Slaved axis, 2 steppers on Y axis with a PLC4x-G2 ? what about the XP23 connector ?

[pierantoine]

Hi,
You are right, i have the confirmation from Purelogic that there is no hardware solution to a slaved axis solution and that "Usage of one channel for two drivers-motors controlling" But i think that the AM882 requires to much current for this solution.
but there is a topic where i could read that there is a big interest un doing this in mach3 to auto-squaring the gantry with the limit switchs.

I will also have a problem with the relay because i have a 2.2Kw spindle wich seems to much for the onboard relay... maybe a relay controlling another one with better current specs.

"If it can helps here is some infos that i've received :
In XP23 connector there are pins control outputs, PWN, enable.
When necessary these pins can be assigned for extra axis control. (it can be slave as well as independent)
You can also connect up to 6 axes to PLC4x-g2 (instead of the relay and spindle speed control).
If there is no such possibility, there is a perfect solution such as PLCM-E3 and PLCM-B1."

[JAZZCNC]

Using one signal to control 2 drives is not recommended. It as nothing to do with the current setting on the drive it's to do with Resonance and how the drives compensate for resonance.
If using just one signal then resonance compensation on one drive can throw the other into resonance and vise versa. This can lead to poor performance, stalled motors or lost steps or mixture of all 3.!!

It's standard practise to use the Limit switches to square the gantry.
The way Mach and most Motion control cards home is to decouple the slaving feature while homing and drive each motor individual but simultaneously towards the home switches. Which ever switch is triggered first that motor is stopped and reverses off the switch while the other keeps going and does the same. When both motors find a switch the homing is finished.
In practise this is very difficult to see. If Gantry is square and switches are correctly set then Both motors will stop/reverse exactly together in one seemless action.

Also the Relay will be fine with 2.2KW spindle. I think you maybe don't fully understand what the relay is used for.?

It's only used to switch on/off low current signals that control the VFD. You don't use it to turn on/off power to the VFD.
Cutting power to the VFD while spindle is spinning is not recommended so never do this. Always stop the Spindle with the VFD Stop input then remove power.
Also NEVER put any switch or Relay between the VFD and Spindle other wise you risk damaging both.

Paulro's problem was a simple set up issue and slight wiring problem go check is thread to see why.

[pierantoine]

Ok, thanks for this informations, very instructive.
maybe you could write a "Cnc builder's guide" Book that "do's and don'ts" the beginner in electrical, mechanical aspects.. (seriously).

"It as nothing to do with the current setting" yes, for sure ! i was talking about the current of the signal,input signal current for an AM882 is typically 10mA, minimum 7mA minimum.

> Also the Relay will be fine with 2.2KW spindle
Good news ! +1 point for the PLC4X-G2

> I think you maybe don't fully understand what the relay is used for.?

yes it is not very clear for me, the confusion certainly come from the 30A relay for the spindle on the pmdx-126 and 10A for auxilliary,
maybe it is as you said "not recommended" but they do this just in case you want to do it, or something like opening the power circuit while the watchdog isn't received.
http://www.pmdx.com/pmdx-126

• Provides one 30 ampere rated electromechanical relay useful for spindle control
• Provides one 10 ampere rated electromechanical relay for auxiliary functions

But if using low current is safe and is the standard practice i'll do like that.

[Boyan Silyavski]

Relays are very simple. You have signal output on your board - you could add external relay for 2$ each. You only need to have the output so it triggers the relay with 5-24v, having in mind that the LPT breakout boards have limited number of inputs and outputs and the more industrial boards could have 50 digital inputs or outputs or even 100.
Some boards have integrated a couple of relays for the coolant, spindle and so, some dont have. As i said relays are very cheap.
Thats all you will ever need to know.

[JAZZCNC]

Ok, thanks for this informations, very instructive.
maybe you could write a "Cnc builder's guide" Book that "do's and don'ts" the beginner in electrical, mechanical aspects.. (seriously).

Yes been asked that many times.!! . . . . Same answer.!! The days are not long enough now so certainly haven't got time to sit down and do this.!

yes it is not very clear for me, the confusion certainly come from the 30A relay for the spindle on the pmdx-126 and 10A for auxilliary,
maybe it is as you said "not recommended" but they do this just in case you want to do it, or something like opening the power circuit while the watchdog isn't received.
http://www.pmdx.com/pmdx-126

• Provides one 30 ampere rated electromechanical relay useful for spindle control
• Provides one 10 ampere rated electromechanical relay for auxiliary functions

Well your kind of right but still wrong.!!
The relays built into the PMDX and Other Bob's do show there relays controling spindle power. But these are Spindles like routers, Kress etc that use AC mains voltage directly. They don't use them or recommend using them for cutting power to Spindles controlled thru inverters.
You will damage the VFD sooner or later if you do this.

Regards the Sharing of Signal to control 2 drives then again Current won't be the issue and it will work even with the AM882. But It won't work correctly as you'll get all kinds of strange behavor mostly revolving around pulse timing and resonance issues.
Unless you like wasting time then best avoided.!!