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Thread: CNC ROUTER TABLE FLATNESS

  1. #13
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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by hughes674 View Post
    Hi Christian
    I was hoping to end up with something a bit more accurate and don't think using a spirit level will be at all accurate. Even the digital ones only give you + -0.02 degrees accuracy which is a large error over 1800mm.
    I have read about using Epoxy under the rails but unless you have an accurate means of checking the rail seems pointless.

    Thanks for the link will check it out.

    Cheers
    Yes, the height between the rails may be off by up to 1 mm if using a normally good spirit level, but the mounting surface for each rail should be very flat and parallel (both level). Unless the gantry is extremely stiff and fully machined with reference surfaces for y-axis carriage blocks and x-axis rails, I don't think a relatively small height difference between y-axis rails is going to be most significant for accuracy of the machine as a whole. As long as the axes are perpendicular, when the spoilboard is machined it will make almost no difference to accuracy, except loading the carriage blocks slightly unevenly. I have also seen someone previously connecting the two sides for epoxy levelling, then removing the "scaffolding" and excess epoxy afterwards, but I think this requires a deeper epoxy mold in addition to the waste in between - it was also on a smaller machine.

    Related to this, if you get it machined, how will you check the result of that? At work I deal with large parts machined to a few 1/100 mm tolerance, that something is machined does not tell me if it is within specification. Being machined in one setup, but not being a solid piece, I would expect up to 0.2 mm deviation in flatness on the length and width of your frame, unless a very accurate machine or grinder is used.

    Alternatively if you are thinking of not machining a spoilboard, or making any other compomises, I would no longer call it a router



  2. #14
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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by mactec54 View Post
    All the good machines are machined even the Chinese machines are
    When you have the required machine yourself or are doing series production, this is of course also the cheapest.



  3. #15
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    Default Re: CNC ROUTER TABLE FLATNESS

    We have nothing like that here or even close. If he has one like that or close enough to drive too, that would be perfect.

    Here is the Location https://precisiongrinding.com/about-...nd-directions/

    Wonder what the cost would be?

    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4


  4. #16
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    Default Re: CNC ROUTER TABLE FLATNESS

    There are a couple of things to point out here. First any reasonably low cost frame will twist upon installation. You really do need a precision level or other tools to install a machine. I mention a level as the low cost solution but there are other ways to align a machine. My point is a level is a fairly basic tool not to be dismissed.

    Look at is this way you get your frame machined and the machinist does a wonderful job. You still need to transport that frame to the installation site and then set it up. At the basic level that requires a level other wise you most certainly will have a twisted frame. In a nut shell everything is impacted by gravity.

    The second item is your concern that machining the spoil board will just curve it to match the imperfections in the machine. This is very true. However even if you have perfect rail mounting surfaces you still need to flatten the spoil board. In most home builds the mounting for the spoil boards just isn’t that accurate Further the board material may not be that accurate. Frankly I wouldn’t worry about the spoil board mounting and instead pursue a design that assures that the two frames for the linear rails are straight.

    As for grinding it isn’t required a milling machine in good repair can leave a surface suitable for linear rails for a router. If for some reason you don’t thing they are good enough you can always hand finish the surfaces. As for machining costs it isn’t going to be cheap for a machine this size. However if you look for a machine shop that has a horizontal boring mill or similar you might get quotes we’ll below a machine and grind solution.

    Lastly one needs to be realistic about what a machine built out of low end materials can actually do. This especially if you don’t have access to or no budget to hire a machine shop. There is no doubt in my mind that somebody with the aid of a machine shop can build very impressionable be CNC routers. That isn’t most of us! So you either need to be willing to pay the fees machine shops charge or be willing to look at alternatives like epoxy leveling.



  5. #17
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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by wizard View Post
    There are a couple of things to point out here. First any reasonably low cost frame will twist upon installation. You really do need a precision level or other tools to install a machine. I mention a level as the low cost solution but there are other ways to align a machine. My point is a level is a fairly basic tool not to be dismissed.

