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

[Graham Owens]

I think I would have to see it to understand properly, as I cannot figure
out how the arduino can calculate the kinematics in realtime, as this
information is not contained in the gcode, and also how you would touch off
the workpiece (touching off usually (for me anyway) involves moving the tip
of the tool to the datum for the cut to within a cigarette paper's width
(why machinests who do not smoke carry cigarette papers), moving.  after
this point i guess you could run from the gcode arduino device (assuming
that kinematics are handled)

Would it be possible for the interested parties to meet up at the space one
night this week (pref not friday) and we can get it set up, i can show you
how I use the machine just now, then then you guys can figure out how to
run the same thing without a permanent PC in the loop.

PS just had a better look at the grblweb tool, that could work assuming it
was almost realtime for touching off, and there is some security to lockout
anyone who is not actively using the machine

On 17 September 2014 13:31, Justin Mitchell <justin at swansea.hackspace.org.uk
> wrote:

> 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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