Ready Steady Eddy

[EddyCurrent]

In the interest of practicality I'm proposing these changes

*emergency stop button pressed - strategy 1
*limit switch activated (NOT home limits) - strategy 1
*Charge Pump error - strategy 1
*'Stop' button pressed - strategy 2 or strategy 4
*spindle over temperature switch activated - strategy 5
*Stepper driver alarm relay activated (e.g. AM882) - strategy 2

The reasons being,
* If the spindle is overtemp then sound an alarm and let the operator take action at the Mach3 screen or otherwise.
* If the stepper driver alarm relay operates then it should be sufficient to issue the 'enable' signal, if not then the emergency stop can be operated.

finding a suitable off delay for the VFD contactor AT THE RIGHT PRICE is proving a challenge right now. There are some cheap ON delays which could be used but would not be fail safe.

[EddyCurrent]

This seems to be the document required, have not read it yet but the title is "Application Note
Interfacing AC Drives with Safety Relays"

http://www.ab.com/support/abdrives/p...lays_Rev04.pdf


Also a section in this

http://www.bara.org.uk/info/safety/A...pplication.pdf

[cncJim]

finding a suitable off delay for the VFD contactor AT THE RIGHT PRICE is proving a challenge right now. There are some cheap ON delays which could be used but would not be fail safe.

This seems to be the document required, have not read it yet but the title is "Application Note
Interfacing AC Drives with Safety Relays"

http://www.ab.com/support/abdrives/p...lays_Rev04.pdf

Excellent doc eddy, spot on. Also very handy as it details hooking up a AB msr138dp which I have just bought on ebay for £30! After looking into the specs there are 10 different varieties (various voltages/delay ranges) and I think this is the right one/most useful (hope so, I've bought it now!) - 440R-M23143 (24v - 0.15 - 3 seconds delay)?

Also, I spoke to the guy and he said he has another which he is willing to sell for the same price. Let me know if you are interested eddy and I will pass on his number

Cheers.

[Boyan Silyavski]

Kill all power, no doubt.

Here is how i have my CNC working:

-the PC id surge protected and connected to a 1500w UPS. Also the CNC is conected there
-the VFD enables the BOB
-the charge pump enables the BOB and the VFD

Typical everyday scenarios:

Power interruption from outside of the house. It happens a lot here in Spain. Or a fuse trip. I have a lot of stuff at that fuse :-)
-the VFD stops and stops Mach3. I go and see which line the process is. I write it down on a piece of paper. If power comes for the next half hour , i just continue from there. If not, i stop the PC and when i have power again, simp[ly continue from the line.

My mistake
-Spindle digs, VFD trips, Mach3 stops, Usually reset, lift the Spindle, check Z0, usually that is the mistake, Z0 and voilaaa

Mach3 goes down and decides some crazy movement. Happens rarely but happens.
-the bit digs, spindle stops and trip signal stops the process. if nothing is damaged, i check the xyz0 and if ok i continue from there, if not, i throw in the garbage and do it again

PC stops, restarts alone or whatever similar.
-VFD stops

I hit the EStop
-no power to the drives, no power to the BOB, VFD stops

I greatly recommend a pause button also on the machine. Sometimes when not sure what is happening if nothing crashes is better to just pause the process and contemplate. Though an extra second is lost meanwhile

[EddyCurrent]

I greatly recommend a pause button also on the machine. Sometimes when not sure what is happening if nothing crashes is better to just pause the process and contemplate. Though an extra second is lost meanwhile

What would you have it do ?

Stop the VFD
Send a FeedHold signal to Mach3 and let it control the stepper motors


Is it not just as easy to do it from the PC ?

[Boyan Silyavski]

What would you have it do ?

Stop the VFD
Send a FeedHold signal to Mach3 and let it control the stepper motors


Is it not just as easy to do it from the PC ?

Sometimes i am not sure what happens, so i just hit the pause / feedhold/ button, instead of the estop. Spindle still rotates and i check. if everything ok, i hit the "cycle start" button which is also at the machine, so everything continues, as if nothing have happened.
The keyboard is 2m away in my case, so its not easier.

I do this if i want to check if the material has loosened on the fixture, clean some bearings, remove sticks from the vacuum shoe and so, without further interrupting the process.

On next machine i will have flood and vacuum buttons also. Sometimes when i want to do something with the keyboard i accidentally touch the wrong buttons. last time somehow i zeroed the machine coordinates. So had to stop, go to home, zero again, get out of Mach3,save fixture, then again in, zero on the work piece and start again the job.

