Regarding cradle slides....

[Moonboy242]

... What are they for? My first guess is that they help the base move laterally to accomdate platen placement flush with a book. Is this correct? I see a pretty even mix of designs that do and do not incorporate this feature. What are the results?

[Tim]

Basically the idea is that the platen (the glass or acrylic) stays fixed and holds the page a fixed distance from the camera. Then the cradle that holds the book can move side to side as the pages of the book are turned. You basically need as much sideways movement in the cradle assembly as the book is thick. Designs that don't use the slides can't hold the pages a fixed distance from the camera. That's not the end of the world, but for the sharpest consistent focus, the fixed distance helps.

[Moonboy242]

Thank you. I guess it's time for another redesign and a trip to Loews Depot for more parts.

[univurshul]

... What are they for? My first guess is that they help the base move laterally to accomdate platen placement flush with a book. Is this correct? I see a pretty even mix of designs that do and do not incorporate this feature. What are the results?

The drawer slides are precision movement from a DIY standpoint. The lack thereof still gets the job done, but I suppose it depends on your resourcefulness, budget, functional tolerance and weight sensibilities. Spamsickle did point out that if you scan outdoors or any place where there's dust and dirt, you might want to rethink movement with exposed ball bearings, aka drawer slides.

My first builds were milk crates guided by 1/2" acrylic tracks. As long as movement is perpendicular to the platen direction, anything goes.

In about a week I'll have a new build complete that utilizes a type of sealed-bearing track wheel system: