Newbie Manual quick change for ER20 collet/chinese spindle?


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Thread: Manual quick change for ER20 collet/chinese spindle?

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    Default Manual quick change for ER20 collet/chinese spindle?

    So a couple of things to start. First, I'm new to CNC, so appreciate any opportunity to learn something. Secondly, from reading a bunch of threads, I realize "relatively" low cost ATC is a pipe dream and it looks like even quick change tool holders are just not readily available for the cheaper chinese spindles with ER20 collets.

    So after thinking about it for a while, it seems to me a viable quick change system is really no more than a tool holder extension with a 1/2" (12 or 13mm) straight shaft about 1.5 inches long with a should of maybe 5/8" diameter and a ER20 collet on the other end.

    Of course you'd need one for each tool, but it seems like you could simply insert the extension until it shoulders and tighten it down. Might not be accurate enough for guys working in metal, but for those of use mostly working in wood, it should be repeatable enough.

    I can think of a few potential issues, but would appreciate feedback on the idea? It seems like an area with demand and no solution?

    Thanks,
    Mike

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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    What's the goal from this, having repeatable Z height, just not having to swap collets when you switch to different sized bits or something else?
    If it's just to not have to swap collets, you could keep using 1/2" tools directly in the collet, but use ER16 extensions for 3/8" and ER11 for 1/4" tools to keep the overall length a bit shorter.
    Biggest downside I see is adding a couple inches to the length of the unsupported spindle. Defletction of a beam is proportional to length cubed.. By using smaller extensions, this is reduced a little, and of course 3/8 and smaller tools tend to exert less radial force on the spindle.



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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    Why not just have your control automatically do an auto zero when you change the tools? Only takes a few seconds longer, and doesn't require buying a bunch of tool holders.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    So the objective is repeatable Z. My current setup is not fitted for auto zero, so I'd have to do rig up a touch plate I guess and do the coding.

    I've been giving myself a crash course in Gcode and actually Gerry's suggestion would have been scary a few days ago. Now it just seems to be some work. The machine in question is one of the Probotix Nebula machines. I got an excellent deal on a fairly new machine (about half price considering all the tooling and some other items I ended up with as part of the sale.

    The Probotix guys offer the ATLAS sensor as an upgrade, but rather than the plug and play solution I think I'd enjoy figuring it out myself.

    In theory all I need is to wire up a touchplate and create a sub routine to drive over and touch off each time.

    One additional question. I see that most of the tool length sensors use a microswiftch. Is this type of setup necessary or would a simple flat touch pad work as well?

    In my head, the bit is grounded to the machine frame. So I could connect the probe ground to the frame somewhere convenient, then put the 5V pin to the touch pad. I was thinking that having a circuit board over a hole in the spoil board would provide some protection against run away probing as the most likely result will be breaking the circuit board and hitting the Z limit?\

    Does it need to be more complex than this?

    Appreciate the feedback,
    Mike



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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    Don't count on the bit being grounded to the frame. Not sure if it's only on spindles with ceramic bearings, but it's not uncommon for the spindle shaft to be insulated from the spindle body.



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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    To do it properly, you need two plates. One to set Z zero on your part, and another as the reference position, that you use when doing a tool change.
    What you do, is auto zero to set the Z, and then touch off the tool to the fixed plate, and store it's position. When you change tools, you just go to the fixed plate, and set the tool tip to match the previous plate coordinates.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    I have checked my spindle a couple of different way (ohmmeter and using the zeroing puck I have) and the continuity seems to be consistent.

    Because it's the way I think about things, I always reference the zero to the bottom of the part. So I'm thinking for many of the things I do, doing the tool touch off could be the zero as well?

    So maybe something like this:

    sub
    G53 G90 G0 Z-0.1 (machine coords, abs distance, raise spindle to near max)
    G53 G0 X18 Y1 (machine coords, drive to front center, just convenient based on where I usually stand)
    M6 T(x) (change to tool x)
    G0 X(a) Y(b) (drive to location of my touchplate a b)
    G91 G38.2 Z-5.0 F10 (incr distance, probe down 5" at 10"/min)
    G92 Z0 (set Z axis to zero)
    G53 G0 Z-0.1 (machine coords, raise spindle to near max)
    G54
    end sub

    Do I have the basics of it?

    Thanks,
    Mike



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    Default Re: Manual quick change for ER20 collet/chinese spindle?

    After typing the above, it occurs to me that maybe I should have inserted G54 before the G92, otherwise how does it know which coordinate offset to change?

    Edit:
    Conversely, I guess after a little google fu on G92 I could have used G10 L20 and just set the G54 Z zero immediately?

    Second edit:
    After a bit more reading, using G92 for the above definitely seems like the wrong way to do it.

    Ok I know this is a lot of questions, but can someone clarify the G10 L10 behavior? According to the linuxcnc.org reference

    G10 L10 P1 Z1.5 (set the current position for Z to be 1.5)
    This implies that we aren't actually setting the tool table offset directly, but actually telling the machine current position is 1.5 and the tool offset will be set as a derived value to make that true?

    Sorry, realize some of this may be fairly newbie questions.

    Thanks,
    Mike



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Manual quick change for ER20 collet/chinese spindle?

Manual quick change for ER20 collet/chinese spindle?