SP-457: 5x7 Sheet Film Processing System
People have loved our SP-445 system for 4x5 sheet film. The loudest comment? "Build a bigger one!" Well, here's the 5x7 version.
SP-457 Film Processing System
- 4 sheets of 5" x 7" sheet film.
- 1 liter (32 oz) of processing chemistry.
- Easy to load film holders.
Tank: We're very confident in the SP-457, after all it's the same height and less than four inches longer than its little brother, the SP-445. (Check out the 4x5 version here: shop.stearmanpress.com)
Note the symmetry: each end now has its own set of baffles. This means you can fill/drain from either outlet.
(Note: the cover photo is of the SP-445 tank; the SP-457 tank is still being machined.)
Film holders: we've a learned a thing or two about film holders!
First, you'll notice we rotated the film holders by 90 degrees. This lets us keep the tank shorter and easier to handle.
You'll also notice we've renovated the interior. The honeycomb pattern will provide plenty of strength while making sure that the back of the film is getting wet.
In addition, we've shortened the “fingers” that hold down the film. More fingers should make the film easier to guide into place. And we've increased the gap between the finger and the bottom of the holder. (We sized the original film holders for some vary thin films, which we don't believe are available in the larger formats.)
The prototypes are white because that's what Rod had left in the 3D printer and he forgot to change it.
Caps: We evaluated a larger cap but determined that it didn't really improve flow rates significantly. The rate that you can fill or drain the tank is limited by the internal baffles (and by how accurately you can pour.) So we opted to keep the same caps as the SP-445, just to keep life simple.
4x5 film holder option?: Maybe someday, but not in the immediate plans. However, you could modify a 5x7 holder for any smaller sized film, (see the video on modifying a SP-445 holder for 9x12: https://www.youtube.com/watch?v=-o0Io9dmDgc).
Alpha Prototypes: Sample film holders have been 3D printed and used to verify basic mechanical fit and function. They also allowed us to optimize the design for rigidity, loadability etc.
Pre-production Prototypes: These will be machined from solid material and will be fully functional. No, you can't have one.
Production: All parts will be injection molded from ABS plastic.
Shipping: We've opted for a simple world wide flat rate shipping plan. And yes, this time we'll definitely be shipping in a box.
Where's the SP-4810? We figured somebody would ask that:
The short answer is: we're still working on it.
Risks and challenges
Mold size: the molds really aren't all that big compared to other products, (try molding a case for a 72” television). However, they are quite a bit longer than the SP-445. This may force us to a larger, and more expensive, injection machine.
Sealing: The O-ring cross-sectional contact area is the same regardless of length. Thus, it shouldn't matter how long the O ring is.
It's really the pressure when inverted that matters. The inverted pressure in the SP-457 will be identical to the SP-445, since they are the same height. There shouldn't be a problem.
Pricing: The main issue affecting price is the post-campaign volume. We expect we'll have to amortize the development effort over a much smaller sales volume.Learn about accountability on Kickstarter
- (34 days)