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Homing/limits-g28
« on: October 05, 2008, 06:21:58 PM »
Hey Guys,

In config, homing/limits, I have my soft limits set at X @29"  Y@ 12.75"
I have g28 set at X 14.5 Y at 6.375 to bring my X and Y to the center of travel.
When I do a g28 in MDI. the X just comes off home and stops. Y is ok.  :o
Sometimes it works and sometimes not.
Whats my problem?

Ed V
Ed VanEss

Offline jimpinder

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Re: Homing/limits-g28
« Reply #1 on: October 06, 2008, 04:59:56 AM »
I have just tried this on the office computer - it would appear that the G28 settings on the limits page are in absolute co-ordinates i.e. machine co-ordinates, not program co-ordinates, so after homing, you must also zero your program co-ordinates, before doing a g28 so that they are all in sync. (This should not actually make any difference if you have home switches fitted - see below)

You make no mention of whether you have home switches fitted, only referring to soft limits. If you do not have home switches fitted, after you run your machine to 0.0.0 position, make sure your machine co-ordinates are also zero by pressing the RefAllHome button, so your zero position is the same for machine and program co-ordinates.
Not me driving the engine - I'm better looking.
Re: Homing/limits-g28
« Reply #2 on: October 06, 2008, 01:53:28 PM »
Jim,
   Yes , I have home/limit switches. g28 did work without zeroing program coord at machine coord.

What I did last night was lower my velocity speed in motor tuning, and now it works again.
I'm now wondering why it worked before, and now had to lower my motor velocity to get it working again.

Thanks for your reply.

Ed V
Ed VanEss

Offline jimpinder

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Re: Homing/limits-g28
« Reply #3 on: October 07, 2008, 02:46:29 AM »
I must admit, it is the old speed versus reliability thing.

I have noticed (well I can't help noticing) that every so long my X axis sticks. It must be a tight point on the bed. It doesn't happen at all often, so you are tempted to up the speed on the rapids - and everything goes fine, until, one day, it sticks ! :'( and you've ****** another piece of work.

Yes - I can get up to 40 inches per min on rapids - but I have to use 24 to guarantee no foul ups! ;D

My latest thing is machining copper clad for electronic circuits - and the tolerances there are quite tight - so it is even more important.

What I really want to do, is set the machine going, leave the room, have a cup of coffee, or lunch or whatever, and come back and find it finished. I am not at that stage yet !!
Not me driving the engine - I'm better looking.
Re: Homing/limits-g28
« Reply #4 on: October 07, 2008, 03:00:01 PM »
Jim,

  Yes , I know what you mean. Put a machine and a computer together , and you never know what can happen next.
 I had my velocity set at 150 ipm on both X and Y. had to lower the X to 132 ipm.  :'(
Still working on bugs.

Ed
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Offline Chaoticone

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Re: Homing/limits-g28
« Reply #5 on: October 07, 2008, 03:39:44 PM »
Ed, that still isn't bad. Your doing good man!

Brett
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Offline budman68

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Re: Homing/limits-g28
« Reply #6 on: October 07, 2008, 05:25:05 PM »
Quote
What I really want to do, is set the machine going, leave the room, have a cup of coffee, or lunch or whatever, and come back and find it finished. I am not at that stage yet !!

Jim, I actually did this the other day with a small job for the first time. It's funny, I felt like I did when my daughter was a little girl and she got out of eyesight from me. A very sickening feeling but when I got back into the shop, all was done and absolutely fine. The work was just sitting there waiting to be removed from the table and the blank material that was next to go in was screaming at me: "where the hell have you been?"  :D

Dave
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Offline jimpinder

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Re: Homing/limits-g28
« Reply #7 on: October 08, 2008, 03:41:03 AM »
Now - back in my mind I remember that Mach 3 can be made to SPEAK.

Something like - "Get in here and give me some attention!" would seem to be appropriate - obviously with a loudspeaker extension to where ever you are reclining.
Not me driving the engine - I'm better looking.