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DC motor replacement for 3D printers

Posted by rklauco 
Re: DC motor replacement for 3D printers
May 07, 2016 12:06PM
What I don't understand is inkjet printer.
If you sum up the components - 2 dc motors, 2 optical encoders, one long strip and one rotary strip, power source, usualy a hardened rod, too, you end up with a bill of cca. 70-80 eur (if you find encoding strips this cheap, of course). However, the whole inkjet, including electronics, mechanics, a lot more rods for paper feed, ... costs 40eur. You can even get one more motor/stepper if you buy multifunction device - costs 3-5 eur more, yet contains a lot more additional components... Smells like monopoly or something.
Re: DC motor replacement for 3D printers
May 07, 2016 12:46PM
When you produce like 100k units.. prices will drop A LOT in china smiling smiley
Re: DC motor replacement for 3D printers
May 07, 2016 12:53PM
Quote
rklauco
What I don't understand is inkjet printer.
If you sum up the components - 2 dc motors, 2 optical encoders, one long strip and one rotary strip, power source, usualy a hardened rod, too, you end up with a bill of cca. 70-80 eur (if you find encoding strips this cheap, of course). However, the whole inkjet, including electronics, mechanics, a lot more rods for paper feed, ... costs 40eur. You can even get one more motor/stepper if you buy multifunction device - costs 3-5 eur more, yet contains a lot more additional components... Smells like monopoly or something.

The printers are sold with a loss. They make the profit with the ink cartridges.
eg. I have a brother printer with 4 separate tanks. Although I only print black, the printer noticed me yellow and magenta tanks were nearly empty and have to be replaced.
Re: DC motor replacement for 3D printers
May 07, 2016 02:16PM
The price model for printers is nuts, a set of genuine toner cartridges for my color laser is nearly as much as buying a printer. Obviously I'll buy cheap refills and hope for the best smiling smiley


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Re: DC motor replacement for 3D printers
May 08, 2016 10:54AM
Just FYI, here is another thread [forums.reprap.org] about a readily available DC motor with gearbox and encoder from Pololu used for an ultralight extruder.
Re: DC motor replacement for 3D printers
May 08, 2016 05:36PM
Well, I suspect the whole project will be a big success now smiling smiley
I used parts of 2 old Canon printers - paper feeders for the both Z axis, belt from one of its printhead and DC motor for the paper feeder, too. I re-purposed the tensioning mechanism from the printhead, too. I had to do that - without the dynamic tensioning, the axis started VERY slow.
However, the circular strip has a VERY high resolution. I am tracking just one of them (no need for now to track both if they are powered by a single motor).
To move few cm down, I had to simulate 50000 steps (!!!).
Here is the video out of it.
Not only is it extremely precise, it's also fast.
The motor operates on 9.08V now, however it is capable of running on 24V apparently.
I start to love DC servo.
Re: DC motor replacement for 3D printers
May 09, 2016 03:39AM
LOL smiling smiley
Today I measured the physical resolution.
The system does 350.000 steps per 94mm of movements. Therefore the resolution is 0.000268571mm per step smiling smiley smiling smiley smiling smiley
I think this is beyond any practical usage, so I'll introduce 10x multiplier to step input...
Re: DC motor replacement for 3D printers
May 11, 2016 02:06AM
rklauco,
How can steps per second maximum?
Re: DC motor replacement for 3D printers
May 11, 2016 02:14AM
Quote
pamalofeev
rklauco,
How can steps per second maximum?
What ? :-/
Re: DC motor replacement for 3D printers
May 11, 2016 02:43AM
You mean speed?
Well, with the current setup (8mm threaded rod) and 9.08V of power supply, the Z axis moves 97mm in 18 seconds.
Re: DC motor replacement for 3D printers
June 07, 2016 03:49PM
Well, I found one unexpected issue with the Z axis.
Due to VERY high resolution of the movement (4096 steps per mm) I run to the limit of ATtiny85.
While driving it using serial port, the ATtiny is OK and can drive the movement quite fast.
However, when connecting it to RAMPS, it has to cope with interrupts for both the optical encoder inputs AND the step input.
And this is too much - as for each mm of movement it will receive 4096 + 4096 interrupts.
The result? It will try to move the axis, but after 7-8mm of movements it gets "wild" and starts to move uncontrollably in one or the other direction full speed sad smiley
I have to connect oscilloscope and find out, what's going on...
Re: DC motor replacement for 3D printers
June 07, 2016 08:33PM
For round numbers, 100mm/20secs * 4000 * 2 = 40KHz interrupt rate = 25 microseconds processing time per interrupt. Pretty fast!

What speed are you running the CPU at? Looks like you can run it to 20MHz with an external crystal.

What processing does each interrupt have to do? What happens if the next interrupt arrives while the previous one is still running?

