Rejected part because of Servo fault?No more!

[kolokithas]

Hi,

I dont know how many of you had the idea how to save a machined part from beeing ruined.I come up with some idea that i will try it tomorrow(i have to open my electronics box of the mill).

Note: This post applies to those who use Gecko 320 servo drivers to drive their motors!

Here is the thing...

You machine a part with BIG! Gcode(Normally 3D machining).At 90 percent of the machined file, one servo faults by a reason(electronics do fail irrelevant of their quality etc).Normally the rest two axes continue to work, ruining the part
all you can do is to hit E-stop and have a face something like that>
Even if you realised fast the servo fault and be faster enough to hit the pause button and then re engage the servo,i dont think that you re faster than electricity!!!And the file may be 2 or 3 lines ahead from the position that the servo faulted.The contoller of DeskCNC doesnt know that there is a problem and continues to send commands to the drivers loosing the current position of the servo fault.I dont think that anyone can find the particular line when the servo faulted,and continue to machine the file from there!!! The only solution to this problem is the one here:

G320 has an ERR/RES terminal.When a servo faults the red light comes up and this terminal goes to GND.You can make a wiring(the wiring diagram is inside the manual of the drive) to externally read the state of the drive by a LED and if you like to engage it or disengage it via a switch.The manual states that you can signal your controller that an error has occured and put the machine in E-stop.Thats the key to the solution.Instead of an E-stop (and consequentially a ruined part) you can wire up the ERR/RES terminal to PAUSE the machine!Solve the problem of the servo fault,if there is any and then UNPAUSE the machine to continue machining the file.Normally as i think it the Pause state will be instant(with some milliseconds delay) before the file moves to the next line or point.I know that your endmill might move some distance before the PAUSE, but If you have slow feed rate i think that this problem is minimized!That way the file stops executing together with servo fault.And you have all the time to correct the problem,engage back the servo and continue your work, by Unpausing the program!You have to wire the drives that way when ANY of the three drives fault the pause command will be send to controller.
To do that remember to activate the option "Enable external Pause" inside the machine setup of DeskCNC.
I think that this solution comes 90% close to success of saving your machined part.

PS:I will have to verify that the drive will continue to work from the same spot and go to the commanded one,even after all steps are zeroed because of the fault.

If you have any comments,welcome!!!

Panos

[IYWD]

I'm very new to CNC so I'm still learning A LOT. But you've touched on a problem that we've been trying to figure out. We are running a CNC router doing a lot of 3D designs and have had problems with a fuse blowing occasionally and ruining a part. Inevitably, on a design that does 3 roughing passes and then a finish pass, it's usually when it's at least halfway through the finish pass that something goes wrong, and like you said, one axis quits but the other two keep going and you're totally screwed.
I heard somewhere, (I can't remember where), that there was possibly some way to hook up the Geckos so that when one dies the other two stop, (without doing a E Stop). If you have a good solution to this problem I'd love to hear more about it. It is a horrible sinking feeling when you go in to check on the machine and you see one axis not moving.

Thanks in advance for any suggestions!

Susan

[Bubba]

If I remember correctly, there is a file in the gecko group files over at yuhoo that will do exactly what you want!
The breakout board that I have utilizes a circuit like this and if one drive faults, the whole machine STOPS NOW! The output goes to an input on my port and stops the program.

[IYWD]

If I remember correctly, there is a file in the gecko group files over at yuhoo that will do exactly what you want!
The breakout board that I have utilizes a circuit like this and if one drive faults, the whole machine STOPS NOW! The output goes to an input on my port and stops the program.

I looked at the yahoo gecko group for a while and never found anything, but there's a lot of stuff to sort through and I may not be using the right search term to find it. If someone can post a link to it, or anywhere else that has information that might help, I'd really appreciate it. I've got a couple of people wanting me to do some carving on their front doors, and I'd like to get something set up that would stop the machine if something goes wrong (like a fuse blowing) before I ever attempt carving on somebody elses stuff...I would want to crawl in a hole and die if I ruined someones front door.

[Bubba]

Well, I couldn't find the file I was thinking about there either. However, there is mention of doing it in the Gecko 320/340 manual and how it was implemented in the "Wonderboard" breakout. The file info for this is located in the Cad/Cam group at:
http://groups.yahoo.com/group/CAD_CA...lel-Port-Intf/
I know the wonderboard works because I have the only one in existance:})

[kolokithas]

Guys,Guys!!!!!

The problem here its not just stoping the Geckos from moving.The thing is...
TO STOP EXECUTING THE GCODE when ANY or ALL three axes fail.By halting the three Geckos at the sime time is a good practice(because you dont ruin something),BUT how you going to find in what Line of G-code the problem started,If you have a part of 23000 Blocks or more???Or you going to move the spindle to X0 Y0 Z0 of the part and then restart the machine to move in the paths it moved before,cutting air?
No, the thing is to stop the program,as Bubba said.But i don't need searching in Yahoo to find what its already in here.Its a simple wiring.Last night i tested the Geckos,i was suspecting that by Faulting a drive in the middle of an executing movement,after the reengaging the coordinates will be gone!WRONG!!!
I set in my MDI box a command G01 X200 F500,then the axis start moving.I hit the pause button and disengage(manual fault) the X axis Drive while watching the DRO of my PC(i also have attached an external DRO to my X axis)the PC DRO said we moved 30mm, the ext. DRO the same.Then i reengaged the drive and waited to see what happens.Normally the axis should move another 170mm even after the drive fault.SUCCESS!!! the two DRO's said 200.02mm of movement.So after a fault the drive will continue the commanded work.
Be patient and i will give you a schematic how to wire your three geckos with your Breakout board/DeskCNC controller.

Any questions?
See you later!

[xjmaxim]

Hi all,
This is my first post ever on the zone after lurking for quite a while so hear goes...

I have got desk cnc up and running for sometime and have come across the problem Panos has raised. I contacted Panos privately and he kindly sent me a wiring diagram. I see he has still not posted it to the group so I am going to attach it with this message. I am using the older type desk cnc board , sorry I dont recall the version I dont know if it will make a difference here.

Anyway the point is I cant get it to work though the idea seems sound to me at least. I am hoping that someone here can try it and or figure out what is wrong. I am pretty sure I have it wired up as per the diagram but I am a bit electronicaly challenged. Feel free to post it elswhere on the zone if you want.

Thanks Dave, (xjmaxim)

[307startup]

I'm just subscribing to your thread.