Stop limit switches aren't stopping Laser head from banging against limits on startup

I’m not sure if this is the right place to put this or not if anybody can direct me to where I should put it if it’s in their own place please let me know. I’ve been a member for you know a while but I’m not really active on the forums.

So the controller I have is Ruida RDC6442S-B(EC) I found one other thread talking about this but it didn’t seem to go anywhere.

Anyways yeah so everything’s been fine up until just now it had done this one time before but only once like I turned it on it tried to go past the limits like it’s trying to zero somewhere else and then I turned it off and turn it back on and it’s been fine this was a year ago maybe 9 months ago. Anyway now it does every single time and I can’t figure out what’s going on I don’t know how to even mess with the settings because it’s trying to do it it’s just homing sequence and banging up against its limits I’ve pressed the limit switches with by hand to try and get to stop it doesn’t work I don’t know if it’s a wiring issue I don’t know I can’t find the specific manual. I don’t know if that really matters all that much. But yeah I need to get this thing working again and any help would be appreciated.

I’ve attached a video of what I’m talking about and pictures of the controller with the lights on but only before the real startup sequence happens otherwise it starts banging.

Or rather i uploaded it to imgur.
This one shows the wiring of the controller.
This one is more direct with what’s happening.

I went through this nightmare, my fix was to open Machine Settings and load a backup from a few weeks back. These backup files are automatically stored by Lightburn at various intervals. The machine was restored and works perfectly.
I wasted a whole day before I stumbled on this. Well done Lightburn!

Just to be clear, when you’re speaking about a Ruida, they have home and limit switches, they are different… your switches are home, not limit.

I call them limits sometimes out of habit and I shouldn’t. Just be aware they are different…

You can press the esc key if the machine tries to run away and get control of the console with power on…

Going to Z/U → diagnosis and watch the indicators as you trigger the home switches.

If that doesn’t show it’s operating you can check at the input leds for proper operation… press the Y home and the Y home (Y-) should illuminate.

If that fails, the wiring or switch may be failing or the Ruida input circuit may be damaged… Usually that isn’t what happens …

A simple voltmeter check of the inputs will reveal if the switches wiring is working or not…

Make sense?

If that fails then you can re-load the backup file… This should be what you do when you get a new device with modifiable software…

Save the configuration just in case…

Good luck


1 Like

Thank you for the replies. :pray: I had to spam my Esc key but after the third press it did stop. Which was my main problem. I haven’t been able to have the machine on at all without it banging around.

So this is what I found in the diagnosis and look at what we have there.

How would something like this happen?
How do I prevent it from happening again? I didn’t change anything from the night before this started happening. Is this something that could have happened inside of lightburn?.. You know what as I’m thinking about it outloud, this happened right after I updated to lightburn 1.4. I didn’t even think about it till just now, but that’s the only thing that changed…

If it’s the switch or the wiring, (which seems likely) then it’s probably not something you or anyone else did. Unless (in all the excitement) you accidentally hit the switch sharply with a rotary device or your workpiece.

It looks like it’s something under the hood of the engraver but you’ll need to check.

I feel that this statement is an example of what @JTR called “Post hoc, Ergo Propter hoc” in a meeting last month. Analysis and diagnosis should always come before assigning a cause.

Don’t worry about this. It happens very frequently. One of my co-workers used the phrase; “I upgraded my LightBurn, now my dog is on fire.” We see dozens of folks make assertion before analysis.

Even though the controller says there’s a problem it can’t really measure anything past the terminal blocks where the wiring is fastened. Loose wires or a loose sensor mount would be the first place to look. Second would be verifying the switch behavior by slowly, physically moving the engraver back to where the switch should change states and observing whether or not the change happens.

Switches also fail randomly between switch events.

If the engraver isn’t resting on the switch right now, then you may have found the reason the switch doesn’t tell the controller to reverse direction.


I think the Ruida is busy with more important stuff and it takes a few presses to get it’s attention.

The diagnosis screen indicates the Y axes home switch is active… is it?

Is the head over there?

Most of these are hall effect and any Ferris metal will activate them… Usually when activated they have an orange glow…

This is a relatively older video.

It shows how the lights and stuff works for most of these…


1 Like

So this is in response to your comments. I meant to post this thread other day, it took longer than I thought to upload and I forgot about not actually posting until now.

Thanks you guys. :+1:

It’s a Ruida from the console, but you didn’t get a look at the controller…

This is mine…

The machine itself it a common Chinese model, some call them tangerine types, but it could have been manufactured by anyone…


I’m sorry, I thought it was in the first post I made. It should be there. Here it is again.

I could have missed it… sometimes it’s easy to get confused with all of these posts…

Do the switches show they work in the Z/U → diagnosis panel?


the x and y show that the switch is being hit, but still goes past it. the z doesn’t show that it’s being hit, but stops when it is. If you follow that link that I posted. it’ll take you to a 2 min video that I uploaded to imgur.

I take a look at the console, and other things.

“sometimes it’s easy to get confused with all of these posts…”

It’s no biggie, and I can only imagine. You guys spend most of your time trying to help and fix people’s problems. I applaud you good sir. Not all hero’s wear capes. That’s for sure.

But yeah, my problem is with the 10000 value’s that are on the x and y now.
Or I guess that I think that I’ve identified it as a problem. that and I only have the 3 limit switches, no more. I would think that having them on both sides of the gantry would be … beneficial.

You can add 4 (2 for each end of each axes) more switches and enable limits… You will lose some of your work area doing this… since the limit switches must be outside of the work area.

The machine has to move out of the work area to detect a limit actuation.


how do i change these values?

Use the arrow keys this is the machines known location …

The machine has failed to home, so these will not be what you expect until the machine is functioning properly.

Why is the Y limit lit?

Does it go out when you move the head away from the home location?


Best I can tell is I am dealing with the same problem, but I have some differences in my machine. Mine is a red and black 80W using hall effect limits. The machine can’t home to the Y limit switch and crashes repeatedly. It seems to have started about 5 days ago. I am not sure what other information helps here. Any assistance is greatly appreciated!

Did you watch the video in post #16, about homing on the Ruida…?

Where does yours fail?

The Y home switch is showing active…

If you manually (arrow keys on console) move the head away from the home corner, does the YLimit- indicator turn off?

If it doesn’t, that’s the homing problem.


Thanks for the reply! If I hit escape I am able to see the light on the limit switch turn on and off when it should. This happens on the light on the switch, on the controller and in the diagnosis screen of the laser.

Here is a picture of the machine settings for the x Axis.

That shows the switch is working to the Ruida input.

If the issue is on the Y axes crashing, why are you showing me the X axes information… confusing…


I mistyped. It is the x axis that crashes.

Did you apply these diagnoses to the X axes?

Didn’t see anything that indicated the X axes limit switches were working. Did you check that axes for proper operation.