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IndustryArena Forum > CAM Software > BobCad-Cam > trouble with retraction heights - adaptive roughing
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  1. #1
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    trouble with retraction heights - adaptive roughing

    currently machining a pocket with one open end using V30. im using mill 2 axis - advanced pocket - adaptive roughing

    3/4 of my retractions, travel to my clearance plane, and 1/4 of them raise .015" above the machined surface and rapid dangerously across the interior of the pocket.

    how do i get all of the retractions to exit the part all of the way to the clearance plane?

  2. #2
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    Re: trouble with retraction heights - adaptive roughing

    try setting yur "rapid plane " equal to yur clearance plane,,,which I believe is 1 inch

  3. #3
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    Re: trouble with retraction heights - adaptive roughing

    Quote Originally Posted by jrmach View Post
    try setting yur "rapid plane " equal to yur clearance plane,,,which I believe is 1 inch
    thanks for the reply Jr. i tried this and it did move the rapid plane..... but only for the retractions that are actually happening. there are still 25% or more retractions that are not happening.

  4. #4
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    Re: trouble with retraction heights - adaptive roughing

    ok I think on the adaptive tool paths,the idea is to keep the tool close to the actual cut,hence 'high speed" cutting.You should be able to also set yur feed plane higher,,but I do know that %100 of the time that won't always work,,,but give that a try too

  5. #5
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    Re: trouble with retraction heights - adaptive roughing

    ok, if that is the way it is meant to be, i can accept that, but why is it that 75% of the cuts retract to clearance plane, and 25% dont? i would think it would be all of them, or none of them...

  6. #6
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    Re: trouble with retraction heights - adaptive roughing

    jay_dizzle,

    What you are seeing is the difference between rapid retract and link clearance. When using adaptive tool paths you should set the "Rapid Plane" taller than your max pocketing depth. So, if the pocket is .500" deep you should make
    the "Rapid Plane"at least .600". This value is relative to the pocket depth. Bobcad assumes at this height it can move freely without hitting anything in your setup. If you had a hold down clamp that is 1" thick; add that amount to the rapid retract height also making it 1.600".
    The .015" height you are seeing in the code is the adaptive link clearance. It is set to .015" by default. This setting is meant to lift the tool slightly off the work to make a fast feed move from the end of one toolpath to the start of another without dragging the tool across the work and marring the finish. The feed rate is controlled by the "Maximum Cutting Feedrate" setting in the "Machine Parameters" under "Current Settings" in the CAM Tree. Bobcad has the pocket geometry so it knows if there is anything in the way so it shouldn't do more than give you a heart attack if you don't know the fast feed rate is coming. One thing to be careful of, if Bobcad is posting G00 instead of G01 for these adaptive linking moves make sure your machine doesn't do "dogleg" rapids like my HAAS does. This will lead to crashes. You will have to contact Bobcad Support and get your post processor adjusted to fix this.

    Hope this answers your questions.
    Attached Thumbnails Attached Thumbnails bcd 2d adpt pkt rpd.jpg   bcd 2d adpt pkt link clear.jpg   bcd max feedrate.jpg  

  7. #7
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    Re: trouble with retraction heights - adaptive roughing

    I need to fix a mistake:

    When using adaptive tool paths you should set the "Rapid Plane" taller than your max pocketing depth. So, if the pocket is .500" deep you should make the "Rapid Plane"at least .600". This value is relative to the pocket depth. Bobcad assumes at this height it can move freely without hitting anything in your setup. If you had a hold down clamp that is 1" thick; add that amount to the rapid retract height also making it 1.600".
    This applies to 3D adaptive roughing tool paths not 2D.

    I realized the "Rapid Plane" setting for 2D pocketing is an absolute Z value relative to the "Top of Feature" not the bottom of the pocket.

    Sorry for my mixup.

  8. #8
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    Re: trouble with retraction heights - adaptive roughing

    If you are using Haas,there is a way to configure Preditor so you will at least see Dog Legs

  9. #9
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    Re: trouble with retraction heights - adaptive roughing

    ya........ i dont know..... none of that changed anything, just made the ones that are retracting much higher. maybe im not articulating my problem properly. here is a screen cap.

  10. #10
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    Re: trouble with retraction heights - adaptive roughing

    called BobCAD, no solution, guy on the phone didnt see it as a problem....... maybe im just being too picky?

  11. #11
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    Re: trouble with retraction heights - adaptive roughing

    True,not a problem,until it is a problem,,like dog legged rapids.
    I only know this will work on Haas,(maybe others ??)
    But this is how at least you can get Preditor Editor to show Dog Legs and prevent a bad day
    computer/windows c/program files (x86) /preditor software /common files /machines /haas3AXVMill.mch,,,scroll down to "enable dog leg" make the = "1",,,save and close

  12. #12
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    Re: trouble with retraction heights - adaptive roughing

    jay_dizzle,

    I see what your complaining about now, but you have nothing to worry about. The tool isn't going to crash. It drives me crazy too. I would want it uniform. My preference is to have the tool stay down, not to rapid out. Bobcad's toolpath algorithm is making linking decisions based on how large the gap between passes is. Presumably, if the gap is larger than 200% of the tool diameter bobcad retracts the tool, but if it's smaller bobcad does a fast feed using linking clearance. Your pocket must be right on the edge of max gap size to tool diameter ratio. Try tweaking some parameters like "Stepover", "Side Allowance" and "Minimal Curvature Radius" . You could even lie to bobcad about your tool diameter. A few thou on a roughing tool won't make a difference. I was able to re-create your results on a test pocket I drew by playing with these parameters. A little more side allowance closes the link gap just enough keep the tool down and vice versa. It really is all about tool diameter to link gap ratio here.

    There is only .002" difference in side allowance between the 3 pictures I'm posting.

    Do not make the "Link Clearance" excessively high. Bobcad actually makes helical entry and exit moves when linking like this. All it will do is slow down your machine and bloat your program. .010-.020" is all you need.

  13. #13
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    Re: trouble with retraction heights - adaptive roughing

    i see... well, i guess it helps me get over it a little now that i at least understand whats going on ha ha. again, thanks for the replies guys, i really appreciate your time!

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    Re: trouble with retraction heights - adaptive roughing

    i see... well, i guess it helps me get over it a little now that i at least understand whats going on ha ha. again, thanks for the replies guys, i really appreciate your time!
    No problem! By helping others I educate myself in the process. It's a win/win. :cheers:

  15. #15
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    Re: trouble with retraction heights - adaptive roughing

    Another thing for you to look at, is the NAME of that toolpath is basically "High Speed" in old terms. And you have selected to use "One way". Which will FORCE tool stops and retractions, etc.

    You could look at letting the "High Speed" do it's thing (Untick one way) and go from there. Or try one of the other strategies that will allow you to avoid the "in pocket movement"....

    2 cents.

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