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  1. #1
    Join Date
    May 2009
    Posts
    25

    Help me fill in the gaps with laser cutting

    Hi everyone,

    I have been into CNC for several years, have scratch built wood router and plasma tables that I use regularly. I want to get into cutting/engraving with a laser. After weeks of research, I have come up with a list of what I *think* I have learned but would like to ask you all to comment wherever you can on my list! As always, I appreciate the help! (Sorry for the long post!!)

    1) I have read that cutting and engraving are best done on dedicated machines designed for each type of work. But I understand that you can accomplish both to a degree with one machine, possibly not with the BEST results, but workable.
    I'd like to cut Plexiglas as my major use of the tool, but wouldn't mind etching glass and or tile.. does this seem feasible?

    2) Given that my main goal is to cut plexi (mostly in the 1/4" range), I am considering a 40 watt laser tube and supply (adjustable current output) to start with to keep costs a little lower while I learn. One thing I can't seem to find data on is if this is adequate power to engrave with? I have found much on cutting plexi with this power laser and although a little slower, seems adequate.

    3) I insist on building the machine myself (probably using 80/20 this time). I know there are Chinese machines out there that are cheap and easy, but half the learning is by building it. I understand the concepts of this and where all the mirrors need to go etc... wondering if there is any advice on what to do or not to do in this area? (Outside of the standard safety issues please, I realize that "playing" with a high power CO2 laser is very dangerous and it doesn't take much work to accidentally shoot the beam somewhere it doesn't belong causing great damage)


    4) Focusing optics are something I can't seem to find info on. I understand what they do, and how they do it... but how do you determine what focal length you need for your machine? I understand optics with an air nozzle are just about a must.... what kind of air pressure does this require? Are optics from China reasonable to consider?


    5) If anyone has any resources to point me to to continue learning "the basics", I'd be very happy to spend the time reading on my own, I am just starting to hit a brick wall with finding these things on the net!!


    Thanks everyone, I appreciate any input and advice!
    -James

  2. #2
    1) I have read that cutting and engraving are best done on dedicated machines designed for each type of work. But I understand that you can accomplish both to a degree with one machine, possibly not with the BEST results, but workable.
    I'd like to cut Plexiglas as my major use of the tool, but wouldn't mind etching glass and or tile.. does this seem feasible?
    Sure you can, there are dedicated engravers but these tend to be either low power Gantry machines or GalvoScan lasers.

    2) Given that my main goal is to cut plexi (mostly in the 1/4" range), I am considering a 40 watt laser tube and supply (adjustable current output) to start with to keep costs a little lower while I learn. One thing I can't seem to find data on is if this is adequate power to engrave with? I have found much on cutting plexi with this power laser and although a little slower, seems adequate.
    40 watts will cut 1/4 plex but not very quickly, it will engrave very well though.(engraving requires fractions of the power cutting does) The upper realistic limit for a machine that's going to be used for engraving is 80 watts, above that it's hard to get the tube to fire at the lower powers required.

    3) I insist on building the machine myself (probably using 80/20 this time). I know there are Chinese machines out there that are cheap and easy, but half the learning is by building it. I understand the concepts of this and where all the mirrors need to go etc... wondering if there is any advice on what to do or not to do in this area? (Outside of the standard safety issues please, I realize that "playing" with a high power CO2 laser is very dangerous and it doesn't take much work to accidentally shoot the beam somewhere it doesn't belong causing great damage)
    You seem to be on top of the safety issues, nothing to add really

    4) Focusing optics are something I can't seem to find info on. I understand what they do, and how they do it... but how do you determine what focal length you need for your machine? I understand optics with an air nozzle are just about a must.... what kind of air pressure does this require? Are optics from China reasonable to consider?
    Chinese optics are fine, unless you are in to medical level lasers or don't mind paying $250 for a lens. Air pressure required is a product of volume over venturi size, until you have a design for your nozzle I can't really say what pressure you need. a 2mm nozzle will run great on 5psi, an 8mm nozzle would need closer to 40 psi. As to focal lengths?

    OPLaser support forum • View topic - Understanding Depth Of Field (DOF)

    hope that gives you some kind of starting point,

    best wishes

    Dave

  3. #3
    Join Date
    May 2009
    Posts
    25
    Thanks Dave, those are all excellent points!! So maybe I should look at a 60 or 80W tube instead of a 40.......

    Also, thanks for the informative link on optics. Do you have any advice on where to buy such optics? I figured ebay has things, and I'm sure there are suppliers all over, but learning what search term to use seems to be key

    Also, just out of curiosity, is there a chart or table somewhere that has a general "in order to cut this size of this type of material, you need this much power" kind of thing? I know that there are a LOT of variables, but wondered if such a starting point type of table existed to give folks like me that are just starting out an idea of what is needed for each type of job.

