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A Few General CO2 Questions

Discussion in 'Laser Cutters' started by Kevon Ritter, Feb 24, 2018.

  1. Kevon Ritter

    Kevon Ritter Veteran
    Builder

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    Hey everyone,

    I hate to start a new thread as it isn't a build or specific design. I kind of got bitten by the laser bug, spent a bit of time looking into as much of it as I can, but still have a few general questions.

    Background:
    After learning that a diode laser (405-450nm) is incapable of cutting white depron (modeling foam), I started looking into the CO2 side. The minimum desired working area would be 700mm x 1000mm. The max would be 800mm x 1250mm.

    With regard to motion, I listed the three major differences I've found from my research, but was unable to find out why they differed.

    Router/Mill
    1. fixed belt with moving steppers
    2. dual steppers on one axis
    3. GT2-3M belt
    Laser
    1. belt loop
    2. single stepper with a shaft drive to connect both sides of one axis
    3. GT2-2M belt
    Why aren't there any dual stepper setups?
    If using much longer lengths, why are GT2-2M belts more common?

    As for the laser itself:
    1. Does the reflector mirror size matter? Although I wouldn't mix sizes, would that also matter?
    2. Are there any drawbacks to using a longer focal length? The standard length I found is 2" (50.8mm), but have found up to 5" (127mm).
    3. tube, reflectors, head, laser PSU, cooling system (pump, reservoir, radiator)- Is there anything missing from that list? *edit* I forgot air assist components


    With the above mentioned, the build I liked the most would be the one in this video. This is for a business, so of course it's as obscure as possible. From what I can tell it's an H-Bot built with 2020 with a fixed bed. Its purpose is purely for cutting foam and other thin materials, which would be my purpose as well.


    I do realize that I haven't asked towards the progression of a particular aspect/type of CO2 laser.

    Thanks,
    Kev
     
    #1 Kevon Ritter, Feb 24, 2018
    Last edited: Feb 24, 2018
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Contest Winner! Builder

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    I'll briefly reply to one question: why no dual steppers?

    Because of Flying Optics, if left/right is not rigidly and mechanically connected (Driveshaft being the best, drive both left and right side carriages, using a single Driveshaft, single motor) you risk the carriages going off square. With flying optics, 1 degree off square is enough to miss the next mirror mount entirely, the pencil sized, unfoccused beam now skips past the mirror and does one of the following:
    Blinds you
    Burns your house down
    Sets your machine on fire
    Damages components.

    If theres one lesson i want to drive home, its that one! Dont skip on that, invest in a Driveshaft based design (see my builds, FreeBurn and Freeburn2). Dont even trust corexy/h-bots either, if it can rack, it will throw the beam off. Remember, its mirrors, half a degree shift in axes, is double that in the beam path (entry and exit off the mirror causes twice the misalignment)

    That, and the 22kv drive voltage will stop your heart before you even notice the arc jumped onto you!
     
    Mark Carew and Kevon Ritter like this.
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Contest Winner! Builder

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    Oh, and dont follow that videos advice! You really really need and enclosed Machine!!
     
    Mark Carew and Kevon Ritter like this.
  4. Kevon Ritter

    Kevon Ritter Veteran
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    I went back after your stern warnings and came up with this. The Y drive shaft setup still needs a little tweaking, but it's more than enough for the idea. Aside from the laser components themselves, everything is there. There should be plenty of space for whatever. The total area turned out to be 810mm x 1230mm, but the long dimension may lose a tap if the laser head projects far enough out. X uses a nema 17. Y uses one nema 23. Z uses two nema 23s, each driving two corners and connected by a 9mm closed loop belt.

    What is everyone using for shaft stock? Is regular linear rail applicable?
     

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