Full Spectrum 40W Hobby Laser *SAFETY* review -- problems and possible mitigations

[jfawcett]

All of us have dangerous tools in our shops. We have saws, lathes, routers, chisels, planes, and many, many other things that can harm and even kill us. We all know and accept the risks of using these tools as a standard part of working with wood. We mitigate the risks by first understanding them, then considering how we can minimize both the probability of occurrence and the impact should everything go horribly wrong. In most cases, though, The tool distributor (Rockler in this case) and/or the manufacturer generally provides knowledge about the danger and recommendation for mitigation, and that’s what’s missing here, especially if you remove the bottom panel. This review is an attempt to provide my fellow woodworkers with information I’ve gained about operating this machine in a relatively safe manner.

It all starts with understanding what you’re dealing with. Most people simply can’t visualize what a 40-watt class 4 laser can do, so we'll use an analogy – water. All of us have turned on a tap and placed a hand under it, or even turned on a hose. If you add a nozzle to the hose, you get a more directed stream that you might not want to stand in front of. If you keep decreasing the size of the nozzle and increasing the pressure, like with a pressure washer, you get a very energetic stream that can very much hurt if it contacts you.

None of these are like your laser. Your laser is like a water jet – a very, very small nozzle backed by a very high-pressure stream of water. The water leaves the nozzle at a rate high enough to cut cleanly through many surfaces. The operator has control over the speed the jet moves and the pressure of the water coming out. If you substitute high-energy photons traveling at light speed for the water, and increase the danger factor by a couple of orders of magnitude, you begin to approach the destructive potential this laser has.

Now think about the water jet as it’s running. If there is material there, the water cuts through the material, expending some, most, or all of the energy imparted by the pressure. If the jet can’t cut through, then all the energy is used up in the work and everything’s good. If, on the other hand, the jet cuts all the way through, some of the water will come through to splash against the backstop. The force with which the water hits the backstop is a function of the thickness and density of the material you were cutting through, combined with the speed and pressure of the water jet.

The worst-case for the water jet, though, is when it’s firing and there’s nothing for it to hit. In this case, the entire force of the water jet stream (force that can cut through many surfaces) is expended on the backstop. If the backstop doesn’t hold, there will be at least a big mess, and there could be some very serious damage or injury.

You have to use the same considerations for your laser. It’s not just about the surface you’re cutting or engraving; it’s about what’s behind it. With a water jet you need something that can stand the pressure of the stream. With a laser you need something that’s not flammable.

I ran a series of experiments to find out exactly how dangerous this device is. I created a 1” square box in CorelDraw and used that for a number of runs. I set the laser head at the highest possible position, and put a piece of ¼” MDF on the very bottom of the laser (in other words, the head and material were as far apart as they could be while still within the bay. The laser beam itself should have been very defocused). I then ran different speed and power settings to see what happened. At 5% speed and 100% power, the MDF lit up like kindling. At 100% speed and 100% power, it was still charring with a nice red glow visible. It was not until I got down to 100% speed and 35% power that the charring even started to disappear. The laser head, friends, is capable of charring something at least 5” away when running at very low powers.

With this in mind, then, these are my tips for working with this laser:

1. Material selection and cutting parameters: As many reviewers have noted, there are no recommendations for speed/power settings for anything at all, anywhere that I could find. I refuse to speculate about why this information is not provided, but I can state from experience that figuring these things out consumes both time and material unnecessarily. Mitigation: I highly recommend a site called laserbits.com, and their Laser University. Of particular value is a Laser Settings table (also available as Android or iPhone apps) that provides recommended settings for both engraving and cutting a wide variety of materials including acrylic, stone, leather, and wood.
2. Air flow under the honeycomb table: If you’ve tried to cut either wood or acrylic over the honeycomb table, you’ve no doubt had to deal with charring from the underside. This happens because the honeycomb table provides no air flow underneath, so the air becomes trapped and stagnant. If you have the honeycomb table sitting over something flammable, then any unused energy just shoots through to the bottom, where it does not have the air assist to blow it out. This is also why you’ll sometimes hear a big FWHOOP from the material bay – it’s the hot air escaping. Mitigation: Add something to the bottom of the honeycomb table to get it up off the floor. It doesn’t have to be big, but as long as you’re going to do it, you may as well improve the thing and add little rubber feet like you put on cabinet doors. Then it won’t move around either. An alternative would be to just stick some pennies or dimes under the edges. Just get it up off the floor.
3. Use a fire-safe backstop, especially if you’ve removed the bottom panel: I strongly recommend ceramic. I used 4” black tile squares that I attached to a piece of MDF using Liquid Nails. Once the tiles were down, I put sandless grit between them and let everything dry. When placing the tiles, I put them at a very slight angle (~3 degrees) to minimize the probability that I will track a grout line. If you use 100% power and 5% speed, you can mark the tile to draw a grid, but you’ll never be able to ignite that stuff, and you’ll never be able to cut through it. I don’t recommend using metal, like the bottom of the laser, because it gets hot and stays hot. The ceramic will be cool enough to touch almost immediately after the laser stops firing. Using ceramic virtually eliminates flare-up, blowback, or charring. If you use ceramic tiles as I’ve described above, you don’t need to use feet on the honeycomb table unless you want to. The grout lines will provide sufficient air flow to put out any flares that pop up.
4. Consider power routing: Neither of the blowers are electrically joined with the laser itself, so cutting power to the laser has no effect on either of the pumps. Normally, this isn’t a problem but if you have a fire in the material bay and shut the power down, the still-running blower fan will actually feed the fire so you end up with a nice column of flame shooting up from the middle of the material bay. Impressive, but not really desirable. Mitigation: I’ve purchased a separate, long, workshop-grade power strip that I’ve screwed to the front of the bench, and everything plugs into that. I can reach the master power switch on that strip no matter what’s going on inside the laser, allowing me to completely cut power.
5. Use clean power: In my shop, the lights dim for a second when I start the table saw. Power fluctuations like this are bad for computing devices, so you need clean power. Mitigation: Use a surge suppressor at a minimum. For my shop, I’ve purchased a server-class uninterruptible power supply that not only cleans up and conditions the power, but provides me a few minutes of controlled shutdown time if there is a complete failure. I keep everything for the laser, the laptop, and the CnC machine plugged into this UPS, and it’s able to handle all three at once.
6. If you remove the bottom, be extra careful: Keep in mind everything I said about water jets, and remove the backstop. By removing the bottom, you’re unleashing the full power of this laser to whatever happens to be under the laser head. Use caution, and use ceramic!
   
