Hello Guest it is October 17, 2019, 12:40:25 PM

Author Topic: Drives falut out  (Read 8334 times)

0 Members and 1 Guest are viewing this topic.

Re: Drives falut out
« Reply #20 on: September 13, 2011, 05:00:54 PM »
Hood
As I see it and correct me if I am wrong in my thinking, if the drives fault then the original point of origin is lost and if this point has been machined away then there is no way to recover to that point again with out doing what i have been doing in the past or make a fixture to locate point of origin and start over from there.
 In the past when the above has occurred and i reset and tell Mach to run from there since it has no reference to point of origin mach runs the code as if it were homed at this point and does some nasty stuff to the part.
 As to the drives i use the recommended oils and went through the machine very thoroughly making sure it's up to snuff before trying to operate it, i can get the drives to fault by jogging if i do a short jog input by just briefly touching the key.
Dennis 

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: Drives falut out
« Reply #21 on: September 13, 2011, 05:24:12 PM »
If you have accurate Home switches and Home when you start the machine then touch off where you want the zero position to be (and zero the DROs) you will have set up a work offset. If the drives then fault all you need to do is re-home and the work offset zero will be where it was before because the original homing set that up. So in your situation all you would do after a fault is reset the drives, re-home Mach and then do a Run From Here (taking note of the prep move to make sure its correct ;)  )

Not sure how much hassle it would be but if you could disconnect the connection between motor and axis and try and see if jogging faults it. If it does then its an electrical issue, possibly even a loose wire in the geckos or bob that expands as it heats and makes better contact or could be a dry solder joint somewhere.

Hood
« Last Edit: September 13, 2011, 05:26:32 PM by Hood »

Offline BR549

*
  •  6,902 6,902
    • View Profile
Re: Drives falut out
« Reply #22 on: September 13, 2011, 05:34:39 PM »
Just a note, running the motors at 1/2 voltage will reduce the overall torque somewhat. I would bump the voltage up to just below the Gecko max leave a small bit for safety reasons. Volt x amps = watts = HP usually the more the better(;-)

Also Hood is correct it sounds like sticktion I would change the way oil to a less viscous oil.

On the Point of Origin WorkZero When I set up the material for the part and have established 0,0 I woul d move over to a known point on the table that is NOT going to be machined and record the position of that known point. It can be a square edge a hole or a simple centerpunch mark , just something you can rereference back to. Write it down.

 Say it was X-2.000 Y-1.000

If you have to restart simply move back to the known postion and reset the axis dros to that location X-2.000 Y-1.000. NOW  0,0 will be exactly where it was before you started machining.

I normally use a Probe to probe a circle BUT any method of accurately finding the ref point will do fine.

In my opinion low end switches are NOT accurate enough to do accurate refhome repeatably.  

NOW for the record I am ALL for doing it by the book BUT not to a fault(;-).

Just a thought, (;-) TP

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: Drives falut out
« Reply #23 on: September 13, 2011, 05:44:57 PM »
Terry, Optos are cheap and very accurate, only problem is keeping them dust free or dry (depending on machine type) Making a housing for them that is enclosed is not too difficult and having a rod sprung at both sides to centralise it then a flag on that rod makes a nice water/dust proof setup which is very accurate, also makes a nice project for a person to do especially if new to CNC :)

Industrial Hobbies, I think, used to sell them but dont think they do any more, when the ones I got from them eventually packed up I just made more as it was easy enough and I used the optos I always use, OPB 916B or 917B
Now I do homing in the servo drives I use as they home to a switch and then seek the index pulse.


Hood
« Last Edit: September 13, 2011, 05:57:57 PM by Hood »
Re: Drives falut out
« Reply #24 on: September 14, 2011, 12:36:02 PM »
Thanks guys i appreciate your input.
But correct me if i am wrong when the drives fault out reference to point of origin is lost right, i can't get it to go back to where i first zeroed it.
I don't see how referencing the machine to a hole in a fixture would get it back to a point of origin on the material unless it's machined from there but then this would move the part being machined in the material i don't see this working so huh!

Dennis 

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: Drives falut out
« Reply #25 on: September 14, 2011, 01:36:24 PM »
When you home to switches  you are setting the machine coordinates and Mach keeps track of them. If you move to your work and touch off and zero the DROs you have set up a work offset (default G54) so if at any time you fault and are out of position you rehome and then you can go yo X Y Z zero and it will be exactly the same place as it was when you set before as Mach knows the position relative to machine coords. Terrys way will also do it but it means you are basically not homing but touching off the work and setting the offset zero then moving away to a point and touching off that and taking a note of the DROs so if you fault you again touch off that point and then set the DROs to the values you noted for that position.
So basically both do the same but to me homing is easier, nothing to note down, no second touch off, no having to touch off again after loss of position. Homing to switches is all thats needed and its automatic.
Hood
Re: Drives falut out
« Reply #26 on: September 14, 2011, 04:08:56 PM »
Hood
Again many thanks to you and the others that make this a great forum for help and information. my machine has limit switches but thats not the same as a home switch wouldn't they be movable in your method otherwise terry's method would work probably with the least amount of playing with a working machine.
On the subject of the drives faulting out, if i slow the machine way down with V and accel set at 250 then i don't have the drives faulting but man it's slow moving fault seams to only happen when i kick it up to over 1250.

Dennis

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: Drives falut out
« Reply #27 on: September 14, 2011, 04:25:42 PM »
See how accurate your limit switches are by enabling them as Home switches also and doing some homing (RefAll) then jogging off a bit and touch off something and zero the DROs. Then do a Ref All again and  then again jog and touch off the same part and see if the DROs read zero or very close and repeat a few times.
Sounds like the servos are just not quite powerful enough for your machine.
Hood

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: Drives falut out
« Reply #28 on: September 14, 2011, 04:41:55 PM »
In fact another way to test, assuming you are not losing any steps at the time is to RefAll, jog off a bit and do the Verify button and see what the message says it is out by.
Hood
Re: Drives falut out
« Reply #29 on: September 14, 2011, 06:56:55 PM »
Another method ... Ref the machine then go to Home/Limits and uncheck Auto Zero for the axis (s) you'd like to check.
Hit ref button repeatedly and the dro will show the variations in the switches.
Might surprise you.
My first switches were off .003", next ones were .0002 - .0004"
Russ