Machine traveling past z home limit switch

[sgibson]

I have recently purchased an Acorn control board and wired it up to my CNC router. I am using NC proximity switches for home switches and end of travel limit switches. I have the X home, Z home and Y primary home wired is series and connected to input 1. In the wizard I have designated this input as HomeAll. I have the Y slave home switch wired to input 2 and have designated that input as SlavedHomeInput. Finally, I have all of the end of travel limit switches wired in series and connected to input 3. Input 3 is designated as LimitAll in the wizard. I have done all of the tests with these switches and they are all working properly. The machine uses the home switches to home and square the machine with no problem.

The problem is when I lower the Z axis and set a new WCS Z zero. Then when I move the Z axis back up it blows right through the limit switch and crashes the machine. I have tested this at a very slow speed and can plainly see that the switch trips but the axis will keep moving up until it crashes. I have set the software travel limits but it seems like the axis should always stop immediately when a limit switch is triggered.

I have attached my report.zip file. Please let me know what other info I can provide. Thanks!

[cnckeith]

use of home switches rely on software travel limits to stop before hitting the home switch

a limit switch trigger should always stop motion no matter what, you are correct

if you can jog past a home switch after homing the machine this could be from

1.) travel limits are not set. maybe you blew them away by pressing estop in the middle of an auto square routine? this is an annoyance of setting up auto squaring in v4.82. double check the travel limits are set it is entirely possible that they are set to zero.

2.) z axis is losing steps, which result from any number of causes. loose stuff, steppers not set up correctly.. etc..

where do you have the home switches located on the machine?

[cnckeith]

report show invalid steps per rev.

read this post.
https://centroidcncforum.com/viewtopic.php?f=63&t=1801

[ShawnM]

Report also shows he's running cnc12 on a laptop.

[Centroid188]

The report shows the switches setup as home switches on input 1. The report shows the limit switches set on input 3 and should be 1 if you want them to be limits.
So the control did not see the switch as a limit and did not stop.

[sgibson]

Thank you for the replies!
I did not realize that 400 steps/rev was not supported so I have changed that to 1600 and that works fine.

I have noticed that a couple of times my software travel limits have been reset to zero and it is likely that this was the case when I blew though the z home limit switch. I have not hit the e-stop button so something else must be causing this problem. Is there something I can do to keep this from happening? Do we know if Centroid is looking into this problem? In the meantime, I guess I need to always check the settings to make sure they have not been reset.

The other issue is that it should stop when it hits the limit switch no matter what. Is there some way to assure this will happen? Is this a bug in the software? Centroid188 posted that all of my limits should be wired to input 1 but that would mean wiring all of the home switches and the end of travel switches in series together. That doesn't seem like it would work? Besides, my problem is that it is traveling past the z home limit switch which is connected to input 1.

BTW: I am using a brand new Intel NUC computer that has been configured exactly as Centroid specifies. Nothing else is on the machine.

Thanks again for all of the help! Steve

[CNCMaryland]

The issue is how you have it setup.

You do not need limit switches. You need to setup soft limits of travel. Once homed, it will not go past these values.

Here is your limit table:

CNC12 v. 4.82 coordinates file
Axis Minus Plus Return Return Return Return
Limit Limit #1(G28) #2(G30) #3 #4
X 0.0000 50.0000 0.00000 0.00000 0.00000 0.00000
Y 0.0000 50.0000 0.00000 0.00000 0.00000 0.00000
Z -4.0000 0.0000 0.00000 0.00000 0.00000 0.00000

[cncsnw]

I don't see that anyone has addressed the question in the initial e-mail.

It sounds like he is saying that he has a Z+ limit sensor, wired (with all the other limit sensors) to INP3. We are to assume that this limit sensor is above the home sensor that is wired to INP1.

His report values seem to show the Z+ Limit as INP3, and the Z+ Home as INP1.

If that is all correct, then CNC12 should have stopped motion with a "407 ... limit tripped" condition when INP3 opened.

[CNCMaryland]

I don't see that anyone has addressed the question in the initial e-mail.

It sounds like he is saying that he has a Z+ limit sensor, wired (with all the other limit sensors) to INP3. We are to assume that this limit sensor is above the home sensor that is wired to INP1.

His report values seem to show the Z+ Limit as INP3, and the Z+ Home as INP1.

If that is all correct, then CNC12 should have stopped motion with a "407 ... limit tripped" condition when INP3 opened.

He did say " and end of travel limit switches."

I'm assuming its below the home switch at the end of travel.

He should post a picture which would make much of this clear.

[sgibson]

Sorry for any confusion. There is only one proximity sensor at the top of the z axis. It is wired in series with the home sensor for the X axis and the home sensor for the primary Y axis. These are all wired to input 1 and designated in the wizard as HomeAll. The home sensor for the secondary Y axis is wired to input 2 and designated as SlavedHomeInput. The end of travel sensors on each axis are wired in series to input 3 and designated as LimitAll.