First Ever CNC Build, Help wanted

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  1. #1
    Member FotatoPotato's Avatar
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    Default First Ever CNC Build, Help wanted

    Hello Everyone,

    I'm a High School student here in Pennsylvania and for a while now I have wanted to build my own CNC machine but I didn't have the know-how or funds to do it. However after doing a lot of research I have learned a lot and gathered up some money to start to build my own machine. Here is what I had in mind:

    My main goal for this machine is to be able to mill PCB's and soft metals (Aluminum, copper, brass etc.). After looking around I found that there are a lot of plans to make your own online and they have definitely given me a place to start. I want to make the main frame of my machine out of 3030 extruded Aluminum profiles and 0.25” aluminum plates since they are cheap and come in every length imaginable. For the motion system I want to use either Nema 24 or 23 Stepper motors and ball screws so that I can obtain the highest accuracy and repeatability possible. I also want to use linear rails rather than linear bearing rails (the round ones). For the motor I am planning on using a 3000W water cooled BLDC motor from hobby king and then coupling it to the shaft of the spindle using a belt and pulley so that I can get a max RPM of at least 40,000 RPM. For controlling this whole mess I'll probably just use the classic Chinese CNC controllers since they are super easy to use and they support the ubiquitous Step direction interface.

    For the frame I'm thinking of just using a normal Cartesian design since it is the easiest to make and provides good stability and there are plenty of examples out there. For the final build I want a working area of at least 12x16 inches with a Z height of 3in. The motor carriage is gonna be pretty big due to the way I’m mounting it so I’ll need to make the frame at least 6 inches larger on X and Y.

    I do have a few questions:

    Is it necessary to go and buy fancy ball screws over their Chinese counterparts? The fancy ones have some benefits but the cost so much and it seems overkill for me.

    Where can I get low cost linear rails in custom lengths? I want to avoid the cheap ones here since I hear that they have terrible amounts of friction and usually don’t last long, so I want to stick with the name brand here.

    Lastly, Is there an all-in-one solution for the controllers and drivers for a CNC machine, so like the motor controllers and Main CPU board that is plugged into the PC. If not, do you guys have any recommendations for controller modules.

    For now that's all I have, I know it’s not much but that's why I'm here, if you guys have any suggestions or advice for me I'll gladly take it since I'm a total noob at this.

    Thanks,
    John Hofmeyr

    Links:

    Motor: https://hobbyking.com/en_us/turnigy-...ess-motor.html

    Motor Controllers: https://www.aliexpress.com/store/pro...551edaf5snmczI

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    Last edited by FotatoPotato; 04-08-2019 at 12:45 PM.


  2. #2
    Member awerby's Avatar
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    Default Re: First Ever CNC Build, Help wanted

    Since you're talking about machining metals, I'm assuming you want to build a mill, not a router, but the other components (the extruded aluminum frame, the thin aluminum plates, the high-speed spindle) sound more like a router. Do you have a design drawn up? Does it have a moving gantry, a fixed "bridge", or a "C"-shaped frame with moving table? When you talk about "the highest accuracy and repeatablilty possible" you need to qualify that with your budget - possible for a $1000 build, a $10,000 build or a $100,000 build? Ball screws, for instance vary a lot in quality, the C7 Chinese ball screws are what many people here use, but they may not meet your expectations. I'm not sure that you can build a spindle with belts and pulleys that spins at 40,000 RPM; I've certainly never seen one. I think the whole thing would be likely to fall apart on the way up to that speed, unless you spent a lot of time dynamically balancing everything. I'm not sure what you mean by "classic" Chinese CNC controllers, but if that's a euphemism for "dirt cheap but they seem to be selling a lot of them" you might find they don't actually work.

    As for your questions:

    Precision-ground ball screws cost considerably more than rolled ones. If high precision is more important to you than low cost, buy them.

    Reputable brands of linear profile rails include SKF, Misumi, and THK.

    There are companies that sell complete motion control solutions, but few of them are focused on 23-frame stepper motors. Usually they are AC servo systems. But feel free to take a look at the companies listed on my site for various alternatives: https://computersculpture.com/links#Miscellaneous



    .

    [FONT=Verdana]Andrew Werby[/FONT]
    [URL="http://www.computersculpture.com/"]Website[/URL]


  3. #3
    Member peteeng's Avatar
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    Default Re: First Ever CNC Build, Help wanted

    High John - Start here. They make kits that will do PCB work and are excellent starter machines. Peter

    Sharp Software - Software & Electronic design | Gold Coast & Australia



  4. #4
    Member awerby's Avatar
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    Default Re: First Ever CNC Build, Help wanted

    I'm skeptical about the ability of those light-duty Sharp routers to machine copper, brass etc. effectively. And shipping from Australia to Pennsylvania would add a lot to the cost of those kits.

    [FONT=Verdana]Andrew Werby[/FONT]
    [URL="http://www.computersculpture.com/"]Website[/URL]


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First Ever CNC Build, Help wanted

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