Universal 4x5 Glass Negative Carrier for Beseler

Ever wondered why a chunk of machined aluminum with a piece of glass in it goes for $200 on eBay? Me too.

After printing for years using my Beseler 45MXT and glassless negative carriers in all major formats (35mm, 6x6, 6x7, 6x9, 4x5), I finally ran into some issues with film flatness and decided it was time to make this design.

Please feel free to remix, or comment if you have ideas to improve the design.

Bill of Materials:

Printed Components

• (1x) Base
• (1x) Handle
• (1x) Lid
• (1x) Hinge
• (1x) Mask (one for each format you want a mask for; masks are arguably optional)

Non-Printed Components

• (8x) M3x4 socket head screws
• (8x) M3 threaded brass heat set inserts (4mm tall)
• (6x) 10mm diameter x 3mm thick circular neodymium magnets
• Superglue and/or epoxy
• (2x) Rectangle of 3/32" or 2.5mm float glass, 135mm x 110mm in size - I just cut down inexpensive 8x10 sheets from Home Depot, and sanded the sides to remove sharp edges. I have not found ANR glass to be necessary, but if you want to use ANR glass, you can get it here.

Printing Instructions:

With the exception of Hinge.stl, print all pieces from the most opaque, least reflective PETG you can find. PLA is not recommended due to its low glass transition temp and the fact that it will be used in close proximity to fairly hot light sources. I have no experience with printing ABS, PC, Nylon, or anything else more exotic than PETG, but some of those might be good choices too. Rigidity is nice, but opacity and heat resistance are non-negotiable.

Hinge.stl should be printed from TPU with 95A shore hardness. The hinge will feel flimsy and I probably wouldn't let the lid swing around from it. But it keeps the halves together, makes it easy to close properly, and when I tried thicker/stiffer layers for this component, I found that it didn't want to close flat anymore.

I am using this Matte Black PETG, and although it was a bit of a gamble with the unknown brand and less-than-stellar Amazon reviews, my Ender 3 had no issues printing it, and I found the surface quality to be excellent, and significantly less reflective than other PETG filaments I've used.

For all parts, I am using 0.2mm layer height, 0.4mm walls, 3x bottom layers, 4x top layers, 3x perimeters, and 30% cubic infill for extra light blocking. The design is optimized for being printed with 0.2mm layer height.

Each component WILL fit on a stock Ender 3 bed… barely. Make sure things are good and level. Watch carefully for orientation on Handle.stl and Lid.stl - they're not natively oriented properly, you need to flip them to avoid overhangs.

No supports are needed.

Assembly Instructions:

It's pretty much what you'd expect. See photos on this page if you're lost on placement for anything.

1. Glue the magnets into place in their corresponding holes in Base.stl and Lid.stl, paying close attention to polarity.
2. Glue Handle.stl into Base.stl. Keep an eye on squeeze-out, you don't want anything to mess up the flat top surface of the base.
3. Glue Hinge.stl into both Base.stl and Lid.stl.
4. Put in the threaded heat-set inserts on the left and right side of the center rectangle opening on Base.stl. You can use four M3 screws here as guide pins for either 35mm or 120 film strips, and easily toggle back and forth between the two configurations. The heat sets are better than direct-threading into plastic for the kind of repeated use these alignment pins are expected to get.
5. Clean the glass pieces thoroughly and carefully, and glue them into Base.stl and Lid.stl. Ensure they're fully seated and flat. Epoxy would be better than superglue here. I recommend closing the negative carrier immediately after seating the glass pieces into their respective recesses, so that the faces are pressed flat against each other. Then add some weight on top while the glue cures, to ensure the best possible contact between the glass plates when it's closed.
6. Finally, screw 4 more M3 screws into the bottom of the Base piece (directly into the plastic). These serve as centering lugs to keep the negative carrier from sliding around when actually placed in the enlarger head (same as the ones on OEM negative carriers). They shouldn't ever need to come back out, so I didn't bother with heat set threaded inserts.

Usage Instructions:

Dust off both surfaces of both glass plates, and both surfaces of your negative. Place the negative of whatever format on top of the glass in Base.stl, emulsion-side down. Close the lid carefully over the negative, sandwiching it totally flat. If desired, add a mask on top of the lid to block extraneous light around the edges of the negative. Print. Revel in the satisfaction of knowing your negatives are not curled or sagging at all. Think of things you could buy with the $200 you saved by not buying an OEM glass negative carrier. That's gotta be at least 3 or 4 sheets of Ektachrome, right? Worry about newton rings and wonder if you should have sprung for ANR glass. Scan your finished prints and post them somewhere. Tag me. I want to see them.