Help with helical interpolation and spindle orientation
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  1. #1
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    Default Help with helical interpolation and spindle orientation

    Hi all,
    I have an unusual part, that I think is makeable, but am having a hard time wrapping my head around exactly what the code will look like. Maybe one of you can help?

    The part has a bore, about 3/4" diameter. In that bore I need 2 helical grooves, 180 degrees apart, with a pitch of .8 revolutions per inch.

    I don't think a keyseat or threadmill type cutter will work because of how steep the helix pitch is. The grooves need to end up about an 1/8" deep radially, and about 2" deep in the bore. What I've been thinking I would do is grind a piece of HSS (to the shape and angle of the groove) to basically use like a threading tool on the lathe. What I'm hoping to do though, is to put this in my mill (Haas VF), and the use something like a rigid tapping cycle. I'd do it in .010" (radial) depth increments. Here's where it gets tricky. I don't want to pull the cutter further out of the holder with each pass. I want to keep using a predictable spindle orientation, and do helical interpolation to make the groove deeper (in XY) in subsequent passes.

    Is there a way to incorporate XY motions into a haas rigid tapping cycle? Is there another way to set spindle orientation, do a helical interpolation op, and pull the tool to the middle, back to clearance Z level, and do it again with a larger radius? I included a sketch of the part.

    I haven't found a good way to do this in my CAM software (rhinocam or Fusion360)...

    Thanks in advance!

    Bernie

    screenshot-29-.jpg

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    You could do it with a single point tool with appropriate clearances.
    It’s a simple helix. Start with X+ move, helix down. Back to top, X-, helix down.

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    If you don't have a lathe, put the part in a toolholder and put a single point cutter on the table. Tap cycle, move over a bit in x, tap cycle, etc.

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    Quote Originally Posted by mhajicek View Post
    If you don't have a lathe, put the part in a toolholder and put a single point cutter on the table. Tap cycle, move over a bit in x, tap cycle, etc.
    That's an idea along the lines I was looking for. Thanks for the idea!

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    Im back around to wondering if there isn't a better way to make this part on the mill. It must be possible to have 15 or 20 of these parts on the table, and to mill the 2 grooves 180deg off in perhaps 5 thou increments with a single point tool. I just don't know how to program it.

    How can I tell the spindle to start a helical move at a given spindle orientation? I have a single point tool, with appropriate relief ground into it. I'm envisioning something along the lines of the tool starting at 0 degrees, interpolate helix, unwind back out, tool back to 0 degrees, interpolates a helix with a .005" bigger radius, rinse repeat until depth (radius of helix) is correct. Orient spindle 180deg, restart the process for the second groove. Move to the next part, etc.

    Is there a way to command spindle orientation outside of tapping cycles? A tapping cycle would work if it weren't for that I also need to be interpolating the helix... The machine has a spindle position encoder for tool changing and tapping, so it seems like it MUST be possible to use it for my purpose. Just can't figure out how...

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    It only orientates to one spot I don’t think you will get the other side at 180
    Don


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    Quote Originally Posted by D Nelson View Post
    It only orientates to one spot I don’t think you will get the other side at 180
    Sure you can, just start it up one pitch higher in Z, like on a lathe.

    However, I don't think it'll work. MAYBE the helix isn't high enough to cause interference with a single-point tool but I wouldn't take bets on that. I bet you're stuck with haveacheck's plan. Or a lathe, which would be about 1,000 times easier.

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    Hadn’t thought about that maybe 1/2 a pitch higher


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    Usually M19 will orient the spindle on a mill. On one of my machines M18 will orient it 180 degrees from M19.

    Time to take a look at your machines M code list

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    The Haas mill wont do what you're looking for. There is no "C-axis" you could program along with XY interpolation.

    You can orient to any angle you want with M19 R up to 2 decimals.

    But to reliably program it to follow a path? It wont. It may orient as you like once or twice, but it may or may not go around multiple times to find the angle you commanded. Then your part or tool is ruined.

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    I think your machine needs spindle contouring control to do this. Fanuc calls it Cs contouring control. It allows interpolation between the spindle axis and the feed axes.
    Maybe the Haas has a similar option?


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