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  1. #25
    Member planckscale's Avatar
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    Default Re: feed rate mismatch between planes

    Hi all,
    Hard to follow up the pace, great answers all along. Thanks!
    I am gently heading to make the ultimate tuttifrutti CNC : Rack and pinion for the Y axis, ballscrew on the Z and belts over X (Everman or not, undecided yet). At least I will have learnt a few things along the road.

    Quote Originally Posted by peteeng
    So Planck you have a lot to ruminate on
    That's an understatement ... I couldn't imagine my innocent question would bring me so far, no choice but to undertake it now ¯\_(?)_/¯.
    Sure I will go take a deep look to the Maximus. And by the way thanks for posting the belt profiles, I was looking for them.

    Thanks wizard for your comments and good advices. Just wanted to rebound a little on this one:
    Quote Originally Posted by wizard
    The first thing that came to mind seeing the drawing is jam ups and glitches due to material getting caught in the belt drive.
    I also had this kind of thoughts, but concluded that with a decent air compressor, found in most workshops, it is plain easy to add a few well positioned "blowers" in between the 2 belts aperture and chase out the chip and dust. But yes, just another avoidable tinker one could argue.

    Quote Originally Posted by wizard
    By the way it would help if you could define usage a bit better.
    I think it can be classified as "unflat Interior design" applications. On top of the usual sheet drilling and forming, there will be hardwood and medium carving, but rather simple smooth surfaces as well as articulation parts. Nothing barocco although with respectable carving depths. At some point I intend to append a lathe axis to do "colonnades" type carving. For this to work I should have a good feed rate range and be able to mount heavier tools. Also on the list is thin surface works for insertions and veener, with 0.1ish accurate milling of relatively large surfaces while keeping very clean edges (speed + accuracy + stiffness required). If possible a little soft metal milling too, for assembly parts. Overall nothing especially demanding for a CNC machine I think, but in any case I don't expect to be able to do all I imagine. It is more about opening new possibilities in my everyday work.

    Quote Originally Posted by wizard
    While I don’t have a formal name for the design a similar approach is to drop the glued down belt.
    If I understand well this is the straightforward U approach with a single loose belt right, or is something else?

    And yeah, I will try to KISS this as much as possible.

    Cheers,



  2. #26
    Activation process peteeng's Avatar
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    Default Re: feed rate mismatch between planes

    Hi Planck - soft metal milling... Hmmm you really need a very stiff machine to do this. It's a big step up in stiffness unless your depth of cut is very small. But you will figure that out. Peter



  3. #27
    Member planckscale's Avatar
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    Default Re: feed rate mismatch between planes

    Hi Peter,
    Did you look into Optibelt Delta Chain Carbon products ? It seems to mesh pretty well for face to face applications. Only available in 8mm and 14mm width though, but they advertise that "Carbon cord achieves unmatched length stability and outstanding breakage resistance". However I am not sure the price will be any lower than a helical rack.

    Cheers

    Attached Files Attached Files


  4. #28
    Community Moderator ger21's Avatar
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    Default Re: feed rate mismatch between planes

    If you're going to do a "ServoBelt" type drive, stick with T5 belts.
    Bell-Everman probably spent years of R&D to determine that T series belts worked best for that application.

    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)


  5. #29
    Activation process peteeng's Avatar
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    Default Re: feed rate mismatch between planes

    Hi Planck - Yes I looked at them but they are not recommended for the application. In regards to the Everman system the T5 belt is needed as it is less stiff then the other belts. Everman states that the T5 is a matching profile, this is incorrect by the way. If you use a stiff belt you cannot stretch them far enough over the short idler distance to remove the tooth clearance. Personally I think there are enough unknowns in the concept to stay away from it. Have a look at Maximus I have just put up some calculations on belts & motors for it.

    On another track. I mentioned elsewhere I was considering putting a motor at each end of a drive to remove the short belt/long belt problem. Thinking thru it its not a good idea as the "pushing" pulley has to transfer load through the pulling pulley and its unlikely they will be in perfect sync so this will create an elastic conflict. So KISS wins again. I suggest you look at a simple static motor with a motor drive pulley and a return pulley. This puts the 15-20kg you will have in your motors and their associated stuff off the gantry. Or use the U drive and then your in known territory either way. Its your first machine and it should use reliable solutions otherwise you will be in for a big redesign if something does not work out. Cheers Peter S

    Last edited by peteeng; 05-22-2019 at 08:53 PM.


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