Re: 3D printer progress

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@...> wrote:

> Seems there's got to be a way to shift from dance and pre-print to
> carriage travel... Cuz that's the only way we're gonna seamlessly
> use existing printer routines...

The way I intend to do it is to monitor the paper feed encoder, detect
the high frequency when it actually feeds (much faster than dancing)
and then take over control. Its not seamless but as the system is
going to need something to control the supply/build bins anyway and
will already need two stepper drivers why not have a third. It also
means you can size the gantry motor appropriately for carrying the
counter roller or whatever else.

There is a way to mechanically do what we want but its only half the
story, the printers themselves have a special mechanism that means
that when the paper roller goes in the reverse with the print head in
a certain position a clutch/ratchet engages and the paper pick up
roller turns, you could in theory make some kind of clutch system that
works on that principle.

But even then you have to mess around to get the gantry to return, its
actually easier to just take control.

>copiers, so parts and replacements should be easy to get.

I wondered about some form of electromagnetic clutch, it would make
engagement easy but you still need to mess around to do the reversing
for gantry return (assuming you don't want to sit there for an hour).

> Trying to cover your back<G>,appreciate your efforts,

Please keep on thinking, I'm bound to miss all kinds of options.

> P.S. Doesn't the propeller seem custom made for multi-axis motion
> control!?

Yes, in fact I implemented Grex type pulse generation in about 10
lines of code, each processor has two counters that can be used as
programmable numerical oscillators, so each cog can generate two pulse
trains well into the 10's of Mhz without doing anything, so you set a
fixed length loop up to act like the Grex interrupt and modify the
frequencies each time just like the Grex does.

What I haven't done is the pre-motion calculation stuff, if you read
the G-rex documentation and follow the example you will see that it
doesn't work for just any old maximum velocity and acceleration
because of the way it works, you need to tweak these so you end up
traveling the correct distance.

Graham