Video Shows Power Isn’t Everything In Laser Engraving

When it comes to power tools, generally speaking more watts is better. But as laser maestro [Martin Raynsford] shows, watts aren’t everything. He shares a brief video showing his older 100 W laser being handily outperformed by a newer 30 W machine. Shouldn’t the higher power laser be able to do the same job in less time? One might think so, but wattage isn’t everything. The 30 W laser engraves and cuts a wooden tile in just under half the time it takes the 100 W machine to do the same job, and with a nicer end result, to boot.

Why such a difference? Part of the answer to that question lies in that the newer machine has better motion control and can handle higher speeds, but the rest is due to the tubes themselves. The older 100 W machine uses a DC-excited (big glass water-cooled tube) CO2 laser, and the newer 30 W machine uses an RF-excited laser that looks a bit like a big metal heat sink instead of oversized lab glassware. Both tubes output what is essentially the same beam, but the RF tube is overall capable of a more refined, more stable, and more finely focused point than that of the glass tube. Since engraving uses only a small fraction of even the 30 W laser’s power, the finer control that the RF laser has over the low end of the power scale results in a much higher quality engraving.

Embedded below is a short video showing both machines engraving and cutting the same tile, side by side. You may wish to consider watching this one full screen, to better see the fine details.

Glass tube CO2 lasers have a big advantage: they are much cheaper than RF tubes. The hacker-friendly K40 laser design uses a glass tube, which is one reason is can be so economically priced. Laser cutting and engraving are wonderful tools, so if you’re interested, first spare some time to read up on all the ways it can go wrong and you’ll be ahead of the game.

22 thoughts on “Video Shows Power Isn’t Everything In Laser Engraving

      1. There are a few manufactures from china who are now making this sort of systems with a 30rf, the top maker of the rf tubes in china is davi lasers currently. The 30w is apparently pretty good and not that expensive 2-3k if i remember correctly, the higher powers are not so reliable.

        1. I’ve been laser engraving since 2000 with the same machine. I am about to replace the Coherent Gem 25A tube for the 3rd time. The 25A is no longer available and I investigated fitting a new Gem 30C, The price quoted was $6000 Australian. I came across the Davi brand while hunting around for a reconditioned Gem 30C. The Davi’s stated specifications are identical to the Coherent, so identical in fact that the Davi tube is either a copy or Coherent are connected in some way? Anyway, I have decided to take the plunge and fork out $3000 Australian on the Davi. I’ll also have to swap out the power supply to 48V from 30V. I’ll report back in a month when the changeover is complete and hopefully successful!

    1. You leave the gantry on but mount the Galvo head to the gantry. That’s how we build the laser micromachining systems where I work. They start around 300k for a low end model.

      The Galvos are coordinated with the linear axes, it pretty neat. Cambridge technologies makes a motion controller that will control galvos and a stage all in one called SMC.

  1. “Glass tube CO2 lasers have a big advantage: they are much cheaper than RF tubes.”

    Yah. I’ve been thinking about getting a K40 and I usually read articles like this as good news but not at face value. It’s not to say there is some new, better tech that is available to me though but that maybe the old tech I was already planning to buy will be cheaper because people with more money to spend will be going for the new one.

    But… “the newer 30 W machine uses an RF-excited laser that looks a bit like a big metal heat sink instead of oversized lab glassware.”

    So are these new tubes more durable then? Longer lived? Even a higher price once can be less than a lower price multiplied by multiple replacement purchases!

    1. Its not really an old vs new tech, but more price vs function/requirement.
      Most people buy the cheapest glass tubes they can find and then are disappointed to discover its rubbish.
      Spend a little more on a top of the range glassware and you will be surprised how well you can cut and engrave. Glass (dc) will always be limited with raster engraving due to the time it takes to ignite the gas, RF is much much faster. When it comes to vector engraving and cutting there is no reason a good DC system cannot match the results of an RF tube. Especially when you consider the cheapest RF tube (from china) easily costs 6 times the top of the range DC glass tube from china. Sure if the durability could be guaranteed then its interesting, however I have yet to find an RF tube with a warranty over 2 years, even though they all like to say they could last for 10 years…

      So DC or RF is essentially a financial question, will the increased speed (potential quality improvements) = more profit to cover the cost of the RF, in many engraving business cases yes, but for the cheap hacker maybe not.

  2. I will second the sentiment regarding rating them in terms of output. Its like the whole incandescent light bulb thing again. I still dont get why LED bulbs still advertise brightness in “wattage of incandescent equivalent”. Consumers dont know what a lumen is, because manufacturers aren’t fazing out the use of watts to describe brightness. It wasn’t the ideal unit back in the day of incandescent bulbs, and its only getting sillier and more convoluted to use as we move away from incandescent bulbs.

    We care first foremost about a product’s OUTPUT. This determines if a product will meet our needs (will this bulb be bright enough for my bathroom? Will this truck pull my trailer?) NEXT, we care about INPUT. Sometimes its to gauge efficiency, sometimes its to make sure we can actually supply the product with what it needs, and sometimes we dont care about input at all as we know it will work and dont care about its efficiency (when have you ever bought a soldering iron and were concerned about your house mains being able to power it or the soldering irons electrical efficiency?). My point is, if only ONE metric is going to be used to define something’s performance/capabilities, it should be based on the product’s OUTPUT. The next line/smaller font can then describe it’s input requirements, efficiency, etc.

    1. Something else that isn’t usually stated is the light quality, usually measured in CRI. I have a 50w COB LED that I don’t bother using because its blinding light is probably only 50-55CRI (Direct sunlight being 100); in other words, the light that it gives off is simply awful!.

  3. Heh, imagine when fusion power goes to net energy production for the first time and they’re all “Yeah we have a terawatt torus now producing power for 20 homes!!!” then they scale it to that equivalent and a decade later news “40 Yottawatt fusion plant comes online today for the town of Springfield MO…” Engineers screaming “No it’s not a tenth the size of the sun!

  4. The RF-excited lasers can’t operate continuously and must be pulsed, so a 100 Watt laser, at any output level, is sending out a few hundred Watts, when the pulse is on. For high-temperature materials, like Kapton, it works better than a glass tube laser, but for most other materials, it leaves a rougher more scorched edge.

  5. The real issue here is not the actual power of the laser but the limits of the controller/hardware of the 100 watt laser. He says that the 100 watt laser cannot physically move as fast as the 30 watt. This is not the lasers fault but the hardware. If he were to compare apple to apples, the 100 watt would win every time.

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