Hard Limit Triggered in the middle of the work space?

creADDive · August 14, 2025, 8:14pm

Hi all,

Long time lurker and recent convert to LightBurn. Loving all this program can do, but regularly get the “Hard Limit Triggered” both when I’m Framing and during a 4-6 hour burn. It’s seemingly random to my layman brain - sometimes it doesn’t trigger during the Framing and it seems to trigger at different spots X and Y positions.

I’ve read through a bunch of other “Hard Limit Triggered” posts, but still cannot figure out how to solve my own issues with this, and hoping one of you can.

To be certain, my designs are at least 24mm in from the boundaries (though I’m noticing the trigger seems to happen when the laser is more in the middle of the work space), and I’m using Absolute Coordinates.

Here’s a screenshot of the latest project that triggered this.

Here’s where the latest error happened while I was framing this project. Thanks in advance for any help! This forum has been really useful and I really appreciate the community here.

Waiting for connection…

Project loaded in 22 milliseconds

Waiting for connection…

ok

[xTool D1Pro:ver 40.31.006.01 B2]

ok

start_home x

left limit trigged

start_home y

up limit trigged

MPos:0.000000,0.000000,0.000000

M28

MPos:0.000000,0.000000,0.000000,0.000000

ok

Starting stream

Stream completed in 0:00

MPos:279.000000,328.420000,0.000000,0.000000

MPos:279.000000,288.240000,0.000000,0.000000

ok

time out 1s

err:limitCheck

ALARM:1

Hard limit triggered. Machine position is likely lost due to sudden and immediate halt. Re-homing is highly recommended.

ok

[MSG:Pgm End]

MPos:0.000000,100.000000,0.000000,0.000000

MPos:0.000000,0.000000,0.000000,0.000000

M314 N2

ok

MikeyH · August 14, 2025, 8:39pm

How old is the machine? You could have a limit switch going bad. These switches are usually wired Normally Open, but a N.C. loop with a loose connection can cause this.

Another possibility is there might be an intermittent short between a pair of wires running to one of the switches.

If your machine has a flame sensor, this could be giving false triggers (bright light) but I would expect an Alarm 3 here. xTool has its own way of doing things.

The final possibility is that you are using Current Position or User Origin instead of Absolute Coords for your Start From choice.

creADDive · August 14, 2025, 9:07pm

Thanks for the quick reply!

The machine isn’t more than 1.5 years old. I don’t use it regularly, either. Is there a way for me to test the limit switch without buying a new switch?

The D1 Pro has a flame sensor though, but I’ve got the laser in a box w/ windows, and bright light generally doesn’t reach it. It happens day or night, too (eliminating the possibility of sunlight triggering it).

I have Absolute Coords selected, yes.

MikeyH · August 14, 2025, 9:59pm

xTool is not GRBL friendly but you can try. Enter ? in the Console window and see if it reports something. It should start out with <Idle | MPos: if it works for you. If it does, copy and paste it in a reply.

Do it before you start, and again when it stops with the alarm. Copy and paste in a Reply.

creADDive · August 15, 2025, 9:07pm

I got around 40% through a 25 min. project when the Hard Limit Trigger set off. I had ? sitting in the command window so I could hit Return as soon as it triggered, but it doesn’t look like it got the <Idle | MPos:

I appreciate your help, really. Do you have any other suggestions?

Waiting for connection…

ok

[xTool D1Pro:ver 40.31.006.01 B2]

ok

<MPos:0.000000,0.000000,0.000000,0.000000

Project loaded in 9 milliseconds

<MPos:0.000000,0.000000,0.000000,0.000000

?

<MPos:0.000000,0.000000,0.000000,0.000000

ok

<MPos:0.000000,0.000000,0.000000,0.000000

ok

Starting stream

Stream completed in 0:00

ok

[MSG:Pgm End]

<MPos:30.000000,130.260000,0.000000,0.000000

Starting stream

Layer Cherry-Walnut Fill

M8 N1

time out 1s

err:limitCheck

ALARM:1

Hard limit triggered. Machine position is likely lost due to sudden and immediate halt. Re-homing is highly recommended.

On or near line 1:

Job halted

Stream completed in 10:50

ok

[MSG:Pgm End]

<MPos:0.000000,100.000000,0.000000,0.000000

ok

?

