CNC router build


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  1. #1
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    Default CNC router build

    Hi everyone. I have been thinking of building a "better" version of my current 6040 Chinese CNC router.
    I basically do wood, plastic, rubber, brass and aluminium on my current machine. Obviously due to rigidity and design flaws my machine handles only 0.2mm runs
    on aluminium. Otherwise its very good, i have rebuilt the electronic controls and installed a Kress router.

    Anyway i have been thinking of doing this build for a long time. Due to my poor cad skills i am unable to draw up a nice 3d model.
    I would really appreciate some input on my design ideas.

    If i can mill aluminium at 0.5 to possibly 1mm runs then it would be great.

    My current machine is similar to this one...CNC router build-6040-jpg
    What i found to be the major problem is the open pillow blocks on my machine's y-axis.

    Here is what i have come up with thus far...

    1) Clamping area 1200 mm x 850 mm.
    2) 80 x 80 mm Aluminium profile for frame and table
    3) Two 1610 ball screws for y-axis
    4) Four HGH25CA linear blocks for y-axis
    5) 20 mm side plates/brackets
    6) 25 mm (unsupported) round shaft for x-axis
    7) four linear bearings for x-axis.
    8) Additional 25 mm shaft added for rigidity of the x-axis
    9) 1605 ball screw on x-axis
    10) 1605 ball screw on z-axis
    11) 16 mm unsupported round shaft on z-axis
    12) Four linear bearings on z-axis
    12) Nema 23 stepper motors

    Please feel free to comment

    Similar Threads:
    Attached Thumbnails Attached Thumbnails CNC router build-6040-jpg  


  2. #2
    Community Moderator ger21's Avatar
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    Default Re: CNC router build

    I'd go with 20mm rails and 1610 ballscrews on both X and Y.
    discounted automation products: BLH Linear Guideway, BLH 20mm Linear Guideways

    And 15 or 20mm rails for the Z axis.
    discounted automation products: BLH Linear Guideway, BLH 15mm Linear Guideways

    Take a look at this thread for some ideas:
    New DIY build - design suggestions/ideas welcome

    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: CNC router build

    Quote Originally Posted by ger21 View Post
    I'd go with 20mm rails and 1610 ballscrews on both X and Y.
    discounted automation products: BLH Linear Guideway, BLH 20mm Linear Guideways

    And 15 or 20mm rails for the Z axis.
    discounted automation products: BLH Linear Guideway, BLH 15mm Linear Guideways

    Take a look at this thread for some ideas:
    New DIY build - design suggestions/ideas welcome

    Thank you Gerry



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    Default Re: CNC router build

    What is a 0,5 or 1mm RUN?

    The diameter of the cutter, depth of cut, step over and oyher parameters are all a factor here.

    In any event it looks like you are about to build a machine that will be notably pooer performance wise!
    First you dont want to be using unsupported rails in this sort of machine.

    Second things like gantry supports should be box sections to increase stiffness.

    Third The gantry beam needs to be large. 80 mm extrusions may work for the table frame but id prefer a much larger bean for the gantry. Your gantry will have to span close to one meter, while not as big as some DIY builds it is enough to be concerened about machine rigidity. Gantrys are a common weak link in DIY designs so i would focus a lot of attrnyion on this area.

    Fourth unsupported rails generally should be considered a no no in DIY machine designs. Ive seen slide assemlied that might be suitable for a light duty machine , on the Z Axis, but most home shops simply aren't equiped to work to such high precision. You are far better off in a DIY design too use profile rails. Unsupported rails should never be used on the longe axises, there are better approaches that frankly dont impact costs much.

    Notes:

    Your current mahine is apparently not meeting your expectations. If this is the case it doesnt make any sense to build a new machine with a poorer design. Unsupported rails are just a bad idea. If you want satisfaction with the new machine keep your expectations at hand when designing or selecting a design. Write them down on paper.

    Read the stickies here as there are good threads where things like gantry design are covered. Go through some of the calculations to make sure your design comes close to your expectations. If you dont want to do the math at least get an understanding how the gantry components work together

    I dont see the point in building a machine that is somewhat better than the one you got. It isnt even clear that the materials listed woild even lead to a somewhat better machine. If you are unhappy with your current machine then adrees its shortcomings with a much more robust design. Sometimes going the robust route often has little impact on the overall cost, supported rails or profile rails being one example.

    Always consider steel as a way to control costs. Yes it can be heavy but it is also available in a number of tubular sections that give you a weight savings while remaining stiff.



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    Default Re: CNC router build

    Wizard.....i really appreciate your input on this. That is the reason i posted on this forum, to get advise like this. I took Gerry's advise and started changing my design....The RUN is depth of cut
    My initial design did have supported rail on the y-axis.

    Would it be okay if i use (2x) 40 x 40 extrusions for the gantry beam. I will add a 20 mm plate behind for additional rigidity??

    Thanks



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    Default Re: CNC router build

    Had a chat with a mate who's also looking at building a machine. He got me curious cause he is building one with a fixed gantry....Does anyone have any information about this type of design??

    Thanks



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    Gold Member handlewanker's Avatar
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    Default Re: CNC router build

    Hi, my 2 cents worth as I'm not into gantry routers but mills.........I'd only consider a moving table CNC router in the 6040 size as you can make the frame side supports pretty hefty to increase rigidity that a moving gantry lacks in that area........I'd also only consider steel tube for a build and all welded too.

    To completer the wish list.......profiled linear rails not SBR rounded type.

    The table would have tapped holes not tee slots.......just my opinion.

    Steel is heavy which is good for vibration damping and rigidity and can be welded much more simply, whereas aluminium is too complicated to consider anything but a bolted mode.

    The Chinese CNC routers are relatively cheap because they are made by the hundreds to specific cut sizes without having to cut and try in the build.

