[Swansea Hackspace] An old PC with parallel printer port?

[Justin Mitchell]

You do (mostly) still need a PC.

Idea is :-
Software on pc sends g-code down USB to arduino
arduino does the timing critical stuff down the parallel port

If the arduino is running Marlin firmware then you can use any standard
reprap style gcode sender, such as Pronterface, or possibly even
OctoPrint.

If the arduino is running GRBL then there are specific gcode senders for
that such as grbl-controller, Grblweb, etc

http://zapmaker.org/projects/grbl-controller-3-0/
http://andrewhodel.github.io/grblweb/


either way you remove the need for a pc parallel interface, and also
remove the timing critical stuff the pc was trying to do, which desktop
class hardware is just not good at.

Whilst firmware like Marlin can do stuff like printing from SDCard  (and
run its own little LCD based UI) the speed of print is lower, and its
more difficult to stop it, so using sender software is preferred.



On Wed, 2014-09-17 at 12:56 +0100, Graham Owens wrote:
> Perhaps i am missing something still, but how exactly do you control
> these things without a pc? I understand the how of toggling pins etc,
> but i mean the practical aspect of actually setting up the machine and
> running it?
> 
> Ho for example do you do a touch-off on an arduino controlled cnc?
> 
> > On 17 Sep 2014, at 12:38, Justin Mitchell <justin at swansea.hackspace.org.uk> wrote:
> > 
> >> On Wed, 2014-09-17 at 11:44 +0100, Justin Mitchell wrote:
> >> So after we have jury rigged one using a standard arduino, we can then
> >> mill the pcb for a custom made one :)
> >> 
> >>> On Wed, 2014-09-17 at 11:39 +0100, Gerrit Niezen wrote:
> >>> It seems a solution appeared on Hackaday the same day that you were
> >>> discussing the problem:
> >>> http://hackaday.com/2014/09/16/usb-to-db25-adapter-uses-grbl-for-parallel-port-cnc-communication/
> >>> 
> >>> 
> >>> Guess what: It’s Arduino-based and runs GRBL.
> > 
> > This also seems to apply to laser cutters, at least the cheap ones with
> > parallel port connectors. They appear to be the same level of dumb
> > step-stick style driver inputs that many CNC machines are.
> > 
> > So a cheap laser cutter could be adapted to work (the supplied software
> > is notoriously bad) without even changing the electronics.
> > 
> > Further research has shown that these cheap cutters tend to have two
> > control boards, one is the psu, and connects to the safety interlocks,
> > the HV laser tube drive, stop switch, etc.  this in turn gives 5v, laser
> > trigger, and motor drive voltage (24V?) outputs.
> > 
> > the second board is then the stepper controller / interface board,
> > theres often just two steppers X/Y, end stops, and the TTL level laser
> > on/off trigger, which can be driven with PWM for finer control.
> > 
> > So replacing the stepper controller with something more modern is going
> > to be pretty easy if you need to, but if its a parallel port one you can
> > just as easily put an arduino with GRBL/Marlin on the outside and get
> > the same level of control.
> > 
> > 
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