Has anyone tired a positioning system based on an inkjet printer style “opto stripe” (no idea what the correct terminology would be)? See an example in this video (@https://youtu.be/mMcTFUJYMGI?t=166&t=2m46s if the time code below doesn’t work):
https://youtu.be/mMcTFUJYMGI?t=166
Seems cheap, fast and quiet!
Never mind, I should have Googled first!
http://reprap.org/wiki/Optical_encoders_01
Boom tish! 
I would not doubt it if we need more precision than that, but it should surely be useful to see if the 3D printer is still on track when at specific places. On a side note, I am sure that it is easier to use the DC motors when you do not need to match x and y position.
Yes, and there are merits to it. The biggest issue in regards to using it is how 3d printers work compared to how normal inkjet printers work. When a normal inkjet printer realizes that it’s not in the correct location anymore it can decide not to spit out ink. In a 3d printer, you don’t have that luxury. This is why optical encoders have not been used much in 3d printers.
This is nothing new. Closed loop motor control has its benefits in allot of systems, but requires a bit more effort.
And this particular system in our “high quality” printers was not for better printing.
It was only for reducing costs.
The older printers used steppermotors for the carriage too.
But its cheaper this way you need only a dc motor that alone is cheaper as an steppermotor and you don’t need an stepperdriver ic.
But that’s only for this particular case.
Normally Jan de jager has right closed loop systems are for better control behavior.
It works at some point, where torque is essential (easy fix with brushless linear) higher speed compared to steppers (and you don’t need torque) major fix for firmwares using steppers, but extra build design and materials are required (unlike the belt driven steppers) but lighter than using steppers
@Justin_Nesselrotte I’m not sure that the stepper motor would prove any better in a situation where your position is off. You’d still get a garbage print…only the print in the case of no optical guide may just keep going wasting time, energy, and filament. I think it would be interesting to try a hybrid system or use some type of incremental shift in order to correct its course. What cases could you foresee where the optical encoder would miss a beat in the first place?
In the simplest case (w/o error correction in firmware) you will not have anything to alter in firmware.
@Justin_Nesselrotte that’s not the way to apply it. You won’t get much out of sync because the drive circuitry will apply whatever control effort it can to compensate before it gets noticeably out of sync.
To add to an earlier comment, one doesn’t even absolutely need to alter firmware to take advantage of positioning feedback, some servo drive systems simply take step, direction and enable signals and the motor driver handles the positioning and compensation. The controller won’t know about any problems, but the motor system will generally be able to handle upsets and quickly get back to where it should be.
Thanks everyone. If you’re removing a stepper and it’s driver the cost could be comparable or less. As Jeff says, the advantage is that the drive system will always try and get to the target, where as a stepper just skips. In the case where you can’t get to the target your print is doomed either way, but at least with a closed loop you know about it. It mainly appeals to be because it’s such a neat solution.