[Boyan Silyavski]

Eddy,
what is this one: *spindle over temperature switch activated ?

Where did you find a cheap temperature sensor with digital display that has a contactor or signal at programmed temperature?

I have bought a cheap 7eur battery one with temperature alarm, and thought of using the alarm output ~3v to connect to the BOB, but forgot about this project.

Once i accidentally switched off the water pump and spindle worked all day before i touched it and saw it was hot. Nothing happened. Still works. Though was just V carving.

[EddyCurrent]

Good timing lads !

@silyavski, the temperature switch was already built into my spindle, it is closed normally and opens at high temperature.
@cncJim, see latest drawings

Here are my latest drawings



Features
---------
Strategy 1

* Emergency stop immediately signals VFD to stop and several seconds later (time to be assessed but possibly 6 seconds) delayed contacts of Guardmaster safety relay open to operate STO (Safe Torque Off) feature of VFD which disables control voltage and power semiconductors.
* Power removed from Stepper Drivers via Guardmaster safety relay and K1
* Stop command issued to Mach3 via K1 (even if Mach was still active the VFD and Stepper Drivers would still be disabled)

Strategy 2

* Stop signal sent to VFD via K3 relay
* Stop command issued to Mach3 via K3
* Enable (ENA) signal activated via Mach3 and BOB to disable stepper drivers

Strategy 3

Not implemented - same as Strategy 2

Strategy 4

* Stop signal sent to VFD via K4 relay
* FeedHold command issued to Mach3 via K4
* Enable (ENA) signal activated via Mach3 and BOB to disable stepper drivers

Strategy 5

Not implemented


Notes:

Strategy 3 could be implemented by incorporating a relay contact from K3 into K1 coil circuit however because all 4 contacts of K3 are being used another single contact relay would have to be connected in parallel with K3.
Strategy 5 could be implemented by removing the Pause push button and having only K4-4 contacts operational.

* A PAUSE push button has been added, this will stop the VFD and send a FeedHold signal to Mach3, to continue the ON (RESET) push button is pressed.
* A Charge Pump relay has been added to the Emergency Stop circuit this so the system can initiate an Emergency Stop if the software stops or communication is lost.
* If the Circuit Breaker for the Stepper Drivers trips then K1 will de-energise and send a STOP signal to Mach3.
* ENA signal now connected from BOB to all Stepper Drivers

( ** As yet I have not cobbled together the Charge Pump relay but I think a small 5v coil one will do the job as my BOB can source 20mA. **)

Relays K2,K3 and K4 are these
http://www.ebay.co.uk/itm/1set-Base-...item5d388b7d84

[cncJim]

Good timing lads !

...

( ** As yet I have not cobbled together the Charge Pump relay but I think a small 5v coil one will do the job as my BOB can source 20mA. **)

Good stuff EddyCurrent, I'm still working my way through your diagrams trying to fully understand :) - Do you have any provision for activating your estop circuit from the controlling software? I suppose the argument could be made that its not needed unless the pc a distance from the machine?

Relays K2,K3 and K4 are these
1set Base+OMRON coil power relay 14pin 4NO 4NC MY4NJ MY4N-J 5A DC24V 4PDT | eBay

I have just acquired 10 of these from a control panel I stripped down (7x 24v and 3x 230v) which seem to be a similar spec to yours:-

Finder TYPE 55.34
The 5A rating, is that for the entire relay or for each contact?

There are also 4 contactors which I haven't taken out yet. Are there any practical/safety differences between a relay and a contactor?

[EddyCurrent]

Good stuff EddyCurrent, I'm still working my way through your diagrams trying to fully understand :) - Do you have any provision for activating your estop circuit from the controlling software? I suppose the argument could be made that its not needed unless the pc a distance from the machine?

Yes that's what the Charge Pump relay is doing. The BOB is turning a 12khz signal from Mach3 into a 0 or 5vdc output, on my particular BOB the output of ENA is 0v when Mach3 is healthy and +5v dc when it stops.

I have just acquired 10 of these from a control panel I stripped down (7x 24v and 3x 230v) which seem to be a similar spec to yours:-

Finder TYPE 55.34
The 5A rating, is that for the entire relay or for each contact?

Those look just right, I looked on Farnell and they appear to be 4 pole Change Over which is what you need if using my diagram, the 5A rating is for each contact.