CNC ROUTER TABLE FLATNESS


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Thread: CNC ROUTER TABLE FLATNESS

  1. #1

    Default CNC ROUTER TABLE FLATNESS

    Hi All

    Not new to the forum but a new project.

    I want to build a router with a table size of approx 1800 x 1250. My plan is to use 100mm square tube for the table base. I was thinking of welding 10mm x 100mm flat on the table area in four places and the same to where the linear rails will run for the gantry. (Please see picture attached). I was going to then get the plates ground so that the table is running perfectly with where the rails will bolt.

    After loads of phone calls to various machine shops I am struggling to to get this machined. Very limited on who can do it and the companies that can want what I consider too much money.

    I have scanned this forum and many others trying to find another way to fit the rails so that they run perfectly with the table but haven't found anything. There are loads of suggestions just to skim the spoil board but this makes no sense to me unless your rails are perfectly aligned and flat in the first place. EG If you have a 0.05mm bow in your Linear rail so will the table. Or if the opposite rail is not set to the exact same height there will be inaccuracy aswell.

    I have also read about the use of lasers but again very expensive and the cheaper rotary lasers only have accuracy of +- 0.3mm /M.

    Any suggestions would be great or point me in the right direction of a thread that has covered this.

    Many Thanks
    Mick

    Similar Threads:
    Attached Thumbnails Attached Thumbnails CNC ROUTER TABLE FLATNESS-router-bed-1-jpg  


  2. #2
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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by hughes674 View Post
    Hi All

    Not new to the forum but a new project.

    I want to build a router with a table size of approx 1800 x 1250. My plan is to use 100mm square tube for the table base. I was thinking of welding 10mm x 100mm flat on the table area in four places and the same to where the linear rails will run for the gantry. (Please see picture attached). I was going to then get the plates ground so that the table is running perfectly with where the rails will bolt.

    After loads of phone calls to various machine shops I am struggling to to get this machined. Very limited on who can do it and the companies that can want what I consider too much money.

    I have scanned this forum and many others trying to find another way to fit the rails so that they run perfectly with the table but haven't found anything. There are loads of suggestions just to skim the spoil board but this makes no sense to me unless your rails are perfectly aligned and flat in the first place. EG If you have a 0.05mm bow in your Linear rail so will the table. Or if the opposite rail is not set to the exact same height there will be inaccuracy aswell.

    I have also read about the use of lasers but again very expensive and the cheaper rotary lasers only have accuracy of +- 0.3mm /M.

    Any suggestions would be great or point me in the right direction of a thread that has covered this.

    Many Thanks
    Mick
    It would depend on what part of the country you live, although there are big machines every where they are where you might not expect that is not very big of an area to machine EG is no good for rail mounting would be ok for table leveling

    Because of your design you would have a hard job of finding a Grinder that could Grind the table but could Grind the 2 outside rails it all could be machined though, you would have to stress relieve it before any machining, the bottom needs its mounting pads machined as well then it would sit on the machined pads to do the top

    Mactec54


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    Default Re: CNC ROUTER TABLE FLATNESS

    Are you talking about machining the top rails or the rails at the bottom where the spoil board sits? Go look at some commercially built welded steel frame machines and see how they attach and run the gantry.

    1000x750 Workbee CNC - Mach4 - PMDX USB - Windows 10 Pro


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    Default Re: CNC ROUTER TABLE FLATNESS

    Have you looked into epoxy levelling for the rails?

    For a "normal" router I think it should be sufficient to get good flatness for each rail, and height between them only as accurate as possible with a good spirit level or digital level. No matter if you align your x-axis rails (on gantry) to be parallel to a straightedge between the y-axis rails or just level them, as long as the x-axis rails are perpendicular to the y-axis and the z-axis rails are perpendicular to both x and y, you will get orthogonal movement.

