We cant access or robot, so season is almost over - we cant meet except on discord. So I have decided to start a project of my own. I am retired so I have the time. I got my printers and a lot of HIPS and some PETG and some ABS and also some Nylon 910 (taulman). 3DP has been good to us but most of the stuff was not really tested it was often hand broken or we print a thing like the Hook we use and tested it like this
Now with all the stuff we did I cannot tell you is it barely strong enough or is it way overkill? So I decided on what is hopefully going to be the last build I am involved in that is based on guess work
I am in the processing of 3d printing (of course) a tester that is supposed to break plastic under certain circumstances. Some inspired by some youtube videos like CNC kitchen but I intend to test parts that are printed for the use in a robot and answer questions like how much can a 3d p plate made from xxx plastic of that dimension hold with a 608 bearing in it or when will a gear skip that has a 1.5modulus is double helical with a width of … How does abs/hips/petg/nylon change when I print it 10mm thick instead of 4mm etc.
At the heart of this tester is going to be a 128:1 planetary with a beveled 19:41 input so overall a 276:1 reduction. The initial print is done in HIPS and what fails will be replaced in Nylon 910. I want the cost to stay low. The power will come from up to 3 CIM motors that will drive the input bevel. something like this
Thats the input stack with the first sun on top initially the input will be on the bevel but there is allso provision for a belt an gear input from another source The 2 planetaries are 2.25mm module and the gears are 30mm wide. In my guess (and unfortunatley its a guess) it should handle the torque generated.
The Cim Motors will be run as torque motors that means I will design and build some drivers that control current and with that the torque of the motor. So the initial task will be to set a current and then measure the output by stalling the motor. So i can set the motor to stall at 10 amps if I so choose. The "sweet spot " on a Cim is at about 30 Amps where it puts out about 64 oz/in so about 4 inlb so with one motor mounted the output torque will be about 1000inlb (thereabouts give or take depending on loss)
ring on the input is 63 tooth
The Ring1 slides in the holder the holder is static and has a race for bearings where some 608s run in it like wheels tied to the axles of the planet to take off some load as the planet carriers will spin at about up to 1000 rpm
Planet carriers are also going to be used to help with allignment during assemble and in case something gets misaligned its supposed to bind and jam and stall the motor(s) before we develop shrapnel.
For assembly reasons the planet stacks come in 3 pieces
with holes for M5 bolts and also some press fits for 608 bearings As Ring 2 is 64 tooth compared to the 63 of ring one (with that and the p1=21 tooth and p2 = 22 we get the 128:1) and R1 is 63 each P2 in relation to P1 is rotated about 1.4 deg (360/256)
The Output has first a 138 tooth dual pulley on the ring itself
Which then gets support from a plate with a 3rd pulley tied to the main axle The planet holder also rides on this side on the main axle
Which then will mount to output ring - like everywhere else the bolts are countersunk with Nylock nuts embedded in the plastic. So nothing sticks out and can catch something.
Mounted to that is an output gear also running on the main shaft with bearings
with about 4in diameter and a 3.5mm module this gear will drive 2 pairs of those stacks
Which will allign and guide the output rack that hopefully will lift up to 600 lb on 1 motor like this (1 pair shown
The top gears ar 2.25mm module the bottom 3.5 the bottom ones mesh with each other the top ones with the rack the rack has a 1/2in steel 16 gauge square tubing in it as reinforcement here shown with an al. tubing on a test piece (out of al tubing at my house)
Also shows how they are concatenated and printed on an angle with custom supports to avoid ?drooping on the long inside of the square cutout or putting supports inside and its no fun cleaning out supports out of a 1/2 in by 500ish mm long square tube. (prints diagonally on my chiron)
This then is held by 2 plates like this
The channels are for aforementioned 1/2 in square steel tubing.will be held to the plastic with M5 bolts and the 8mm or (5/16) bolts working as axles for the rack and pinion will rest on said steel tubing. A 660 lb crane scale will be mounted to initially verify the output and then adding motors the intent is to scale it up until something breaks to get the data
The 138 tooth pulley will have enough torque to lift up to 250 lb per motor at 30 Amps. As we can go up to 3 motors that is why there is 3 pulleys as a properly tentioned gates HTD belt (the ones andymark is claiming to sell) is guaranteed to not skip up to about 300lb of static load and also should not break (according to the gates spec) This should answer as to how much torque can you take off a ring on a 3dp 2 stage planetary.
One of the goal is to collect some data - based on the attachments that will (hopefully) break test pieces under controlled circumstances. I hope it will help to develop some custom brackets, mounts, frame pieces, components, gearboxes that are not overkill but still strong enough for the task. Gearboxes for climbing a single robot, lifting stuff or doing a 3 robot buddy climb. Right now I am a little over 4 kg of HIPS (at $10/kg) into it have made and printed a little over 50 individual drawings and getting pretty close to putting it together.
Guess thats what happens if a retired old dude is locked up in a house with some filament and 3D printers lol. So far I got about 2 and a half weeks into it.
If it works I intend to share are drawings on my grab cad site - maybe someone wants to print it in Onyx lol. Also all test results will be published here - and maybe on grabcad or my website.
So far everything is printed on my Anycubic Chiron with a Volcano and a .8mm nozzle. All prints are printed solid here is a slice pic of one of the gears
So as close to injection molded as you can come with 3DP
Of course comments welcome