RepRap using DC Motors! June 07, 2014 05:24PM |
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Re: RepRap using DC Motors! June 07, 2014 05:32PM |
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Re: RepRap using DC Motors! June 07, 2014 05:33PM |
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Re: RepRap using DC Motors! June 07, 2014 07:08PM |
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Re: RepRap using DC Motors! June 07, 2014 07:35PM |
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Re: RepRap using DC Motors! June 07, 2014 09:21PM |
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Re: RepRap using DC Motors! June 07, 2014 09:27PM |
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Re: RepRap using DC Motors! June 07, 2014 10:37PM |
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Re: RepRap using DC Motors! June 08, 2014 02:06AM |
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Re: RepRap using DC Motors! June 08, 2014 07:15AM |
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Generation 7 Electronics | Teacup Firmware | RepRap DIY |
Re: RepRap using DC Motors! June 08, 2014 01:57PM |
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Re: RepRap using DC Motors! June 08, 2014 02:04PM |
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drmaestro
It may be wise to start with a smaller project, using a few DC motors and an Arduino Mega and programming it with the "processing" language to see if you can achieve the required precision for this type of project. There are tutorials on using DC motors with Arduino.
Re: RepRap using DC Motors! June 08, 2014 02:52PM |
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Traumflug
Teacup firmware has disconnected step pulses (dda_step()) from acceleration calculations (dda_clock()) already, so the task would be to collect positional data from the encoder strip and calculate appropriate motor voltage / PWM values according to the position.
I don't think that's simple, either, but if you don't try, you'll never find out how well it works.
Re: RepRap using DC Motors! June 09, 2014 07:46AM |
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Re: RepRap using DC Motors! June 09, 2014 07:46PM |
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Re: RepRap using DC Motors! June 09, 2014 08:13PM |
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mappler
As drmaestro suggests,I would recommend breaking this problem down to separate parts. It sounds like you already know that getting accurate, repeatable linear motion is going to be a problem. I think I would want to solve that problem before investing in the other portions of the project with less risk.
Perhaps start by building a 2-axis plotter? It would be much less effort to build a small rig that would move a pen or marker over a sheet of paper and write some simple code to draw some simple shapes. This would allow you to experiment with your motors and encoders and see what issues their might be for your design.
Re: RepRap using DC Motors! June 09, 2014 08:17PM |
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Dejay
I'm a total newbie to mechanics and electronics, but I think this idea has merit. Because if it works it would allow not only for less precision motors, but also for less precision mechanics, and cheaper costs. Backlash and other effects could be eliminated because you are measuring the precision not at the motor, but closer to the actuator, or the actual platform. For example a spectra line belt might wander on a pulley (or has this been solved?) and it wouldn't matter because the linear encoder catches that. Belt tension and vibration might not matter that much. For some projects like the Lisa Simpson, a high lead screw is needed (e.g. lead of 25mm or 1") which are expensive so people are thinking about a threadless lead screw (wheels on a smooth rod). Unfortunately threadless lead screws aren't very repeatable, but with a linear encoder it would work. Check out this thread about threadless leadscrews.
As a project, I would try a simple single linear guide rail, reading the optical encoder and adjusting the PWM with an arduino board, and then measuring the results with a "DRO". I don't have any experience with any of this this either though, but afaik the heater outputs of the usual printer boards output PWM so that might work to control acceleration of your dc motor.
Good luck!
Re: RepRap using DC Motors! June 09, 2014 08:28PM |
Registered: 10 years ago Posts: 210 |
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lucasmun09
Also, what is "DRO"? I heard of it but it is not ringing a bell for me. Thanks for your feedback!
Re: RepRap using DC Motors! June 09, 2014 09:32PM |
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Dejay
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lucasmun09
Also, what is "DRO"? I heard of it but it is not ringing a bell for me. Thanks for your feedback!
I don't know exactly lol! I assume it is a brand name for a large digital caliper. You can see it in the pictures that cozmicray made of his test rig. Basically to read the error manually when move the threadless lead screw nut back and forth.
I assume that the maximum acceleration that a specific system can take to safely move and stop at a specific position might could be actually autocalibrating / measured by the firmware. If you knew the firmware code inside and out, it probably would be very easy to add this to the basic motor movement function.
Re: RepRap using DC Motors! June 09, 2014 09:50PM |
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Re: RepRap using DC Motors! June 09, 2014 10:29PM |
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mappler
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lucasmun09
P.S, I still need a Z axis right? Cause I would need to lift the pen or the writing utensil some how!
You can "cheat" on the Z-Axis initially and either a) don't support lifting the pen or b) make lifting and dropping a "binary" up or down condition.
-Matt
Re: RepRap using DC Motors! June 10, 2014 04:15AM |
Registered: 14 years ago Posts: 7,616 |
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lucasmun09
To be honest, I have not really focused on the firmware and the coding part
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Re: RepRap using DC Motors! June 10, 2014 12:22PM |
Registered: 10 years ago Posts: 24 |
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Traumflug
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lucasmun09
To be honest, I have not really focused on the firmware and the coding part
You should. Building a printer with DC motors is the trivial part. Developing electronics and software to get it running is the meat. And no, I won't do this for you. :-)
Re: RepRap using DC Motors! June 10, 2014 04:02PM |
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lucasmun09
you know where I can get documentation about what you mentioned? Thanks!
Re: RepRap using DC Motors! June 11, 2014 11:14AM |
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Re: RepRap using DC Motors! June 11, 2014 12:03PM |
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Re: RepRap using DC Motors! June 11, 2014 04:16PM |
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Re: RepRap using DC Motors! June 11, 2014 05:06PM |
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Re: RepRap using DC Motors! June 11, 2014 05:22PM |
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Re: RepRap using DC Motors! June 11, 2014 10:32PM |
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vn
There are several similar threads on RepRap forum. People tried this many times before. However, I haven't seen any real success even though recently there have been several crowdfunding 3D printer projects deploying DC motors -- e.g Rappy, Micro, MOD-t and upcoming ServoStock. The truth is that, with existing technology, it is not possible for dc motor driven 3D printer to have the same performance (e.g. accuracy and speed) as those using stepper at the same price point. The beauty of simplicity and effectiveness inherited by the stepper motor is often taken for granted until people try to replace it with DC motor;-)