   Be aware that these units lack any sort of cutoff save the ones on top. There are the big red button and the top-open interlock, but that’s it. There is no tilt switch, no front-side cutoff or interlock, and nothing to prevent you from either picking the entire unit up, or sticking your hands underneath the thing and inside while it’s running. If you place the top cutoff (big red button) and interlock out of reach, your only remaining option is the power strip.
   
   These are the additional things you need to think about if the bottom is removed:
   
   1. Don’t stick your hands inside while it’s running
   2. Get something to stick in front of the thing to remind you when it’s firing. I use a piece of MDF that I have to move to get to the material bay. When firing, the MDF is in place. When I’m done and have disconnected the interlock, I remove it.
   3. If you can’t get the lid opened up all the way, use a block – just make sure you disconnect the interlock
   4. Make sure it’s level and steady when it’s up. You absolutely do not want that thing falling, especially if it’s only the back side that falls down. Remember how far and with what force a water-jet would exit the bottom with, and go up a couple of orders of magnitude. If it falls off the supports, the laser will continue firing straight out the bottom of the thing, hitting what or whom-ever is in the way.
   5. Because of C above, do not stand directly in front of the laser when it is raised
   6. Also because of C above, do not ever, ever pick up the laser while it is firing. It will not stop firing.
   
   

Yes, I had a fire and burned mine up. I'm not going to go into any details about the incident, except to say that I have reported it to the FDA and the Attorneys General of the states of Nevada and Washington. The laser has value, though, so I now have a second one. This time, I've got some understanding of exactly what the thing can do and how to mitigate, and the new laser is providing a much, much better experience. I hope this information helps someone else prevent a fire, and I hope it makes a lot of people have better, and safer, experiences with the laser.

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[ger21]

Why would you ever remove the bottom?

A laser is not a toy. It can be an extremely dangerous device, which is why it's in an enclosure.

And a laser cut's by burning through items.
Burning flammable items can and will result in fires.

A laser should never be run unattended, as the risk of fire is always present, even in the most expensive high end machines.

Sounds to me like your blaming the manufacturer for not understanding what you're doing, and the risks involved.

[jfong]

It's so you can put in a taller object that may not fit otherwise. They even have models that the front and back can open up. You can slide in a longer piece in to be lasered.

My cheap k40 laser only has 3.3" from the bottom to focal distance. Really not work space for taller objects. Was thinking of cutting away the bottom of the laser box.

Installing tile on the bottom of the laser is a good idea. Scrap paper that falls to the bottom does get charred if the laser passes over them.

[jfawcett]

The laser is advertised and sold as having a removable bottom. There are instructions to remove the bottom, including a video. They sell a rotary attachment to do glasses and the like that is all but useless without the bottom removed.

I am not blaming the manufacturer for anything except failing to provide information about the safe operation the the machine, especially with the bottom removed. At what point above did I blame the manufacturer for anything else? Yes, this is a dangerous machine, and they should give you some information about what those dangers are and how to mitigate them.

Since the manufacturer didn't give the information, I decided I would. How is this a bad thing?

[jfawcett]

By the way, once you get the bottom off it's very difficult to get it back on. There are many tiny screws.

