I was thinking about some of the design constraints I set up myself for the new printer. One mental issue I was having with my initial fork of the Kossel Clear was the perpendicular distance of the belt from the center line of the bearings. I’m thinking I’d like to minimize that and get it close to the bearings a possible. Another issue was that I have a bunch of stepper motors in inventory that are not to a standard nema frame.. It would be sort of nice to use them. The thought occurred to me is that if I rotated the drive pulley 90 degrees and put it on a bearing block I could get that real close and I wouldn’t be dependant on motor frame or shaft size. Now that being the case, if I did that, it would be trivial to extend the shaft and perhaps mount an encoder on the shaft end… Hmmm. That would be open up the possibility of loosing the stepper motors and coming up with some type of Servo Drive… (I getting way ahead of myself here..(but that would be one way of getting this system to really fly)
If I did this one thought I was having was direct mounting the motor on the shaft with a rigid coupling. Many moons ago I worked as an application engineer engineer for a power transmission company.. One of the solutions that I saw was a torque arm for a planetary gearbox. If someone is reading this you can see what I’m talking about on here: http://www.automation.siemens.com/mcms/infocenter/dokumentencenter/md/Documentsu20Catalogs/MD20.3_PLANUREX-Planetengetriebe_de_en_fr.pdf
This one of the most elegant solutions I ever seen for keeping radial loads out of a gearbox, and is something I’ve been wanted to try in one of my projects. This would be total overkill (even for me) for this. But it’s definitely in the bucket list of things to do. (Perhaps for my cnc mill project) I’m thinking that probably I corporate some standoffs to make room for some type of flexible coupling and and adapter plate for whatever I want. Putting these constraints is going to change the way things look.
I was looking at the shaft orientation of the Kossel clear.. I like that.. I was looking at the misumi site for details on the extrusion. http://us.misumi-ec.com/vona2/detail/110300465870/?KWSearch=KHFS3-1515-2000
It looks like the corner rad is 1mm. I looks like the misumi u-grooves are 2.5 mm http://us.misumi-ec.com/vona2/detail/110300424840/?KWSearch=v-groove
My inclinations is to find some roller blade bearings and machine some custom pulleys to fit around them.