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Thread: DIY Converting old engraver to full CNC router

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    Default DIY Converting old engraver to full CNC router

    Well the mods didn't like the wording of my last post so it's now collecting dust in the engraving machines forum. Let me be clear that I am NOT asking for help with software or anything related to the original machine I started with. I've thrown out most of the original components of the machine already, just looking for guidance in figuring out how to make the machine capable of milling out softer metals like aluminum with reasonable precision.

    I started out with an old New Hermes Vanguard V3400. Replaced the motion controller and PC with an Arduino + GRBL, and a Raspberry Pi + bCNC/f-Engrave. Now I've replaced the stepper motors with higher torque motors, and replaced the lead screws. It's made the machine quieter, and quicker, but my real goal is to make it capable of milling out pieces of aluminum, maybe other softer metals. I'd like it relatively precise, enough to make, say, brackets for my car. I'd also like to cut fine traces in PCBs for my own personal projects. I have questions on how to get my machine there, because I really don't have experience in CNC.

    First, the axes I have are lead screws, and the nuts are entirely plastic. If I wanted to, say, mill out pieces of aluminum, would the lead screw bend or fail? Would it be relatively easy to upgrade to a ball screw?

    Another thing. The original spindle motor is in the CNC housing, and a series of belts connect it to the spindle. The belt doesn't feel very tight and it runs at a fixed, high RPM, for engraving. The big question I have is, will I need to get rid of the belt drive and mount the spindle motor on the Z axis, or can I keep it the way it is?

    Lastly, I was curious about GRBL. Is it powerful enough for a hobbyist like me? Or should I look into upgrading?

    I do apologize if there's write-ups on all this that I'm not missing. I'm no CNC expert, in fact when I started this project I barely even knew what the acronym stood for. But any guidance would be greatly appreciated.

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    Last edited by katemonster; 08-07-2019 at 05:22 PM. Reason: trimmed it down from the original


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    Ok, well I think based on my own research, the lead screws I will keep for now. It seems the more pressing issue is the spindle. I have to figure out exactly how I'm going to fit a properly sized motor in this little area. I'm no machinist but I have a few tools, I know how to tap holes, so maybe if it's just a matter of an aluminum bracket or two, this won't be so bad?

    If you look at the pictures you can see what I'm working with. The wheels and the little rubber band looking things make up the existing belt drive. It slips easily so it clearly has to go. Here's kind of what I'm thinking...

    I'm going to use a dremel to cut out the portion of the gantry where all the wheels are. I'll make a large square flat section where I can thread some screws for some kind of bracket for the new motor. So it will sit pretty much on top of the lead screw, and a short belt will connect it to where the spindle head currently is... which I guess I will need to change out. Is there a good guide for setting up a short belt drive? Like with teeth so it doesn't slip? The reason I was thinking a belt, was because there isn't much room between the spindle head and the Z axis.

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    Default Re: DIY Converting old engraver to full CNC router

    Have you actually made any parts with the machine?I would suggest doing so before demolishing whats there as it will give you an insight into the capabilities of what you own and will allow you to learn a bit about generating the code to run the machine.Even engraving a few small plaques will acquaint you with the principles of establishing a part datum and loading a program.Similarly you might think about what kind of program you intend to use to create the parts you ultimately want to produce.This way you also have the option of taking the design to either a friendly hobbyist or a professional to get something made.

    Decent ballscrews can be found on ebay for not too great a sum and you will have to do the measuring to see if they can fit in the space you have available.If the machine still runs you may be able to make or modify any components to adapt it to suit.By using a CAD program to do this it gets you one step closer to being able to make the parts for your ultimate project efficiently.

    If you look on youtube you will see any number of hobbyists using GRBL on their homebrew machines.On pretty much all of them I get a bit alarmed at the way the machine is plunged into the job before the spindle has reached full speed.You may get away with this on foam or wood but I can visualise tools getting broken on metal items.I expect a small addition to the postprocessor would allow for a 3 second pause before cutting and save some damage.I looked ar Arduino based solutions for my own basic machine but decided to go with LinuxCNC as I have more Linux experience than Arduino familiarity and the cost is the same.I have a suspicion that your machine will be better suited to the PCB projects than to removing large volumes of metal.



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    Default Re: DIY Converting old engraver to full CNC router

    I've engraved with the machine, yeah. My dad gave me some small plaques to test with when he gave me the machine originally. It worked OK but the one bit I have is dull. I haven't tried anything more intense, are you suggesting I should test the limits of the machine on my own to see how much it's able to do? I guess I hadn't thought of it like that.

    Regarding your comments about GRBL - Maybe it's just the way f-Engrave generates its g-code, but the spindle starts before the Z axis moves at all, and it plunges very slowly, so I personally haven't had problems with the spindle not being at full speed.

    So you mention you gave up Arduino in favor of LinuxCNC. I've always been a little confused about this. How do you hook up stepper motor drivers to Linux? Doesn't it miss steps because it's not a realtime OS?



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    Default Re: DIY Converting old engraver to full CNC router

    Actually Linux is a realtime OS, or can be used that way. It can run stepper drives as well as servos, although the realtime function is only relevant to closed-loop operation. The problem with the Arduino/GRBL systems I've checked out is a lack of power. If you've replaced your steppers with higher-torque versions, you're probably up against the power limits already.

    I agree with Routalot that you probably will be happiest running this engraver as is. Once you start changing things, you'll need to change everything, and it still won't work that well as a mill. If it does a good job with engraving projects (or will once you sharpen your tool) that's a good thing to have. If you want a machine for making brackets or whatever, that would be a different one; keep your eyes open for suitable retrofit candidates or likely parts and you can build one of those as well.

    Andrew Werby
    https://computersculpture.com/


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    Default Re: DIY Converting old engraver to full CNC router

    I'm familiar with that VG3400, we threw one away at work. You will absolutely have to dump the spindle at minimum, as they use a proprietary tool that threads in on top of the spindle, and only come in small engraving points. The belt drive is just awful, and the adjustable spring tension collar won't work for actual milling. The rest of the machine is built like most small routers, except not much Z travel.

    Tiny aluminum can probably be done in it after mods, but only with very small tools, like <1/8". If your wanting to do large brackets and whatnot, a much heavier machine would be a better choice.



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    Quote Originally Posted by awerby View Post
    Actually Linux is a realtime OS, or can be used that way. It can run stepper drives as well as servos, although the realtime function is only relevant to closed-loop operation. The problem with the Arduino/GRBL systems I've checked out is a lack of power. If you've replaced your steppers with higher-torque versions, you're probably up against the power limits already.
    Is that why I'm having strange issues like,past a certain acceleration/speed value, every once in awhile when initiating a movement with a given axis, it moves backwards for a second? It's only done it with these new motors. The old ones would just start to lock up.



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    Quote Originally Posted by underthetire View Post
    I'm familiar with that VG3400, we threw one away at work. You will absolutely have to dump the spindle at minimum, as they use a proprietary tool that threads in on top of the spindle, and only come in small engraving points. The belt drive is just awful, and the adjustable spring tension collar won't work for actual milling. The rest of the machine is built like most small routers, except not much Z travel.

    Tiny aluminum can probably be done in it after mods, but only with very small tools, like <1/8". If your wanting to do large brackets and whatnot, a much heavier machine would be a better choice.
    Yeah small brackets was my goal. Honestly I'll probably use it more for PCB milling, which hopefully won't be too intense.

    When you say it's a proprietary tool, do you mean I will have trouble buying bits for it?



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DIY Converting old engraver to full CNC router

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