CAD draw cylinder with 4th axis path
Close
Login to Your Account
Results 1 to 10 of 10
  1. #1
    Join Date
    Mar 2016
    Country
    AUSTRALIA
    Posts
    8
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    1

    Default CAD draw cylinder with 4th axis path

    Hi all,
    I just spent the last day trying to draw a motorcycle gear shift drum which is basically a cylinder with 3 tracks (paths) for the selector fork pins to follow. I've been CAD drawing for some 15 years and have done some rather weird jobs but this one has me stumped and I'd like to hear the opinion of others who may have done something similar. The problem is that I don't know how to draw the tracks/paths (8mm wide x 6mm deep) to end up with parallel walls. I started off this job using Fusion 360 and then switched to SolidWorks (at my work) when I realised that Fusion can't do a full wrap of a cylinder. I then realised that wrap in SW produces NON parallel walls everywhere EXCEPT for the concentric paths. Right now it seems I'm left with 2 options which are:
    (a) take the job as is and turn it from solid to surfaces and using offset surfaces and trims obtain what I want then convert back to a solid
    OR
    (b) waste no further time and leave the job as is and use the CAM (Fusion 360) to sort out the tool paths so that I get parallel walls.
    I'm inclined to go for option (b) but just wanted other professionals to weigh in on this. Maybe this kind of thing is only achievable (easily) with high end packages such as Catia or Siemens NX but I don't have access to those.
    Attached Thumbnails Attached Thumbnails shiftdrum-1.jpg   drum.jpg   shiftdrum-2.jpg  

  2. #2
    Join Date
    Feb 2013
    Country
    UNITED STATES
    State/Province
    California
    Posts
    801
    Post Thanks / Like
    Likes (Given)
    491
    Likes (Received)
    472

    Default

    I just went to use Fusion 360 today and there was a patch with a debuted "Manufacturing Extension". It has a bunch of stuff in it like automated in cycle probing and such but the relevant part to your question would be the Rotary Multi Axis stuff. It is showing full cylindrical toolpaths, definable areas on the cylinder and basically a ton more 4th axis continuous stuff than was previously in there.

    I do recall the guy from NYCNC doing a work around for the no 360° thing which looked like a pain. I guess if you spring for this new "Manufacturing Extension" you can do that stuff. Be interesting to see if it's useful or just another thing to have to buy to make Fusion 360 useful. I thought the deluxe package already did full 4th so not thrilled if I have to buy something else to get continuous 4th but not surprised.

  3. Likes Skippy59 liked this post
  4. #3
    Join Date
    Mar 2016
    Country
    AUSTRALIA
    Posts
    8
    Post Thanks / Like
    Likes (Given)
    4
    Likes (Received)
    1

    Default

    Thanks Jaxian,
    I'll check it out.

  5. #4
    Join Date
    Jan 2015
    Country
    UNITED STATES
    State/Province
    California
    Posts
    775
    Post Thanks / Like
    Likes (Given)
    114
    Likes (Received)
    400

    Default

    Wrap is the wrong feature. It gives "sloped" walls since it is projecting towards the center.

    Use a swept cut if you want perpendicular walls.

  6. Likes Kyle Smith liked this post
  7. #5
    Join Date
    May 2014
    Location
    ca, US
    Posts
    300
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    81

    Default

    I do that on the CAM side. I lay out the tracks on a plane in CAD then import it to CAM and wrap it around a cylinder. The tool diameter and depth of cut determine the groove size.

  8. #6
    Join Date
    May 2002
    Location
    South Central PA
    Posts
    13,897
    Post Thanks / Like
    Likes (Given)
    2434
    Likes (Received)
    3682

    Default

    In Solid Edge I'd use a swept path, but I'm at a loss how to draw the path. The shift drums I've examined had varying widths of the grooves, they were only close to the follower size right where the follower rested in each detent position when in gear. I believe the increased width in between those positions is to prevent binding when the machined groove geometry conflicts with the round follower's geometry. To do that you'd need 2 paths, one for each side of the groove and perhaps even a 3rd path between the 2. I didn't take the project any further than that.

  9. #7
    Join Date
    Jan 2005
    Country
    CANADA
    State/Province
    Saskatchewan
    Posts
    10,238
    Post Thanks / Like
    Likes (Given)
    1396
    Likes (Received)
    3696

    Default

    I'm not certain that spending all the time modelling the theoretical groove shape actually helps you to machine it. It's a different animal if you are going to use 3d surfacing techniques to machine the groove, which I highly doubt would be the case.

    That being said, I have laid out some parts using offset helices (with correctly proportioned radius and lead) and then surfaced between all pairs to make the surfaces I wished to display. But for a part that will be machined with wrap, you really only need a flat layout and its not worthwhile to create the model.

  10. #8
    Join Date
    May 2014
    Location
    ca, US
    Posts
    300
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    81

    Default

    Selector forks that I have seen have a round pin in the groove of the shift drum. As long as the pin is pointing at the centerline of the drum there is no reason for the groove to be wider between the stop positions.
    If the fork pin is a larger diameter than the cutter you can draw two paths parallel with a half round cap at the ends. Otherwise machine one side of the line with a negative offset of half the difference between the cutter and groove widths then the other side of the line with the same offset.
    Sales people like pretty pictures but they do not help the machinist.a65_5spd2.jpg

  11. #9
    Join Date
    Jun 2012
    Location
    Tennessee USA
    Posts
    918
    Post Thanks / Like
    Likes (Given)
    612
    Likes (Received)
    536

    Default

    A swept profile cut may work unless the amount of twist is too great. That seems to depend upon how far around the cylidner you're going. You can create a path or a slot on a plane and project it on the cylinder face, there may limitations to this as well. You can create a 3D sketch by using the "convert" call for extruding the cut but the ends of the profile will be affected by the vector direction you choose. This may work fine if you work in short sections and attach/merge one to another. I've not tried to create an entire drum with the shift paths but I tried using a loft cut long enough to find the failure point. The profiles and the path need to intersect at some point, a "Pierce" constraint may be needed, depending upon whether you're using a sweep, extrude, or loft. Once you select the closed profiles (Two or more) you use the projected/wrapped curve as a "Centerline Parameter" rather than a "Guide Curve". Pick the same corner point in each profile (Upper Left - Upper Left for eg.) or the loft will rotate accordingly. It may/may not work for what you're doing, I'll leave that for you to determine. Seemed to leave parallel walls and not twist to the profile. The images are below, hope this helped.

    drum-over.jpg

    drum-x-sect.jpg

    drum-over2.jpg

  12. Likes gkoenig liked this post
  13. #10
    Join Date
    Jun 2012
    Location
    Tennessee USA
    Posts
    918
    Post Thanks / Like
    Likes (Given)
    612
    Likes (Received)
    536

    Default

    Can't edit my previous post for some reason. I should have noted that I used SolidQuirks (2014) for the above. The different versions of Pro-E should, as I recall, work about the same. Inventor probably will also. Haven't tried with Catia yet but I'd be surprised if a similar approach didn't work. A combination of "Revolved" / "Extruded" / "Swept" / and "Loft" should get you there. Interested in hearing the results from somebody that tries this in CAD, I've never done a shift drum either and am up for learning something.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •