DC motor replacement for 3D printers Thanks to the work of [url=https://plus.google.com/113179837473309823193]Miguel Sanchez[/url] I started to experiment with DC drive for 3D printer. My original goal was to experiment, but it starts to be usefull now. I build a [url=http://www.thingiverse.com/thing:945156]ToyRep printer[/url] and it was failure - motors overheated, it was painfully slow and useless. But thanks to [url=https://github.com/misan/dcservo]Miguel's github repo[/url] I am now using the toyrep as a platform to create closed-loop feedback for 3D printers. For now, I feel like the progress is worth communicating. The axis movement is working great - for now I've built X axis, working on Y and Z. I am using motors from old Inkjet printer. I also salvaged the encoder strip and optical sensor - working no problem at all. Yesterday I made a small startup routine, that is able to search for minimum and maximum position, eliminating any need for min/max switches. The final goal is to produce a small board - drop-in replacement for stepper controllers - with pin-level compatibility. As I am using motor driver for 2 motors, for the time being I plan to do a single board that will replace 2 stepper drivers. The advantages are obvious - thanks to direct position information, the printer will never run out of alignment. Steppers have to be oversized with plenty of torque so one can be sure the printhead will ALWAYS move to desired position. This is not necessary with closed loop - the logic always know where it is and is able to compensate its position by temporary increasing torque. Result is much smaller current requirement and way quieter printer. And, depending on the motor size, much faster movement, too. I know about one more project - servolulu - that is trying to do the same, but unfortunately for now it's closed source. Should anyone have comments, questions or any suggestion, please, start the discussion below. https://reprap.org/forum/read.php?1,659992,659992#msg-659992 Sat, 10 Oct 2026 13:45:08 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,659992,856767#msg-856767 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,856767#msg-856767
[www.linearmotiontips.com]]]> alim2018 General Thu, 18 Jul 2019 07:20:15 -0400 https://reprap.org/forum/read.php?1,659992,738074#msg-738074 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,738074#msg-738074
[www.aliexpress.com]]]> AleksClark General Thu, 12 Jan 2017 11:36:38 -0500 https://reprap.org/forum/read.php?1,659992,692564#msg-692564 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,692564#msg-692564 http://hackaday.com/2016/07/29/3-phase-bldc-motor-controller-will-run-you-20-in-parts/
I have to try this...]]> rklauco General Fri, 29 Jul 2016 07:45:01 -0400 https://reprap.org/forum/read.php?1,659992,691005#msg-691005 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,691005#msg-691005 www.americanmotiontech.com]]]> misan General Fri, 22 Jul 2016 10:51:09 -0400 https://reprap.org/forum/read.php?1,659992,676571#msg-676571 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,676571#msg-676571 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...]]> rklauco General Mon, 20 Jun 2016 18:48:11 -0400 https://reprap.org/forum/read.php?1,659992,676514#msg-676514 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,676514#msg-676514
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?]]> DjDemonD General Mon, 20 Jun 2016 15:45:14 -0400 https://reprap.org/forum/read.php?1,659992,676500#msg-676500 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,676500#msg-676500 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 :(
So for now, the quiet operation (and option to salvage the parts from 2D printers) remains my primary motivation.]]> rklauco General Mon, 20 Jun 2016 15:11:56 -0400 https://reprap.org/forum/read.php?1,659992,676088#msg-676088 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,676088#msg-676088
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.]]> DjDemonD General Sun, 19 Jun 2016 15:58:29 -0400 https://reprap.org/forum/read.php?1,659992,674074#msg-674074 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,674074#msg-674074 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.]]> rklauco General Mon, 13 Jun 2016 14:38:57 -0400 https://reprap.org/forum/read.php?1,659992,673308#msg-673308 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,673308#msg-673308 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 ;)]]> rklauco General Sat, 11 Jun 2016 03:18:48 -0400 https://reprap.org/forum/read.php?1,659992,673283#msg-673283 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,673283#msg-673283
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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 ;)
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?]]> ipcalit General Fri, 10 Jun 2016 23:20:09 -0400 https://reprap.org/forum/read.php?1,659992,673183#msg-673183 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,673183#msg-673183 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 ;)
Not really usable, but it's amazing this is achieved using only scrapped parts from old 2D printers.]]> rklauco General Fri, 10 Jun 2016 15:52:24 -0400 https://reprap.org/forum/read.php?1,659992,672175#msg-672175 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,672175#msg-672175
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?]]> frankvdh General Tue, 07 Jun 2016 20:33:14 -0400 https://reprap.org/forum/read.php?1,659992,672088#msg-672088 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,672088#msg-672088 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 :(
I have to connect oscilloscope and find out, what's going on...]]> rklauco General Tue, 07 Jun 2016 15:49:29 -0400 https://reprap.org/forum/read.php?1,659992,662554#msg-662554 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,662554#msg-662554 Well, with the current setup (8mm threaded rod) and 9.08V of power supply, the Z axis moves 97mm in 18 seconds.]]> rklauco General Wed, 11 May 2016 02:43:51 -0400 https://reprap.org/forum/read.php?1,659992,662549#msg-662549 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,662549#msg-662549
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pamalofeev
rklauco,
How can steps per second maximum?
What ? :-/]]> B4Me General Wed, 11 May 2016 02:14:03 -0400 https://reprap.org/forum/read.php?1,659992,662548#msg-662548 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,662548#msg-662548 rklauco,
How can steps per second maximum?]]> pamalofeev General Wed, 11 May 2016 02:06:14 -0400 https://reprap.org/forum/read.php?1,659992,661785#msg-661785 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661785#msg-661785 Today I measured the physical resolution.
The system does 350.000 steps per 94mm of movements. Therefore the resolution is 0.000268571mm per step :) :) :)
I think this is beyond any practical usage, so I'll introduce 10x multiplier to step input...]]> rklauco General Mon, 09 May 2016 03:39:43 -0400 https://reprap.org/forum/read.php?1,659992,661715#msg-661715 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661715#msg-661715 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.]]> rklauco General Sun, 08 May 2016 17:36:10 -0400 https://reprap.org/forum/read.php?1,659992,661590#msg-661590 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661590#msg-661590 forums.reprap.org] about a readily available DC motor with gearbox and encoder from Pololu used for an ultralight extruder.]]> ipcalit General Sun, 08 May 2016 10:54:14 -0400 https://reprap.org/forum/read.php?1,659992,661327#msg-661327 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661327#msg-661327 bobc General Sat, 07 May 2016 14:16:35 -0400 https://reprap.org/forum/read.php?1,659992,661297#msg-661297 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661297#msg-661297
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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.]]> o_lampe General Sat, 07 May 2016 12:53:13 -0400 https://reprap.org/forum/read.php?1,659992,661296#msg-661296 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661296#msg-661296 B4Me General Sat, 07 May 2016 12:46:33 -0400 https://reprap.org/forum/read.php?1,659992,661287#msg-661287 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661287#msg-661287 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.]]> rklauco General Sat, 07 May 2016 12:06:48 -0400 https://reprap.org/forum/read.php?1,659992,661258#msg-661258 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661258#msg-661258
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o_lampe
I made a mental pro/con list and one of the cons was the limited access to dc motors, sensors and strips.
Would it be possible to make my own encoder strip? Say, I have a laser engraver and would like to make a different strip...( longer, more/less signals per mm, UV resistant material, etc...)