    Look at is this way you get your frame machined and the machinist does a wonderful job. You still need to transport that frame to the installation site and then set it up. At the basic level that requires a level other wise you most certainly will have a twisted frame. In a nut shell everything is impacted by gravity.

    The second item is your concern that machining the spoil board will just curve it to match the imperfections in the machine. This is very true. However even if you have perfect rail mounting surfaces you still need to flatten the spoil board. In most home builds the mounting for the spoil boards just isn’t that accurate Further the board material may not be that accurate. Frankly I wouldn’t worry about the spoil board mounting and instead pursue a design that assures that the two frames for the linear rails are straight.

    As for grinding it isn’t required a milling machine in good repair can leave a surface suitable for linear rails for a router. If for some reason you don’t thing they are good enough you can always hand finish the surfaces. As for machining costs it isn’t going to be cheap for a machine this size. However if you look for a machine shop that has a horizontal boring mill or similar you might get quotes we’ll below a machine and grind solution.

    Lastly one needs to be realistic about what a machine built out of low end materials can actually do. This especially if you don’t have access to or no budget to hire a machine shop. There is no doubt in my mind that somebody with the aid of a machine shop can build very impressionable be CNC routers. That isn’t most of us! So you either need to be willing to pay the fees machine shops charge or be willing to look at alternatives like epoxy leveling.
    Epoxy is totally useless for linear rail mounting, you obvious have never done it or even tried it

    The costs to Grind something like this can be less than to mill the surfaces, lot less setup time to Blanchard Grind something like this

    Mactec54


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    Default Re: CNC ROUTER TABLE FLATNESS

    What kind of work are you doing that requires ultra extreme levels of accuracy?



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    Default Re: CNC ROUTER TABLE FLATNESS

    I am located in the UK.

    First any reasonably low cost frame will twist upon installation.
    If the frame twists whilst being moved then I agree that machining the rail surfaces will be pointless. I think it would be easy enough to check this doesn't happen prior to getting it machined. A lighter cheaper material might as well be used if this is the case.

    The second item is your concern that machining the spoil board will just curve it to match the imperfections in the machine. This is very true. However even if you have perfect rail mounting surfaces you still need to flatten the spoil board.

    Alternatively if you are thinking of not machining a spoilboard, or making any other compomises, I would no longer call it a router

    I did plan on machining the spoil board or aluminium bed but my point is the rails need to be flat and level before doing this.

    I agree that milling the surface would be good enough as opposed to grinding.

    Can anyone offer any pointers on De-stressing the frame. Is this something that can be done DIY or does it need out sourcing.

    Cheers







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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by routalot View Post
    What kind of work are you doing that requires ultra extreme levels of accuracy?
    It has nothing to do with the work you are doing, If you want to mount Linear Rails they require a surface flat ness to mount them, if you use preloaded Bearings you have no clearance in the Bearing so if the surface is not machined scraped flat your bearings are going to bind and not last very long

    Mactec54


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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by hughes674 View Post
    I am located in the UK.

    First any reasonably low cost frame will twist upon installation.
    If the frame twists whilst being moved then I agree that machining the rail surfaces will be pointless. I think it would be easy enough to check this doesn't happen prior to getting it machined. A lighter cheaper material might as well be used if this is the case.

    The second item is your concern that machining the spoil board will just curve it to match the imperfections in the machine. This is very true. However even if you have perfect rail mounting surfaces you still need to flatten the spoil board.

    Alternatively if you are thinking of not machining a spoilboard, or making any other compomises, I would no longer call it a router

    I did plan on machining the spoil board or aluminium bed but my point is the rails need to be flat and level before doing this.

    I agree that milling the surface would be good enough as opposed to grinding.

    Can anyone offer any pointers on De-stressing the frame. Is this something that can be done DIY or does it need out sourcing.

