take a look at this article (PCB Etching Using Toner Transfer Method | MAKE) to know more about this method.
You may be asking yourself: "why not simply paste the template on the polystyrene?".
Well, this will works too, but with toner transfer method the precision and consequently the final look will be better.
Now it's time for the iron! With it hot (really hot, not maximum, but almost), pass over the paper making circular movements.
Take a look if the drawing "get stuck" well on the polystyrene. If not, repeat the process till get a good result.
The pieces tends to become wavy. So, try setting it to stay flat while hot.
Then start the holes for screws. Initially with 1.5 mm drill, in only one piece (the one that goes on top).
Now, with 2.5 mm drill, start to drill holes in line to facilitate the removal of the internal chunks of the servo motor housing. (The sharp blade facilitate it even more. Take a look on the video.)
Keep a border of approximately 1 mm beyond the line.
Linear cuts can be made more easily using a metal ruler as a support. Curved cuts require more patience. Anyway, after a few cuts the piece can be easily broken.
Rounded parts can be easily cut with scissors.
With the two pieces cut, they must be prepared with thin sandpaper and then joined with instant adhesive.
Remove the residual material of the servo motor housing with the sharp blade.
With the metal ruler involved by thick sandpaper, make the internal adjusts.
Now, the definitive diameter of holes will be made (they vary in 2.5, 3.5 and 8 mm).
To give a good finish, thin sandpaper.
The final result.
Note 1: If repairs are necessary, it can be made with epoxy.
Note 2: If you are not seeing well the annotations on the videos, you can click here and watch the videos as a playlist.
Note 3: The whole part took me about 2 hours to be made. I tried to show every detail of the production work, without making this a too extended presentation. The sanding step was the longest! If you will reproduce this, be patient! :)