    One example:
    https://www.cnczone.com/forums/cnc-w...060-cnc-3.html



  5. #5

    Default Re: CNC ROUTER TABLE FLATNESS

    Hi
    Yes I was talking about machining both the top rails and lower table rails. I would have thought commercially built machine beds would have been ground prior to fitting the rails.
    I was looking for an alternative method. If there is one?



  6. #6

    Default Re: CNC ROUTER TABLE FLATNESS

    Good point about the bottom pads. How critical would stress relieve be? Is there an easy way of doing this?

    Cheers



  7. #7

    Default Re: CNC ROUTER TABLE FLATNESS

    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



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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by hughes674 View Post
    Hi
    Yes I was talking about machining both the top rails and lower table rails. I would have thought commercially built machine beds would have been ground prior to fitting the rails.
    I was looking for an alternative method. If there is one?
    All the good machines are machined even the Chinese machines are

    Mactec54


  9. #9

    Default Re: CNC ROUTER TABLE FLATNESS

    Yes I think your right. Ill try digging a few more companies out that would do it at a reasonable price.



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    Default Re: CNC ROUTER TABLE FLATNESS

    Your going to find it difficult to find a machine shop capable of surfacing milling or grinding a piece that large. I know in this area there are none. I have never seen any Chinese router with machined rails. If you go look at Camaster for example the rails are mounted so they can be leveled and trued anytime the machine is moved. The bottom where the spoil board goes, as long as its level both directions, all the rails are the same height when you install the spoil board or bed it will be made parallel to the gantry when its surfaced with your spindle and facing bit. Remember your building a router, not the space shuttle.

    1000x750 Workbee CNC - Mach4 - PMDX USB - Windows 10 Pro


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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by wmgeorge View Post
    Your going to find it difficult to find a machine shop capable of surfacing milling or grinding a piece that large. I know in this area there are none. I have never seen any Chinese router with machined rails. If you go look at Camaster for example the rails are mounted so they can be leveled and trued anytime the machine is moved. The bottom where the spoil board goes, as long as its level both directions, all the rails are the same height when you install the spoil board or bed it will be made parallel to the gantry when its surfaced with your spindle and facing bit. Remember your building a router, not the space shuttle.
    If you are mounting Linear Rails the mounting surface needs to be machined or for a none machined surface you could use round rails which have more tolerance for mounting on uneven surfaces

    That is really small area he has to machine, there are many shops all over the US that can do that simple machining, A business friend in China has very large CNC Mills that machine both sides at the same time 10meters long is one of there standard machines and build 5 axes machines up to 30meters long all machined plus they do smaller machines as well

    Photo below is one of the 10meter 5 axes machines and some smaller ones all stress relieved and machined, it is a requirement for Linear Rail mounting or there would be no point in using them

    Attached Thumbnails Attached Thumbnails CNC ROUTER TABLE FLATNESS-10-meters-long-5-axes-machined-surfaces   CNC ROUTER TABLE FLATNESS-machined-rail-mounts-jpg   CNC ROUTER TABLE FLATNESS-closer-look-rail-mounting-machined-jpg  
    Mactec54


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    Default Re: CNC ROUTER TABLE FLATNESS

    Quote Originally Posted by hughes674 View Post
    Yes I think your right. Ill try digging a few more companies out that would do it at a reasonable price.
    Where are you located

    Here is one that is near me, but I have another even closer than this which is just 10miles away

    At PGI, we have over 30,000 sq. ft. dedicated to machining. We are equipped to handle a wide variety of custom steel parts, from small pieces to projects as large as 162” long, 110” wide and up to 42” tall.

    Grinding
    Vertical Spindle Rotary Grinding
    128” diagonal grinding capacity
    45” high
    Vertical Spindle Reciprocating Grinding
    48” x 200” vertical spindle
    16” high
    Horizontal Spindle Reciprocating Grinding
    36” x 200” surface grinding
    32” high

    Mactec54


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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



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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.



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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?

    1000x750 Workbee CNC - Mach4 - PMDX USB - Windows 10 Pro


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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.



  17. #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?



  19. #19

    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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