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Dependent/limited dimensions ?
Mazigazi
Member Posts: 5 ✭
I'm still a beginner in CAD as a hobbyist, but this sketch that i am trying to get working is driving me nuts. The large circle diameter is variable and can/will change. The construction line between the small circles is of fixed length. So I want the construction line to always be on the edge of the big circle or a bit outside it so that the minimum distance of 3mm between big and small circle is always respected but can be more depending on the size of the big circle
Thanks !
Best Answer
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eric_pesty
Member Posts: 1,951 PRO
I see…
You won't be able to do this in a single sketch.You can do this with a layout sketch to figure out the "transition diameter", and then use a couple measured variables and the ternary operator to construct the "solution" sketch, see example:
https://cad.onshape.com/documents/6d74ce66a0ac3960c291a454/w/aec6d9caa339a80fd8e54fe2/e/6a73627ba2c411a9c707ab93?configuration=Diameter%3D0.35000000000000003%2Bmeter&renderMode=0&tangentEdgeStyle=1&rightPanel=configPanel&uiState=66da4c8c8a292d47c17e1bb3
2
Answers
Not sure what the issue is, this should work fine no?
This sort of arrangement may be what you're looking for. Note that the second small circle is a mirror to keep the pattern symmetric. This will maintain the 3mm distance circle to circle. Try changing the variables to see the sketch update.
https://cad.onshape.com/documents/fa40a8e0adf37af8a2dd7498/w/91a671687060dc5bdeb87877/e/e18f85581c371964edd3d244
If you want to test motion with limits, you probably need to do this in an assembly:
https://cad.onshape.com/documents/6d74ce66a0ac3960c291a454/w/aec6d9caa339a80fd8e54fe2/e/9eb0b595427da9867b23bcff?renderMode=0&tangentEdgeStyle=1&uiState=66d9e1177d5725327306254b
Hi, thank you both for the answers, it was quite late at the time of posting and I see now that the shared picture may be misleading with what I want to achieve with my design. I'll share 2 scenarios, dependent on the size of the "Large circle". Basically, I want to create a part (a cover of a sort that is to be bolted down) where one will be able to change the size of big circle and the final part will be adjusted (So, no motion limits).
Keep in mind the construction line should always be tangent to the big circle or be parallel to the tangent of the large circle (and not crossing the large circle).
Scenario 1: Construction line is tangent to the large circle since it its small enough that the "Rule 1" where distance between Large and Small circles is > 3 mm (14,9 in our case) and "Rule 2" does not cross the Large circle, are respected. If I would set the fixed distance to Large and Small circles "Rule 2" would not be respected (which is the case in the purposed answers)
Scenario 2: If we increase the diameter of the Large circle, at a certain point just keeping the construction line as a tangent to the Large circle "Rule 1" would stop being respected. So the picture below would be the desired result, where the "Rule 1" would basically be set to 3 mm, and in turn this would cause the the construction line would become parallel to the tangent of the Large circle (forming a gap between the two) and "Rule 2" would be respected as well.
I hope this helps with understanding what I want to achieve, but I fear it may be impossible with OnShape.
I see…
You won't be able to do this in a single sketch.
You can do this with a layout sketch to figure out the "transition diameter", and then use a couple measured variables and the ternary operator to construct the "solution" sketch, see example:
https://cad.onshape.com/documents/6d74ce66a0ac3960c291a454/w/aec6d9caa339a80fd8e54fe2/e/6a73627ba2c411a9c707ab93?configuration=Diameter%3D0.35000000000000003%2Bmeter&renderMode=0&tangentEdgeStyle=1&rightPanel=configPanel&uiState=66da4c8c8a292d47c17e1bb3
Thank you ! I still need to figure out how exactly it works, but I think I should be able to do that
I'm unclear about the 80mm dimension between the two small circles- does this change for various configs. or is it a constant? My first thought was to use variables with If/then logic to solve mathematically and or geometrically , but I'm not sure if this would work - might be something to look into though.
As a different approach, you might consider using one config. that solves rule 1, and a different config. that solves rule 2 (two separate logic problems) - then use which ever configuration that does not fail after you input all of the criteria. Yes, not a very elegant solution, but hey, if it gets you there.
Truth be told, I'm not sure if either way is sound - just food for thought.