I think we have just hit upon a high performing drive mechanism that is also very reprappy.
http://www.youtube.com/watch?v=PKkfn1GKuMo&feature=share
make it push a 500g weight back and forth 10000 times, and then look at the wear on the string, and the slop/backlash in the joint.
I don’t know if we can hit that many cycles to failure. Luckily the string is cheap. I have some ideas on how to make stringing it faster. It took me 15 minutes to do my first one but it wasn’t a pleasurable experience.
Slop and backlash won’t be a problem. I will have a guitar tuning peg and a spring on the terminating ends. Every print you just turn the knob until the spring is extended to a designated position. In the biz this is called “wear compensation”.
For completeness sake, I will be measuring cycles to failure. I have a few different types of lines that I want to try if the spectra doesn’t perform as needed.
This is it!
One quibble though… As a technician the hairs in the back of my neck raise when I hear “wear compensation”. In my opinion it is just another way to say “our engineers have not found / bother to find a viable solution to the problem yet, but we found this cheap workaround that works most of the time”
This little arm is worth the effort… with a bit of fine tuning it will definitely be the game changer. I will contribute where I can to make this one fly!
I added the “wear compensation” comment so I could laugh a little on the inside. In all seriousness, plastic gears will have to work themselves together over a period of time. It is my experience that they will asymptotically approach a certain level of wear. Adjustments will have to be done often during the break in period but after a while the machine should stabilize. Prints will improve over time as the parts get smoother.
True… The point is to get it broken in before it is broken…
Do we now need to solve stringing problems again
Very cool mechanism. Impressive work!
B.t.w. do you have file uploaded already? If not, you could upload them to YouMagine! We’d love to see you share there. Your design will remain your IP, and it’s easy to choose a permissive license (e.g. GPLv3 or CC-BY). Also, the site is constantly developed with the community’s feedback. </end shameless plug>
Just wondering of can drive with a belt or cable to increase strength. Thinking of a rideable spider bot
What about using Synchromesh like in the Bukobot
http://www.asahi-intecc.com/industrial/product/synchro_mesh.html
@Eric_Moy Definitely possible. I don’t think use of any device with a pitch is needed. If you tie the cable to the drive pulley, you can perfectly control the amount of cable on each side of the pulley. If I was to build a rideable spider as @Glenn_West suggest then I would probably go with spear gun line which can be rated in excess of 1000lbf. (Use some bearings in the big version instead of the sliding contact and you are good to go.)
So when do u think we would see in a simpson derived printer
@Glenn_West Are you talking about the bearings? The bearings complicate the string management on the small scale to a level that is downright unmanageable. I have bearings that would work but no one would want to string this. On a large scale, stringing becomes a lot easier as your hands are much smaller proportionally when compared to the task.