I agree - lack of access to low-cost encoders is probably the biggest issue with using servos over steppers. Really cheap DC motors with encoders show up in all sorts of equipment, but trying to buy just a few is nearly impossible. It shouldn't be so hard. Making your own code strips or wheels with decent resolution (say 150 LPI) is pretty tricky. You also have to make the strip match the resolution of whatever sensor you are using.]]> LoboCNC General Sat, 07 May 2016 10:26:23 -0400 https://reprap.org/forum/read.php?1,659992,661200#msg-661200 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661200#msg-661200
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Traumflug
How about reducing motor current? A printer design isn't at fault if you don't adjust such things properly, nor is the concept of having stepper motors.
Of course I did that first. But the steppers were simply too weak to move the gantry then. I'd suggest you first look at the steppers used within ToyRep to get the idea ;)]]> rklauco General Sat, 07 May 2016 07:43:34 -0400 https://reprap.org/forum/read.php?1,659992,661196#msg-661196 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661196#msg-661196
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rklauco
motors overheated

How about reducing motor current? A printer design isn't at fault if you don't adjust such things properly, nor is the concept of having stepper motors.]]> Traumflug General Sat, 07 May 2016 07:39:41 -0400 https://reprap.org/forum/read.php?1,659992,661139#msg-661139 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,661139#msg-661139 Would it be possible to make my own encoder strip? Say, I have a laser engraver and would like to make a different strip...( longer, more/less signals per mm, UV resistant material, etc...)]]> o_lampe General Sat, 07 May 2016 03:39:01 -0400 https://reprap.org/forum/read.php?1,659992,660969#msg-660969 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,660969#msg-660969
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o_lampe
I agree with your torque theory, but in certain moments you need this huge torque ( immediately ). At turning points of a move ( inertia ) or when you start to move you have to deal with more friction.
The PID is not very helpful then, because it's not part of the planner in firmware. You will reach the desired position eventually, but not necessarily in sync with the other axis/extruder.

In practice, you can usually tune your servos so that the maximum position error is comparable to that of a stepper. (Keep in mind that even when using microstepping the position error with a stepper can be up to +/- 1 full step.)

Regarding the motor torque issue in comparing steppers and dc motors, with steppers, the "holding torque" is the absolute maximum torque available, and it decreases with speed. At typical motor speeds used for 3D printers (5 - 10 rev.sec), the actual available stepper torque is maybe 1/2 to 1/3 of the holding torque. And as rklauco points out, because there is no feedback with steppers, you need a safety factor on top of that. While a DC motor has a much lower rated torque, the peak torque is maybe 5x the rated torque, and you can run at the peak torque for short periods as long as your average torque is no more than the rated torque.

Lastly, what you really want to do is compare the power rating of the motors (power = speed x torque). A DC motor may be rated for only 1Ncm, but the motor can deliver that torque at speeds up to maybe 5000 RPM. Meanwhile, your 7Ncm stepper is probably only delivering 3Ncm at 600 RPM. Hence the DC motor can deliver more power. The drawback with the DC motor, though, is that to get that the maximum power out of it for 3D printing applications, you usually need an additional 5:1 (or so) gear reduction beyond what you'd need fro a stepper.]]> LoboCNC General Fri, 06 May 2016 11:53:09 -0400 https://reprap.org/forum/read.php?1,659992,660962#msg-660962 Re: DC motor replacement for 3D printers https://reprap.org/forum/read.php?1,659992,660962#msg-660962
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o_lampe
I agree with your torque theory, but in certain moments you need this huge torque ( immediately ). At turning points of a move ( inertia ) or when you start to move you have to deal with more friction.
My current solution to this is to limit the jerk movement distance, provide safe acceleration and feedrate speeds.
However, if I succeed to get the planner part working ok, I think this will be way faster then my cvurrent "safe" 220mm/s.]]> rklauco General Fri, 06 May 2016 11:39:30 -0400