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

Cradle that moves/applies pressure?

Built a scanner? Started to build a scanner? Record your progress here. Doesn't need to be a whole scanner - triggers and other parts are fine. Commercial scanners are fine too.
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dbb
Posts: 8
Joined: 30 Mar 2011, 22:00

Cradle that moves/applies pressure?

Post by dbb » 01 Apr 2011, 12:08

I am researching various things and drawing up some plans before I start building my scanner. Part of my reasearch has been looking at commercial units and how they work. Most of my questions come in the platen and cradle construction.

I have seen many that have a cradle that actually pushes the book up into the platen as well as being able to adjust to accomodate the spine of the book, so far I cannot tell what they use to apply the pressure, but it appears to close the book on the platen somewhat before the image is taken. Has anyone here tried this? Or is it just a frill that is essentially not needed? Obviously a lot of you get great images without doing this.

Also, what is the best angle to attempt to get on the cradle/platen? I have seen units advertised as low as 80 degrees up to 110 degrees, some are adjustable. 90 degrees seems to be the simplest, is it also the most optimal?

Thanks in advanced.

spamsickle
Posts: 596
Joined: 06 Jun 2009, 23:57

Re: Cradle that moves/applies pressure?

Post by spamsickle » 01 Apr 2011, 20:15

The next unit I build will have a 1-piece platen curved at 140 degrees. It will be designed to stand upright on a tabletop, held in place by suction cups, and the books will be pressed against it in the upright position -- no cradle but my own two hands.

Lights, cameras, platen.

I had originally planned to use mini-tripods to hold the cameras, but I just discovered that the mini-tripod can't support the camera when it's turned to "portrait" mode -- the weight of the camera and the center of gravity just cause it to fall over. Because of that, I'll be building little stands for the cameras, which will permit me to make the height adjustable.

The 140-degree platen may seem to open the book wider than it needs to, but I want it to be able to handle those pocket paperbacks as well as other formats, and experimenting has led me to settle on that angle. Having a "sideways" scanner on a table will also benefit from the more open platen -- the table itself is 30" wide and 5' long, so the more open the platen the further away I'll be able to place the cameras.

If it doesn't work out -- and it seems there are always surprises when the shooting starts -- I can always make a platen with a smaller angle. The 90-degree platen I have on my floor unit is 2-pieces, and I think I prefer to use that vertically rather than sideways, but we'll see.

I think this no-cradle design will make for a better fit between book and platen, but it's not something I'd spend a lot of time obsessing over for your first build. I've gotten good results with a 90-degree cradle and a 90-degree platen, even though the pages of the book weren't always pressed up right against the platen. When you throw a book in between, the geometry isn't going to be perfect, but it's going to be good enough. The only real problem has been with the inner margins of some books, and more pressure or different angles isn't going to help that.

I would really go with 90 and 90 for your first build, because it's going to be the choice for 90 percent of the books you shoot. This oddball design will (I hope) help with the other 10 percent, but I don't expect it to become my primary scanner.

dbb
Posts: 8
Joined: 30 Mar 2011, 22:00

Re: Cradle that moves/applies pressure?

Post by dbb » 02 Apr 2011, 12:08

My idea is to use gas springs to press the book onto the platen once it has been lowered into the centerline of the book. Basically what you will be doing with your hands.

As for the tripods, I got two of these to mount to horizontal pipes on my unit. http://www.amazon.com/gp/product/B000ABB4HC I am hoping they are better with holding the cameras for me, and I like that I can attach them to pipes to rotate and adjust them.

90 and 90 is what I am planning on right now. I hope to design the scanner so I can swap out components as I make improvements. Being an engineer by profession its hard for me to go simple with anything. :) I'm trying though....kind of.

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Gerard
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Location: Berlin (Germany)

Re: Cradle that moves/applies pressure?

Post by Gerard » 03 Apr 2011, 08:41

maybe some elastic foam on the cradle would have the same effect, i think the cradles with pressure just reduce the friction on the book from the platen,

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