    Thanks again! -James

  4. #4
    Join Date
    Jul 2012
    Posts
    0
    Quote Originally Posted by jcizek View Post

    Also, just out of curiosity, is there a chart or table somewhere that has a general "in order to cut this size of this type of material, you need this much power" kind of thing? I know that there are a LOT of variables, but wondered if such a starting point type of table existed to give folks like me that are just starting out an idea of what is needed for each type of job.
    Yes that would be useful, I'd also like a comprehensive list of optimal lens size to be used for certain application... ie. this size lens will work best for fine detail engraving on x,y,& z substrate.. I know there's a ton a variables such as laser wattage, speed, and power %.. just a guideline would be awesome.

    thanks.

  5. #5
    Join Date
    Jan 2006
    Posts
    2985
    Synrad has a nice little application you can download from their website. It lets you select a laser power and material and tells you how fast you can cut it. A Synrad laser is much higher quality than a glass tube laser and most likely will cut better due to better beam quality, however it should give you an idea.

    Matt

  6. #6
    I'm not sure why you want to re invent the wheel , you will have learned very little by the time you are finished and in terms of cost , you will have spent close to buying a complete machine and all you end up with is a compromised machine. I got into CnC 20 years ago and even with my experience , would NEVER build over buying a working machine. What exactly are you hoping to "learn"
    Rodney , Cape Town , South Africa
    www.tokerbros.co.za

  7. #7
    Join Date
    Mar 2007
    Posts
    26
    Quote Originally Posted by Rodney Gold View Post
    I got into CnC 20 years ago and even with my experience , would NEVER build over buying a working machine. What exactly are you hoping to "learn"
    Never would have thought I'd read that here....disappointing. I got into CNC 20 years ago too and I would never ever EVER buy a working machine which I know I could build for 20% of the price. Thing is, its never the cost saving that inspires me to do it, but because there is oh SOOOO much to learn.

    jcizek, I wish I could help you with your questions but Im going down the same path myself right now. 12 months from now we will both know more about the topic than 99.99% of the sales guys out there and most of the manufactures too
    All the best.

  8. #8
    I have been there and done that....Would you build a car from scratch? I wouldn't...

    You will never build the laser at 20% of what it will cost you to buy a good working model , a 900 x 600 with an 80w RECI tube with a raft of spares , blower , air assist , chiller etc will cost you under $4k Ex china excluding freight, you will be very lucky to come in on your build below that price point. It is HIGHLY unlikely that you will have a better machine on your home build...

    Here's a listing of just some of the spares pricing and im listing prices at the real "cheap" end ...
    80w tube + power supply $600
    Control board and LCD panel $300 minimum
    Stepper motors and drivers for 2 axis $200
    Lenses and mirrors , $100
    Bearings and linear slides $300
    Mirror mounts and head nozzle $150
    Chiller $300
    That's already $2000 and you have no chassis or anything else that you need.
    Rather learn the ins and outs of laser engraving, what lenses and optics do , how different materials are processed and then decide whether you want to build or not.

    This forum is not the right place to learn about the vagaries of laser engraving , go to Sawmill Creek Woodworkers Community - The Sawmill Creek Press and join the laser forum and read all the posts.
    Rodney , Cape Town , South Africa
    www.tokerbros.co.za

  9. #9
    Join Date
    Mar 2007
    Posts
    26
    If you insist on "good" working model, (in other words not Chinese) ...make that 10%.

  10. #10
    Join Date
    Jan 2006
    Posts
    2985
    I'm not sipping the Chinese Kool-aid that Rodney is serving but he is correct in that home builds rarely save much. You are buying all the parts at retail rather than wholesale so the cost there is at least double what the manufacturer pays. If you charge yourself for your time, it could easily cost double or more what a finished machine would cost. That is not to say I wouldn't do it myself or that I wouldn't recommend you do it. Some people like to build the machine, some like to use it. As has been said before, if you want to know every part of your machine and spend 2 years working out the bugs, build one. If you want to just start using it then buy one.

    With a laser, the bread and butter is really in the software and control. Any idiot (no offense to anyone) can build the mechanical aspects of the machine. Getting the software to control the laser is the tricky bit. Vector cutting is rather easily handled but raster engraving takes more brain power.

    Good Luck
    Matt

  11. #11
    Join Date
    May 2009
    Posts
    25
    I appreciate the info from everyone. I never intend to start a war on build vs buy, I realize that everyone has their opinion on that one.

    I am not choosing to build to save money or time. I guess it's a little disappointing to see opinions like Rodney's that I will learn nothing. I started into CNC a couple years ago, have scratch built 3 machines and have learned a TON! I knew almost nothing about CNC before that. Now I understand CAD/CAM, drive systems, etc... I built all my own electronics (stepper drivers and all) and built my own torch height controller (all the way down to etching the PC boards, then using my CNC machine to drill them!!)

    I wouldn't say I have a compromised machine, I'd say I have a machine that has *exactly* every feature I want that fits *exactly* in the space I have available for it!

    Finally, something that means a lot to me: I have a lot of pride in the things I have built.

    I think keebler said it best when mentioning that some like to build things, and some just want to use them! I guess I'm in the earlier category.

    Anyway, I think I have found a 60 watt tube and a power supply brand new and both here in the US. Looks like if I can find some focusing optics, i'll have nearly everything I need!

    Thanks to all for the comments, I an open to listening to anything more, every little bit helps! -James

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