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Author Topic: Homing Problem  (Read 3878 times)

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Offline PSG

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Homing Problem
« on: January 02, 2009, 01:52:11 PM »
Happy New Everybody!

Slowly but surely getting to where I want to be with my machine. Its maiden voyage went great and the issue with the backlash seems to have been corrected with adjustment of the shuttle.

I have have another issue that I am am trying to figure out. 99% of the time, referencing to home works great. On occasion it seems to act up and I cannot see what I am doing wrong. I am playing with setting a couple different table offsets and auto squaring of the dual-drive gantry. When double checking that the machine will do what I want it to do, I will jog the machine away from home and again select "reference all home". Sometimes the machine will properly home to the neg, hit the proxy, stop, and trigger an e-stop. (The machine has to proxies on the X and one on the Y)

Under most circumstances I will click RESET and everything is fine. 1% of the time though when I click on RESET I get that box that says that there is an external influence preventing the machine from re-engaging. looking at the diagnostic screen shows that there are no inputs active. The option of "fix this for me" does not work. In order to get around it I must shut Mach down and restart.

I have tried a few different things such as selecting "Home Sw. Safety" on and off (not sure what it does) and have tried various levels of debounce. Neither of these have provided a remedy.

Another "sometimes" issue is that if I have the limits enabled in port and pins (home switches and limits are the same proxies) I will get an e-stop when referencing all to home. Turning off the limits stops it but I would rather not have them disabled if at all possible.

I have posted a copy of my XML if anybody can see what I am doing wrong.

Offline jimpinder

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Re: Homing Problem
« Reply #1 on: January 05, 2009, 01:29:45 AM »
The problem is that the computer works differently when homing or limiting.

When homing, it hits the switch, then backs off until contact is broken again (so the switch is not now live). When limiting, the machine hits the switch, stop - so the switch is still live. I do not understand what you mean when you say a proxy.

It seems to me that you are trying to do something that the software is not designed to do. It works ok for one axis, but the sequence of events and the  different possibilities with two axis are quite complcated.

As I remember it, you have the A axis slaved to the z axis, presumably driving opposite sides of the gantry. All you want to do is have both sides home together, so that they are square. You do not say how much out of square this gantry could be, I assume not a lot, and the problem is also, I assume, that even with one side of the gantry powered, the other side will move in sympathy anyway.

In such a position, I would set to and write a macro for what you want. You can do all the functions in Visual Basic, and just replace the Vis basic on the Set Home button.
The sequence would have to be something like this:-

1. Turn off the limit switches.
2. Start moving gantry towards switches
3. Monitor the limit switches.
4. When one is pressed, stop that side of the gantry and wait until the other hits it's switch.
5. Reverse out, monitor both switches.
5. When one opens, stop and wait for the other
6. Set DRO to zero.
7. Rest limit switches.

The problem is that there are so many combinations of switch settings while all this is taking place, that unles you write what you want, I do not think you will find that the Mach3 software will do it, without the odd hiccup now and again.

Jim



« Last Edit: January 05, 2009, 01:32:19 AM by jimpinder »
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Offline Chaoticone

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Re: Homing Problem
« Reply #2 on: January 06, 2009, 04:27:29 PM »
http://www.machsupport.com/docs/Mach3Mill_Install_Config.pdf

Page 91 may help

Home Slave with Master Axis, if checked, homes both motors of a master/slave pair at the same time.
This will not do axis straightening, however.

Page 95

Brett
« Last Edit: January 06, 2009, 04:31:40 PM by Chaoticone »
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Offline Chaoticone

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Re: Homing Problem
« Reply #3 on: January 06, 2009, 07:08:33 PM »
I would turn the soft limits off for now as well.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline Chaoticone

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Re: Homing Problem
« Reply #4 on: January 06, 2009, 10:40:08 PM »
Also, go to config. config plug-ins and disable any plugins you aren't using.

Might want to raise your debounce to test as well.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline PSG

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Re: Homing Problem
« Reply #5 on: January 07, 2009, 01:50:46 AM »
Jim,

Maybe the odd hiccup (or gremlin) is what I am experiencing. The machine seems to run great and nothing that I have posted about is anything that would put me out of commission. The RESET condition has not happened in the last dozen tests. If it does occur I will watch the limits and see what they do. The proxies I refer to are proximity switches/sensors that see metal as compared to micro switches.

As complicated as the coding behind Mach is, the setup is easy if one pays attention to the details (sometimes guilty here) :) I do not have the confidence in VB yet but I am slowly getting there.

Brett,

The one thing that I did not do was turn off the plug-ins. I have since added a Shuttle Pro but I did just turn off the Flash and Video plug-ins.

As I originally said I am slowly getting there :) My jogging issue has been long gone, RESET problem may be gone, and I am narrowing down a possible intermittent referencing problem.