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DC motor extruder control

Posted by alex.me 
DC motor extruder control
January 29, 2017 12:58AM

I have a problem and was hoping you could help.

I am building a 3d printer from "junk" .
So far i was able to make the x,y,z axis work , even tested them with a pen n paper since i cant use extrusion wich is where my trouble comes in.

Im using an arduino uno board to control everything and the Teacup Firmware. Its all nice and good until i get to configuring it to use a dc motor extruder.
The reason for the dc motor is i also built the hot end myself and the extruder using gasstove nozzles and such. Happy to say it extrudes plastic if i run the motor.

Now if someone could explain to me where and what i should define in the printer.h and board.h files of teacup , or the config tool and how to configure / determine the pin i need to use to send controls.

And before someone says "just use a stepper" thats a no no . I have to use a dc motor beacause of a future mod i might do to it.

Ty in advance and sorry if i didnt post in the right forum or if my post is in some way bad.
Re: DC motor extruder control
January 29, 2017 06:16AM
What are you using as a dc motor controller? as it depends on what signals its expecting.

This is what we used to use [reprap.org]

A3949 H-bridge motor drivers so there may still be some legacy code about to control these.. But even then it expected a external controller board

I Would definitely ask in the Teacup firmware forums.

Edited 1 time(s). Last edit at 01/29/2017 06:19AM by Dust.
Re: DC motor extruder control
January 29, 2017 03:27PM
Sorry for being so dry on the details, to be honest im not even sure where this will go since its mostly a development / experimental rig (i like tinkering with "unconventional") stuff.
My ideea was to somehow use teacup to give a simple on/off signal to the dc motor, wich woul be preferably be controled by a mosfet. ON motor turns and extrudes, OF motor wont turn, wont extrude.
Was thinking of this because later i might fit some different things wich will be on / off as well no direction control etc (like an electrovalve for example, or an LED for light painting ... justto give some sort of ideea about what im aiming for)
Wich is why i was hoping someone could tell me how to cofigure teacup to drive a dc motor as an extruder or if it is even possible to do something like a simple "on / of" system in Teacup. I might equate this to the grbl spindle on and spindle off capability.
Ty and i hope it wasnt too vaguetongue sticking out smiley
Re: DC motor extruder control
January 30, 2017 05:30AM
Extruding with a simple On/off signal to a DC motor? No speed control or encoder? That'll be fun, make sure you have a camera at hand smiling smiley
Re: DC motor extruder control
January 30, 2017 09:56PM
Oh you bet i'll have a camera at hand when trying "unortodox" stuff grinning smiley
But as i said its not just about extruding, its abot being able to control other things, say for example if you have someting with a constant precise uncontrolable speed, or things that dont have a speed like the light painting example above, wich would just be an on/ off led

Just to clear things out a bit, for plain 3d printing i can and will use a stepper motor for the extruder, but my ideea is to use this platform for other stuff.

I might just try hooking the direction pin to an oscilloscope to see how the signal looks , but i will have to wait for an osciloscope to arive tongue sticking out smiley
Re: DC motor extruder control
January 31, 2017 02:00PM
I don't know the rambo card but look on the schematic for a fan pin that is driven through a transistor. You can hook up a dc motor to this and control the speed with pwm the same as you control a fans speed.
You will not be able to run it in reverse with this.
Any spare pin can control an external FET to drive a motor as well.
Re: DC motor extruder control
February 01, 2017 09:17PM
Ty for the info george i wil try that,

To elaborate on what im trying to do

I used to work in a factory where we had a machine that was embossing models on different materials using a kind of silicone wich was sprayed with a very thin jet.
The spray head itself used compresed air and an electrovalve wich opened and closed to spray it.
That is one of the setups i want to try out, wich is why speed control is not crucial, since the head itself does not have speed control.

As of now im still brainstorming, since im waiting for the head itself to arrive, and then i'll need to fix it , cause thats why im getting it (most probably either cloged or the valve is screwed).
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