After digging around, I've found out about spring balancers. They sound like the thing I've been looking for (see previous log) in that they're a tether used to counterbalance tools to prevent strain on workers. The cool feature is that the balance force is adjustable, which is even better than a constant force or gas spring strategy. It also requires much less effort on my part to implement.
I'm thinking that it might be possible to connect the cord ends together for SecSavr installations that have a Z height that exceeds the cord length of a single spring balance.
So I did some quick maths and deduced that the tubes alone for the gantry (that moves) is 9kg for the Z axis to move. Making the bed move is not possible as this would fail the belt bed solution. That constant force spring I got a while back is a clock spring and the Aliexpress seller probably just threw keywords in the title to get shown in more search results.
Voron uses KeyBak for their switchwire, which is a retractable lanyard, but the price to force (and usable length) is pretty poor. All other lanyards also seem to be of low constant force. Retractable dog leashes might be an exception but I doubt it.
So I'm scrolling pages, feeling defeated, when I see post #3 on this forum page. So I go onto Ebay and he's right: they're cheap and can be find in a range of strengths and lengths. This is the first listing I clicked on, which prices a 400mm 800N spring at £11.99. I'll be looking for an eyelet version.
Oh. How convenient. That worked out rather nicely.
I feel like I can use some of the excess 608 bearings and M8 bolts to make some pulley. I can't imagine a suitable cable would cost more than £8, so I could potentially have a new solution for under £20, down from the > £63 solution I was originally thinking of with the clock springs.
Oh but pulleys can only be set up in integer values. Hmm.
800N / 7 = 114N
114N = 11.62kgf
I'm sure that's close enough.
Obviously, this also means that it should be much more scalable than the constant force spring approach. The SleepCinema only needs around about 0.7m-ish and not 2.5m like if it was a single SecSavr going from the floor to the ceiling. That would only need a 100mm extension so even the smallest (150mm) spring would suffice. I'd still like the option to reconfigure a taller SecSavr without having to buy new components, especially if I'm only saving like £3 per shorter spring.
[E1 - 16:17] The only concern now is if the springs I've seen are damped or not. Next, I just realised/remembered that the springs are described by their max length, not by their stroke length. Lastly, this image makes me think that it's not all that constant, though the forces are not labeled so I don't know.
I think the design of the Y Slider went well. It should do the job of clamping the X axis tubes and look sleek doing it. I made sure that the X tubes were aligned with the Y tubes so that there would be no additional height lost because the X slider is sticking out.
I feel kind of lost since this is the moment when I start thinking of the actual details that turns an idea into something that would actually work, but I'm currently modelling the Z Slider. I'm doing a bit of a "Merge/Insertion Sort" like approach when it comes to housekeeping.
I'm using a 12 sided polygon as the clamp interface between the Y axis tube and the Z axis slider. This gives some tolerance in the design.
I originally thought of having the clamps oriented the opposite way, but I'm thinking that the design can get a higher space utilisation this way.
I've just realised that the 55x60 cm tiles originally for the SecSavr Space are not going to work for this new SecSavr inside the SleepCinema due to the fact that the Z axis tubes are almost twice their length.
Using 42.4 or 27mm tube would cut a large chunk of Z height, so I'm thinking of using M12 or M16 threaded rod. I think it would be cool to design the SecSavr to only use M2, M4, M8 and M16 threaded entities, with the occasional M3 for electronics mounting.
I'm also trying to compute a bed solution that uses up a minimal amount of Z height, and being able to use the space otherwise taken up by a tile could be benificial. Also, those tiles are heavy which, while may dampen oscillations, would be somewhat difficult to adjust to a different Z height,
I'm planning for the mount to either look like, or attach to, Key Clamp 179 which is fixed to the Z axis tubes.
I still have an idea to use the tiles on the bottom of the printer section for aesthetics, and maybe oscillation management.
The past two days, I've been thinking about possible ways to automate the bed levelling process. This was because different features require different beds, meaning that they will be swaped out more than usual, as well as the W axis (rotary bed) would likely need a good amount of precision to reduce failed prints. I also wanted to see if I could further open up my bed size options to 3x2.