<MPos:0.000000,0.000000,0.000000,0.000000

ok

<MPos:0.000000,0.000000,0.000000,0.000000

M314 N2

ok

[MSG:Pgm End]

<MPos:0.000000,0.000000,0.000000,0.000000

ok

start_home x

start_home y

up limit trigged

<MPos:0.000000,0.000000,0.000000

M28

<MPos:0.000000,0.000000,0.000000,0.000000

creADDive · August 15, 2025, 9:28pm

I’m hopeful that I might have this figured out. I bought these line management clips, (https://www.etsy.com/listing/1213386165/air-assist-line-clips-xtool-d1-and-d1?ref=yr_purchases) and it looks like the stress from the head moving along the x-axis is pulling the Limit Cord loose. It’s strange because I had checked these limit cord connections yesterday on your suggestion, and they were all connected, though one felt loose on the Y-axis limit. I just re-ran a project and the x-axis limit cord was completely unplugged. I just took these clips off the machine, re-checked/re-inserted the axis limit cords, and I’m running the project now. Fingers crossed! Will update.

soniclab · August 15, 2025, 9:34pm

What happens if you place your shapes in the center of your workspace?

Can you show us what you see in your Preview window now? (Alt+P)

creADDive · August 16, 2025, 5:57pm

It seems to trigger the limit alarm when things are in the middle, also. Here’s a piece I started this morning. It went around 2.5 hours before triggering the limit alarm. This is what the preview window looks like.

And this is how far it got before the hard limit triggered alarm went off.

jkwilborn · August 16, 2025, 6:33pm

It would be better if you answered the questions more clearly. Such as, is the work piece you have, arranged in the middle of the machines work area in the left/right or X axes?

I agree with @soniclab that you should move your work piece to the center of your work area, at least along the X axes.

In the preview, I can see the left side of the work area (green line), but are you centered within the X direction work area?

creADDive · August 16, 2025, 7:02pm

Oh, I understand now. Sorry, you are correct. The pieces are more left aligned. I’ll move the material to the center of the machine and give it a go. I have L-bracket magnets that square the material to the honeycomb, which is why I had the material more to the left of the workspace. Thanks both for the suggestion!

creADDive · August 17, 2025, 12:19am

Moving the material to the center of the work area did it!

Those clips I was using were definitely one issue, but once those were taken off I was getting the Hard Limit Trigger. Not anymore - I just completely the first 5.5 hour continuous burn since owning this.

Can’t thank all of you enough! Really appreciate the quick responses and clarifications.

jkwilborn · August 17, 2025, 7:24pm

It means something isn’t correct with how the machine is being emulated on your machine. The controller values might need to be updated.

This is usually in the Edit → Device settings → Additional settings and click on read from controller.

I use Lightburn V1.7.04

creADDive · August 22, 2025, 5:05pm

Guess I spoke too soon. After knocking out the project mentioned above, I’ve been getting the Hard limit triggered alarm continuously again. I’ve moved the material to the middle of the work bed each time as instructed. I also updated the controller values as you described, but got the error again shortly after restarting the job from the failed position.

Should I be restarting the machine after the alarm and re-homing the laser? Very frustrating again.

I’m using Lightburn Core 2.0.02

Pasting in Device Settings for my xTool D1 pro with the extension rails in case something looks fishy to you. Thanks again for the help! Greatly appreciated.

jkwilborn · August 22, 2025, 5:12pm

In the laser window, there should be a start from and a job origin. A screen shot would help with this.

creADDive · August 22, 2025, 5:26pm

Sure thing. Here you go.

jkwilborn · August 22, 2025, 5:30pm

How does this look in preview?

Using absolute coordinates, it should show up on you’re workpiece in exactly the same place you placed it in your workarea on the screen.

Might include a screenshot of your whole screen with the layers visible.

I’ll be out for a couple hours, will check in when I get back.

creADDive · August 22, 2025, 6:54pm

Thanks, Jack.

I drew this black line at 355mm in the main workspace of Lightburn, which is almost exactly where it is vertically on my machine.

Here’s how it sits in the actual work space. I put the square edge as close to where the laser is homed as possible, but the top I was measuring in the preview is measuring roughly 35.5cm. I also put dash marks to the right of the cutout in the 4 different places I got the Hard Limit Trigger (3 on the bottom, 1 on top). Note that I cut out the topmost last night, and got the 1 Hard Limit Trigger, and cut the bottommost today and got 3 more. The bottommost is what matches the preview screen above.

jkwilborn · August 22, 2025, 7:47pm

A hard limit usually means you have tripped a limit switch. Does it move anywhere near the limits?

You might have a faulty switch that the machine movement is causing to be an intermittent.

creADDive · August 22, 2025, 7:59pm

No, no where near the limits. I ordered some new wires from Geeks at Large that just arrived. I guess next move is to get some new switches from xTool?

jkwilborn · August 22, 2025, 8:01pm

Since it’s intermittent, it’s more likely something like the switch itself… even more so, it could be as simple as something being loose.

Generally speaking, things, like wires break when they have some type of movement, so I’d think it would be unlikely to be a cable. Anything is possible.