The focus system:
There are four SLA printed parts:
1. wheel
2. worm
3. motor mount
4. worm mount
Focus board:
One of the most tricky things was the connection of focus wheel with the lens holding ring. You cannot imagine how much I hate glue, that's why you didn't see any glue connection in the whole design. But...unfortunatelly there were no other cheap and easy way to connect this two parts. Small drops of cyanoacrylate on each tip of the focus wheel allows to reliably connect this two parts so, that I cannot break it by hand. I also tried epoxy, but the adhesion was very poor, so cyanoacrylate is the best for gluing this type of plastic. At the same time the whole focus mechanism is quite lightweight and there is no need to apply much force to make the lens move.
The lens holding ring thread allow to make 5 turns of the focus wheel, until it fully unscrews and falls out, that's why we can use 4 turns to adjust the focus. The focus distance changes non-linearly with the wheel position, and that is very good, because a single turn from the fully closed position allows to cover focus distances from ~30cm to infinity, while for macro you will need to make few other turns.
You can also see a photomicrosensor that allows to precisely control the lens position. It is mostly needed to keep the lens away from endpoints, preventing lens lock and unscrew. Also this sensor will be helpful for autofocus! The wheel has 25 teeth, the worm has a single thread and 4 blades, that cross the photomicrosensor slot, so if we detect both rising and falling edges of the pulse, we will have 25x4x2 = 200 points of lens position per a single turn, i.e. accuracy of 1,8 degree.
The focus board thickness is 3mm, it also has 2 additional support points (two 10mm white threaded spacers), that allows to keep sufficient construction rigidity.
The worm mount has a special brass sleeve, that helps to minimize the wear.
The focus motor is a 6mm dia coreless motor with 3 stage built in planetary gearbox (1:136). It is very powerful and consums few energy, but motor vibration is high and rigid connection to the PCB causes some sound amplification. But I have a solution for this, the motor mount is to be redesigned, I'm planning to add a special silicone cover for the motor that will damp the vibrations.
Two words about focus gears reliability. In fact I do not see any wear of the worm or wheel, because after proper UV curing this type of plastic becomes very strong. But I plan to make a continues stress test to define the possible wear level. Making this complex parts on SLA printer is quite cheap and at the same time quality and reliability is high, that's why I'm planning to use this solution in release design. I have a small experienсe with SLA printing, that's why feel free to point out flaws.
Some common view:
Of course, all plastic parts STEP models will be avaliable.
P.S. no video yet, but maybe you can enjoy animation