For this kind of stuff, it's useful to turn on a GPIO output at the beginning of the interrupt and turn it off again at the end, so you can see how much time is being used by each interrupt. What does the CPU have to do, apart from processing interrupts? Are there enough CPU cycles left for it to be able to do that?
Re: DC motor replacement for 3D printers
June 10, 2016 03:52PM
Major achievement here.
Changing one word in the source file and all of a sudden, everything works!!!
I had to define the target1 in source code as LONG, not INT - as the Zaxis has mental resolution.
I am now able (while still having multiple of 10 steps) to do movement on Z axis with precision of 0.0025mm.
I call it quite good - that's 2.5 microns winking smiley
Not really usable, but it's amazing this is achieved using only scrapped parts from old 2D printers.
Re: DC motor replacement for 3D printers
June 10, 2016 11:20PM
Quote
rklauco
Major achievement here.
Changing one word in the source file and all of a sudden, everything works!!!
I had to define the target1 in source code as LONG, not INT - as the Zaxis has mental resolution.
I am now able (while still having multiple of 10 steps) to do movement on Z axis with precision of 0.0025mm.
I call it quite good - that's 2.5 microns winking smiley
Not really usable, but it's amazing this is achieved using only scrapped parts from old 2D printers.

Great resolution there. What is the speed you can reliably move your Z and how accurate & repeatable is the move compared with the same setup with steppers?
Re: DC motor replacement for 3D printers
June 11, 2016 03:18AM
Can't compare to stepper as this platform never had one winking smiley
Repeatability is 100%, no problem there.
The speed is determined by the usage of 8mm rod - therefore I can do 90mm in 12 seconds currently at 12V, but the motor is 30V capable winking smiley
Re: DC motor replacement for 3D printers
June 13, 2016 02:38PM
So, for those interested, I made a small video demo.
I am missing an extruder for now (working on it), but the rest works 100% with precision beyond my expectation.
A this is what I love about closed loop.
Re: DC motor replacement for 3D printers
June 19, 2016 03:58PM
Its really good that you can use these cheap and readily available parts to build a 3d printer. But that is the real selling point. To paraphrase Digital Dentist the closed loop control with the carriage returning when pushed away, looks awesome but has no practical use. If the carriage deviates from the required path the print is at best significantly reduced in quality, at worst ruined. Under normal circumstances nothing will be pushing it. It might be helpful for the extruder motor but if filament isnt flowing its usually a physical problem, such as a jam, pushing the motor harder might not overcome it anyway.

Please don't take this as a negative overall, its not, the fact that it might be possible to reuse the massive pile of old 2d printers to make 3d printers is in itself wonderful.


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: DC motor replacement for 3D printers
June 20, 2016 03:11PM
This is an excellent point!
However, my original motivation was a bit different - I am looking for something much quieter then my NEMA17 printer - that is seriously loud. My wife cannot sleep in the next room when I print something.
And, I can already tell you, that the DC motors, although still having some issues, are WAY quieter than this.
The other motivation was price - but, as I found out, the cheap price is probably only for OEMs, not for general public - as I was not able to get my hands on a quadrature encoder or the encoding strips within a pricerange that would not closely copy a price of a whole 2D printer with such parts sad smiley
So for now, the quiet operation (and option to salvage the parts from 2D printers) remains my primary motivation.
Re: DC motor replacement for 3D printers
June 20, 2016 03:45PM
What would you say the resolution of the x and y motors is?

So you've written some code to control each axis using the at tiny 85, does just it accept step and dir signals from your printer controller?


Simon.

[www.precisionpiezo.co.uk] Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters. PT1000 cartridge sensors plug straight into duet boards and others.
Published:Inventions
Re: DC motor replacement for 3D printers
June 20, 2016 06:48PM
Current resolution (due to low-res strip) is 23 steps per mm.
And yes, you can check the code yourself - I'm only using step and direction as inputs.
I was thinking about using enable signal to home the axis, but I had slight problem with that for now...
Re: DC motor replacement for 3D printers
July 22, 2016 10:51AM
Another direction of getting quieter closed-loop motors (not cheap but your wife may appreciate it) [www.americanmotiontech.com]
Re: DC motor replacement for 3D printers
July 29, 2016 07:45AM
Re: DC motor replacement for 3D printers
January 12, 2017 11:36AM
Fwiw, I'm looking into this as well: Ali express has encoder strips for $17 / 9m. These are 1.5cm wide, something that could easily be cut in half, providing enough strip for 6 1Mx1Mx1M printers.

[www.aliexpress.com]
Re: DC motor replacement for 3D printers
July 18, 2019 07:20AM
Are you guys talking about absolute encoder strips? I feel like those would be ideal for a feedback system with a rotary encoder on the dc motor, but I am having trouble finding absolute encoder strips. This does a good job at explaining the differences in encoder strips:

[www.linearmotiontips.com]
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