Some advices for my CNC router build = Appreciating! - Page 4


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Thread: Some advices for my CNC router build = Appreciating!

  1. #37
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    Default Re: Some advices for my CNC router build = Appreciating!

    Quote Originally Posted by wizard View Post
    Letomoto

    The desire not to want to go to the expense of welding and machining is understandable but you make an assumption here that Aluminum extrusions are perfect. They aren’t, though often good enough for wood working. Generally machining aluminum implies a higher degree of accuracy and straightness. This can mean that an aluminum structure requires machining too. If not machining other remediation methods may be required.

    As for designing in a channel for motion hardware, that isn’t a bad idea if needed. Do realize though that the linear rails and bearings already create a fairly substantial dead space under the axis saddle. Often you are better off working within that space provided by the rails. In n any event this should all be resolved in up front design.


    Well , yeah i understood extrusion was good for wood but not stiff enough for alum . i redid the whole frame with the rectangular steel tubes real dimensions available locally , using 3"x8" tubes for the beam and the tall sides . i asked quote for 3"x6" tubes and it would cost 160$ , also asked for the 3"x"8" tube and it god damn jumped to 433$.... will retouch the positioning of the sides , just sitting on the 3"x3" beams who connects them , will look a bit less cute but will save 273$ and would shorten the size of the gantry plates , this wouldnt be bad for the wallet .

    And for the Axis bearings i am not very understanding your opinion , " linear rails and bearings already create a fairly substantial dead space under the axis saddle" is the saddle one gantry side plate or it is the distance in between the two plates ? And Up front design means what ? I am sorry not understanding everything , i am a frenchie

    i am appreciating the opinions , i am learning quite a lot of things



  2. #38
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    Default Re: Some advices for my CNC router build = Appreciating!

    Quote Originally Posted by routalot View Post
    I find one aspect of the proposed design a bit puzzling.Those steppers on the side look huge and you are planning to connect them to the leadscrew by means of what appear to be quite light belts.Why not locate them in line with the leadscrew and use a direct coupling?You might have to move the leadscrew along the machine to allow them to align.What size did you finally select?

    My final thought on the machine isn't meant to be as negative as it might appear,but did you investigate buying a second hand Bridgeport and converting it?You could then gain experience of the control software,the machining processes and produce the parts for your router.The machine is intended for cutting metal and after a conversion you would be able to sell it and recoup some money.You might even find it is the only machine you actually need.
    For the steppers they are Nema34 and i found the 3D on Grabcad and took a belt drawing to just add them on the project design. The belts ordered are about 5/8" width , will be strong enough

    The Direct coupling would be adding about 8 inches of lenght to the machine and i have to build it compact because of the small space i have in my workplace ...

    Not sure about your suggestion moving the leadscrew along the machine , arent they already along the machine ? the ballscrews are SFU-1605

    And converting a manual benchtop mill to cnc i did it last year , some pictures of the build ongoing but now is done and working but way very small surface can't work on anything bigger than 6 inches Y-axis and 16inches X-axis , this is why i am starting a 3'x5' router table

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  3. #39
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    Default Re: Some advices for my CNC router build = Appreciating!

    Having that mill will be a huge advantage when you need to make parts for your router.The experience of making it work as a CNC machine also gives you a big head start on configuring the software for the router.I suggested moving the leadscrew and stepper to eliminate the possible weak link of the toothed belt.If you need to reduce the footprint of the machine and use a belt it would probably be a good idea to make a cover of some kind to eliminate the risk of anything getting snagged by the belt or a fragment of the workpiece falling in there.A chunk of debris in the wrong place could be catastrophic.I know a man who wrecked a racing engine when a small clip got into the camshaft drive belt and that was a much bigger belt than the 5/8" quoted.



  4. #40
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    Default Re: Some advices for my CNC router build = Appreciating!

    Yes a cnc mill like that is ideal for making parts for a router....wish i had one of those



  5. #41
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    Yeah for sure the belts are gonna be covered ! Just not designed yet , waiting to get the pulleys, belts and steppers orders and put them together physically to prepare the holders/covers designs



  6. #42
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    Default Re: Some advices for my CNC router build = Appreciating!

    Aboutthat dead space comment that resulted in confusion.

    You mentioned that you used two beams in your gantry design so that you would have room for a leadscrew. What I was trying to say is that such channels are nit always required and may not be desirable. The reason being is that your linear rails and the Bearing cars that ride on them, form a channel between the often good enough for a leadscrew. The specifics of the parts used obviously comes into play but by leveraging this “dead space” you can reduce build complexity.

    The other thing here is that mechanical you want to avoid a heavily cantilevered leadscrew nut bracket. The bracket then becomes a lever arm that can flex or put an undesirable toque on the saddle.

    By the way I’m not saying that you should never build in such a gap as a combination of factors can make it to be the right solution. Rather what I’m saying is that I would avoid designing in such a feature first and instead try to mount everything on one beam. If your components don’t allow for a single beam solution then a dual beam approach might be the right idea. The complexity I’m talking about here is getting the two beams assembled and in the same plane. It can be done but the lure is extra work involved.



    As for the extrusion comment:


    A lot of people assume that the T-slotted extrusions are perfectly flat out of the box. They aren’t and like steel beams may require machine shop work to flatten. Generally they aren’t bad for wood working but may not be good enough for machining aluminum. It really comes down to your expectations but generally people need better results in Aluminum than would be acceptable in wood.

    So the extrusion comment was more about nit assuming that they are good enough flatness wise the meet your goals whatever they may be. There is a whole discussion about the precision one can achieve in simply mounting linear rails to t-sootted extrusions.



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Some advices for my CNC router build = Appreciating!

Some advices for my CNC router build = Appreciating!