Cheap Chinese Laser Cutters

Discussion in 'Project Construction Technologies' started by Ian, Feb 11, 2018.

  1. Ian

    Ian Administrator

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    I've been interested in getting a laser cutter for many years, but until recently they have been prohibitively expensive. A few years ago, there was a flood of cheap K40 CO2 laser cutters/engravers from China - with matching cheap construction/hardware. However, it looks like the quality of these K40 machines has slowly improved over several iterations. They'll likely still need some tinkering to improve the safety/calibration.

    I've got no experience with laser cutters, although I've got plenty of experience building/using 3D printers and a little general CNC experience. I often want to build an enclosure or panel and this would be an ideal workshop tool. Using a scroll saw and hand tools doesn't give as clean a finish, particularly with plastics. I could even use @(*steve*)'s box generator :D.

    I had a look at AliExpress and found these two machines that stand out as good options:
    It's far from certain that I'll buy one of these, but I am very tempted. I was hoping that someone here may have had experience with one of these cheap Chinese made laser cutters and could offer their thoughts - even if it is "avoid at all costs" ;). I'm going to go to our local FabLab and see if I can use their larger machine, to get a feel for it - although it is going to be in a different league to these cheap laser cutters, so won't be like-for-like.
     
    Last edited: Feb 13, 2018
    Ian, Feb 11, 2018
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  2. Ian

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    300mm x 200mm is tiny.

    The small one I use has a 300mm x 500mm bed, and there are plenty of times when it's too small.

    I would agree that getting to know your local hackerspace's laser cutter would be a great idea.

    Be aware that CO2 laser tubes require cooling. Our cutters have an external chiller. What do these small tubes use.

    Also beware the really high voltage inside. As the materials you cut leave smoke deposits you can have problems with the high voltage arcing over. This is a cleanliness and maintenance issue. If the laser cutter doesn't have exhaust fans, the problem will happen sooner.
     
    (*steve*), Feb 11, 2018
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  3. Ian

    Harald Kapp Moderator Moderator

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    Sounds interesting. Where would I find that?
     
    Harald Kapp, Feb 11, 2018
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  4. Ian

    Ian Administrator

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    Thanks for the advice Steve, perhaps if I do go for one it may be better to go for the slightly larger 400x400mm one. I would love a larger one still, but the prices go crazy if I go any bigger (plus, I'd need to find the space).

    Our FabLab has an Epilog laser cutter, but it's so busy that it's not something that I could use other than projects planned weeks in advance or for testing out. Great for me seeing how it works and getting some hands-on advice though :).

    These cheap laser cutters don't have a separate chiller unit, but they use a small pump to circulate water from a container. It should be good enough for hobby usage, as long as I keep it clean (perhaps with some anti-freeze/fungicide). There is an extractor fan, which I can vent outside easily enough - I suspect I'll just use this in the garage and open the door to vent the hose outside.

    Some of my biggest concerns are with the software used to drive the machine, but I think if I can find one with the appropriate control board then I can use this open source software:

    http://www.scorchworks.com/K40whisperer/k40whisperer.html

    Here's a thread with some more info :D:

    https://www.electronicspoint.com/threads/laser-cut-boxes.272156/
     
    Ian, Feb 11, 2018
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  5. Ian

    Ian Administrator

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    Whoops, I just realised that I neglected to add the link to the 2nd machine. I've edited the first post now and updated it with the link :).
     
    Ian, Feb 13, 2018
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  6. Ian

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yeah, that's a much more serious machine.

    Points to note:
    1. It doesn't seem to have automatic Z height. That's not a huge issue if it's used by trained or experienced people though.
    2. There is nothing below the honeycomb. Small pieces will drop through. This is just a cleanup issue mostly. A removable honeycomb is easier for cleaning. It will get mucky fast if you cut MDF.
    3. there is no provision for a longer tube. Many laser cutter have a square hatch at one end that a long time can protrude through (you need a box-like attachment to cover it.
    4. I notice the air tube running to the laser tube. This is for cooling, and also to keep the lens clean. A worthwhile modification is to have additional air blowing across the mirrors to help keep the smoke of them.
     
