finally! 3D printing file for Bronica S/S2/C/C2/EC rear lens cap

[removedacct2]

these caps are hard to find, and when some show around usually expensive. For a while there was no 3D model (STL file) for printing. I have been searching again, couple months since last time, and finally last month a brave soul has scanned a cap and produced a file. Open source, so here it is:

https://www.thingiverse.com/thing:4616679

I badly needed replacements, was using homemade alternatives fitting more or less well.
After I found this STL file I have contacted couple guys doing 3D printing for ok rates, and ordered in three different materials in order to compare and test: PETG, ABS, FLEX.

 

[jvo]

now that's great to hear... for all those little parts, etc. that could be similarly produced!

 

[grat]

Yep. My SQ-A has a crank that I 3D printed. Average selling price of a replacement crank on eBay is $120 right now.

Similarly, I printed a battery pack for my GX680-- I went with a newer battery type (only 2 batteries) instead of the old 6AA pack, but those (a small plastic box with 14 metal terminals and some wire) go for ~ $200.

For the OP, PETG is my preferred-- it has a very small amount of flex, is durable, and less prone to melting in hot cars than PLA. ABS is the old standby, but it's smelly to print, has a tendency to warp while printing, and requires constant temperature to print. I'm interested in your experience with flex-- due to the design of my printer, flexible filaments are tough-- I'm limited to certain types of nylon, which is only "mildly" flexible.

 

[Deleted member 88956]

Does anyone know if there is 3D STL file for Mamiya RB67 front cap without Mamiya on it, just flat in the middle? Could use it for pinhole mod. Sure can use original cap, but it looks ugly after required work.

 

[grat]

There is-- there's a guy with three models, two with text, and one without. It looks like a straightforward slip-on lens cap, so you might also consider looking for Kaiser lens caps. I've bought a few from Amazon for various lenses, and had no complaints.

With a little bit of work, though, the existing STL could be modified to hold a pinhole disc.

 

[Deleted member 88956]

@grat Asking for Front Body Cap, nothing to do with lenses. it needs to lock in just a lens does on the body.

 

[grat]

Whoops! That's what I get for reading forums while writing my weekly report.

There's a 645 body cap design out there, but it looks somewhat incompatible with the RB (unsurprising).

 

[removedacct2]

now that's great to hear... for all those little parts, etc. that could be similarly produced!

yes, and it's done now for some time for the most popular camera brands, but until recently I found no 3d files for these older Bronica S series. An item must be 3d scanned in order to produce a file for printing, so unless you have your own scannerand printer for prototyping, you have to find ready available 3D files.

one advantage I find with 3D printing is that I can have different colours, so I spot easily the lenses I want to pick from the bag:

 

[removedacct2]

For the OP, PETG is my preferred-- it has a very small amount of flex, is durable, and less prone to melting in hot cars than PLA. ABS is the old standby, but it's smelly to print, has a tendency to warp while printing, and requires constant temperature to print. I'm interested in your experience with flex-- due to the design of my printer, flexible filaments are tough-- I'm limited to certain types of nylon, which is only "mildly" flexible.

in the above picture the first cap on the left is PLA, the 2nd (yellow) and the next white are PETG (last one is an original Bronica), and yes PETG is better. I found it has the perfect amount of flex and feels less brittle (yet of course I didn't try to the limit). The guy I got the prints from is not local and he told me that a cap he made in FLEX was really very flexible maybe too much for such a loose bayonet connection, so in the end I didn't buy one. Should have just for curiosity I guess. I got one in ABS and it's bad, too stiff, yes feels sturdy.
In fact the PETG prints I got do fit better than the original Bronica !

 

[Spot V]

In fact the PETG prints I got do fit better than the original Bronica !

That is no surprise, given how awful the original design is (such great cameras, such horribly bad rear lens caps). But the main reason for the good fit has to be that these aren't just copies of the original design. This is either a rework of a scan or a complete new design. I'm pretty sure that the outer diameter close to the bayonet wings is a tad larger than the original caps. Some people put tape around that part of the original caps in order to prevent them from moving and falling off so easily. I haven't done it yet, but think I should, every time I change lenses ...or finally buy a 3d printer

 

[removedacct2]

. Some people put tape around that part of the original caps in order to prevent them from moving and falling off so easily. I haven't done it yet, but think I should, every time I change lenses ...or finally buy a 3d printer

that's what I do since the beginning with the original caps, and still do with the printed ones, because despite the fit tigher it's still not secure enough.
So I cut a thin stripe of velcro hook that I glue on the mount of the lens, it's non intrusive, there's enough gap around the camera mount of the focusing unit.

another piece of velcro hook glued on the cap. I use strong neoprene glue, because the self-adhesive side of the velcro loses adhesive power in colder temperatures (somewhere between 0 and -10c) as well when very warm (over 30)

a piece of velcro soft side, with black duct on the self-adhesive side. (here I added the lens description)

so I lock the cap with that additional piece of velcro, it's safer

 

[Spot V]

that's what I do since the beginning with the original caps, and still do with the printed ones, because despite the fit tigher it's still not secure enough.
So I cut a thin stripe of velcro hook that I glue on the mount of the lens, it's non intrusive, there's enough gap around the camera mount of the focusing unit.

View attachment 263558



another piece of velcro hook glued on the cap. I use strong neoprene glue, because the self-adhesive side of the velcro loses adhesive power in colder temperatures (somewhere between 0 and -10c) as well when very warm (over 30)
View attachment 263568

This is a different way of using tape (well, velcro) than what I have seen before. People usually just put the tape to increase the diameter of the cap close to the bayonet mount to reduce the lateral play. By doing this the chances that the cap comes off seem greatly reduced. Advantage of this method: caps can quickly be put on or removed. Your method is not as fast but is probably pretty bomb proof.

 

[Spot V]

Some people put tape around that part of the original caps in order to prevent them from moving and falling off so easily. I haven't done it yet, but think I should, every time I change lenses

So I finally did it and taped two of my Bronica rear caps. So far this works like a charm - will have to see how durable it is. While the caps could still turn loose (though it takes quite some force) they won't wiggle loose again, which was the problem with the original caps.
It only takes an additional ~0.7mm in diameter to convert a disappointing design into something functional. For those who think in imperial units: 0.7mm is roughly 859/311694th of an inch ;-)

 

[Trask]

I've got five or six Bronica S lenses with caps, and on most of mine the factory caps work just fine. Once rotated on, the thumb-activated pivoting lock mechanism prevents the caps from rotating back off the lens, and the molded tabs around the circumference of the lens caps also stop the cap from rotating too far. Except I have a couple where the tabs have worn down over time, and they are much more likely to be problematic. So it strikes me that the real issue with these caps is the size of the molded tabs and their durability. Couldn't a 3D printer be used to make the tabs a bit larger and thicker?

 

[Spot V]

I've got five or six Bronica S lenses with caps, and on most of mine the factory caps work just fine. Once rotated on, the thumb-activated pivoting lock mechanism prevents the caps from rotating back off the lens, and the molded tabs around the circumference of the lens caps also stop the cap from rotating too far. Except I have a couple where the tabs have worn down over time, and they are much more likely to be problematic. So it strikes me that the real issue with these caps is the size of the molded tabs and their durability. Couldn't a 3D printer be used to make the tabs a bit larger and thicker?

It sure is possible for someone with basic knowledge in CAD (not me, then). I also think that the tabs should be a bit larger / wider - aside from the better fit it would also take them longer to be worn out.