Laser Surgery: Expanding The Bed Of A Cheap Chinese Laser Cutter

Don’t you just hate it when you spend less than $400 on a 40-watt laser cutter and it turns out to have a work area the size of a sheet of copy paper? [Kostas Filosofou] sure did, but rather than stick with that limited work envelope, he modified his cheap K40 laser cutter so it has almost five times the original space.

The K40 doesn’t make any pretenses — it’s a cheap laser cutter and engraver from China. But with new units going for $344 on eBay now, it’s almost a no-brainer. Even with its limitations, you’re still getting a 40-watt CO2 laser and decent motion control hardware to play with. [Kostas] began the embiggening by removing the high-voltage power supply from its original space-hogging home to the right of the work area. With that living in a new outboard enclosure, a new X-Y gantry of extruded aluminum rails and 3D-printed parts was built, and a better exhaust fan was installed. Custom mirror assemblies were turned, better fans were added to the radiator, and oh yeah — he added a Z-axis to the bed too.

We’re sure [Kostas] ran the tab up a little on this build, but when you’re spending so little to start with, it’s easy to get carried away. Speaking of which, if you feel the need for an even bigger cutter, an enormous 100-watt unit might be more your style.

Thanks to stalwart tipster [George Graves] for the heads up on this one.

29 thoughts on “Laser Surgery: Expanding The Bed Of A Cheap Chinese Laser Cutter

  1. I keep going back and forth about getting a laser engraver/cutter. I’ve pretty much ruled out a mill because I don’t like doing 3D CAD, but I think I ought to be able to do bog-standard 2D drawings. But, then I start reading about all the hazardous things (i.e., blindness, toxic fumes, fire), then decide it’s not worth the risk. Then again I keep coming across projects that are done with a laser cutter and think it’d be nice to have one.

    Nice project, BTW.

    1. We have had a laser cutter/engraver in our hackerspace for about 1.5 years now and it has been safe to use. I find the risks to be very small when all the necessary safety points are taken into account. Yes, the beam can harm your eyes and even cause blindness but it is easily prevented: Firstly, never open the lid when the laser is turned on. The lid usually has a window which is made of acrylic or some other see-through plastic that absorbs the IR-wavelengths but lets visible light go through. Also the beam is focused only on small spot so the radiation is scattered and a lot weaker elsewhere. Toxic fumes are also easily prevented: We have the rule not to cut anything that releases toxic fumes, for example PVC, ABS, polycarbonate etc. That is of course a restriction but we haven’t found that to be a problem as the most oftenly used materials are safe-to-cut acrylic and plywood. We of course still have a fume extraction pipe leading outside to minimize the amount of smell and fumes. Works very well! Fire can not always be prevented (we have had some experiences too… :D) but that’s why you should never leave the machine unattended when it is operating! There have been a couple of times when the material slightly caught fire put it was quickly put out as there were people around. We also have a fire extinguisher and a fire blanket in case something really starts to burn. (Those should ALWAYS be around anyway.)

      With these tips it should be very safe to use a laser cutter/engraver so don’t hesitate to buy one! :) Of course it is worth looking a bit to find a good one – the quality varies.

    2. Perhaps think about getting a scroll saw. They are much lower in cost (a mid range one is the price of a dirt cheap laser cutter), and it can do much of the same things. The limitations are obviously on engraving (you need to cut all the way through) and on some precise shapes (if you need a perfect circle there are other techniques you can use). However there are some benefits, too – you can cut thicker material, there are no burns on the edges (unless you use a dull blade), and after a bit of practice you can cut faster than the cheap laser cutters can. Plus you have the pride of workmanship that you may not get with an automated tool.

  2. Where did you come up with the 5x bed area figure? I couldn’t quite find it. :(

    I’ve been thinking about buying a K40 for about a year now, but am having trouble justifying the price for such a small cutting area…

    I wonder how much [Kostas] spent on this mod? I didn’t see much of a writeup anywhere, just the files and photos.

    1. Once you removed the ridiculous letterbox thing that’s supposed to clamp the work and add some sort of honeycomb table, the working area of the K40 is about 300 x 200mm. I can just about get A4 sized acrylic sheets in mine.

    2. I didn’t spend too much… lets say 150-200 euro for the alu extrusions , belt, bed, led,laser pointer,radiator(used),temp controller .. the rest parts i have it already .. and i have also upgrade the board with smoothie based board ..but this is optional.

    I recently snagged this linear assembly from a Roka automated pipettor machine. The lab where I worked had the machine serviced, and rather than replacing just the bad part, a WHOLE ASSEMBLY got shipped for the tech to install. They stripped the old assembly of it’s motors (left the bad one), but other than needing to replace the motors and belts, the entire assembly is intact.

    Overall, It’s 46 inches (116 cm) long and 28 inches (71 cm) deep. The linear mechanism is nearly 41 inches (104 cm) long, so accounting for end stop sensors, it would presumably allow a 20 inch (50 cm) bed to move 20 inches (50 cm) along the axis of travel… That’s still an decent amount of potential build volume, even if it’s just one axis. The mounting points (where you’d attach the bed) are 23 inches (58 cm) on the inside edge, and 26 inches (66 cm) on the outside edge, so bed depth would be based on how you mounted it to the traveling linear mechanism. Honestly, it’s probably easiest to mount on the inside.

    All I know, is I need just the vertical and depth mechanisms added to this to have the mechanical base for a reasonably sized 3D printer. I suppose it’s not dedicated to any specific task. Could easily be a laser cutter too. This thing has so much potential! I suppose, if I suspended it, and mounted the y axis to it directly, I could potentially get even more travel out of it, and then make the bed into a massive Z axis…

    I’ve never built anything like this before, so I’m really kinda at a loss as to even where to begin! This post just made me think about custom beds and such though.

    1. Hi, is the BOM complete?
      There are only Profoles, Screws, Rods, Linear Bearing.

      What kind of MXL Belt we need? or did a GT2 belt the same job?

      I also miss the bearings for the x-axis, all the scres, pulleys etc.

      or can we use all other parts from the original K40?

      Thanks for the great built
      and thanks for your help

  4. When my laser gets to the “bottom right” of my machine it has less power in the bean than at “top left” and that’s on a standard cutting bed (200mmX300mm) if I enlarge that NOTHING will get cut or engraved in the “bottom left” anymore, is something wrong with my setup??

    1. Probably you haven’t properly aligned the mirrors. And the further the head moves te more notizable the misalignment gets. A few degrees near the laser turn into quite a bit of inaccuracy when in the furthest corner.

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