    In the end, all CNC routers follow the same design it's just the fixing that alters.

    A 6040 "look alike" DIY build with improved characteristics will cost you twice as much as the original bought item and not give you more bang for the buck....and you will not get paid for your labour/time input.
    Ian.



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    Default Re: CNC router build

    Quote Originally Posted by handlewanker View Post
    Hi, my 2 cents worth as I'm not into gantry routers but mills.........I'd only consider a moving table CNC router in the 6040 size as you can make the frame side supports pretty hefty to increase rigidity that a moving gantry lacks in that area........I'd also only consider steel tube for a build and all welded too.

    To completer the wish list.......profiled linear rails not SBR rounded type.

    The table would have tapped holes not tee slots.......just my opinion.

    Steel is heavy which is good for vibration damping and rigidity and can be welded much more simply, whereas aluminium is too complicated to consider anything but a bolted mode.

    The Chinese CNC routers are relatively cheap because they are made by the hundreds to specific cut sizes without having to cut and try in the build.

    In the end, all CNC routers follow the same design it's just the fixing that alters.

    A 6040 "look alike" DIY build with improved characteristics will cost you twice as much as the original bought item and not give you more bang for the buck....and you will not get paid for your labour/time input.
    Ian.
    Thanks Ian....he is going to make a rigid steel unit. Basically i have decided to make mine that way too. I looked at a guy's machine on youtube, steel unit, he mill's mild steel too.



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    Gold Member handlewanker's Avatar
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    Default Re: CNC router build

    Hi....rigid steel unit?.......is that a fixed gantry type?.....lets have a sketch.

    Here's a pic of my favourite design type.
    Ian.

    Attached Thumbnails Attached Thumbnails CNC router build-toolcrafter-fixed-gantry-router-jpg  


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    Default Re: CNC router build

    Quote Originally Posted by handlewanker View Post
    Hi....rigid steel unit?.......is that a fixed gantry type?.....lets have a sketch.

    Here's a pic of my favourite design type.
    Ian.
    Yes, a steel unit with a fixed gantry



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    Default Re: CNC router build

    As the others said...
    For milling, it is called a double-column mill, and is how all or almost all really Big industrial machines are made, think 10-20 m in size.

    Mine (milling steel, VMC, large) is actually the same double-column design, *mostly* through experimentation, full-time, 13 years.
    And some industrial education from the industrial-production folks who make cnc machines as their only business.

    The bigger you make the columns, the better, the skin can be thin, most-especially for a router.

    Do not worry about mass, heavier is better, a tiny nema 23 stepper of 3Nm at 48 V DC, with chinese 2M542 drivers (55€) moved my previous table, 200 kg, very easily.
    With 1:3 belt drive, HTD 5/15 mm, 16:48 teeth.

    My current "best" VMC column, of 1600 mm table span, is == 700 kg in mass, going up-down = z axis.
    I will add compressed-air pistons at both ends, to reduce load, of whatever capacity is finally needed in the vertical z axis direction.

    Drives are ac servos, tiny, 400W, 1.27 / 3.8 Nm peak, 1.27 Nm constant torque, iirc.
    At 1:3, approx 600 kgf push force.


    Bigger columns are vastly more stiff - and cost about the same, since they can use thinner skins.
    I did this 4 times, and now my 5th time the columns are 25 x 40 cm in section size (10-20 mm skin thickness, in steel).

    You wont need anything like that, I am just pointing out that experience, time, experiments, have proven that the best solution is thin-skin structures, preferably stressed-skin- thin-skin structures like all modern machines.
    Most-All modern machines are stressed (preloaded) thin-skin structures, loaded at max to == 2% of their breaking load.



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    Default Re: CNC router build

    I'm getting way behind on these threads, too much OverTime and too many summer projects.


    Quote Originally Posted by ericks View Post
    Had a chat with a mate who's also looking at building a machine. He got me curious cause he is building one with a fixed gantry....Does anyone have any information about this type of design??

    Thanks
    Here is my take on building a fixed gantry mill vs a moving gantry mill:
    1. A fixed gantry mill by design is going to be a bit longer that a moving gantry mill. How mcuh depends upon the specific designs you are considering. Oftne the difference is a wash due to movign gantry designs often requiring clearance all around the machine. In any event make sure your design will fit in the area you intend to install it.
    2. Personally I see moving table /fixed gantry designs as easier to build and far more likely to maintian alignment. Either approach will require that you obrtain suiitably accurate machinist tools to align the machines (squares, dial test indicators, gage stands and the like)
    3. Depending upon the approach you take for a moving table deisng you can drive the table from the center without too much problem. You need to be careful here as some designs do not engineer the spacing of the linear bearings correctly for the table to be driven this way. This can save you a lead screw, motor and accessories required for dual lead screw solutions.
    4. Frankly stationary gantry, moving table designs are very popular with industry on bigger machinery. The design leads to very stiff machines as opposed to trying to cnatilever a milling head. You will see this apporach in planner mills, large grinders, very large "vertical" mills and other tooling.
    5. Antoher nice feature is few moving part, expecially the need for drag chains. Less moving parts means fewer failures for flexure in cables and plumbing.
    6. Simialr to above you only need to worry aobut the dust extraction hose moving in one axis. This assumes you are doing stuff that generates rust.
    7. in any even for a given dollar amount I see the fixed gantry machines as being stiffer and more suitable for a wider array of usage. The biggest negative is the larger size which is sometimes overstated.
    8. By the way if yo so desire and take the time to engineer the solution you can mount an axis on both sides of the gantry beam fairly easy. This would give you two different heads to work with.
    9. In theory a fixed gantry machine makes implementing an automatic tool changer a bit easier. You just make the Y axis a bit longer to run the head over to a tool changing area.




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