Re: [CAD_CAM_EDM_DRO] Bridgeport CNC Mill???

"hanermo" - CNC 6-axis Designs wrote:

> Jon .. a Q at top ..
>
> Does EMC23 support multiple spindles in lathe, mill or both ?
> With step/dir control, or +/-10V or something ?
>

Do you mean live tooling? I think it CAN support this. There has been
discussion
for some time on how you switch between a (main) spindle and a C axis,
and there
is no consensus on the best way to do this. If you use it as a spindle,
the spindle
encoder will wind up to a large value. If you then switch it to the C
axis, you have
to get rid of the large number of accumulated rotations. One way, of
course, is
to have to home the C axis every time you switch from spindle to C.

I believe this is the only thing that hasn't been nailed down for support of
live tooling-type operations.

Since EMC2 supports custom kinematics, then having a lathe-type machine with
an aux spindle and making the main spindle a positioning C axis seems
not too hard. Maybe there are some other gotchas like how to handle cutter
radius offset for lathe tools against the spindle, and also for the live
spindle
against the work on the C axis. I've never run a machine like that, so
I don't
know all the intricacies.

OK, reading down to the bottom, it sounds more like you are interested
in multi-spindle
routers. Well, of course, a multi-spindle duplicator would be no
problem, and even
if the other spindles needed different Z offsets, this could be done
with some trickery.
But, multiple, totally independent spindles is a real problem. There is
no way to
specify this in the G code. You'd have a separate X, Y and Z for each
spindle.
Is that the kind of multi-spindle you are talking about?

>> WHAT "max rate" exactly, is "far too low" on EMC?
>>
>
> The possible max servo speed that emc2 supports directly in software,
> wiht the PP, qwithout additional hw, just as I said, you said, emc2
> manual said.
> And that has been used endless times as a justification for emc2 ... "it
> supports servo !"
>

My boards do not send software-generated steps out the parallel port.
The board reads the
encoders, and sends a position report to the computer when asked. EMC2
computes
a new velocity and sends it out to the board. The board then converts
this to step
pulses, a pulse-width modulated signal, or an analog voltage, depending
on the
type of motor drive. This is done at the default rate of 1000 Hz, or
other rate you select.
"Max servo speed" ie. velocity is unbounded. You do want to have a
reasonable distance
traveled per servo cycle. It does become a consideration somewhere
above 400 - 600
IPM.

>> I could send you the program if you'd like to compare.
>>
> You are an authoritative source.
> I will try to run it on a lathe or grinder, later this fall, with interest.
>

Well, I'm having trouble finding this program. I know it is on one of
the computers here.
I'll let you know when I find it.

> On teh other hand, very good large step/dir servos are now available
> from many sources, and they are getting more common, cheaper and better
> all the time.
>

But, the problem is driving them with software-generated step pulses is
a really GROSS
solution. For instance, my minimill happens to have 128000 encoder
counts/inch,
due to 500 cycle/rev encoders on the motors, 4:1 belt drive to 16 TPI
leadscrews.
At 60 IPM, this would require 128000 step pulses/second from the
parallel port.
Doing this at all with software is iffy, and the timing resolution is
going to be
rough for sure.

Driving a servo amp with an analog signal is much easier, you only have
to update the
velocity a few thousand times/second. The 16-bit DAC on my PPMC analog-out
board provides 32,768 discrete velocities in each direction.

> Also with support for brushless ... which is great news.
> For all of us, regardless of the sw platform.
> Step/dir is a simple std that provides for easy vendor independence, in
> my experienec, and in my opinion.
>

Step/Dir is very simple, and for desktop machines with steppers and
lower positional
resolution, it is FINE. No argument. But, for higher resolution,
faster movement,
and true servo operation where the computer is monitoring position all
the time,
it leaves some things to be desired.

>
>> You really need to check out what Stuart Stevenson has done with his
>> Cincinnatti 5-axis
>> machine. He has some interesting Youtube videos of it doing a ball test
>> showing the
>> accuracy of 5-axis coordinated motion. I really don't think you can do
>> this on Mach
> Of course you can do this on mach3.
>

No, Mach is a 3-axis cartesian program with additional coordinated axes
added on.
And, that would be fine for me, I have no desire to get into 5-axis
machining.

But, EMC2 allows you to PROPERLY handle multi-axis coordinates. So, you
can have
EMC2 aware of all the links and joints in the rotary axes and how they
affect tool
position relative to the table. So, as you rotate the B axis, the X
slide will move to
keep the tool tip correctly positioned relative to the workpiece. This
allows you
to generate 5-axis programs that do not need to be adjusted for the
specific machine
and the offsets between all the joints, etc. Chris Radek has a video of
cutting s
sphere on a 5-axis machine, and at least a lot of the hard work is done
by EMC2
in handling the machine's specific kinematics.

> No kinematics in mach3.
>
> OTOH, kinematics correction is not really on my list of things to have ..
>

Yeah, just thinking of all the special cases that make the math more
complicated
just makes my head hurt.

> But things like absolute e-stop with maintained reference woud be nice.
>

Well, I've had that since 2001 on the PPMC, and any of my boards with
encoder
feedback will do it. You can punch E-stop and move the machine
manually, maybe even
touch-off with an edge finder manually, and then go back to CNC.

Jon