I’ll go more into the design of this later… But this thing, which I printed last night, is the prototype of the base scanner module for my slide scanner.

Like I wrote a couple of days ago, I was struggling with the design of this part. I need two of these, in fact, one for the main slide photo itself and another for the image of the slide mount along with anything that was scribbled on the mount itself.

The previous designs were all based on a sliding base that either opened an aperture for the slide to drop through in one position, or to swing a pair of arms to pretension the slide in the other position. I had an even earlier design which was based on springs and stuff and that was a complete disaster. (I would have been able to make that work with enough tweaking, but I likely would have had to machine something out of something other than plastic to make it work correctly)

Sliding has a couple of problems, the biggest one is that automating the sliding is somewhat hard. Most servo motors are spinning things, so you would require additional components to transform the spinning into linear motion. There are a number of ways to do it, but all of them come with some drawbacks that mainly increase the complexity of the device. The other problem was that the arms would have a tendency to get into the shot for the mount pictures.

Over the weekend I had a brainstorm. What if I could do the whole thing with a rotational device?

It turns out that this works way better and solves all of the problems with the previous designs!

I have a port that allows the side to drop through as before — but in this case, it’s at a certain rotational position. To get the positioning and flatness I have a pair of arms that clamp the side from the sides instead of on the face — again, all driven by the rotation of the roller. Fewer moving things to go wrong… the arms don’t block the view of the slide because they are to the sides of the slide… rotational instead of linear actuation.

Win all around!

This doesn’t have any mounting flanges since it’s only a prototype… but I think the overall design has been shown to work! A little victory to make me a tiny bit happy.