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Author Topic: Mach ignoring limit switch broke my machine :(  (Read 9277 times)

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Offline jevs

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Mach ignoring limit switch broke my machine :(
« on: March 14, 2015, 05:22:23 PM »
Mach3 broke my machine last night while I was trying to repeat another issue I was having.

I was having issue where an axis would not stop running randomly when I let go of the enable button on the pendant. Pressing it again would stop it, but more than once the limit switch was the saving grace.
While testing the possible fix on that, the limit switch in Z got ignored by mach. This is not the first time for that except this time it broke.
 
I think a pokeys update MAY have fixed the first problem. I could not replicate it after the update and correcting the direction of the encoder (was set to move the wrong way). So after a long time trying everything to duplicate the runaway axis, I could not. Everything was working perfect. I decided to do a Reference home. Bad move....
Bam, Z never stops, it goes up, rotates the turret, but then keeps driving even though the limit switch is tripped and lit on mach.

Well, I had an update document that came with my machine on a part that needs to be replaced for safety from who knows when...1980s maybe. They never put the part on and I don't have it. Well sure enough, this last crash snapped a bolt and two bent and then it proceeded to rip my ratchet rod ball link apart (pulled the lock ring out), then the giant linear bearing hit the rubber pads and that was the end. I did not notice any of this happened until it got to the end and made motor noise still. I hit the E-stop.

 So, I took the Z motor belt off so it could spin free. Sure enough you hit the ref button and it spins forever, even when your hitting the limit switch manually and Mach shows it activating.

I was told this could be normal??? This is super dangerous on my machine. This is not a $600 Chinese mill. The AC servos are strong and will break things. It has crashed before like this and broke my link rod, but the other part was able to stop it.

So, how can you reference home and zero everything out without breaking the machine??

Something must be up with Z that it loses its location or I am doing something to make it lose its location since it never stopped.

This machine has a weird Z, where the upper portion of Z is used for the tool change. I wrote the macro and got it working a long time ago, but this is not going to be safe. I have to figure something out.....

Here is the old thread on that.
http://www.machsupport.com/forum/index.php/topic,18069.0.html

So far I do not recall X or Y crashing since I have been done. When they kept going using the pendant, the switch made an E-stop like I would expect. Then I am able to just override limits and back it up.

If you cannot use the switches at some point to set home, how will it ever know where it is if it loses position?

Offline Hood

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Re: Mach ignoring limit switch broke my machine :(
« Reply #1 on: March 14, 2015, 05:36:15 PM »
As I said on the BobCAD forum, Mach ignores limit switches whilst homing and also I mentioned the reason.
Nowadays with the external controllers and plenty of I/O really it should be an option to have them adhered to if you use separate home switches.


Now on to your problem, few questions.
Are you using an external controller? If so which one.

Do you have separate home and limit switches for each axis or are you sharing limits and homes?

If you attach your xml it may help me asking lots of other questions about your config as I will be able to see it myself.

Hood

Offline jevs

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Re: Mach ignoring limit switch broke my machine :(
« Reply #2 on: March 14, 2015, 06:02:54 PM »
Here is the XML. Here is also a schematic of my machine I did years ago when I built it.

This should help while I finish cleaning up my mess and get the machine back together.

I have to research it all over again to remember what I did way back then....

I did change to an Ethernet SmoothStepper when my computer died and I built a new one. I wanted to run windows 7 and quit fighting with parallel ports...
So, the schematic is the same except the smoothstepper feed into the Machmotion I/O boards parallel port connectors.

Offline jevs

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Re: Mach ignoring limit switch broke my machine :(
« Reply #3 on: March 14, 2015, 06:03:40 PM »
By the way, that stupid "there is already a file with this name" thing is super duper annoying and made me try like 5 times to post this grrr...

Offline Hood

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Re: Mach ignoring limit switch broke my machine :(
« Reply #4 on: March 14, 2015, 06:34:29 PM »
Ok I see you have shared the limits and homes for the X and Y but the Z has separate.
That should not be a problem as long as your Z Home switch is working.
You mentioned during the testing on the bench that when you did a ref all and pressed the Z Limit the motor kept turning, that is normal as I explained earlier. If however you press the Z Home switch it should stop, reverse and then stop when you again release the switch, does it do that?


Regarding limits and Mach, as I mentioned I had asked for an option of having Home switches adhered to if using seperate homes and limits but that never got done, should be fine in Mach4 I think but no chance in Mach3 now.

Personally I do not rely on software for limits, powerful machines should really have hardware limits, I do mine via safety relays, that then kills the drives, so even if for some reason Mach ignores my home switches when homing then the limits will kill things for me.

Below is a pic of a section of the E-Stop wiring on one of the machines.

Hood

Offline jevs

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Re: Mach ignoring limit switch broke my machine :(
« Reply #5 on: March 14, 2015, 07:54:41 PM »
I moved that xml on accident and then started mach. It started going through the start up stuff. I exited and put the xml back. Now it lost everything.

Offline jevs

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Re: Mach ignoring limit switch broke my machine :(
« Reply #6 on: March 14, 2015, 07:56:29 PM »
NM fixed it. Had to run a restore to an old save.

Offline jevs

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Re: Mach ignoring limit switch broke my machine :(
« Reply #7 on: March 14, 2015, 08:06:59 PM »
Ok, now that everything is back in one piece. The home of Z is at the top of the cutting area. The tells it where home is for its actual cutting area use.
It has to go up past this to do a tool change.
The Limit switches are actually at the very top of z and at the very bottom of Z. This encompasses all of the tool change area as well as the cutting area.

Z does stop running if I trip the home switch.

It does not stop when I hit the limit switch.

What I suspect happened is that Z got above the home switch into the tool change area by me jogging around.
Then I hit Reference All Home.
Then I guess it did like you say and ran out of control past the limits and never saw the home switch because it was already past it.

X and Y do stop at the switches during a reference home. They are tied as limits and homes.

So, this is making more sense now.

So, now I have to figure out what to do to fix this so it does not happen again.
« Last Edit: March 14, 2015, 08:16:56 PM by jevs »

Offline Hood

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Re: Mach ignoring limit switch broke my machine :(
« Reply #8 on: March 14, 2015, 08:14:15 PM »
Not sure how the ESS handles Home switches that are active when you ask for a home move. Reason is on the machines I have the ESS and SS the homing is done in the servo drives and Mach/ESS/SS know nothing about it until they are homed. On these machines and also on my Chiron with the CSMIO/IP-A and the wee lathe with the CSMIO/IP-S, if the limit is active when a homing request is made it will back off first. My home switches have the trigger such that the axis can not travel past the home switch as the trigger is long and goes right to the end of travel.

There is an option in General Config called Home Switch Safety or something like that, you could try using that and trigger your home switch manually and then press RefAll and see what happens, it may pop up a message telling you the Z switch is active. If it does then you could extend the trigger like I have done so that the switch once triggered does not become inactive again as you move further in that direction..



Hood

Offline jevs

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Re: Mach ignoring limit switch broke my machine :(
« Reply #9 on: March 14, 2015, 08:18:03 PM »
My home switch is not active once Z moves up past it. It is just a dog hitting a roller. Once it goes past, it is off and not being seen as an issue.
So if you hit Reference Home, I guess it just runs forever even when the limit trips.