Welcome to the Onshape forum! Ask questions and join in the discussions about everything Onshape.

First time visiting? Here are some places to start:

  1. Looking for a certain topic? Check out the categories filter or use Search (upper right).
  2. Need support? Ask a question to our Community Support category.
  3. Please submit support tickets for bugs but you can request improvements in the Product Feedback category.
  4. Be respectful, on topic and if you see a problem, Flag it.

If you would like to contact our Community Manager personally, feel free to send a private message or an email.

Splitting a solid only part way through

benn_banksbenn_banks Member Posts: 20
Im trying to plit the lower paddle off this part without slicing all the way up the part.
I tried splitting with a sketch but i cant select a sketch when splitting. 
Whats the best way to remove just the lower portion without affecting anything higher on the part??


Comments

  • _Ðave__Ðave_ Member, Developers Posts: 712 ✭✭✭✭
    I would draw a sketch with a thin slot on the face and do an extrude/remove.
    _Dave_
  • øyvind_kaurstadøyvind_kaurstad Member Posts: 234 ✭✭✭
    edited January 2016
    Draw a line on a sketch in a plane perpendicular to where you want the split, and extrude a suitably sized surface from that, and then use the extruded surface as the split tool.
  • jakeramsleyjakeramsley Member, Moderator, Onshape Employees, Developers Posts: 584
    As øyvind_kaurstad said, create a surface and use that.  Surfaces are bounded.  Planes are infinite which will split through more of the part.
    Jake Ramsley

    Director of Quality Engineering              onshape.com
  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,331
    It is not possible to create an infinitely thin 'split' part of the way through the part AND (in the test i ran) a surface used to split a part that extends only part of the way through, is treated as infinite and split the part entirely.
    _Dave_ is actually correct, create a sketch defining the width of the slot and cut it to the desired depth.
    Philip Thomas - Onshape
  • kevin_o_toole_1kevin_o_toole_1 Onshape Employees, Developers, HDM Posts: 449
    edited February 2016
    @benn_banks ;
    Phillip is right that a planar surface will split infinitely, just like a construction plane.

    To work around this, you can split with a surface that's only partially planar to get the behavior you want.

    e.g.:


  • øyvind_kaurstadøyvind_kaurstad Member Posts: 234 ✭✭✭
    Useful info, but quite unexpected (so much that I didn't actually test it when I wrote the reply) that Onshape splits all the way though even if the surface is bounded. That cannot be the desired behaviour, so I gather that's a bug?

  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,331
    Kevin's trick of a 'not completely planar surface' is pretty cool.
    Note that this is valid because it still produces manifold topology (in this case two bodies).
    The OP asked to make an infinitely thin slit - this is non-manifold topology (a valid solid may not have more than one face meeting an edge and no two faces may be coincident - there is a more technical definition, but this will do for now).
    The original ask is for a non-manifold body and Onshape won't let you do this - moreover, its non manufacturable.  i am not chastising anyone, this is just an interesting discussion. Any of the methods espoused here are valid.
    Philip Thomas - Onshape
  • øyvind_kaurstadøyvind_kaurstad Member Posts: 234 ✭✭✭
    @philip_thomas I'd argue that Kevin's trick should not be necessary. The surface he drew should be valid for splitting even without the half circle at one end (to not make it not completely planar).

    If a surface is bounded, then why would it (attempt to) split anything outside it's bounds. This surface should not split the upper part of this solid, but it does:




  • benn_banksbenn_banks Member Posts: 20
    Awesome!! thanks guys!! that worked
  • øyvind_kaurstadøyvind_kaurstad Member Posts: 234 ✭✭✭
    I'd still like to have some feedback from Onshape as to whether this really is the intended behaviour? While the proposed workaround gets the job done, it is really difficult to see why it is necessary in the first place. In this regard, Onshape clearly treats a bounded planar surface as if it is unbounded (i.e. as it it were a plane).
  • philip_thomasphilip_thomas Member, Moderator, Onshape Employees, Developers Posts: 1,331
    I'd still like to have some feedback from Onshape as to whether this really is the intended behaviour? While the proposed workaround gets the job done, it is really difficult to see why it is necessary in the first place. In this regard, Onshape clearly treats a bounded planar surface as if it is unbounded (i.e. as it it were a plane).
    Oyvind - I checked with the VP of UX and this is the intended behaviour. You (as is everyone), are free to submit an enhancement request to change the behaviour so that users can vote on allocating resources to work on this.
    Philip Thomas - Onshape
  • kevin_o_toole_1kevin_o_toole_1 Onshape Employees, Developers, HDM Posts: 449
    @øyvind_kaurstad:

    You're right that the current behavior feels inconsistent. I believe it was a conscious UX decision, the reason being, once we start allowing people to split with faces, rather than just surfaces, a planar extension is the natural thing to do, e.g.:



    The reason we don't extend non-planar surfaces is more a mathematical problem than a UX one :smile: 

    This specific case has been filed as a bug, since you're right that we don't have a good (i.e. discoverable) way of solving it, or other cases like it. As with all things in UX, the solution here will be a matter of balancing a number of different considerations, and the exact solution could be changing the defaults, or adding explicit options, or something else entirely.

  • øyvind_kaurstadøyvind_kaurstad Member Posts: 234 ✭✭✭
    @philip_thomas Thanks for checking. However, it still escapes me how on earth the devlopers could even think that this was a good way to do it. If you want to split infinitely, then it would be easier to just split by a plane, which by definition is unbounded. Are there any other cases where a bounded surface acts as if it is unbounded?
Sign In or Register to comment.