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Addidng extruder to EMC driven mill

Posted by goaran 
Addidng extruder to EMC driven mill
June 30, 2010 02:43AM
Hello,

i have a extruder controller 2.2 which uses a stepper motor as drive.
I want to wire this to EMC2 using the python scripts from sam: [github.com]
To wire it up i use the usb-ttl converter right? or is it easyer to use the rs232 port at the pc and use a max232 to use the uart?
Now my question.
normaly the i2c interface has to be connected to the extruder controll when driving steppers. I dont want to use the mainboard, so how do i tell the extruder controller to use the stepper? Do i have to change the firmware? if yes has someonde used EMC with a stepper extruder before so i can use that firmware or do i have to write it myself?

Thanks in advance..


my projects: [www.robotik.dyyyh.de] ...
emt
Re: Addidng extruder to EMC driven mill
July 06, 2010 10:23AM
Hi

I have added an extruder to EMC. I used the A axis output from the parallel port to drive the extruder stepper drive direct and use 5D G Code. I don't use the extruder controller at all.

If you use Skeinforge you can use replace.csv to get G code with extruder as "A" instead of "E" which is the reference the Host uses for the extruder.

Edited 1 time(s). Last edit at 07/06/2010 10:24AM by emt.

Regards

Ian
How about temperature control ?
I was thinking: If you translate the Reprap M-commands for controlling the extruder temperature into a bit pattern on the parallel port you could make the extruder choose from a set of preset temperature settings, For example:
Bit 0 1 Setting
-----------------------
0 0 200deg
0 1 210deg
1 0 220deg
1 1 230deg
The bits can be controlled by EMC's gcode for turning on cooling etc.
This way you eliminate the analog stuff from your EMC setup...
Re: Addidng extruder to EMC driven mill
April 28, 2011 06:17PM
Bigman: I don't know that there's any advantage to that? You still need a microcontroller to interpret it, so you're not saving on hardware. And as long as you have a microcontroller, you may as well use the built-in serial interface, which gives you a lot more flexibility and control...

It's true that there's a time delay on the serial link, but for temperature stuff that doesn't matter.

goaran :

For using an extruder controller with EMC2, you could use it as a "poor mans stepper driver". The default firmware (i.e. the mainstream mendel firmware for gen3) is set up such that the extruder controller "listens" to the state of two of the pins and behaves like a stepper driver using the on-board dual h-bridge chips. (i.e. it reads one pin for "step" and another for "direction") This is a "constant voltage driver" and doesn't work as well as the constant current drivers like the pololus or any of the other reprap stepper drivers. You also don't get any microstepping. (which is a noise problem more than a accuracy problem, really)

So this is a two step process:

1.Hook the serial up to the extruder controller (directly from USB on PC) (I think that works... hook it up the same way you would when burning the firmware!) and use that for temp.

2.Get a real stepper driver for driving the extruder stepper.

Or...

2. Hook up the extruder controller to the parallel port too, and use the "nasty hack" of the h-bridges driving the steppers. Read up on it before you try that though. Worst case, it'll either not work or you'll fry your h-bridge chips or both. In which case you'd need to get a new stepper driver anyway... so I suppose there's no harm in trying it, maybe it'll work.


--
I'm building it with Baling Wire
emt
Re: Addidng extruder to EMC driven mill
April 29, 2011 02:11AM
EMC reprap details here:-
[fabmetheus.crsndoo.com]


Regards

Ian
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