4th axis Tombstone drill and pocket milling?


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Thread: 4th axis Tombstone drill and pocket milling?

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    Default 4th axis Tombstone drill and pocket milling?

    I have a 4th axis that will function like a tombstone. It is going to be parallel to the table. The parts need to be drilled on one side and then milled 90 degrees to the drilled side. The parts will be bolted down to the tombstone. My question is, when making the Gcode in Fusion 360 any ideas of how to make the tombstone rotate 90 degrees after the drilling cycle is done so that It can then mill the pocket? Any ideas would be great.

    Thanks,

    Jeff

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    Community Moderator Jim Dawson's Avatar
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    Default Re: 4th axis Tombstone drill and pocket milling?

    You could just add this line of G code after the drill cycle: G0 A-90.0 or G0 A90.0 depending on what direction you want to turn.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: 4th axis Tombstone drill and pocket milling?

    Jim, Thanks for replying. I think that is the only way to make this work correctly.

    Thanks!



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    Default Re: 4th axis Tombstone drill and pocket milling?

    I've not started driving my 4th with Fusion yet, in other CAM packages it was a case of creating a new operation with a different coordinate system that was offset 90º. Might be worth investigating that sort of thing if you want it driven from the design files without having to mash bits of manual code in there.

    If it's only a single 90º swing, though, it's probably going to be quicker to edit the code and chuck the line in. As long as you remember to do it each time you revise the design!!



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    Default Re: 4th axis Tombstone drill and pocket milling?

    There are some good videos on F360 tool positioning, but here's the basic process for a single setup with a trunnion table (or tombstone) I use:

    (Assuming 4th axis is along X)

    1. Model part
    2. Model table & fixtures. Add a construction axis in a model sketch along the axis of rotation
    3. Import table/fixture in to Model
    4. Add a point on the part model at the intersection of the construction axis and a convenient edge/face for touching off the X origin. Use "Project" and put the point sketch on the part model.
    5. CAM setup. The origin will be the point you created that is the intersection between the rotation (A) and the part. The origin orientation will be with the Z+ along the hole(s) axis (assuming that's the first op).
    6. First operation (drill) - select tool, and then under Geometry select tool orientation. Choose the hole axis (or a perpendicular face) for the tool orientation.
    7. Next operations - select tool, select geometry to mill (side surface), and go to tool orientation again. This time, select some feature that causes the tool to be oriented properly for the operation.
    8. Repeat for any other features.

    9. Optional - select the table & clamping as "Fixtures". This will let you see if you're going to crash during simulation.

    When you run the simulation, you should see the tool in the correct orientation for each operation. The part won't rotate in F360 simulation, but the tool will approach the part appropriately.

    Touching off the assembly on the machine: set Z0 & Y0 at the center of rotation (even if the part is offset), and X0 at the point on the part you set in #4 above. For example - if your tombstone is a 3"x3" square, then Z value should be at +1.5" when the tool is touching the top of the tombstone (and you have the correct tool length offset active!).

    Remember to set the tombstone top face flat along Y with an indicator and set A0 before doing any Z or Y touch-offs.

    Also - once you have the part in the table and the origin touched off, check the part offset from the rotational axis with the wiggler or probe, both in Y and Z. Compare that with your model and adjust the values in the model joints so that F360 knows exactly where the part really is - not where it 'ought' to be. Your clamping or fixturing won't be perfect, and a 0.005" deviation will cause features to be out of position in Z and Y the moment the A axis starts to rotate.

    Final sanity check - run it in air first.
    Second sanity check - run it again with the tool set to a larger diameter and slightly longer in the CAM operation (tell F360 you're using a 3/4" end mill instead of a 1/2") so that the tool will get close to the part but shouldn't actually touch. Run it at slow feeds and watch it for any unintended tool movements.

    Basic idea to remember: there is a "Setup orientation" that defines the position and rotation of the part & fixturing, and there is a "Tool orientation" that F360 uses to calculate the A-axis rotation and Y/Z offset from that rotational axis.

    I use this method rather than simply hand-coding an "A90" as it permits me to have parts mounted anywhere on the trunnion table and set the origin once for the entire process. I have a dowel pin stuck in the trunnion table outboard axle that lets me touch-off for Z and Y pretty accurately.



  6. #6

    Default Re: 4th axis Tombstone drill and pocket milling?

    spumco is spot on. Pay attention to steps 7 through 9 with emphasis on tool orientation. You will want to explore multiple work offsets as well (g54, g55, etc), this can greatly aid in setup in my experience. I do exactly as spumco says, I probe all the parameters and then enter them in Fusion as they exist. Its much easier than trying to match a model. I have a piece of trued ground rod in the center of the trunnion axial center just like the dowel method. I use it to probe and find center.

    One other thing, you need an Ultimate Fusion360 package to get the 4th and 5th axis stuff. Sign up as a student or instructor and you can get it for free.



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4th axis Tombstone drill and pocket milling?

4th axis Tombstone drill and pocket milling?