Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

A failed platen movement design

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rob
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A failed platen movement design

Post by rob » 29 Apr 2010, 15:09

So I made a glass platen out of two "floating" frames that I found at the local crafts store. These are picture frames with two glass panes and no backing. You put whatever you want in between the two panes, and it "floats" in the middle. The two panes together measured 1/8", which is nice. So I removed the panes, cut the frames so that they would join up at 90 degrees, put the panes back in, and ran a small bead of clear silicone (intended for waterproofing doors and windows) along the ends of the panes where they came together (so they don't fall out!)

I decided to try using two drawer slides on either side of the platen:
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Here is a close-up of how the frame attaches to the slides. I had to be very delicate when drilling the holes for the bolts, since I would be drilling the triangular 3/4" MDF through the side.
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However, I discovered that because the platen is a bit flimsy, you have to raise it by using both hands, one on either side! That's not the point of a movable platen!

So I think that next, I'm going to try something similar to what the Smithsonian Institute did, which is to attach the platen on either side to levers which go to an axle. I would turn the axle, by means of a crank or (later) a motor, and it raises and lowers the platen not vertically, but along the path of a circle:
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--Rob
The Singularity is Near. ~ http://halfbakedmaker.org ~ Follow me as I build the world's first all-mechanical steam-powered computer.

spamsickle
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Re: A failed platen movement design

Post by spamsickle » 30 Apr 2010, 11:53

I'd be wary of using an axle, it seems to me that it would be difficult to make the platen fit flush in the "V" of the book as the thickness changed due to a variable number of pages. Maybe I should go back and watch the Smithsonian video again. When I saw it, I noticed that their platen was wider than 90 degrees (something I'd also be wary of), but it didn't register that they were supporting it on an axle.

Edit: I see, the Smithsonian design actually has two axles: one handles the "lift", and the other makes the platen float, to solve the problem I allude to above. Now that I notice, that's reflected in Rob's drawings already. I withdraw my wariness...

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