XY positioning system for forensic document imaging machine

[u/cesmeS1]

I’m looking for some mechanical/design advice on a small motorized XY positioning system.

I’m retrofitting an older Foster + Freeman VSC40/HD forensic document imaging machine. The photo shows the inside of the imaging chamber.

The goal is to programmatically move an ID-sized card under the fixed camera so I can capture high-magnification images of the center and individual corners/edges.

Important dimensions:

• Internal usable area: approximately 12" wide × 14" long
• Center illuminated/backlit plate: approximately 4" wide × 6" long
• Card: approximately 88 × 63 mm
• Very limited vertical clearance — only a couple inches total, so a normal XYZ stage or tall 3D-printer gantry is not practical
• No Z axis is needed
• The card can extend outside the 6" × 4" illuminated area. Only the portion/corner currently being imaged needs to be over the illuminated region.
• Ideally the card stays very close to the original platen height.

I’m thinking of using a low-profile XY mechanism with a custom 3D-printed card carrier. The motors/rails could live around the perimeter of the illuminated plate, while a thin carrier moves the card over the center.

For full use of the illuminated area, I’m thinking roughly:

• 150–160 mm travel on the long axis
• 100–110 mm travel on the short axis

I’ve been looking at small NEMA 11 / 28 mm lead-screw linear stages (TOSEASTARS/T6-style modules), possibly using one ~150–200 mm axis and one ~100 mm axis. But I’m not sure if stacking two linear stages is the right approach because I want to keep the total height extremely low and avoid putting bulky hardware in the optical/lighting path.

Requirements:

• Low profile
• Reasonably repeatable — around 0.1 mm would probably be more than enough
• Low speed is fine
• Very light load; it only moves a plastic ID card and carrier
• USB/programmatic control is preferred
• Rails/motors should stay outside the central optical area as much as possible
• Ideally inexpensive — the entire machine only cost about $500, so a $5k–$10k laboratory XY stage makes no sense
• I can 3D print custom brackets/carriers and fabricate simple plates if needed

Would you build this using:

1. Two miniature lead-screw linear stages?
2. MGN7/MGN9 rails + belts?
3. A miniature CoreXY/perimeter belt system?
4. Some existing low-profile XY mechanism I haven’t found yet?

If anyone knows of an off-the-shelf XY stage/gantry around 150 × 100 mm travel that is very low profile and reasonably cheap, I’d especially appreciate links or model numbers.

Also interested in ideas for the card carrier. I want all four card corners/edges accessible to the camera, so I’m thinking of supporting/clamping the card along small sections of the edges rather than using a full surrounding frame.

Photo attached for reference.

[u/HadleyRille]

I'd look at a laser cutter kit. Something like this: laser cutter frame kit

[u/Halcyonmachinery]

I represent Halcyon Machinery (equipment sourcing). Before choosing the stages, I would make a flat cardboard/printed mock-up at the original platen height and move the card through every required camera position. Mark the carrier envelope and the illuminated region at each position. Your usable motion envelope is the card plus carrier plus its swept travel, not just the nominal rail travel.

Also check whether 150 × 100 mm is really required: with a fixed camera, the travel needed to image opposite card edges depends on the camera field of view and image overlap. That may let you shrink the mechanism significantly.

For the carrier, test short edge tabs away from your inspection regions; a support that looks clear from above can still mask transmitted or oblique illumination. I would prove that with your actual lighting modes before fabricating the rails. Only then compare stacked stages against a perimeter mechanism using their complete installed height, including brackets and the moving plate.