Recreating Mira from images – #2 iteration [Part 2]

After the initial proof-of-concept-I-am-not-totally-incapable I restarted the mechanics from scratch trying not to clutter my build history and sketch folder inside Fusion360. I enlarged the gap in the center of the two axes so that a 4mm carbon fibre rod can move smoothly. I decided to use such a carbon fibre rod because my Z axis wobbled a bit and additionally I thought that it is not necessary to print ever single part of the mechanic if you can easily substitute it with a more appropriate material. This way the movement of the vertical rod is not hindered by the layers that naturally occur during printing. I drilled a hole at the bottom of the rod and found a nail that fit as an axle. After that I modified the 3D model to adjust the axle to fit the nail.

I also decided to use the servo horns that come with the SG90. I added slots onto the axes for the horns to snap in. Albeit printing such fine features require a) support and b)this support structure is by the nature of its puniness very fragile to remove but it turned out that with a sharp knife and some grinding they fit snug. I still consider adding holes so I could fasten the horns to the two semi-circle axes and eventually to the servos for more stability. Until now I have to glue the horns to the axes. When I installed the servo horn on the axis without the cross strut (I will call it Y axis from now on) I realized that the semi-circle did bend easily when pushing the horn onto the servo. I think a cross strut just as in the X axis would help increasing overall stability.

Another major change that found its way into iteration 2 is that I cut off the feet underneath the main frame that screw onto the raspberry pi. I did this because when printing the frame with feet a lot of printing time would sink into the support which is unnecessary. The feet can either be printed separately or can be substituted by ready-made RPi spacers.

In the coming iteration I will modify the servo mounts. The current mounting holes in which the servos can easily be screwn in (Doh! passive!) are just a bit too far off. The result is that the frame is veeeeery slightly bent due to the servo bulging the frame but this is not that big of a problem. I also incorporated two vertical holes left and right of the servo where a piece of plastic can be screwed down to retain the servo.

 

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