Abort and return to start position

given the 3018 CNC doesn’t have absolute encoders / limit switches etc you set the start position manually where you want it for and then tell it to start from current position which is all fine

if you have to abort it mid processing by hitting stop, its essentially impossible to return to the start origin [ well as far as I’ve worked out so far anyway ]

if 1 layer for instance didn’t actually mark , I want to stop it burning, return to where it started from and then just sit there waiting so you can then tweak that layers settings and then run all or some of the layers again from the exact same origin

I realise this is a bit of a “get what you paid for” problem with having a cheap CNC but essentially it returns to the start if it completes the whole process so why not if you abort it

Andy

Hi, Andy have you tried the ‘preview’ panel?
When you preview your project you can use the slider to go to whichever position you want.
Select ‘start here’ and in the dropdown menu ‘start job on laser from here’.
I’ve used it a few times but i don’t have a cnc machine but hopefully it works for you too.

I think there is a way in Lightburn to resend a layer by itself or a selected object. Can’t remember. You’ll have to look at the docs…

The point here is that when you abort a run it just stops dead where it is.

If it runs to the end it will retourne to the start position.

Typically you just have a random start position to start from that isn’t a known position

All it wants is an abort and return to where you started option as if it finished the full burn

Hit Pause instead of Stop, then hit Stop. The job will end gracefully and you don’t lose your positioning.
It’s a GRBL thing, not a Lightburn thing…

My CNC3018 is packed away so this comes from memory.

What kind of error is it getting that you have to abort it? Many of these wire the abort switch to the cpu reset or do some type of soft reset. Why do you need to abort it? I would not call that a normal operation. Lightburn has a pause button, so you can pause it.

When you have a fatal on those you have to do a ‘reset’ or a manual intervention. That clears all memory from the device or at least invalidates location information. So it’s brain dead at that point, just like you powered it up. I didn’t have these issues mainly because I put limit switches in, so I could reproduce the position. It was still awkward but doable because of the limited capabilities of the controllers. But they are ‘low cost.’

Limit switches are easy to install and cheap and will take you from ‘pushing’ the bicycle to ‘riding’ the bicycle. A much better experience. You will undoubtedly learn a great deal along the way as we all do.

Software to handle these take up lots of code space. When you write software, most of the code is not what you’re trying to do, but handling of errors that come up. Not to mention trying to read some users mind who came from another planet. Most of these controllers have limited memory, hence limited error handling ability.

I’m sure you can find the open source code to the machine. You can easily be a hero to us all, just grab the open source and fix it… :slight_smile: We’d all really appreciate it.

We all struggle with this, sit down relax… All (well most, lol) of this stuff does work, just takes time to figure it out and understand it.

Take care we are here if needed…

ah ok I will try that next time

that just isn’t an intuitive thing to do - if its not burning that layer because the setting are wrong and you realise and want to stop and restart it, stop to me is more obvious than pausing but will see next time how that behaves.

thought there should be a way to abort and return to the origin but hadn’t worked that out!

I do agree that ‘Pause, Stop’ isn’t intuitive, but that Stop while running code causes a reset, isn’t. In any case, if you can discipline yourself to hit Pause first (and THAT is hard when your work piece or table is being burnt up!), then you might be able to recover. As @Kris1 mentioned above, you can use the preview window to start at a particular spot and, as long as you haven’t lost your reference because you physically ran into something or gone off into the weeds, then you should be ok. In this case only your last object burnt may not be quite right and hopefully it can be touched up.

If you really wanted to, couldn’t you add some limit switches. I still have my woodpecker CNC board from my genmitsu 3018 and it has pinouts to add limit switches. I don’t know what kind of board you’re running but if it has pins for limits then it would be super easy and cheap, at $10 on Amazon for a 5 pack, then you would just need to enable it in the console on Lightburn. If you did this you could home your machine and have a set point to begin from every time. So say you home the machine then you have to move 3.5in right and toward you by 2in to get you right over the workpiece, knowing how far you initially moved makes it easily repeatable in the event of a stoppage.

Grbl is a streaming system that has a limited ‘queue’ of instructions. You can pause it, but you have to control your laser physically if you wish to change something.

My CO2 laser can be paused, but you can’t change anything only continue from where you left off. When I stop it with ‘esc’ it’s back to it’s origin.

Most of these work that way. What I’m understanding what you want has never been see by me.

The simple fix, is limit switches. The other option is for you to fix the code yourself. Many people have learned how to code this way :slight_smile:

Good luck, take care.

I did pick up some switches but never got as far as working out how to get them mounted on the axis in a sensible way and place to not reduce the working area too much and to not come adrift

Because you haven’t read the LightBurn GRBL docs…

The limit switches I bought have holes in the circuit board for mounting, I used a m5 bolt and a t-nut to attach it to my v groove aluminum frame. My machine is homemade and at one point in the early stages I even attached the y limit switch with some hot glue haha. As long as you know your soft limits and your not going to crash the machine by placing something way to large or just way off the work envelope, your limits in my opinion don’t need to be hardcore bolted down, the hot glued limit switch lasted for months till I stopped being lazy and finish the build so it would be more professional. When homing the machine the gantry moves slow enough that it just barely taps the limit switches and even if you had a hard crash it might pop the limit switch off but it would definitely still activate it and stop the machine(with hard limits enabled). Anyway just throwing my ideas in the mix.

Best Regards,
Alex