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Dual extruder with anti-ooze system

Posted by Petrus 
Dual extruder with anti-ooze system
April 01, 2013 07:24AM
I wanted a dual extruder since a long time, I could just put two extruders side by side but I would have issues with oozing and the two tips would need to be exactly at the same height. So I made this :

The unused tip is lifted by a few millimeters by a rocking mechanism activated by a RC servo, at the same time the tip is closed :

Test print from the video with a Black ABS / white PLA, the two plastics doesn't stick very well together, so the support is easily removable :

Stl files and sketchup assembly are available on the Heavy Mendel wiki page : [reprap.org]
open | download - dual_extruder.jpg (140.8 KB)
Re: Dual extruder with anti-ooze system
April 01, 2013 08:29AM
I've been considering something similar and it is nice to see it somewhere other than my mind.

Have you experimented with trying to do it with one stepper motor, using the servo as a way to choose which extruder's gears are engaged?

Re: Dual extruder with anti-ooze system
April 02, 2013 12:43AM
Very nice.

You could actually get away with one stepper in the middle and just have the gears engage when the mechanism moves side to side.

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Re: Dual extruder with anti-ooze system
April 02, 2013 07:23AM
Exactly, and in doing so you would reduce the mass of the carriage by quite a lot.
Re: Dual extruder with anti-ooze system
May 13, 2013 09:51AM
Did you have the chance to extensively test this? Is it a public design?
Re: Dual extruder with anti-ooze system
May 22, 2013 10:07AM
I tested it with a 12H white ABS/PLA print, the system didn't fail but I need to do some improvements on the ABS side. The print was contaminated by burned ABS that was in contact with the nozzle for too long.
I am working on a wipe system to solve this issue.
Re: Dual extruder with anti-ooze system
May 22, 2013 10:37AM
Oh well.. If you've got more videos of the current tests, feel free to post them. The system looks promising, it would be great if you could make it work.
Re: Dual extruder with anti-ooze system
May 23, 2013 09:37PM
Pretty sure Stratasys has a patent on a rocking dual extruder setup. You're probably ok for personal use but you may want to look up the patent before you sell/release it.

I like your nozzle wiping solution, that's pretty clever.
Re: Dual extruder with anti-ooze system
May 27, 2013 03:38PM
I'm currently experimenting with dual extrusion too and after googleing for a good anti-ooze solution I found this topic. I really like the concept and would like to test this at home. I already downloaded the files and made some changes to fit everything on my printer. The only thing I don't know is how you control the servo to move the nozzles up (and down) when needed. Do you connect the servo directly to the pcb, change the firmware and use some special gcode? Or do you use another (easyer) way to do that? smiling smiley

Thanks in advance and keep up the good work! grinning smiley


Edited 2 time(s). Last edit at 05/27/2013 11:47PM by isphording90.
Re: Dual extruder with anti-ooze system
May 29, 2013 06:35AM
The servo is driven by a circuit that generate the PWM signal for the two servo positions according a digital input : [reprap.org]
My printer works with linux CNC so I use an output on the parallel port.

I added a wiper for the ABS nozzle at the beginning of the X axis :

And just printed that with it :
Time-lapse : [youtu.be]

There is still some brown ABS on the print but it's much better than before.
Re: Dual extruder with anti-ooze system
June 23, 2013 09:03AM
I changed the electronics to switch between the two extruders. Driving the servo with its electronics was a bad idea, the position was changing with temperature and forcing too much on the ends. Now, I drive directly the DC motor in the RC servo with this circuit :
The current is limited to 400mA during ~0.5s and fall to 200mA after to maintain the position.
The schematic and layout are available here : [reprap.org]
Re: Dual extruder with anti-ooze system
August 01, 2017 12:01AM
that's a great project
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