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IndustryArena Forum > General Manufacturing Processes > Milling > Newbie on cnc milling : my first steps
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  1. #1
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    Newbie on cnc milling : my first steps

    Hello millers,
    i've just purchased a 3 axis cnc machine (router), and i'm a little lost in the wild, 'cause i have almost no assistance from the builder, and the user guide is not about my machine exactly.
    My goal is to mill electric guitars...
    I have seen many videos on guitar cnc milling, but they don't explain all the things, maybe because it's obvious, but for me not that much.
    I've got a T slot table, 4 fixtures.
    I need to mill wood on both sides of the stock.

    Several questions :

    About the spoilboard, what do you do? You tie it on the table with the 4 fixtures, and stick the stock on it? With tape and super glue? It's strong enough for the cnc?

    About pointing the spindle on the origin, you use a special tool?
    What do you do if you have to dismount the spoilboard from the table, to glue something on the stock for instance? How do you find back the origin?

    I use Fusion 360 and i've got Mach3 on the machine...

    For planning, just planning, do you use mach3 only or do you use the cam software?

    That all for now, thanks for your help, and happy milling!!!

  2. #2
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    Re: Newbie on cnc milling : my first steps

    Hi John,
    Making guitars (I presume electric) is a challenge for a newbie. But once understood is relatively easy.
    1) spoilboard - no need to worry about that because I think you will be supporting the billet in air
    2) For setting the tool I use a pointed tool or the actual tool. Once set it does not matter unless you crash or stop the machine somewhere through the program
    3) use fusion for the geometry and the toolpath
    4) because you have to turn your billet over I expect you will have "tabs" (say 3 or 4 ) around the guitar with holes in the tab. These holes will be used to hold the part and when you turn it over register the part for the other side. Once done these are cut off and their surface sanded. You need to make a "sub-board" or a bolster that can be screwed into that is held to the base board. There are other methods but this will work for you. If you search for guitar making videos there's lots on the web... Peter

    other methods are using vacuum clamps or clamps that are used and removed and replaced as the tool moves around. These are complex for a learner.

  3. #3
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    Apr 2004
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    Re: Newbie on cnc milling : my first steps

    What do you mean by "4 fixtures"? Are you talking about some kind of clamps for holding the workpiece (uncarved stock) to the table? The spoil board is just a sacrificial piece of flat stock that's used to protect the bed of the mill and give you something to hold things down to. Normally you would use something more positive and easier to remove than tape and/or glue to hold your workpiece down; carriage bolts are a good cheap way to go.

    Lay out your guitar body so it's in the middle of a larger piece of wood; you need a frame around it that remains after the part is cut out to hold onto that's not going to be in the path of the cutter. The guitar body should be attached to that frame with tabs that don't get cut away until all the CNC routing is done. (You do all this planning in your CAM program; Mach3 is just for controlling the machine.)

    Measure to the center of that slab and draw a line through the center point along the long axis. Drill a couple of holes toward the outer edges of the slab that go through the spoil board as well. These should fit some dowels that keep it aligned. Use 4 carriage bolts in the corners to hold the stock down firmly. Then when you want to flip it over to machine the other side, unbolt it, and slide it back down onto the dowels. That should keep it in registration so the sides line up afterwards. Make sure the part is centered on the same centerline in CAD that you're establishing on your workpiece, and zero it to the same origin in Mach3, touching the tool tip to the top of the stock at the X=0 and Y=0 positions. (Z zero is usually established at the center of the workpiece; so the part you touch down to is a positive value half the thickness of the stock).
    Andrew Werby
    Website

  4. #4
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    Re: Newbie on cnc milling : my first steps

    Thanks for our answers. I just saw this video : https://youtu.be/zVRoDGhFT20 and at 12:48 they make the neck: The blank, the stock, is glued i think on a spoil board. They do the contour, the truss rod slot, and after they remove the stock with the spoil board to glue the fretboard onto the neck. They mill the fretboard. How did they do to tell mach3 which is the new axis? And after they do the holes for the tuners, the headstock is inclined, so they put the almost finished neck on a angle to drill the 6 holes. How did they manage to be sure of the position for mach3 to start this operation? (Yes my fixtures are clamps for t slot)

  5. #5
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    Re: Newbie on cnc milling : my first steps

    Hi John - M3 is a machine controller. The axes never change, all the moves are generated in the CAM system. M3 just carries out the coded movements (Gcode). You have to decide where zero is and what logistics are used for the machining. You need to do some reading on CAM. Cheers Peter

  6. #6
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    Re: Newbie on cnc milling : my first steps

    Hello, i'm there again.
    I have wood stocks that are not exactly plane. Not flat. I saw i can surface with mach3 only, so that's i wanna do first. But my first issue is the clamps that prevent me from surfacing the whole area. Are there claws clamps that take the stock by the sides and not by the top?
    Second, i need to plane one edge of 2 stocks to glue them together and have an invisible joint once glued. How would you do it with mach3?
    Actually i'm afraid to make a mistake that would ruin the machine or hurt me since the tools are very sharp, and i'm alone with my machine, so any help would be appreciated.
    Thanks again...

  7. #7
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    Re: Newbie on cnc milling : my first steps

    Yes, there are clamps https://www.miteebite.com/products/ that hold things by the sides, but they're designed for different sorts of machines, and for metal machining rather than wood carving. Maybe you can adapt one to work for you, though. One thing I've done is used a biscuit cutter on the edge of my workpiece and on some blocks that are screwed down next to it. The biscuits keep everything in place, and since everything is made of wood, except the screws which I sink in counterbores, you can cut over the whole surface without damaging your cutter. Of course, there has to be extra wood on the edges for the cuts that hold the biscuits.

    For making the sides of your boards flat so they can be joined together edge-to-edge, you use a tool called a jointer.
    Andrew Werby
    Website

  8. #8
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    Re: Newbie on cnc milling : my first steps

    If you have a T slot table its quite possible to fix blocks to it that will restrain your stock.They can be any material and ideally would be a little less tall than your stock and to grip the blank you can use finely tapered wedges driven against opposing blocks.It would be best to pack beneath the biggest gaps on the edges to eliminate the risk of the blank moving due to vibration.I suggest that before making the real thing with an exotic and expensive piece of wood you ought to try making a half scale version from something really cheap to gain confidence and experience in the various phases of the process.You don't absolutely have to cut the outline all the way through as part of the initial operation and it is quite easy to use a hand held trimming router to remove the last part.

    The Mach 3 software you have may or may not be limited to 500 lines of code and you should verify whether your version suffers from this limitation.I understand that it is a restriction imposed on some demo versions and can be removed by purchasing a licence.Its a pretty ancient piece of software but is still widely supplied,in spite of Mach 4 being around for quite a while.It only serves to take the instructions generated by your CAM system and make the machine move in accordance with them.You seem familiar with seeking information from youtube and will have to spend a bit more time establishing how you tell the software where your part datum is located.

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