Many have asked for DC motors with encoders for 3D printer usage, and this guy is doing it. Code is based off of Teacup, but if a suitable implementation can be had this looks pretty exciting for reducing overall cost of a machine.
This is some seriously thorough work already 
Excellent! Having done a lot of work with quadrature encoded motors I look forward to the result. The challenge will be overshoot and/or speed. With my robots that have these, trying to do dead reckoning navigation by using the motors feedback is really really challenging. 3D printing is much different of course, many more variables are constrained. The challenge for my robots was that if they wanted to be precise, they ended up ‘creeping up’ on the final position and oscillating a bit when they got there. (not quite critically damped in linear system terminology)
That said, you can do really amazing stuff with this set up these days. I’ve seen pick-and-place machines that are whizzing around all using quadrature encoding on high performance DC motors.
trais impressionnant quelle beaux travaille
@Chuck_McManis
Thank you. Having this same conversation over on Reddit. Yes, almost all industrial robots / CNC equipment use closed loop servo for precision control and torque management. Had I said “servo motor” instead of “pilfered DC motor and optical encoder”… I probably would not have had that discussion… lol
Yes, one of the things learned was that long line segments need to be broken down so that the final segment can slow to target. Small price to pay.
@Jason_Gullickson
Thank you. That’s the plan. Even if I fail… you’ll know why. LOL
Thanks for the exposure! Greatly appreciated.
And as always over on Reddit it’s “you can’t do this!” “stepper motors are used for a damn good reason! (“well, what reasons are those?”) I don’t know, but they’re damn good!”
Pretty much verbatim. LOL
Servomotors aren’t used much in hobby and small 3D printing machines because they’re more complicated and cost more. That’s pretty much it.
As hobbyists start scaling up their machines, they’ll need to start unlearning what works well for small machines and start making different choices. Pushing servomotors forward would be one such choice to make.
I’d love to build alongside! Do you want to get on the Printrbot open source r&d bandwagon? Helping provide the world with servo options sounds totally worthy. If it helps, I’ll pay for r&d by buying hardware 
let me know. I’ll just want to build alongside and blog about results. No strings.
Brook
@Brook_Drumm
Hmmmm… would be awesome to have someone to bounce ideas off of. Are you suggesting starting from a printrbot frame, with servomotor instead of stepper?
Wondering if you would consider a trade. Teensy based controller for printerbot hardware kit…
both start from the same mechanical/electronics ?
Sure! I’m down for whatever you want to build. My man interest is in getting the price down as low as possible… Really cheap. But servos are appropriate for really large things too. Steppers aren’t really broke, especially for the middle price tiers. But closed loop could benefit all! Really, I just love seeing and encouraging innovation. So take your pick of my bots and we’ll have some fun if you like. I do have some incredibly talented folks out there in the community… Surely we can do this together and see how it goes.
Brook
@Brook_Drumm
I will admit that I’m very interested in your offer primarily for the motivation factor. (And assistance when i get mired in code.)
Within the next week or so, I will start a new github, with everything I’ve got. Invite the community to review and start photo and video documenting. I’ll have eagle files ready this upcoming week.
We’ll go from there. Is there anything in particular that you would like to see prioritized?
I’m excited to see where this goes.
I did some work over the summer to figure out what it would take to go school-to-school with a Reprap, printing seed parts and teaching students how to build their own printer (you know, “Johnny Appleseed”-style :). The biggest unreducable cost was the electronics package (even hot-ends have low-cost, fabricatable options).
If I’m following along correctly, if successful this not only substantially reduces the cost of the electronics package if bought new, but also opens the door to re-using or repurposing motors and such that are commonly available (harvesting parts from inkjet printers comes to mind).
That would make the whole “Johnny Reprapseed” project a lot more feasible
So if you go back in my blog ( http://arduino-pi.blogspot.ca/2014/04/my-journey-into-building-3d-printer.html ) You will see that this is how this all started. I repurposed a couple inkjets, but with Arduino pro-minis at 16Mhz… and +Brook Drumm should be happy to see that I referenced his Printrbot project at the time.
A rough “wet finger in the air” estimate of parts to populate the controller board (in low quantities) aside from the $20 Teensy, is around $50 USD.
I’m sure we could do better than that in quantity. I truthfully have no idea what it would cost to have assembled however.
My printrboard costs me around $50 so doing a board at scale with this implementation in mind might get cost down. Even if it is a wash, innovation is worth it.
Brook
@Brook_Drumm
Nothing says we can’t embed the K20 right onto the controller board… Use the Teensy as a devel board, but in run 3 or 4 move the processor onto the controller board.
Sound reasonable. The printrboard started as a teensy derivative. Then teensylu then printrboard.
HP printers and scanner all in one units have theses motors along with a power supply in some cases. My thrift store always has printers.