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## arc perimeter driven by the length of a straight line.

Hi,

I start in Creo sketcher with a straight line (sd3), then I would like to add an arc which has the same (perimeter) length. I think that should be possible with the "Perimeter" function but I cant get it to work properly.

Could someone explain to me how to do it?

see attached image. Tags (3)
1 ACCEPTED SOLUTION

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## Re: arc perimeter driven by the length of a straight line.

Thanks Antonius,

Actually, your solution makes the line length driven by the arc length, but I would like it to work the other way round: sd3 = sd0 instead of sd0 = sd3. But I get an error on that.

Ive figured out why: sd2 cannot be used as a parameter for the arc length, because that doesnt make sense.

So i've modified the function of sd2 so it can be used properly to vary the arc length, its now sd6: cheers.

3 REPLIES 3
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## Re: arc perimeter driven by the length of a straight line.

Perimeter dimensions are limited.

You cannot make the two dimensions equal as you can with other type of dimensions. In this case, a section relation will solve this. But 1st you need the perimeter dimension:

Select the perimeter dimension tool and select the arc; place the dimesnion; and select sd2 as the variable.

Note: this require the radius to be fixed and the end angle will change. You can also make the radius variable.

Next; add the relation sd3=sd(perimeter dim)

Now the line will always be the perimter of the arc. Highlighted

## Re: arc perimeter driven by the length of a straight line.

Thanks Antonius,

Actually, your solution makes the line length driven by the arc length, but I would like it to work the other way round: sd3 = sd0 instead of sd0 = sd3. But I get an error on that.

Ive figured out why: sd2 cannot be used as a parameter for the arc length, because that doesnt make sense.

So i've modified the function of sd2 so it can be used properly to vary the arc length, its now sd6: cheers.

Highlighted

## Re: arc perimeter driven by the length of a straight line.

Thanks for pointing that out... I wasn't sure it would do that and I didn't try.

Sure enough, I reversed the relation from sd0=sd3 to sd3=sd0 and it worked fine.

That means the only limitation is that you cannot use the equal constraint between the linear and perimeter dimension.