Printed gears

The final stage of creating these cogs was to print them out and see if they worked properly as real objects. This experiment has been moderately successful.

The first attempt was the set on the left. Once assembled, the large and medium cog worked together quite well, when I added the small cog the set didn't really work as well. The first problem I ran into was the spindles for the cogs being far too small, a few cogs broke at the spindle as soon as force was applied. I think the cogs were put under extra stress because I didn't align the axes of the spindles on one plane.

Another problem was the smallest cog, the spokes were too small and the height of the teeth were too narrow. This reduced the effectiveness of the teeth. The material itself also became a problem in that the finish of the surface was a little rough on the teeth which created alot of friction and jammed the rotation.

I experimented with running cogs on a 90 degree angle which didn't seem to work at all, whether this was a problem with the rough teeth or the flexibility of the plastic stopping the extra gear from rotating I'm not sure. I noticed that all of the gears flexed a bit so it would be interesting to create them in a more rigid material to see if it is the limitations of the material stopping it from rotating properly.

After reading about a method of smoothing out the surface of printed objects I may find they function more smoothly together. It could also be that I have placed the cogs too close to one another and the teeth are meshing together too much.

The second lot of gears I  made a few alterations. For a start I increased the width of the spindles to make them stronger. Then I increased the thickness of the smaller cogs and made them solid to improve their strength. I also added a bevel to all of the teeth of the three sizes of cogs to improve the smoothness of the meshing of the teeth.

Printing out the block that held the cogs presented its own problems. The first attempt suffered a little warping at one end but still managed to come out square on top, the second block seemed to warp quite a bit  more on the bottom. While the block come out square on top, the warping meant that the spindle of the large cog couldn't fit all the way into the hole meaning it didn't align with the other cogs. This will be easy to fix by drilling through that section and this gave me a better idea to be able to test cogs.

I will take a block of wood and drill holes into it which will enable me to try many different combinations and also see how the gears interact between planes. This will also save alot of time and material, printing the blocks takes an hour for each block and uses three to four grams of plastic per print.

The next step i would like to take will be to design a small functional machine like a wind up car. I will use wood for the body to experiment then once I have the configuration I will make a model to print out.