Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: hightechkey on February 03, 2010, 08:05:13 AM
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Dear Bro
I have some problem with home switch and limit switch. My mach3 cnc machine uses one home switch and two limit switches for each axis. Mach3 cnc software cannot sense limit switch while reference home. I want to use limit switch while reference home. How can I change setting for this problem. Please help me. Thank a lot.....
High Tech Key
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You have to set the Home Switch up to the pin and port it is connected to in Ports and Pins, Inputs page.
Hood
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Dear Hood
Thank for your reply. I had already set for home and limit switch input pins. I use pin number 11, 12, 13 for X, Y, Z home switches and 15 for all limit switches. All of the switch work well at running time.
But the limit switch cannot work while my machine is moving reference home. I press "All reference Home" button and then my machine moving home. At that time I push the limit switch button and it isn't work. After reference home finish, limit switch is work well. I think limit switch must be work while the machine is moving home. How can I solve this problem.
Please help me. My english is so bad. I hope you can understand what I mean. Thank you so much.
High Tech Key
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Ah Ok I see what you are meaning now.
Mach ignores limit switches when homing and I dont think there is an easy way to get around this.
On my machines I dont have home switches in Mach as I do the homing in my servo drives so if a limit is hit when I am homing Mach will E-Stop, but you need drives capable of homing to be able to do that. The other option would be to have the limits connected to your servo drives rather than Mach, but again that would need your drives to support this feature.
Hood
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High Tech Key
can you explain WHY you want the limit switches to work while you are homing?
Ian
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High Tech Key
can you explain WHY you want the limit switches to work while you are homing?
Ian
Dear Ian
My machine has two limit switches and one home switch for each axis. One limit switch and one home switch of X axis exist at the right of the machine. So my machine must be move at the right side when homing. Last four days, my machine X axis arrived between home switch and right limit switch. At that time, I do machine homing and machine move to the rignt side. But home switch exist at the left side and machine touch the right limit switch. But mach3 software ignores limit switch while homing. So, X axis reached at the end of ball screw. Luckily, motor drive got error and stop motor without damage my machine. But it must be dangerous condition.
Some system uses one switch for home and limit together. It may be OK for this system. But my system uses home and limit switch separately. I think mach3 software should sense the limit switch while homing.
I hope you will understand what I mean. Please give me some advice how can I solve this problem? Thank a lot.....
High Tech Key
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I will ask Brian if it could be an option in Rev4 that if separate Home and Limit switches are fitted then you can choose to have the Limits always monitored. I dont need it but I could see why some would and its definitely a feature I would like to see.
In the mean time what I would do in your situation is have the Home switch trigger longer so that once the switch is activated it is always on for the remainder of the travel in that direction. You could then write some VB and place it in the Ref All button. The VB would look at the state of the Home switches and if Active will pop up a message on screen to tell you and you can then jog off the limit and then press Ref All again.
The code in the button would look something like this
If GetOemLED(830) Then
MsgBox("X Axis on Reference Switch, please move off and Re-Reference")
End
End If
If GetOemLED(833) Then
MsgBox("Y Axis on Reference Switch, please move off and Re-Reference")
End
End If
If GetOemLED(836) Then
MsgBox("Z Axis on Reference Switch, please move off and Re-Reference")
End
End If
DoButton( 24 )
DoButton( 23 )
DoButton( 22 )
Hood
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Hi hightechkey
Ok I understand.
Let me see if I can convince you that even if Mach did what you wanted it would be a little pointless.
Suppose the limit did work as you wanted in your example. What would happen? Your axis would hit the limit and stop. You'd then have to jog off the limit and go to the other side of your home switch and then home again. You might as well have jogged to the correct side in the first place and then homed.
FWIW I've never really been able to see any advantage of having a "dedicated" home switch as opposed to a home/limit combination. The whole point is just to reference to a known position - it doesn't really matter what or where that position is.
I'd be intrigued to know why you have this setup - allways willing to learn.
Ian
Hood posted just as I was reviewing this (Hi Hood - how's it going?)
I can see where you're going but afraid I still can't see the point. Clearly I'm missing something. The thing is - how long do you make those trigger arms? and what's the overall purpose?
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Dear Hood
Thank you very much for your advice. I will test them.....
High Tech Key
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Stirling
the triggers would have to be from the Home switch to the end of the axis so that once on the home it will be on until it gets to the end of the travel.
As for the advantage, there are many and I will give you a few, firstly on my lathe I have long travels so its a waste to travel away to the end of the axis to reference. The next is the X on the lathe has two tool stations, a front toolpost and a rear turret, I dont want the X axis to travel to one or other extent when referencing as it could cause one or other of the tools to colide with something, so I have it so the turrets/toolpst are approx equidistant from centreline. Another reason is like I have on my machines, Index homing, mine is done in my drives but Ed Gilbert used to sell a board that was capable of Index homing so you needed separate reference switches.
Hood
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Hood - thanks - as I said - allways willing to learn.
Do you *still* not have to make sure that you're at the correct side of home before you do a "ref all home" though?
Ian
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I dont because my drives will look and see if the home switch is active, if it is the drive will send the axis the opposite way until the switch closes and then it moves back again towards the switch, once it sees the switch it looks for the index pulse on the encoder and then finally it moves back by a user set encoder count.
Hood
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hello,
I have the similar problem. I want MACH3 to reference the machine to Home at beginning. I have connected Home switches for three axes. Now whenever I feel I have lost the position, I need some way by which I can go to home limit and at the trigger of Home proximity switch, the axis will calibrate to Zero.
pl help.
deepak
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Not really sure what you are meaning as if you do a Home it will reset the machine coords, so should put you back to where you were.
Hood