Thus, I started researching motorized 3D printer bed solutions. After remembering that I have a limited amount of wires on the slip ring used for the rotary bed, and noting that I have no inherent need for the ability to have something like a 3x2 segment bed layout, I rejected the idea and the specification change.
However, I still believe that automatic calibration is an important feature to strive towards. It looks like 5 axis CNCs take a non-negligible amount of time to calibrate:
Add this to the multiple bed segments that need to be adjusted, and tool offset calibrations, and there would be quite a bit of overhead time just to get a print started.
Computer vision can be used to calibrate the tool offset for X+Y, as well as Z. I was also thinking of using computer vision to see the top of the bed leveller and use an "allen key and dial indicator" tool head to mechanically adjust the level.
I probably also have to add some self locking washer to the screw to prevent it from moving unintentionally, as well as some kind of endstop so that Klipper knows when the maximum limit has been reached.
Slow progress, but I've started modelling on the basic linear carriages for the large (42.4) and small (26.9) tubes. Singular and double refer to 1 or 2 tubes respectively. I refactored that "stiffener ring" crossbar looking section twice to get the design and timeline to be at the quality I desired. I also started using named parameters more
I'm currently thinking of possible designs for the double tube that will allow the x axes to be as close as possible.
I'm also wondering if I should continue designing from the frame -> [...] -> slime or if I should start working back from the slime -> [...] -> frame.
I was originally thinking that I was going to have the tool rack connected to the Z axis, but since the gantry is so large and the Z axis is doing overtime compared to a standard 3D printer, some weight saving decisions were in order. If I assume each SecSavr Slight is 200g and there's 10 tools installed, that's 2kg of mass to move that doesn't need to be coupled with the Z axis. Hmm, now that I write this, perhaps I can use a "flying extruder" type installation instead of using even more steppers to drive the tool axis. Anyway, couple that mass with the weight of printed parts and it could be 3kg of mass that needs to be moved excessively. I'm no penny pincher when it comes to saving 10g here or 60g there, but 3000g is a different ball park.
There's no such thing as a 42.4 to 33.7mm version of the 161 clamp, so they're the same thickness as the rest of the frame, even if it could be considered overspecked for this use case.
It's looking awfully tight for the dual set of Z axes. I intend for the Slime [gd0088] harnesses to actually be in that centre area between the sets of 4 tubes but things could get a bit dicey. There's about 10mm of clearance for the M16 grub allen key.
kelvinA
I think the design of the Y Slider went well. It should do the job of clamping the X axis tubes and look sleek doing it. I made sure that the X tubes were aligned with the Y tubes so that there would be no additional height lost because the X slider is sticking out.
I probably also have to add some self locking washer to the screw to prevent it from moving unintentionally, as well as some kind of endstop so that Klipper knows when the maximum limit has been reached.
Slow progress, but I've started modelling on the basic linear carriages for the large (42.4) and small (26.9) tubes. Singular and double refer to 1 or 2 tubes respectively. I refactored that "stiffener ring" crossbar looking section twice to get the design and timeline to be at the quality I desired. I also started using named parameters more
I'm also wondering if I should continue designing from the frame -> [...] -> slime or if I should start working back from the slime -> [...] -> frame.
I was originally thinking that I was going to have the tool rack connected to the Z axis, but since the gantry is so large and the Z axis is doing overtime compared to a standard 3D printer, some weight saving decisions were in order. If I assume each SecSavr Slight is 200g and there's 10 tools installed, that's 2kg of mass to move that doesn't need to be coupled with the Z axis. Hmm, now that I write this, perhaps I can use a "flying extruder" type installation instead of using even more steppers to drive the tool axis. Anyway, couple that mass with the weight of printed parts and it could be 3kg of mass that needs to be moved excessively. I'm no penny pincher when it comes to saving 10g here or 60g there, but 3000g is a different ball park.
It's looking awfully tight for the dual set of Z axes. I intend for the Slime [gd0088] harnesses to actually be in that centre area between the sets of 4 tubes but things could get a bit dicey. 
There's about 10mm of clearance for the M16 grub allen key.