    (*steve*), Feb 13, 2018
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  7. Ian

    Ian Administrator

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    Thanks Steve, I appreciate the advice.

    Having auto Z-height would have been a handy feature. I had a look at the M2 Nano controller board and it doesn't appear to have a Z-limit input available, which is a shame as I was hoping to just add my own modifications to do that. Doing it manually should be ok though, as it'll likely save a lot of money on the machine.

    In your opinion, would the 2nd machine justify the price increase? I'm ok with the machine not being able to accept a longer tube - and I'm always happy to add additional modifications, as that's half the fun. My budget was somewhere between the two machines, but it looks like the additional area and quality improvements may be worth the extra spend.

    I'm aware that buying a cheap machine from China is going to come with it's own risks and drawbacks, but it's likely the only way I'll get my hands on a machine like this any time soon, so I'm willing to risk it.
     
    Ian, Feb 14, 2018
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  8. Ian

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The increased size of the bed alone is probably worth the price difference.

    However you need to consider the type and cost of materials you plan to use, and how you're going to source them.

    If you're planning to use acrylic sheet, then you'll be thinking about buying it by the sheet. A full sheet is 2440mm x 1220mm. Unless you have a large vehicle that is too large to transport easily. We can get them cut down to fit our large laser cutter, then use it (or a power saw) to further cut them down to the size required by our small laser cutter (if required). Even this is only economical if we're buying several sheets at once as the cost of getting the sheets cut down is substantial (for us it's pretty much a fixed cost no matter how many sheets are cut). If you are limited to 400x400 sheets (or worse, 300x200 sheets) the cost of this cutting down is likely to totally dominate the price of the acrylic.

    We can purchase MDF and ply in 300x600 and 900x1200 sheets which will fit into our laser cutters.

    A 400x400 bed is obviously better than 300x200, but you need to consider how you're going to get material to fit into it. Practically speaking, you may have to figure out your own way of cutting down sheets (probably with a hand held electric saw).

    With only 40W or 50W, you'll be limited in the material you can realistically cut. This is likely to be exacerbated by the focal length of lens that will be fitted (most likely a short -- 40mm to 60mm -- lens). 3mm or thinner material will be ideal, with up to 6mm possible. Beyond that you'll be battling. If you for a longer focal length lens (say 100mm) then you'll be able to cut thicker material, but your cut quality will suffer (it can't be focused as well, so the kerf is larger and cutting speeds are slower).

    Unless you've already done it, have a good thing about the material you want to cut and the size of pieces you want to cut. Consider the cost of the material, and the overhead in cutting material to fit. As an example, if you want 6 pieces around 175x190, you could cut them all on a 200x300 bed, but you'd have to do them one at a time (with lots of waste if your sheets are pre-cut), or from a single 400x400 sheet on the larger bed.

    However, if you were doing printed circuit boards, which will rarely exceed 200x300 then the smaller laser cutter may be totally adequate.

    Manual setting of the Z height is pretty easy once you know what to do, and you'll probably laser cut yourself a gauge to make it even easier :) . There are times when you want to adjust the height slightly, and if you're doing it manually that can actually be easier.

    The lasers in these devices are perfume enough to blind you instantly, even if the beam is unfocused, or from a specular reflection. NEVER operate them with the covers open. Get yourself a pair of safety glasses to use while you are servicing the unit with the power on (e.g. while aligning the laser) or if there are no interlocks on the doors). The safety glasses won't protect you from a direct hit, but you'll be a lot safer from reflected, unfocused light). For IR, the lenses are typically clear acrylic. A good safety precaution is that the device is unplugged before you open a cover that doesn't have an interlock, and preferably that these covers have locks on them.
     
    (*steve*), Feb 14, 2018
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  9. Ian

    Ian Administrator

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    Brilliant, you've given me a lot to think about and plenty of useful information :). I will do some research on how practical getting acrylic is going to be, as this is likely my material of choice (3-5mm usually). MDF is ok, as I can buy smaller 3mm sheets locally.

    I think if I do go for one, the larger size may be the one I'll get. I found a blog post about the machine here which contains some useful information on how it operates.
     
    Ian, Feb 14, 2018
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