A better platen movement design

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Re: A better platen movement design

Postby rob » 21 Jun 2010, 20:51

Yes, that is completely viable, but there is only one drawback which can be lived with, which is that it would be possible for the platen to hit you in the face with the front pointy end if you are sitting too close!
The Singularity is Near. ~ http://halfbakedmaker.org ~ Follow me as I build the world's first all-mechanical steam-powered computer.
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Re: A better platen movement design

Postby spamsickle » 06 Jul 2010, 21:06

I decided to implement my own version of this design, to address some of the shortcomings of my current scanner: it's too big, too slow, and produces images which are too inconsistent. I still have the current scanner for very large books, but the 12" x 12" (sadly, reflective) plexiglass platen on this one will handle 90% of the books I want to scan, and do them faster than the big glare-reducing model.

I had a bunch of 30" 2x4, and that's what most of it was made with. I gorilla-glued the 3-piece "base" together, and the 3-piece "lever". I like Gorilla Glue and wood, because I can just bang it apart if I want to and re-use it -- 4 of the pieces in this project still have the dried foam from another incarnation.

The lever is attached by two hinges (not shown) to the base.

The platen is attached by silicon sealer to the pieces of picture frame I had left over (because they were miscut) in my earlier platen. They're longer than the platen itself because I'd originally planned to connect them with 2 more pieces, but once I had it together I decided that wasn't necessary.
The fifteen pounds of counterweights are held in place by geometry and gravity through the range of motion of the lever.
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Re: A better platen movement design

Postby jck57 » 14 Jul 2010, 14:46

spamsickle wrote:I decided to implement my own version of this design...


May I humbly suggest starting a fresh build thread for your scanner? I couldn't remember where it was hiding.
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Re: A better platen movement design

Postby n9yty » 30 Jul 2010, 19:29

Okay, I'm having a dense moment here... How does this second one (with the photos with the yellow walls) operate? Are the weights a counterweight, or how does it work? Sorry, not visualizing it.

This one is very similar, and easily visualized for me. Put some camera mounts on there and it would be very nice I think. It's too bad the topic is titled "light mount height" - I am linking it here to help others find it.
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Re: A better platen movement design

Postby spamsickle » 31 Jul 2010, 20:22

Yes, the weights are a counterweight.

It's 3 2x4s in a 3-sided (1 side open) box, sitting on top of another, larger 3-sided box. The top box is attached with hinges to the lower box, but it hangs over the side too, so the bottom box is the fulcrum for the top box. The weights make it so that it's easy to lift with one finger; in fact, once I've lifted it a couple of inches, it wants to lift the rest of the way by itself, and I'm actually pulling it back rather than lifting it. You can see in one picture how it's fully raised without me holding it. It's also fully lowered without me holding it.

I'm not sure if that's any clearer. I see that someone has asked that this be a separate thread, and I'm thinking of putting the platen from my old design on this framework in the next few weeks. When I do that, I'll be sure to do a better job of documenting it with pictures. Meantime, maybe this will make it a little clearer:
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