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  1. #1

    Question 3D printer & CNC design

    Hello everyone. I'm new at "DIY 3D printer" stuff and I would like to ask you a question about what design it should have. I want to build a 3D printer/CNC combo machine but that damn design is a problem here. First I taught that I should make something like a regular 3D printer ( the printing head moving on 2 axis and the bed on third) but an issue appeared..... is it ok to bring 1kg of wood or aluminium that high? (I want to build something quite big). After few research I've found this: https://www.youtube.com/watch?v=Dt7uyuZ4DJA . The problem with this design is the fact that it double the space required with at lest the printing height and I don't even know if the NEMA 17 motors that I have can handle the weight of the CNC drill.

    Can anyone give me some ideas ? But please, don't say something like build 2 different machines because this is not an option



  2. #2
    Super Moderator curious aardvark's Avatar
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    well there are quite a lot of different multi use printers out there for you to look at for design inspiration.

    The main issue you face is how large a drill/motor you want to use for the cnc side of things.
    Weight on the bed isn't as big an issue as you think. If you havea double z screw design with 2 guide rods at each end and maybe one at each side as well. Then the bed will stay stable with an awful lot of weight on it.
    Also you'll be using 2 steppers in parallel, which doubles the lifting capacity.

    Most multi use machines use a very small cnc head - often an adapted dremel type rotary tool.

    Looking at the video - no reason you couldn't stick an extruder and hot end on that machine.

    It kind of depends on which side you want the emphasis to be on: cnc or 3d printing.

  3. #3
    Quote Originally Posted by curious aardvark View Post
    well there are quite a lot of different multi use printers out there for you to look at for design inspiration.

    The main issue you face is how large a drill/motor you want to use for the cnc side of things.
    Weight on the bed isn't as big an issue as you think. If you havea double z screw design with 2 guide rods at each end and maybe one at each side as well. Then the bed will stay stable with an awful lot of weight on it.
    Also you'll be using 2 steppers in parallel, which doubles the lifting capacity.

    Most multi use machines use a very small cnc head - often an adapted dremel type rotary tool.

    Looking at the video - no reason you couldn't stick an extruder and hot end on that machine.

    It kind of depends on which side you want the emphasis to be on: cnc or 3d printing.

    Yeah, that is a good idea and I thing I'll go for it.

    Thanks for your reply

  4. #4
    Super Moderator curious aardvark's Avatar
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    If going for lightweight cnc, then all you need to worry about is a dremel type mount.
    Adding a laser engraver is also a good idea.

  5. #5
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    These bastard machines tend to give you the worst of both worlds. You get a flimsy, underpowered CNC router that can't handle much more than foam, and a slow clunky printer. Dremel tools don't make good CNC spindles; the plastic housings deform after about a half-hour of use and then they die. NEMA 17 motors are fine for printing, but too weak for more than the lightest carving work. I'd say start with a printer, and once you're confident of your DIY skills, attempt a dedicated CNC machine that's as rigid as you can make it, with a decent spindle.

    Andrew Werby
    computersculpture.com

  6. #6
    While i know you said you didnt want people saying stuff like the above, he has a point. Cnc machines and 3d printers have totally different needs and opposing design philosophies. For a 3d printer you usually want fairly quick speeds, this means a light as possible gantry that only needs to resist forces from accelerations. Cnc cutters on the other hand want a rock solid (read:heavy) gantry that can resist cutting forces. The speed of your motion system is not a limiting factor.

    At best you get a printer that doubles as a light duty mill that will do wood and maybe aluminium if you go super slow. Or a cnc that doubles as a slow printer. Dont get me wrong, id love a good two in one machine, but it wont be the best of both worlds.

    If i were to make thr machine, i'd go for a replicator, ultimaker, corexy or other similar 'cube' form factor. Steer clear of prusa style gantries as the cutting forces when cutting in the y direction will do horrors to the vertical part of the frame with the torques they'll exert on it. Build it out of aluminium as a compromise between weight and rigidity, and use nema 23 where possible. And don't cantilever the bed.

  7. #7
    Quote Originally Posted by awerby View Post
    These bastard machines tend to give you the worst of both worlds. You get a flimsy, underpowered CNC router that can't handle much more than foam, and a slow clunky printer. Dremel tools don't make good CNC spindles; the plastic housings deform after about a half-hour of use and then they die. NEMA 17 motors are fine for printing, but too weak for more than the lightest carving work. I'd say start with a printer, and once you're confident of your DIY skills, attempt a dedicated CNC machine that's as rigid as you can make it, with a decent spindle.

    Andrew Werby
    computersculpture.com
    I got your point and I must say you are right. I've made some research and I have found that is not a very good idea but I taught that it could do some lite work (only few mm in wood) but I think that the TRAKYAN's idea with the laser engraving is better than cnc.
    P.S. Even I said I didn't wanted to hear this, this reply has an explanation so it's welcomed

  8. #8
    Quote Originally Posted by Trakyan View Post
    While i know you said you didnt want people saying stuff like the above, he has a point. Cnc machines and 3d printers have totally different needs and opposing design philosophies. For a 3d printer you usually want fairly quick speeds, this means a light as possible gantry that only needs to resist forces from accelerations. Cnc cutters on the other hand want a rock solid (read:heavy) gantry that can resist cutting forces. The speed of your motion system is not a limiting factor.

    At best you get a printer that doubles as a light duty mill that will do wood and maybe aluminium if you go super slow. Or a cnc that doubles as a slow printer. Dont get me wrong, id love a good two in one machine, but it wont be the best of both worlds.

    If i were to make thr machine, i'd go for a replicator, ultimaker, corexy or other similar 'cube' form factor. Steer clear of prusa style gantries as the cutting forces when cutting in the y direction will do horrors to the vertical part of the frame with the torques they'll exert on it. Build it out of aluminium as a compromise between weight and rigidity, and use nema 23 where possible. And don't cantilever the bed.

    Be sure that I didn't wanted to make something like prusa. I don't like the their performance even at 3D printing mostly because that bed...... But I think that I'll go for laser engraving ( it was something like a backup option. until now) as you said

    Thanks for reply

  9. #9
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    Or you could just buy one like this... or if you must DIY build maybe use this as a template.

    https://www.amazon.com/BIBO-Extruder...+printer&psc=1

  10. #10
    Quote Originally Posted by KrYpTOCiD View Post
    Be sure that I didn't wanted to make something like prusa. I don't like the their performance even at 3D printing mostly because that bed...... But I think that I'll go for laser engraving ( it was something like a backup option. until now) as you said

    Thanks for reply
    The laser was CAs idea, so I can't take credit. But now that you've mentiomed you only want to work with a few mm thick wood, I would say something like a 5w diodr laser mounted instead of an extruder would be your best bet as laser cutting and 3d print both dont need to endure cutting forces, and would work fine on the same machine. Be sure to enclose the printer though to protect yourself from the laser, it's dangerous and its an invisible threat if it reflects off something.

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