Author Topic: Problem with index homing  (Read 12457 times)

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Offline jofriedl

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Re: Problem with index homing
« Reply #20 on: September 08, 2015, 11:17:50 PM »
Unfortunately, no. I think the problem is this-   The machine runs over the limit switch, then reverses to find the next index signal. If the machine find the next index signal before it completely backs off the homing limit, it sends the error. This is the reason that the error is triggered about 80% of the time. I did some tests and I found that if I slowed the machine to an unbearable crawl (2 to 5 inches a minute) it wont send the error. I think the macro should be modified such that the machine triggers the limit switch, then backs off the limit switch completely, then moves to the limit switch again at a much reduced rate. Only then will index homing work on this machine. Unfortunately, I don't know enough visual basic to modify the CS labs macro. Oh well.

Jonathon

Offline jofriedl

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Re: Problem with index homing
« Reply #21 on: September 08, 2015, 11:18:48 PM »
In other news, I've gotten the tool changer to work beautifully with the DL06 PLC. I've posted a video under the 'posts your video here' section


Offline Hood

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Re: Problem with index homing
« Reply #22 on: September 09, 2015, 07:09:13 AM »
Didnt't think the Index was looked for before the home switch closed but I had to check before I could be sure. I did a test on my Chiron and I could hear  the switch close and the axes still moved until the Index was found.
 It was going to be hard to manually trip the home switch on the Chiron to keep it closed for longer but the wee lathe was easy to do.
I made a quick video, you can see it here, you can clearly see the axis continues until I release the switch and it then senses the Index.
https://www.youtube.com/watch?v=7dKNaMVlj1E


Toolchanger looks like its working well :)

Hood

Offline Overloaded

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Re: Problem with index homing
« Reply #23 on: September 09, 2015, 09:01:03 AM »
Nice illustration Hood, mine did the same with the -M.

Back to Hood's first reply regarding noise, did you try the filter ?

Russ

Offline Hood

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Re: Problem with index homing
« Reply #24 on: September 09, 2015, 11:26:53 AM »
Would it be possible for you to either manually operated the switch like I did in the video or just wire a toggle switch to the input for testing.
What I am wondering is if maybe your switch has a wee bit of bounce at the release point and  the IP-A is getting confused.
Not even sure if that would affect things but probably worth a try.
Hood

Offline jofriedl

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Re: Problem with index homing
« Reply #25 on: September 09, 2015, 12:25:38 PM »
Thanks for checking on that, Hood. I upped my input signals filer to 60ms and still no change. Thank you for the suggestion though. You may be right about the limit switches, Hood. Although I have triggered them with the mpg and found that once triggered, the machine has to back off past the trigger point for the contacts to open. It's as if there is 'spring' to the switches. Essentially, they don't open and close at the same point I wonder if this would have something to do with it. However, I tested the system by depressing the switches manually while the machine was indexing the axis (z in this case) and wether or not the error was triggered seemed time dependant. If I released it imediately, the error was triggered. If I held it for a little longer than what it would normally take for the macHine to back off the switch, the error would not be triggered. If I held it for even longer, it would send the error again. This leads me to believe that there is a window of oportunity on the encoder wheel during which the limit switch signal must go low otherwise the error is triggered. This is very odd indeed. I'm thinking of trying to contact cs labs direct  in the hopes that they can help resolve the issue. This machine is very accurate for its age, so I'd really like to have the ability to index home. Thanks for everyone's help thus far. I am truly grateful for the community on this forum and especially you, Hood. Your input has been indispensable on this project. I only wish we were on the same continent so I could pay you a proper visit and thank you in person!
Jonathon

Offline Hood

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Re: Problem with index homing
« Reply #26 on: September 09, 2015, 01:57:04 PM »
The trigger point and release point is different on decent switches, so that is definitely not the issue. Not sure if you can see/hear it on the video as the sound is not great but when standing at the machine you clearly hear the click of the switch and the trigger and release are a fair distance apart.

One thing that still puzzles me is the values I calculated, with the assumption of 5mm pitch screws, are exactly half of what you said the CSMIO was reporting on the encoder count, or at least I think that is the case, can't be arsed reading back to check :D
If that is true then afraid  I don't have an answer to why that would be but it may well have something to do with the problem and may help CS-Lab find it.


Hood

Offline Hood

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Re: Problem with index homing
« Reply #27 on: September 18, 2015, 05:43:14 AM »
Jonathon,
 any progress?
I just went and looked at the encoder position you were monitoring, it seems they are internal counters based on the steps per unit set in motor tuning.
What I did was home the machine and did a G53G0X0 (I home to the positive on X) and the counter showed Zero.
I then did a G53G0X100 and the counter showed 480000. As my steps are 4800 per mm then 100mm = 480000.
So I concluded that the value there was dependent on the steps per unit. To confirm I went back to G53 X0 and then changed the steps per unit in motor tuning to 2400 and  commanded a move to G53G0X100 and the reading showed as 240000, so that was as expected.

So basically you can not use that value to work out the encoder counts as it is an internal calculation.
You will need to get the gearing and the pitch of the screws and work it out that way.


Hood

Offline jofriedl

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Re: Problem with index homing
« Reply #28 on: September 22, 2015, 06:07:05 PM »
Hey Hood,

  Sorry for the delayed response. I've been buried under a few other projects for the past few weeks. I did get around to working with the mill yesterday.

As far as steps per unit of distance, I have worked out the pitch of the ball screws and gearing and encoder pulses per revolution.  I have been using the mill with index homing disabled and it moves and cuts accurately. I am sending off an email to the cs labs guys today and including the address to this thread. Hopefully it will be something simple that I missed.

Offline Hood

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Re: Problem with index homing
« Reply #29 on: September 22, 2015, 06:14:31 PM »
Will be good to hear what they say :)
Hood