[derekja]

No issue at all with your reporting the problems here. That's a benefit to the community. Reporting to the FDA and AG's of Nevada and Washington, though, is pretty ridiculous. Why encourage intrusive regulation of devices that merely need education around them? That's what sounds to me like crying about why didn't the nanny state protect you from yourself.

[ger21]

Reporting to the FDA and AG's of Nevada and Washington, though, is pretty ridiculous.

Yes, that's the issue I had.

[jfawcett]

Well, your opinion is your opinion, but the guy at the FDA said they've seen a real spike in reports about these kinds of lasers (he could not comment on FSL directly), as these devices are now making their way into schools and homes.

Nobody is going to change the regulations for a single incident, and I wouldn't expect them to. However, if there is a pattern of incidents, particularly for a specific manufacturer, wouldn't that indicate a change is necessary? Who will keep track of those incidents if they're not reported? Who will recognize the pattern? Who will see that the changes are incorporated? Hiding your heads in the sand to prevent "unnecessary regulation" is not going to do anything at all.

[ger21]

However, if there is a pattern of incidents, particularly for a specific manufacturer, wouldn't that indicate a change is necessary?

No, it indicates that people that don't know how to use lasers shouldn't be using them.

You bought a cheap chinese laser. You got what you paid for.

If you want a laser that doesn't have these issues, buy one that costs 3-5x more. And be aware that they can still catch on fire.

If every chinese laser owner complained to the FDA, all you'll be left with are lasers costing upwards of $10,000.

Wait til the tens of thousands of glowforge lasers get into peoples homes next year, if you want to see a lot of incidents.

[jfawcett]

No, it indicates that people that don't know how to use lasers shouldn't be using them.

And, if you actually read my original post, is what I'm trying to do -- help people who don't know how to use them. If you have a better way, please feel free to follow-up. Otherwise, you're just saying that you're perfectly happy sitting back and watching people end up with damaged property and/or injury, because (see quote above).

Lasers, CNC, and 3D printing are going mainstream now, so yeah, they have to be held to a higher standard. If you want to get out your soldering gun and slap together something on your own, you deserve what you get, but if you're buying a mass-market ready-to-run model, the supplier does, in fact, have an obligation to assume the users are complete idiots and prepare accordingly. The same thing happened to the personal computer a long time ago (you used to have to assemble your own machine), and prices have done nothing but decline while quality and customer satisfaction have increased significantly, all under the awful eye of the "nanny state." Cell phones, televisions, and even cars are all examples of the same change. The morons are coming, Gerry, and our name is Legion.

[Dean448]

I'm not sure how the head of that FSL unit is set up but there are two different methods to provide the air. Most of the low cost units have a nose cone that you force air into. It's very difficult to start a fire when the air is properly applied directly thru that cone. The FSL has a separate tune I think that is designed to blow air on the cut but I guess there is no guarantee that it's set up properly. So my opinion is that you direct air directly in the cut, little chance of fire. Direct it towards the cut and different potential for fire.
You might say but epilog has no cone. To that I would say you can't compare an epilog to a Chinese laser
Btw my unit has a cone and unless the air dies or wasn't turned on I don't expect anything to catch fire.


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[fixtureman1]

I'm not sure how the head of that FSL unit is set up but there are two different methods to provide the air. Most of the low cost units have a nose cone that you force air into. It's very difficult to start a fire when the air is properly applied directly thru that cone. The FSL has a separate tune I think that is designed to blow air on the cut but I guess there is no guarantee that it's set up properly. So my opinion is that you direct air directly in the cut, little chance of fire. Direct it towards the cut and different potential for fire.
You might say but epilog has no cone. To that I would say you can't compare an epilog to a Chinese laser
Btw my unit has a cone and unless the air dies or wasn't turned on I don't expect anything to catch fire.


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Not true I have the nose cone setup and have had flame ups that I had to put the fire out. I cut a lot of acrylic and have had some small fires. That is why I am never to far away from the laser when I am cutting

[jfawcett]

The FSL unit does not have a nose cone, but wouldn't that only impact the top of the piece anyway? I observed that the flame-ups were starting from underneath the workpiece, not above. If the laser is cutting through something, whatever energy is left after the cut is complete is passed on to whatever is behind the thing. If you're using a honeycomb table, as I do, and you don't elevate that table slightly, you'll end up with trapped, unmoving air between the acrylic and the floor, and that's where flame-ups were starting.

My laser has two blowers -- the directed one on the head, and the exhaust. The directed one shots air at the point of highest energy concentration, which is a good thing. If you raise the honeycomb table a little, you let the exhaust blower set up airflow underneath the table, which gets rid of the trapped air and, with it, the flare-ups.

Try putting a penny or dime in each corner of your table and make a run. Your results may differ, and I'd be interested to know if they do, but I've had great success now that I'm both shooting over ceramic and have airflow beneath the table. Since switching to this environment, I haven't had a single flame-up. Not one. Even better, when I cut plywood the bottom looks just as clean as the top.

[fixtureman1]

I have had flare ups while engraving into MDF