Re: Digest Number 197

From: Jon Elson <jmelson@...>
Subject: Re: Re: My CNC Mill retrofit project

Andrew Werby wrote:

> [I was intending to keep as much intact as made sense- is it possible to
> keep both control systems alive at once?]

I actually did this in the early days of EMC, when there were a lot of bugs.
It took about 5-10 minutes to change things over. But, the servo amp
tuning really needed to be tuned specifically for each control. I found a
compromise during the time I had both hooked up, but it was a bit flakey.

[I was afraid this wasn't going to work. What exactly does "tuning" a servo
amp entail? I didn't notice any knobs or anything on the amps I've got-
what do I have to adjust, and what would I be looking for as a result?]

> What about the feedback loop-
> how do I find the output from the encoders?

Well, first thing is to find out what is in use for position readout, shaft
encoders,
linear encoders, resolvers or inductosyns. Could be any of the above.

[What I find on my diagram is something called "TTY", coming out of the T4
plug. I've got TTY In, TTY Gnd, TTY Source, and TTY Signal. On the same
plug, I've got RS-232 In, GND, and Out. On the T3 plug, I've got F.O.S.
3,2,1, & 4, plus S.O.S. 3, 2,1, and 0, Ch A and Ch B. I'm not sure what
this all is- any hints? I couldn't find anything actually labeled as
position readout encoders, resolvers, etc.]

> Does the EMC program require I
> use a STG board or the equivalent?

Pretty much at this point. At some time, other I/O boards will be supported,
but the STG is by far the most compact solution - everything except
auxilliary controls on the one board.

[And I can use the existing auxilliary controllers without a conflict?]

> I think the relay (CR2)
> labeled MAN. TOOL CHANGE is probably just for a tool change light or beacon.
>
> [Does this turn the machine off in the middle of an operation, so one can
> change tools and resume?]

Not exactly. Other commands in the program would bring the machine to a
stop, and position the spindle (if equipped for spindle Z motion) at full up.

[The spindle does do the Z axis moves- the knee is just an ordinary motor.]

Perhaps the tool change command puts the CNC in a wait condition, and
either a continue key or a switch closure from the tool changer tells it to
continue.

[It's got Emergency stop, Opt.Stop, and Feedhold- plus Tool Change Reset
and regular Reset. Is it one of these? ]

> My big question is what are the characteristics of the interface to the
> Lovejoy spindle drive.

Well, the spindle drive probably gets power whenever the machine is out
of E-stop, and the speed would be programmed by either +/- 10 Volts
(more common with DC servos) or a contact closure for each direction and
0 to +10 Volts for AC drives. Might also be a spindle brake signal, and
a spindle ready signal going back to the CNC. You should also check to
see if there is a spindle encoder.

[I know there's a spindle brake, but I haven't figured out if the servos
are AC or DC, though I'm inclined to believe they are DC, to account for
one of the transformers. There is also a spindle error opto, but I'm not
clear what sort of error sets it off.

> [I thought that was the most straightforward connection of the lot- isn't
> it hooked directly to 3 phase 220 (after the fuses)? Then there seems to
> be a 5amp(max ) 110 volt control circuit to change the speed and a spindle
> error opto , as well as 2 optos for spindle CW and CCW. But now, looking
> at it more closely, it seems like there was a modification made, because a
> new spindle speed board is drawn in by hand on my schematic, coming from 92
> on the terminal block. I'm not sure how this corresponds with reality,
> though.]

Hmmm, a little hard to say, but a variable speed command signal would be
most useful.

Jon

[The Lovejoy provides the variable speed to the spindle (I'm pretty sure)
so I'm thinking the 110 volt command circuit must be controlling that.
There's a "Speed Detector Input" coming from the above-mentioned terminal
92, so perhaps that's the spindle encoder you were asking about. Anyway,
thanks for jumping in on this thread- as you can probably tell, I need all
the help I can get...]

Andrew Werby

Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com