Machine crashing when homing despite stop switch

[fgonza2]

I am having now another issue.

-I test the switches manually by pressing them and the machine stops as expected. Specifically the X axis left switch.
-When i press HOME for a full homing with optical, etc. The machine crashes to the left side despite the switch being activated. The switch is working well as i mention above when i press it manually.
-Somehow when it tries to home the machine crashes (yes the switch is activated when it hits the side but it doesnt stop the machine)

Any ideas?

THanks

[JuKu]

By crashing, you mean that the switch stops the machine, it is not trying to keep going, just hitting the switch hard? If so, increase homing acceleration.

[mrandt]

Try moving the machine a bit further away (X+; to the right) before starting homing sequence.

For some reason in TiynG firmware, the X axis is moved slightly before homing switch gets monitored.

I got tired of figuring out why, but this might be the same problem you are seeing.

[JuKu]

That is a firmware bug: TinyG starts to monitor the switches only after the homing sequence is fully started. If the switch triggers while the machine is still accelerating, it is ignored. Increasing homing acceleration and maybe latch backoff and/or homing zero backoff parameter cures it.

To read the parameters, send $_lb or $_zb, where _ is x, y or z. To change, send $xzb=8 (as an example). See https://github.com/synthetos/TinyG/wiki ... -Operation.

@Malte: Sorry, I thought I wrote you about this.

[fgonza2]

I start homing way far from the X=0, so there is enough time, that is not the issue. The switch is pressed and the machine when it gets to the end and the machine keeps going and hitting the rail so i have to turn it off, at this point the switch is pressed. I have the machine homing at a very slow speed.

When i test the switch on its own (by jogging) it works and stops the machine, it just doesnt work when in homing mode. The issue happens about 50% of the time. Any ideas?

[JuKu]

What happens when you start homing and manually trigger the switch? It should stop, back off slowly a bit to clear the switch (when testing, let go at this point) and then back off fast a few mm.

> The issue happens about 50% of the time.

Sounds like a bad connection somewhere.

[fgonza2]

ok, i made a video to illustrate the issue:

https://youtu.be/QjMIq9Lw7YA

There are two passing and failing cases on the video.

My theory is that after the machine crosses certain value on the X axis the stop switch doesnt work anymore, as you can see on the video, when the switch is presed further from the edge it always work, when it reaches the end it stops working. This has to be SW related either TinyG or the liteplacer SW as the HW connections seem to be ok proven by the fact that the machine always stops when you press the button earlier. Please comment on the video, thanks and appreciate your support.

[JuKu]

Yes, something is off. Please send the command $$ to TinyG (that dumps all the settings to the log window in human readable form), click to the log window, ctrl+A to select all, copy and paste to a text document and send that to me. Send also the log of the failed homing.

[fgonza2]

hi, please see attached the logs (two cases). both the settings and the actual homing attempt that ends up crashing the machine. thanks

[JuKu]

Your settings are fine, as far as I can tell. I don't have a explanation right away. Your settings are fine, as far as I can tell. TinyG works as expected when you trigger the switch in the middle of the travel. So, both the switch and TinyG seem to be fine. Yet, the switch is ignored when the machine gets to the far (home) end of X axis. The only thing that I can think of is the cable. Do check with a multimeter that the switch works even when at the end of the travel, when the cables are pulled, maybe even push the chain a bit to get some extra stress. I'll try to repeat this with my machine with your homing settings and see, if I can make it fail. In the meanwhile, please send a log of a good homing (when you trigger the switch manually), I'll see if there is anything strange there.