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  1. #1
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    Drawing an angled slot that follows circumference of cylinder?

    I am trying to draw a 3D model of a part that I need to get CNC'd but I am stuck at a point and really could use some help from you AutoCAD guru's.

    The part in question is a cylinder that has a slot cut into the outer surface around the entire circumference of the cylinder. Now the slot has two sections where it follows in a straight radial direction. One is located at the front and at the top of the cylinder. The second is loctated at the bottom and towards the back of the cylinder. The end of each of the straight slots is connected to each other by a diagonal slot that follows the contour of the cyclinder. Basically this part is a cam. Another part, which has has a pin in it, will follow the slot in the cylinder.

    I have been able to draw the cylinder and the two straight slots but haven't been able to figure out how to do the diagonal slots.

    I have attached the cad file of what I have gotten so far along with a picture showing what the part should look like.

    I just don't want someone to finish the drawing for me but I would like to learn how it is done as well for the future.

    Thanks
    Attached Thumbnails Attached Thumbnails box-cam.jpg  
    Attached Files Attached Files

  2. #2
    Community Moderator ger21's Avatar
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    Extrude a solid along a helix, and subtract it.
    Gerry

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  3. #3
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    I am a newb when it comes to working with Autocad in 3D. Could you explain abit how to do this? What info will I need to know about the helix to get it to turn out properly?

    Thanks

  4. #4
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    The way I would do it is with the 3d slice command..Imagine a round loaf of bread that you cut at an angle twice and then remove the slice of bread that you just cut..You have to draw a 2 d drawing first to show the angle of the cut..Then when you have the slice out of there,hollow out the bread with another circle extruded thru the middle of it..Follow the idea?

  5. #5
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    I will give the slice command a try but I have a feeling the edge of the slot will not be correct. The edge or wall of the slot needs to stay at a 90 deg. angle in relation to outer surface as the part is rotated in the 4th axis.

    I have been playing around with extruding of a helix. Still not getting the correct twist of helix to match the cylinder diameter. Will keep plugging away at it but I have a feeling that AutoCad can't do exactly what I want easily. I may need to have someone with Solidworks give it a try.

  6. #6
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    Quote Originally Posted by Beezer View Post
    I may need to have someone with Solidworks give it a try.
    This may help. Drawn with Solidworks.
    Small bridge across slot to join two halve which you may need to remove.
    See attached IGS file.
    Attached Thumbnails Attached Thumbnails Cam -Cylinder..JPG  
    Attached Files Attached Files

  7. #7
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    Kiwi...That appears to be exactly what I am trying to do. What commands or steps in Solidworks did you need to perform to accomplish that?


    What I had planned on doing to get this part machined was to turn the OD to within .025"-.030" of the finished size and leave the ID .200" undersize. That way the groove could be CNC'd and still holiding the two halves together for the other machining that needed to be done later on. The last step would be to finish the bore till the parts seperated.

  8. #8
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    Quote Originally Posted by Beezer View Post
    Kiwi...That appears to be exactly what I am trying to do. What commands or steps in Solidworks did you need to perform to accomplish that?
    Beezer... Some may say I cheated because I used the sheet metal feature.
    I drew it while in flat mode and rolled it up. I considered this the easiest way
    The dimensions may not be correct, I took them from the DWG model.
    I can alter if required and post a revised IGS file.
    Attached Thumbnails Attached Thumbnails Cam -Cylinder2.JPG   Cam -Cylinder3.JPG   Cam -Cylinder4.JPG  

  9. #9
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    I don't consider it cheating if it works.

    Well the original way I was told how to make this part was to take the scaled template that came with the drawings. Cut it out and wrap it around the tube that had already be machine to it's proper OD and transfer the lines on the template to the tube. Then I would need to cut it out using a hacksaw.
    Then file and grind the piece till the matched the outline.

    So your idea to wrap the sheet into a cylinder was the correct one.

    Here is the 2D drawing of the proper template. Looks pretty close to what you came up with.
    Attached Files Attached Files

  10. #10
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    Beezer...Altered drawing and attached updated IGS file.
    Attached Thumbnails Attached Thumbnails Cam -Cylinder5.JPG  
    Attached Files Attached Files

  11. #11
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    Kiwi...That looks great. Thanks.

    Looks like I need to give learning Solidworks another go. Seems it could come in very handy.

  12. #12
    Moderator HuFlungDung's Avatar
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    While modelling the groove is an entertaining exercise, it probably is a waste of your time when it comes to actually machining the feature (just like modelling threads is a wasted effort for lathe cut threads). Helical grooves are typically cut with 4th axis wrap, and you only need the 2d map of the surface unwrapped and laying on the XY plane.
    First you get good, then you get fast. Then grouchiness sets in.

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

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