David,

Here are all three tach adapters finished machining. Took about 8
hours per adapter.

I was rather surprised to see two contactors wired in parallel. It
appears to be the 3 phase for the knee motor. That huge motor can
probably lift 500 or 600 pounds.

I guess back when the Kasuga was built they did not have contactors
with enough current.

"A contactor is an electrically controlled switch used for switching
 an electrical power circuit, similar to a relay except with higher
current ratings and a few other differences A contactor is
controlled by a circuit which has a much lower power level than the
switched circuit."


I have a new invention I will upload shortly for simplifying some of
 this rat's nest :-)

Paul Lamar


Looks great. I switched to solid state relays, use 5vdc data to
control, no contractors to have carbon Build up or wear out.

David Mikesell San Jose California

Is the idea to turn off all circuits if a limit switch opens some
where?

So all limit switches are in seres? What would the schematic look
like?

I am thinking of a Maxmite and a LED panel that tells you which limit
switch opened.

Or is that feature built in EMC ?  Is it in Mach 3 ?


Paul Lamar

You can put all limit switches in a series So if  anyone of them
opens it goes into e stop, or if it's in homing it takes that as a
limit to whatever axis was moving. It works that way in mach3 also
EMC. I personally wire each one individually as an individual home
switch and it also acts as a limit switch. And then I use software
driven soft limits while running to make sure I never actually hit
the switch when the machine is moving.

David Mikesell San Jose California

Thanks David

I'll  think about that so more.

What is the limit switch voltage?


Paul Lamar

It's a 5vdc logic circuit.

David Mikesell San Jose California


I guess that is the reason some of the Kasuga docs I have recommended
running the limit switch wires in separate conduit. Unfortunately it
was NOT adhered to on this original installation. But I will fix that
and run them in separate conduits.

I am guessing but that would partially explain the dozens of
capacitors used on all the high voltage wires.


Thanks David

Paul Lamar

Paul,

You should also used shielded two strand twisted wire for the limit
switches. You can get false signals from other wires, encoders should
also be shielded to prevent errors.


David Mikesell San Jose California


Personally, I wouldn't connect the limit switches to the E-Stop. It's hard on drives, plus if your homing the machine to the limit switches, you're stopping the drives when you do. Limit switches can be configured to motion stop, or pull power from the drives via software and are then not hammering the drives from the power side if the switch is hit.

I'd also not recommend contactors (or SSR's) between the drive and motor, a good way to blow servo drives.

I agree with shielded wiring, limit switches, encoder wiring and your spindle wiring if it's controlled via vfd.

At least, when I built my mill it's how I did it. Ran very well, never blew a drive. I ran my wiring in a common cable carrier with ~25' of cable all running beside each other and no noise issues. I also star grounded my system, which I think helped with those potential issues also.

Fwiw
Jarrett Johnson

I am not using contractors on the servo drives.

On the spindle motor I am using a Speedcom 3 phase motor controller.
I suspect the EMC software can turn that off depending on the logic.

At least I think so. The limit switches probably feed into the EMC program
and it decides  when to stop an axis drive or the spindle motor.

Is that correct David?

So far I have not found that in the EMC docs. Does not mean it is not there.
As I learn these tidbits of info I have to read the EMC docs again
and again so I learn more and more in the process.

I am saving the contactors for the 3 phase  knee motor which will not
be tied into the EMC software. It will be strictly controlled
manually. I still need a schematic for that. Either that or a good
book on 3 phase motor wiring.

Jarrett, what software did you use for your NC mill?

Paul Lamar

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