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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > How is everyone building a DIY CNC router system that maintains cutting tolerances?
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  1. #1

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    How is everyone building a DIY CNC router system that maintains cutting tolerances?

    Hello Everyone,

    First some background, I'm an engineer with CNC machining experience and GD&T. I have a machine shop and have been thinking about building a CNC router capable of cutting aluminum and wood to within 0.001" repeat ability.I have been researching many sites with many DIY kits and DIY from scratch builds. No one seems to talk about how accurate and repeatable their machines are. From my experience, one cannot simply bolt some extrusions or steel tubing together and get the assembly to be planar within a 0.001". Do you build a flat reference surface/table first, then assemble? Does anyone use the old tight wire technique to ensure their rails and trucks are fastened to the metal base without dips or sags? Please give me some insight on how you are building a CNC router in three axis with precision.

  2. #2
    Community Moderator ger21's Avatar
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    You're not going to find any DIY routers accurate to .001".

    You mention repeatability, but also talk about flatness, which is something different entirely.

    If you need .001 accuracy, you need to weld a frame, have it stress relieved and machined for rail mounting surfaces.

    You'll also need expensive screws, as the cheap ones used by most are only accurate to ±.003" or so per ft.

    Another option is to weld up a frame, and use self leveling epoxy to get flat rail mounting surfaces. That gets you a coplaner surface, but you still need a way to get everything mounted straight.
    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)

  3. #3
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    Hi JFL - To get a machine to 0.001" (0.025mm) you need to machine every component to ensure they all go together to achieve what you want. There are lots of threads here that go thru that process. Plus as Gerry says you need to purchase std parts (bearings etc) that exceed this. Its a long journey from scratch being a machine builder. But you say you have a machine shop so this is possible. A machined bed is the start so you need to figure out who can do the stress relieve and machining/grinding for you. Pick a commercial machine that meets your needs as a reference and copy that as best you can. A router is not best for aluminium you will have to figure if you are doing a router or a mill they are quite different but all things are possible. Peter

  4. #4
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    my CNC Routerparts can position to .001.... but it sure can't cut to .001.

  5. #5
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    0.02mm accuracy doesn't mean anything per se.

    - 0.02mm/100mm is easy to achieve.
    - 0.02mm/1000mm is another story.

  6. #6
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    Yes Jack agreed,,, JFL , How big a machine are you talking about? Pter

  7. #7
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    Your assumptions are correct, you don't just bolt together a bunch of extrusions and achieve <= .001 accuracy or repeatability.

    You mention your an engineer, what type of engineer are you?

    Chris D

  8. #8
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    You will not be able to build one with that kind of accuracy. Commercial routers in the 6 figure range do not achieve that accuracy. May get repeatability in the .005 range if you know what you are doing, accept a limited size range, and are willing to buy high grade parts and machine all mounting surfaces to the requirements specified by the manufacturer. And have proper metrology setup to actually measure your machined parts accurately. Any wood parts will move that much with minor humidity changes. What is it that you are actually trying to achieve?
    Tubular latex pressure vessel configuration engineer

  9. #9

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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    Thank you everyone for your replies. You proved my suspicions. I'm a mechanical engineer in the automotive industry. Specifically block and head machining lines with 120 4 axis and 5 axis CNC machines. So I'm used to holding contours, holes, surfaces within microns. I also work with skilled trades in the maintenance of these machines.

    Any way, I'm looking to build a 48" x 48" CNC router. I already have a manual vertical mill. From everyone's experience what can I expect from 1. a better than average kit. 2.Sub $5000.00 machine? If I machine a contour like an arc how much variation of the profile will I get on average. If I drill a pattern of holes, how much variation in true position of each hole to part datum? In wood and in aluminum. I'm assuming wood tolerances are usually +/- 0.015" (1/64") I'd like to know what everyone really sees in their machines when they compare CAD drawing to actual part.

  10. #10
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    Quote Originally Posted by JFL4066 View Post
    Thank you everyone for your replies. You proved my suspicions. I'm a mechanical engineer in the automotive industry. Specifically block and head machining lines with 120 4 axis and 5 axis CNC machines. So I'm used to holding contours, holes, surfaces within microns. I also work with skilled trades in the maintenance of these machines.

    Any way, I'm looking to build a 48" x 48" CNC router. I already have a manual vertical mill. From everyone's experience what can I expect from 1. a better than average kit. 2.Sub $5000.00 machine? If I machine a contour like an arc how much variation of the profile will I get on average. If I drill a pattern of holes, how much variation in true position of each hole to part datum? In wood and in aluminum. I'm assuming wood tolerances are usually +/- 0.015" (1/64") I'd like to know what everyone really sees in their machines when they compare CAD drawing to actual part.
    I would suggest the one I have a Fine Line Automation Saturn 2 48x48 and mine will do everything you ask, I do not know about +/- .001 inch but I have never tried. The company has had some delivery and QC issues with some of the machines. Its a welded steel frame with NEMA 34 motors and mine is running on Mach4 just fine. I used the pre-built and wired control system from the company below. Yes it cuts contours and circles just fine. Anything a normal CNC machine is expected to do.

    However the CNC Router Parts Pro line kits are pretty much the same only aluminum extrusions. Same control system if you purchase. One person who you will hear from has issues with the trueness of the extrusion cuts, but the machine is pretty popular regardless and widely used.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router

  11. #11
    Community Moderator ger21's Avatar
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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    From everyone's experience what can I expect from 1. a better than average kit. 2.Sub $5000.00 machine?
    Imo, the only "better than average" kit is CNC Router Parts.

    The main difference between cheap machines and more expensive machines is stiffness, rigidity, and power. Generally, a more expensive machine will allow you to make deeper and faster cuts, with a better surface finish.


    If I machine a contour like an arc how much variation of the profile will I get on average. If I drill a pattern of holes, how much variation in true position of each hole to part datum? In wood and in aluminum. I'm assuming wood tolerances are usually +/- 0.015" (1/64")
    I doubt that most people have the ability to actually measure their results. How does one go about measuring the accuracy or deviation of an arc?
    I think in general, almost any machine will be much more accurate than .015". But it all comes down to exactly what you are cutting, and how aggressive you are cutting. If you exceed the machine's capabilities, then the tolerances may be exceeded as well. Note that you can still cut very accurate parts on a flimsy machine, but you may have to pay special attention to stay within the machines abilities.

    There's very little difference if any difference in accuracy between cutting wood and aluminum. Aluminum will just require shallower cut depths in most cases.
    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)

  12. #12

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    Re: How is everyone building a DIY CNC router system that maintains cutting tolerance

    Say if you nested 20 of the same part, such as a 6" x 6" square with 1/2" rounded corners and a hole drilled at the corner radius center point. Will the features in all 20 parts measure to within +/- 0.002"?, +/- 0.005" of the CAD specs? Assume generally accepted speed and feeds for wood and aluminum.

    In my experience, assembling precision machined/cut parts, especially the size and length of a CNC machine, requires precision setup instruments. A new machine generally requires commissioning from the OEM to "tweak" and adjust for each sub assembly to be square, flat, and true to the required tolerance. Especially after shipping. I see no mention of this when anyone is assembling parts from a kit or built by themselves from scratch. Everyone says to use high precision rails, bearings, etc. But assembly is more critical. When scratch building a base for example, what techniques is the builder using to make sure each corner is square, flat, and in the same horizontal plane. What are the generally accepted tolerances for those?

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