Wanting to build 4x2 4 axis machine. Where to start


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    Member Akshooter907's Avatar
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    Default Wanting to build 4x2 4 axis machine. Where to start

    Hello

    I currently run a workbee. Really like the machine it’s been great. But I’ve been doing more and more 3D parts and want to build a dedicated 4 axis machine. My main goal is to machine rifle stocks.

    So the obvious starting point would be to research here. But I’m also wondering if there are any good plans out there. So here is the general plan

    In Alaska so shipping is a concern. Want to build frame out of locally sourced aluminum or steel. Want to use linear rails. Loose the wheels. 16mm or so for lead screws. Most likely buy a 12-inch z axis. See plenty of those

    For 4 axis thinking one of those you see on amazon. Ebay. Allied express.

    Mach 3 or 4 to handle 4th axis. No idea yet on control bits. Lol

    Does not need to be very heavy duty. But want it beefier than the workbee.

    Dust control. I don’t see how you could use a dust shoe? With all the z travel you would need. If I had a 4 foot z I only need 1 lead screw.

    Would it be better to have a 4 foot y. Or a 4 z? Which is inherently more stiff.

    Thanks for any feedback. No access to machines either. Is steel tube straighter than aluminum tube? Also need to research the epoxy leveling too for rails because I can’t machine them flat



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    Member Akshooter907's Avatar
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    Default

    Budget and use. Debated just getting the avid cnc 4x2 Kit. Add their electronics and rotary axis. That about $8k?? So less than that. Lol. Debated just cutting down a workbee. I figured I’d have $2k in that. So somewhere in the middle.

    I have a day job. So mainly hobby use. But might do small batch for sale to support my hobbies. Like the idea of chucking in a blank and completing all operations. I currently have to manually flip for the 4 sides.



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    Default Re: Wanting to build 4x2 4 axis machine. Where to start

    If this machine is to be dedicated to 4-axis work, I'd say keep the Y axis short, like 24" or less. Profile rails are a good idea; they're much more rigid than the round ones. Keep the Z axis short as well; the main limitation is the tool length, so you can't really use most of a really long Z, and it works like a long lever, amplifying any shaking that happens. But don't cheap out on the rotary table, which is the heart of your system. Most of the ones on the sites you mention are pretty shoddy, sometimes nothing more than a chuck stuck on the end of a stepper motor. You want one with a high gear ratio and as little backlash as you can afford. You'll want to provide a tailstock to support the far end of your stock (a used lathe tailstock will work) that can slide back and forth to accommodate different lengths of workpiece.

    Andrew Werby
    https://computersculpture.com/


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    Community Moderator ger21's Avatar
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    Default Re: Wanting to build 4x2 4 axis machine. Where to start

    If you can do the fabrication yourself, you can build a rotary axis similar to the Avid 4th axis for less than half the price. It's not much more than a motor and gearbox, with a chuck mounted on the gearbox.
    Unfortunately, the low cost rotary axes I've seen are just not very good. You're going to get what you pay for.

    You might want to consider machine your stocks as 4 sided indexed work, with the stock just bolted to the table. It'll actually be more rigid than a rotary axis, and probably give a better finish. Alignment is the only tricky issue.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Wanting to build 4x2 4 axis machine. Where to start

    Thanks for the reply’s. Great points on the rotary table.

    I currently flip through the 4 sides. And you are right. Alignment is the tricky part. I wasted some nice pieces of wood when I started.



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    Default Re: Wanting to build 4x2 4 axis machine. Where to start

    Quote Originally Posted by Akshooter907 View Post
    Thanks for the reply’s. Great points on the rotary table.

    I currently flip through the 4 sides. And you are right. Alignment is the tricky part. I wasted some nice pieces of wood when I started.
    The types of stocks are a issue, short stocks for a shotgun or lever action will work better than a long thin bolt action stock in a fourth. You could address the long stock issue with a mid length support.

    As for laying the stocks flat and doing each side that does require some awfully careful fixture work. The problem here is that you still need fairly substantial Z axis clearance.

    I have to wonder if you have considered a 5 axis solutuion with the extra two axises on the Z. Software would be an issue and you would still need on flip. However with a bit of thought with respect to order of operations there should be fairly decent blends. Software probably kills this idea because I don’t know of any low cost solutions.

    In any event back to the fourth axis. If you are doing a long bolt action rest this idea might help. Route out a round feature about where the trigger group may be. Build a steady rest contraption to steady the build there. Route out on both ends, remove the stead and rough out the area where the steady was. The reason to suggest the trigger group area is that that area usually takes some hand work anyways.

    As others have noted the cheap 4th axis solutions are not that great. What might be worth considering is a manual solution that gives you rotations that are 90 degrees apart. This depends upon the specifics of the stocks as to how well it will work but can be done dirt cheap. This would save a great deal on fixturing and other costs. You could build something yourself or retro fit a cheap spin indexer. You could likely recycle your flat maching code two.


    Oh well too much time online today. There are lots of possibilities here.



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Wanting to build 4x2 4 axis machine. Where to start

Wanting to build 4x2 4 axis machine. Where to start

Wanting to build 4x2 4 axis machine. Where to start