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  1. #21
    Member Tkamsker's Avatar
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    Default Re: Choosing y axis design

    Hi you option 2 is. Best Heiz machines do it as this


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  2. #22
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    Default Re: Choosing y axis design

    Question: 80kg for X axis SRB 20 support rails is too heavy or not?



  3. #23
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    Default Re: Choosing y axis design

    Quote Originally Posted by Patuc View Post
    If steel minimum 6mm, and you use 250x100, this is steel, so what to talk about people who made routers from aluminum profiles, if 6mm steel minimum, so aluminum have to be 300x300mm minimum? by what calculations you calculate 6mm minimum? In this forum and youtube you can see that a lot of frames is thinner than 6mm and frames is solid, router work an everything is ok. 250x100x6 is aprox 32kg/m. So I think it have no sense, because a lot of people build cnc from aluminum profile, and some people build cnc frame from steel, because they wand less vibrations and more solid frame; 6mm wall thickness is good, but I don't thinks it is necessary

    And thanks for answer
    Other guys already covered this but I will try to add another perspective.

    One of the drivers for minimal wall thickness is to have enough threads to prevent screw strip out if you use the type of rails that mount with through bolts into the support surface. You also need a little extra for machining allowance if your approach requires machining the gantry beam. At the very minimal you want a beam that is as thick as the screw diameters required for the linear rails. So if your mounting screws are 6 mm then you really need a beam that is 6mm thick or better. The "better" comes from the idea that you really should chamber or slightly counter bore the screw holes on the side the rail mounts on and in doing so you loose a millimeter or a bit more.

    While it isn't as common you can buy profile rials with tapped mounting holes instead of through holes. If you use this sort of rail you can then use through holes in the gantry beam. With this approach the beam can be thinner and the walls no longer need to support the threads for the mounting rails. You could save a significant amount of weight going this route but you need to then be more thoughtful about reinforcements to prevent parallelograming of the beam.

    There is a really fantastic thread in the stickies that goes into gantry beam design. Unfortunately I forget which one it is but the sticky threads are very informative. In a nut shell the big the beam cross section the better (within reason). In a sense you are right, from the mechanical strength standpoint you don't need an excessively thick walls on the beam. Other factors do come into play, including the thread issue and the potential for resonance or vibration .

    One other way to address the beam thickness and weight issue is to weld steel mounting strips to a thinner walled beam. You then mount your rails on these strips which would be thick enough to support the mounting threads. The problem with this approach is that your welding will distort the beam and in an ideal world the beam should be stress relieved and machined afterwards. For many IDY projects this is too much but if you have the resources it does have a few advantages..



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    Default Re: Choosing y axis design

    Thanks to "wizard" for informative answer!
    Question: 80kg for X axis SRB 20 support rails is too heavy or not?



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    Default Re: Choosing y axis design

    Question: 80kg for X axis SRB 20 support rails is too heavy or not?

    sbr 20 dynamic load rating is 860N. It means, that one bearing can be loaded with 86 kg.SBR20 LUU dynamic rating is 1764N...



  6. #26
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    Default Re: Choosing y axis design

    Thanks, so if my Y axis with z axis is about 90kg, X rail is two SBR 20, so for one bearing is 45kg load.



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Choosing y axis design

Choosing y axis design