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More efficient: Sketch or solid patterns?

tony_459tony_459 Member Posts: 206 ✭✭✭
I need to export my CAD parts in STEP files and this has me thinking about file size. All else being equal, which will bloat file size the least---sketch patterns or solid patterns? Or are they equivalent in their effect? Thanks in advance!

Best Answer


  • tony_459tony_459 Member Posts: 206 ✭✭✭
    Thanks, Neil! 
  • tony_459tony_459 Member Posts: 206 ✭✭✭
    edited July 2019
    Question! I notice that an extrusion of a pentagon sketch is larger (in STEP format) than an extrusion of a rectangle chamfered to produce the same pentagon. This is a different case from patterns, but I'm wondering---the geometries being identical, why is chamfering more efficient than adding an edge to the extruded sketch?

    My extruded pentagon sketch is 17.2 KB while my chamfered rectangular extrusion is 16.2 KB. Likewise, an extruded hexagon sketch is 20.7 KB while a twice-chamfered rectangular extrusion is 18.7 KB. And an extruded heptagon sketch is 24.2 KB while a thrice-chamfered rectangular extrusion is 21.2 KB.

    In all cases, the chamfers are specified to produce the same geometries as the extruded sketches. For every face added, chamfering saves you 1 KB over extruding a sketch. Why?

    This may seem like splitting hairs, and it would be if I weren't dealing with very large patterns, where a difference of a few KB per extrusion can add up to MB in the final extruded part! Anyway, just trying to understand why chamfering seems more efficient when the exported geometry is by all appearances the same?
  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 4,802
    Curious. It shouldn’t make any difference. Can you try comparing Parasolid file sizes? (If you have time that is - it’s just out of curiosity)
    Director, Technical Services, EMEA 
  • tony_459tony_459 Member Posts: 206 ✭✭✭
    edited July 2019
    I'll give it a try and post the results!

    Also (this gets complicated): extruding a heptagon sketch with a filleted corner at 0.2" radius... beats filleting an edge of a thrice-chamfered rectangular extrusion at the same radius. 

    Sorry for the tongue twister.

    The solid fillet adds 2.8 KB to the STEP file size while the sketch fillet adds 4 KB. Likewise, two 0.2" solid fillets add 10.1 KB while two 0.2" sketch fillets add 14 KB. 

    In all cases the solid and sketch fillets are specified to produce the same geometries. So with fillets too it seems solid features beat sketch features when it comes to STEP file size!
  • tony_459tony_459 Member Posts: 206 ✭✭✭
    With Parasolid files:

    Chamfering a rectangular extrusion adds 2 KB while extruding a pentagon sketch adds 5.3 KB (relative to the plain rectangular extrusion). Twice-chamfering the rectangular extrusion adds 3.9 KB while extruding a hexagon sketch adds 9.4 KB. Thrice-chamfering the rectangular extrusion adds 5.8 KB while extruding a heptagon sketch adds 13.3 KB.

    So with Parasolid too it seems chamfering solids beats adding sketch edges...
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