Fadal VMC15 Soft limit to hard limit distance
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    Default Fadal VMC15 Soft limit to hard limit distance

    I'll probably go check this with the machine powered down when I get a chance but I've got a part that needs a little bit of extra clearance to profile all the way around and I was wondering if anyone knew how much extra room I get if I take the soft limits off or set the soft limits for a larger machine.

    Not looking to bump anything but I'm guessing there is at least some room there.

    I need to double check, but I think an extra 3/8" will probably get me the room I need.

    Thanks in advance.

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    We just purchased a VMC 15XT and I remember reading in my flurry of literature this value is 0.250”.

    That is unless you actually have the non-XT version with 20” X-travel, in which case you can gain 1” per end of the screw by removing a few thrust washers for a 22” X-travel.

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    VMC15's were all American screws? I know the pitch on the metric screws, but not the american..

    Either way. Move over one ball screw pitch and CS. Then move over to the end, and see if it will do it, go slow and watch the following error, when that gets big, you are on the springs, and that might be fine if you are just zipping around that corner for half a second.. Rinse and repeat on the other end of the travel.. If you go too far, the amp will alarm out, and hopefully not blow up, though the DC amps, in my experience do OK with an overload, the AC's not so much.

    It doesn't seem like the best idea, but I know it has and can be done.. Just be smart about it.

    Question. Is this for a hole pattern? Or do you just need to mill the end?? I've used some really small endmills at the outer end of a part just so that it would fit into the travel.

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    Bob's method works on the 4020's but I've never tried it on a VMC15. Just remember you will have to manually swap tools cause your spindle will move to a higher spot for a tool change.

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    Quote Originally Posted by Tedger View Post
    Bob's method works on the 4020's but I've never tried it on a VMC15. Just remember you will have to manually swap tools cause your spindle will move to a higher spot for a tool change.
    The OP is talking about profiling, it's not going to effect Z height if you CS at the correct Z position

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    Ahh. I didn't read the post correctly.

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    Ran to the limit shut the machine off and put an indicator on the table and moved the ballscrew by hand in the x direction. I could get .150 but it was sort of squishy like pushing against rubber. I.e. when I let go it would move backwards on its own. So its really close to the limit as is.

    Got my code put together and looked through it. Looks like I need 20.097" in X and 16.070" in Y more than my travels. (note that is total so .050 per side will be fine if I center it up perfect. I'm going to give it a go I guess. Hoping I don't screw anything up.

    Bob,
    how do you watch the gain? I'm going to dry run and figured I could run it through low speed and should be able to watch that pressure if I can and shut her down if I start seeing anything fishy.

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    Might be worth mentioning that this will be a 9mm (smidge under 3/8 endmill) for profiling around the part only. Y will likely only be over the limit for a couple seconds. The X will need to travel the full 16" over the limit.

    BTW it was the following error not the gain I meant to ask about above. How to I watch that?

    Also what bob said about the springs was right on. Can feel them by hand. Ought to give me enough travel if I fudge it.

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    Go into the machine parameters and change table size.
    SLOWLY creep up on the end of your table stroke. When you hit the end, youll know, but it wont be viscious.

    I often run a series of parts that need an extra 1/4" travel at each end of the X. No problem.
    Just make damned sure your program isnt going to rapid or feed past the end of the line!

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    Following error... The numbers on the screen to the right of the position of each
    axis.. And I just went to double check, its not there in Jog, only in Auto..

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    soft limit by parameter or by G22 used during tool change macro ??
    .
    on a horizontal cnc there is often a different Z soft stroke limit for every degree table rotation cause square table if at 45 degree will stick out more for column to hit.
    .
    if you set soft stroke limit closer you might hit with spindle or might hit fixture sticking out. for some they use a G22 in program to temporarily reset soft stroke limit and if on tool change the macro resets soft stroke limit back to normal then in the program you can temporarily reset soft stroke limits for the one time job.
    .
    i have tripped many times soft stoke limit while tapping with tap in a hole. if tap holder uses set screw than usually can loosen set screw and handle mode tool holder off the tap stuck in the hole. not all machines can stop on soft stroke limit while tapping and not break a tap. if you reset soft stroke limit and next tool is .100" shorter you might hit soft stroke limit again in the future. just saying tools are not usually exactly the same length there is tool length variability

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    Quote Originally Posted by Bobw View Post
    Following error... The numbers on the screen to the right of the position of each
    axis.. And I just went to double check, its not there in Jog, only in Auto..
    Thanks Bob,

    I chickened out. Decided to go heavier on the roughing cut. (.045 radial DOC) and leave .005 per side put my program .001 from the soft limit. I'll run her there. No messing with the soft limits and regretting my decision later on.

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    So it turns out I wasn't able to run without modifying the soft limits. Because the program was 15.999 wide in Y I would have had to position the part within .0005 of CS position for the program to run. I thought I just needed to set my origin within .0005. It errored out on me and I ended up changing to a 4020 soft limit and it ran fine.

    Still finishing it up but need to remember to change the soft limits back asap!

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    Good man.
    Sometimes you just gotta nut up to get it done.

    DONT forget to change the limits back, or youll be a sad panda, and soon.


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