I’m Stephan, living in the deep forests NE of Gothenburg, Sweden. I bought an LC-60 (did not find any specific forum for the LC-60 but I guess it’s only the size that differs) about a year ago for a project cutting acrylic profile templates. No problems putting all together and start-up. I did a few engravings to start learning LightBurn and the machine and all worked well.
I then got an unexpected halt with that project due to other work. About 6 months later when picking up on the project again, the LC-60 “flipped out”. When I switch it on, the laser immediately starts and all step motors are “humming”. It does not answer to any commands from anything other than the emergency stop button.
I got new boards from SainSmart to both the laser and the main box but it made no difference. I disconnected the laser to try and manoeuvre X and Y or get the “Home” function to run, but nothing works. It seems that all functions getting a signal to operate at the same time, in all directions.
I have checked all cables and switches for damage but did not see any so far. Does anyone has any idea on what could cause this “phenomenon”? SainSmart wanted to replace the whole machine, but at that time it was out of stock so they did a refund and I bought a 3018 PROVer V2 instead to do the templates.
However, I think every machine deserves a “second chance” and it would be very interesting if one could find out and understand what is actually wrong with the LC-60. And of course, I would love to have the complementary functions of a separate laser CNC though I could use the head in the 3018.
I would be ever so grateful of any advice what to look for or a “step-by-step go through” on the different parts to get to the root with this.
It’s definitely a surprise that replacing the control boards didn’t change the symptoms. That plus the steppers humming make me worry about the power supply; they would hum only if they are being held at an intermediate partial step, or are being exposed to power that is somehow modulated, like AC. Is the hum between G and G#? If so, since you have 50Hz mains power, there could be a problem somewhere in your power supply…
Appreciating your quick response. I do have have a multi meter and hopefully know how to use it
I checked the power supply and it deliver a steady 12,3 V DC. I have now also disconnected all components and then connected one by one to see what happens and to more specific locate the “humming”.
The laser behaves the same (laser + cooling fan) and switches on as soon I push the start button. New though, with the laser alone connected I can switch it off by again push the power button.
Connecting the x-motor, one just notice this same reaction by switching on (a minimal movement left or right), and then it seems waiting in quiet for orders. x-motor + Laser = same problem.
Connecting the y-motors is different. Then the “humming” starts and it sounds a bit like a fan starting and work itself up to speed. The sound I estimate to be very close to a clean D in the second octave (D2). One can also feel a soft but clear vibration in the machine body. No reaction in movement as with x-motor.
OK, D2 near 73Hz can’t be a product of mains frequency. I was wondering whether it was passing a high voltage component through that was frying each control board in turn as you added it. That’s not a common failure mode as far as I know…
I suppose since you say “y-motors” that this uses a pair of motors for Y, so you can’t swap X and Y for a test to see whether the problem follows the motor or the drivers.
Does this control board have separate stepper drivers, or are they integrated?
If separate stepper drivers, were they replaced with the control board?
One can connect an off-line stepper control but those were sold-out when I ordered my machine. So the only way now would be to manage connect some via the laptop. I only tried so far to connect the laptop using LightBurn and I did not try to connect again with the y-motors disconnected.
I take it as it is still some other problem as the laser immediately switches on. It feels like one want to find some way of doing a “Ctrl-Alt-Delete” on the motherboard of the machine
Maybe I should disconnect all components and then see if LightBurn connects with the mainbox?
OK, that board has integrated stepper drivers. Means it’s not something where you could try just dropping in a new stepper driver and see if it blew up.
The way I look at it, if the power supply is good, the primary remaining question is whether the laser module is good. It seems unlikely that you magically have a few dead steppers.
However, you can disconnect them all and make sure that all of the coils have about the same resistance with your multimeter. Just connect two pins; they will either be disconnected (infinite resistance) or through a coil. If you find something else, let us know.
Honestly, if it were mine, I’d just replace the control board one of the multitude of 3d printer or CNC control boards available. Today, I’d consider one of the boards at Existing Hardware | Wiki.js some of which are specifically meant for controlling lasers. @easytarget since you have played with FluidNC and I haven’t, do you have thoughts here?
(Also, if it were mine, it would be in an enclosure to protect my eyes, since I was only issued two of them at birth, and apparently the supply of upgrades and replacements is basically non-existent. These blue LED lasers go right through the lens without harming it, and painlessly burn away your retina. The human brain is even better than generative AI at making plausible stuff up, so people often don’t notice the damage until they have a lot of retinal scaring, and that damage doesn’t heal.)
when I check DC power supplies I first check the DC output voltage and then switch the DMM to AC and see how much AC is riding on the DC output. It should be in the milliVolts.
I checked the power supply again. Also the one for my 3018 PROVer + a third one for another 12 V equipment.
The one for the LC-60 gives me 12,3 V DC and 26,3V when I switch to AC (on 200V scale).
The 3018 one says 24,3 V DC and 52,8 V AC.
The third one says 11,6 V DC and 24,7 V AC.
None show only some mV. Am I doing something wrong measuring?
I measured all step motors and they all showed 4-5,5 ohm so I guess they are good. I then found a switch on the board for the laser that I did not notice before or seen any instructions for. It’s the one showing between the laser/fan connectors and the DC connector (south) in the picture of the laser board.
When I deactivate that one, I can switch on the LC-60 without laser turns on. I could now also “home” the axels with the home-button on the control box. Further, I was able to connect LightBurn with the LC-60, it found the right machine and could also do a “home” command from there. The “test fire” function does not work when I deactivated the switch I found so I guess it just cuts power to the laser. If I put it back on, it is the same issue with the laser out of control.
I will now test to load a job with the laser disconnected to see if it will at least move around in a correct way and hopefully operation of the X/Y functions are then all ok.
The 3018 machine has the same laser head as an option to the spindle motor. Would I dare to connect the laser to the 3018 and its main board to see if it runs ok there, or do I risk to “burn” something on that one?
Ignore the AC measurements. @dougl is talking about the ‘ripple voltage’, but it sounds like your meter behaves like mine and gives the ‘AC equivalent voltage’ when you measure DC with it set to AC mode. Ignore this.
The ‘ripple’ is how much a DC voltage varies with time, you often get an ‘echo’ of the 50Hz mains frequency on the DC line varying it by millivolts.
I was wondering whether it was passing a high voltage component through that was frying each control board in turn as you added it. That’s not a common failure mode as far as I know…