    Cheers



    You should have a lot of options being in the UK look for someone that has a Planer Mill there has to be lots of them, a lot of these machines originated in the UK

    To stress relieve the frame there are 2 main method's that work there is a vibratory process or Heat treating both methods work well, or you could throw it outside for 2 years or so, this is how they used to do castings and some still do

    As for twist if you have any twist by moving a small frame like this them you have not built / designed it correctly, large frames can twist that is why machines have adjuster on the feet of the machine, the mounting pads on the bottom of your frame is the first part to machine, then this is the datum face that sits on the machine to machine the top and sides if you where doing any mounting on the sides

    Build a rigid structure and you won't have a problem

    Attached Thumbnails Attached Thumbnails CNC ROUTER TABLE FLATNESS-frame-jpg  
    Mactec54


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    Default Re: CNC ROUTER TABLE FLATNESS

    Its good to see another Brit building,or at least planning,a new machine.I have a few things I don't fully understand about the project and would like to ask a few questions to help me comprehend the choices that have been made.Would I be correct in assuming the size is partly determined by the workshop space available?I understand the likelihood of welding inducing an amount of distortion and the challenge of arriving at a flat surface.My question would be how much welding do you need to hold the machine together in view of the loads that would be imposed versus how much welding could you apply?I'm not enough of a welder to advise on tacking and optimum weld sequence,but there has to be a strategy that would minimise distortion.

    The design in the first post is clearly some way from finished and could easily stand on top of a base frame with built in adjustment.It also needs a gantry and might I suggest completing the design before cutting or welding anything?Its so much easier to amend things at the stage when they are still on screen rather than cutting pieces of steel off or welding them on.



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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by routalot View Post
    Its good to see another Brit building,or at least planning,a new machine.I have a few things I don't fully understand about the project and would like to ask a few questions to help me comprehend the choices that have been made.Would I be correct in assuming the size is partly determined by the workshop space available?I understand the likelihood of welding inducing an amount of distortion and the challenge of arriving at a flat surface.My question would be how much welding do you need to hold the machine together in view of the loads that would be imposed versus how much welding could you apply?I'm not enough of a welder to advise on tacking and optimum weld sequence,but there has to be a strategy that would minimise distortion.

    The design in the first post is clearly some way from finished and could easily stand on top of a base frame with built in adjustment.It also needs a gantry and might I suggest completing the design before cutting or welding anything?Its so much easier to amend things at the stage when they are still on screen rather than cutting pieces of steel off or welding them on.
    His frame he has is all he needs at this point it is how this frame is put together is the important part it going to have distortion no matter how he welds it, although it can be minimized by knowing how to construct with welding of the frame

    It still will need machining if you use linear rails so does not matter about the distortion from welding, alignment is more important when he is constructing this design

    Mactec54


  12. #24
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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by mactec54 View Post
    Epoxy is totally useless for linear rail mounting, you obvious have never done it or even tried it
    I wasn’t commenting on epoxy leveling usefulness but rather that guys look for low cost ways to avoid machining. You may consider it useless and frankly I’m not all that excited by it but that doesn’t mean it won’t work.

    As for using epoxy the only uses I’ve had for it recently is in grouting and the use of Moglice on plain bearing machines. Also anchor setting. But no use for leveling yet, I will not dismiss it though especially when guys in this forum have had success. Epoxy is just like any other material, used properly you can get good results.
    The costs to Grind something like this can be less than to mill the surfaces, lot less setup time to Blanchard Grind something like this
    I guess that depends upon the shop and the tools they have available to them. Setup time on a large horizontal can be well under an hour, probably less than 15 minutes. I can’t think of any automation machinery we have had ground in recent memory. The only thing ground I can think of was on plain ways on specialized grinders.

    In any event my point that I was trying to make is that the original posters quest for precision will blow the cost of his build out of the water. This especially when he has already expressed reluctance to pay the going rate.



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