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Thread: Laser cutter questions. How to set focus?

  1. #1

    Laser cutter questions. How to set focus?

    I'm still shopping for a laser. How do you set the focus on a Chinese laser cutter if you don't have an up/down motorized table? The laser I like wants $500 more for the up/down table and I think I can just block up the rotary fixture with a simple jig I could put in place of the knife bars. I just don't know how the focus is set. Does my plan have any merit? I would pony up the 500 bucks but I don't even know if I will ever engrave a cylinder. I need the laser to cut balsa and ply R/C airplane parts. I thought it might be nice to be able to engrave on a cylinder at some point but I have no projects in mind at this point.

    Adrian

  2. #2
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    Morning Adrian!

    The way you asked your question makes me think you are mixing things up in what you are asking. I will start off by talking about the table and if I missed your point just say so.

    The lens on a laser is fixed. The system does not focus like a camera might by adjusting that lens. Instead, to focus you raise and lower your object until the surface to be engraved or cut is at the correct distance from the lens. Unless I am mistaken, even though the table on the machine you are considering may not have a motor to raise and lower the object it will still have a crank system to raise and lower the table. Same idea, just a different mechanical system to do the job.

    BTW. A rotary device is focused on in the same way as a flat object. You can focus on the object held in the rotary by raising and lowering the table with a manual crank system or a motorized system.

    Dave
    Last edited by David Somers; 05-06-2014 at 2:07 PM.
    900x600 80watt EFR Tube laser from Liaocheng Ray Fine Tech LTD. Also a 900x600 2.5kw spindle CNC from Ray Fine. And my main tool, a well used and loved Jet 1642 Woodlathe with an outboard toolrest that helps me work from 36 inch diameters down to reallllllly tiny stuff.

  3. #3
    Don't buy a laser without a motorized table. I don't even know why the Chinese offer it as an option.
    Equipment: IS400, IS6000, VLS 6.60, LS100, HP4550, Ricoh GX e3300n, Hotronix STX20
    Software: Adobe Suite & Gravostyle 5
    Business: Trophy, Awards and Engraving

  4. #4
    Quote Originally Posted by Ross Moshinsky View Post
    Don't buy a laser without a motorized table. I don't even know why the Chinese offer it as an option.
    Why?

    Adrian

  5. #5
    Quote Originally Posted by Adrian Page View Post
    Why?

    Adrian
    Because the table moves up and down to focus based on your material. Why do you want to make your life difficult for $500?

    What if one day you need to work with 5 different materials? You're either stuck manually moving the table 5 times or moving the lens up and down which is typically not considered the best idea.
    Equipment: IS400, IS6000, VLS 6.60, LS100, HP4550, Ricoh GX e3300n, Hotronix STX20
    Software: Adobe Suite & Gravostyle 5
    Business: Trophy, Awards and Engraving

  6. #6
    Quote Originally Posted by Ross Moshinsky View Post
    Because the table moves up and down to focus based on your material. Why do you want to make your life difficult for $500?

    What if one day you need to work with 5 different materials? You're either stuck manually moving the table 5 times or moving the lens up and down which is typically not considered the best idea.

    Ross,

    My original question indicates that I do not have any idea how a laser is focused.The question itself, "How do you set the focus on a Chinese laser cutter if you don't have an up/down motorized table?" was a clue to this. I was not trying make to my life difficult for $500. I was trying to find out how a laser machine is focused.

    So you can move the lens up and down to focus?

    Adrian


  7. #7
    The big flatbeds all have fixed tables and the lens holder is moved, it's a royal pain in the rear too (until I added torsion tubes to do it)

    cheers

    Dave
    You did what !

  8. #8
    So... is this one adjustable?

    laser head.JPG

    Adrian

  9. #9
    This one says it's adjustable. It looks simple enough. Am I missing something here?adjustableHead.JPG My main mission for the laser will be to cut between 1/4" and 1/16" balsa.

    Adrian

  10. #10
    Yup, you can slide them up and down to get your focal point but it's a pain to do it and get it accurate (although using slip gauges can work quite well under the nozzle) The chinese systems that use threads aren't usually cut very accurately so that adjustment system often leads to miss alignment

    cheers

    Dave
    You did what !

  11. #11
    Thanks Dave! I can turn a height gauge on my lathe easily enough. I don't anticipate changing it very often. It's just good to know there is a simple method to do so. Did you make a custom setup of some sort to do this? "torsion tubes"? If it really bugs me I can fab up a movable table for a lot less that $500. You have to bear in mind that I love to tinker with things. If I had time I would build my own machine. There is no doubt that I will modify whatever machine I end up with. It will merely be a starting point.

    Adrian

  12. #12
    Adrian, was it you that built that plane out of coroplast a few years back? The real, flying, actual plane out of coroplast?
    Lasers : Trotec Speedy 300 75W, Trotec Speedy 300 80W, Galvo Fiber Laser 20W
    Printers : Mimaki UJF-6042 UV Flatbed Printer , HP Designjet L26500 61" Wide Format Latex Printer, Summa S140-T 48" Vinyl Plotter
    Router : ShopBot 48" x 96" CNC Router Rotary Engravers : (2) Xenetech XOT 16 x 25 Rotary Engravers

    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

  13. #13
    No Steve... that was Bob Stevens in Florida. (SignManiac on 101)

    Adrian

  14. #14
    Ahh, that's right.

    I can't wait to see what you do with the laser. I cut wing struts (my name for them) for a guy that makes real planes, but it's on our CNC router because they are too large for our laser. I got a repeat order for them today. Once you get going, you'll be making all kinds of stuff.
    Lasers : Trotec Speedy 300 75W, Trotec Speedy 300 80W, Galvo Fiber Laser 20W
    Printers : Mimaki UJF-6042 UV Flatbed Printer , HP Designjet L26500 61" Wide Format Latex Printer, Summa S140-T 48" Vinyl Plotter
    Router : ShopBot 48" x 96" CNC Router Rotary Engravers : (2) Xenetech XOT 16 x 25 Rotary Engravers

    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

  15. #15
    I hope I get to make lots of interesting stuff Steve. The KS is at $11,600 now. I think I might get a bigger laser!

    Adrian

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