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Author Topic: Homing and limits don't work right  (Read 6279 times)

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daveliz99

• 8
Re: Homing and limits don't work right
« Reply #10 on: March 02, 2009, 02:46:33 AM »
I'll do that.  Do you know why it won't move off of the home switches?  Is it really that big of a deal?

Thanks.

Hood

• 25,838
• Carnoustie, Scotland
Re: Homing and limits don't work right
« Reply #11 on: March 02, 2009, 03:39:59 AM »
It wont move off the home switch because the E-Stop is being seen.
However if you are meaning the Home Off value you have set then it is because you are misunderstanding what that distance is for. When you set  a Home Off value the home position is set to that distance but the axis will not move to it. What it is meant for is if you have your home switches at a position other than true zero you can enter a Home Off value.
To give an example, if your home switches were at 100mm inboard of the true zero position of your travel and you homed the switch position would be set as zero. However  you could set a home off value of 100mm and this would mean when you homed the DRO would read 100 (in machine coordinates) and so Mach would know you still have 100mm more travel to get to your machines zero position and can use that information  for soft limits.
Hood

daveliz99

• 8
Re: Homing and limits don't work right
« Reply #12 on: March 02, 2009, 04:48:19 PM »
I changed the Estop to port 0, pin 0.  It seems to be working.

So just to check my understanding, the machine should move until it touches the home switch and stop right there.  It should not physically move off of the switch. Is that correct?

Since my machine uses a limit switch as a home switch also, my home offset setting should be zero for all axes, since it will be at the extreme end of the axis when it homes.  Is that correct?

What are the G28 home location cooridnates?  My understanding is that G28 is a command that tells the machine to go home, but go to some other cooridinate values first.  For example, it you needed to go around a clamp or something, you could use the G28 command to move around the clamp, then go home.  Should all of mine be set to zero?

If I understand the soft max and soft min correctly, this is so that the table size will appear to be correct in the tool path window on the program run screen.  So to get these numbers accurately, I should home the machine to zero, and then travel to the opposite end of the X and Y axes, and when it triggers the other limit switch, I should type in the number from the DRO into the soft max.  Is that correct?

Thanks again,
Dave

Hood

• 25,838
• Carnoustie, Scotland
Re: Homing and limits don't work right
« Reply #13 on: March 02, 2009, 05:02:36 PM »
I changed the Estop to port 0, pin 0.  It seems to be working.

So just to check my understanding, the machine should move until it touches the home switch and stop right there.  It should not physically move off of the switch. Is that correct?

It should reverse very slightly until the switch closes again then stop.

Since my machine uses a limit switch as a home switch also, my home offset setting should be zero for all axes, since it will be at the extreme end of the axis when it homes.  Is that correct?

Yes, unless you home to the positive direction of the X or Y axis, if so then you should set the Home Off value as the travel you have, so that when homed it will read that distance in the machine coords DRO and if you jog fully negative the machine coords DRO would then read zero.

What are the G28 home location cooridnates?  My understanding is that G28 is a command that tells the machine to go home, but go to some other cooridinate values first.  For example, it you needed to go around a clamp or something, you could use the G28 command to move around the clamp, then go home.  Should all of mine be set to zero?

What I understand is G28 is a location you can set up as your default home position, if you want you can enter numbers into these boxes and when you call G28 it will go there. You can also alter the RefAll buttons code to do a G28 move after the homing move if you wish.

If I understand the soft max and soft min correctly, this is so that the table size will appear to be correct in the tool path window on the program run screen.  So to get these numbers accurately, I should home the machine to zero, and then travel to the opposite end of the X and Y axes, and when it triggers the other limit switch, I should type in the number from the DRO into the soft max.  Is that correct?

More or less, would be best to set the distance as just before you trip the switch. The Softlimits when activated will also stop you from hitting the physical limit switches and should also show you a warning message when you press the start button if the code would take you into a limit switch.

One other thing you may want to look at is setting up the safe Z, I have mine in machine coords and just below my Z home (-2mm). When I do a GoToZero or a Run From here it will move the Z up before moving X and Y then finally move the Z back down.

Hood
« Last Edit: March 02, 2009, 05:04:18 PM by Hood »

daveliz99

• 8
Re: Homing and limits don't work right
« Reply #14 on: March 02, 2009, 05:09:06 PM »
Thanks a million man, you've really helped me a lot.