[old] The Laser Cutter LOCKED OUT Due To Severe Misalignment

After two different users mentioning problems with the laser today, I inspected it and found the mirrors to be severely out of alignment - to the point where the (red) guide laser was not visible, and the top part of the cutting head being hot, indicating a portion of the (invisible) cutting beam might be hitting the inside of the housing.

Due to the risk of damage to the laser and/or its users, I’ve locked-out the laser cutter.

I did this by disconnecting the leads to the switch that energizes its main power contactor, cutting power to both the laser and drive motors. The disconnected leads are behind the door shown in attached image.

Do not reverse this lock-out. The severity of the problems and the fact they’ve returned so quickly mean this requires the attention of an experienced laser technician.

There are probably some fasteners that have come loose and need be re-installed with loctite. We also likely have worn-out belts and/or pulleys, causing one side of the the gantry to slip. But these are only educated guesses.

Seriously, do not try to repair this machine yourselves.


Maybe related: over the past ~2 years I have, on a number of occasions, seen the exit tube collide with the weighting bean bags, sometimes dragging them along, sometimes causing a gear-grinding sound inside the machine. Fewer than a dozen times, all randomly observed just walking into SparkleForge to do something else.

I have told those users that allowing this to happen is harmful to the laser cutter, can cost NB $$$, reduce available uptime, and ultimately make the laser unavailable to other users.

That speech has mainly earned me shrugs.

There’s a kind of hygiene one has to follow when using that machine, which includes moving things like weights out of the way before sending the head to origin, or on a powerless test run, etc. I get the feeling that this hygiene is not universally followed, accepted -or perhaps known of.

I don’t really know of a way to help this be enforced, short of a putting a camera in the thing, or perhaps a bump sensor.

Really not sure how this could have happened. I was there when the tech aligned everything, same with analog.

If it’s mirror adjustment screws then it has to be at the one directly coming out of the laser, correct? (Or the tube itself)

If it’s the gantry going askew then I’m surprised that the beam is shifted downward on the vertical axis but I guess anything is possible.

Happy to hear some people are interested in solving this problem!

  1. If the machine’s head hits an object and you hear a grinding sound …that’s a belt slipping due to too much torque. This damages the belt by grinding the notches off it, stretches the belt, and also grinds the teeth off the driving pulley. If collisions happen often enough, you end up with a system with belts that can slip during normal operation. So potentially we need new belts and pulleys. Not expensive. Available from Mcmaster-Carr.

  2. You can reduce the probability of object hits causing damage by tuning the stepper motor currents such that the current for each motor is set to the minimum the cutter needs for fast travel and no more. All extra current does is damage the system during a collision. Has the system been “tuned” for the correct current on each motor?

  3. Has the gantry, and everything on it been squared / trued and fasteners set with Loctite? I’ve heard reports of parts of the gantry pillars sliding around.

  1. TechShop’s laser cutters were equipped with “idiot heads” held on by magnets. If it hit something, it would just get knocked off, then the user would pick it up and snap it back on. It self-aligned somehow. I wonder if we could do that with our laser cutter.


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Love the idea of “idiot heads.” Your other suggestions good too.

We are planning on setting up a pi and maybe some microcontrollers to get feedback on system performance. Laser tube current, brightness, and maybe bump and vibration sensors as you say. We could also put tamper evident paint on the mirror adjustment screws and probably lock the laser tube cabinet.

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