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Newbie Q: What is the best way to cut a series of rounded, shallow trenches?

john_smith077john_smith077 Member Posts: 109 ✭✭
edited July 2016 in Community Support
Hello

[Preface: I keep finding certain things to be extremely painful to build and I am sure that there has to be a much better/easier way!]

In this case I am trying to create a cylinder (shaft) , on one end of which, I then cut a series of shallow radial trenches each of which are at 30 degrees from each other. Each trench should have a shallowly rounded bottom. (see diagram) What is the best way do achieve this?




Should I: 
A. Create a series of extruded tubes each rotated by 30 degrees and then do a Boolean operation on each of them against the cylinder. (But even if so, what is the best way to create the series of extruded tubes ?)

B. Draw each trench in 2D and then Extrude using Remove, and then Fillet in some way??

C. Do something clever using Patterns?

It would be really helpful to see a video of how to use the Transform tool, but I can't find one.  :^/

J

Answers

  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 3,356
    Sketch the profile, extrude remove, circular pattern?
  • john_smith077john_smith077 Member Posts: 109 ✭✭
    edited February 2016
    I think my problem is that I can't get Circular Patterns to work.

    When I try to create a Circular Pattern of Feature Pattern, all instances of the feature seem to disappear.  [grrr]

    What am I doing wrong... ?   :^/

    https://cad.onshape.com/documents/848b05260887212f608c64b4/w/262a72a4d698ee5c9266f473/e/8a1dcd3408f0d2c2422185b2

  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 3,356
    When you create the cut, Extrude 2, you are removing the outside of the sketch so when you pattern that around it is completely removing the top layer. Make Extrude 2 as adding the material for the "inverted slot" then pattern that instead.
  • john_smith077john_smith077 Member Posts: 109 ✭✭
    NeilCooke said:
    When you create the cut, Extrude 2, you are removing the outside of the sketch so when you pattern that around it is completely removing the top layer. Make Extrude 2 as adding the material for the "inverted slot" then pattern that instead.
    Sorry but TBH, I don't understand that first sentence(!) but I have now tried changing Extrude 2 to Add rather than Remove and I got a message about not changing any geometry and nothing changed on screen.

    And then when I set it back to Remove, suddenly it started to work.

    So, now completely confused, I deleted both the extrude and and the circular pattern to see if I could rebuild what I had before and replicate the original problem. And blow me down the circular pattern appears nicely! 

    All very mysterious, but the problem seems to have fixed itself...  :-/



     
  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 3,356
    edited February 2016
    It was the way you modelled it - the first time you did not add an extrude, you cut the material around it away. Then you patterned the cut which cut away the extrude and all the pattern instances too. 
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