"non driving" dimension as variable?

alexander_potochkin

Hello

Could you help me to understand how I can use a "non driving" dimension as a variable?

I have a square and a variable which defines this square by the length of its diagonal.
Now I need to use the length of the square's side as a variable for the next operation (say extrude).

Is it possible to do it in onShape?

Thanks!

lougallo

This is something we will add but was not in the first build of the feature.  Currently you will need to use a variable to define the dimension you want to reference.  More iterations to come.

alexander_potochkin

Here is a document that illustrates the question:

https://cad.onshape.com/documents/c14f7a86f2624c8082b658cc/w/9757b49885644d65accd48d2

alexander_potochkin

I can certainly calculate the square's side from the diagonal.
But is there a general way to take a dimension and use it as a source of another dimension?

Thanks

_Ðave_

I tried this also and don't believe that it is possible, this would be a very good improvement request.

brucebartlett

No it's not possible to do a measure with the variable tool. 
I put in a request a few days ago when I was trying to do this for the tetrahedron challenge. 

3dcad

I have also put in this request, but I did it with the feedback tool so it's not open for voting.. 

Workaround would be creating enough parameters to be able to calculate equation for the driven dimension you need.

thomas_kozak

This would be an incredibly useful feature.  For a simple example as given above, it's all right to fudge it by inputting an expression using a known variable, but for more complex relationships that's not practical.

shashank_aarya

This is very interesting scenario and can be very much helpful. But I am not sure how practically it would possible. Because whenever square is fully constrained by its sides and equal constrain, diagonal dimension will be driven by side dimensions since it will act as extra dimension than what it is required to get the sketch fully constrain.
I used Creo and Inventor but have not seen the possibility where we are able to change the driven dimension manually. But it can be good enhancement comparing to other CAD platforms if Onshape could make it possible.

alexander_potochkin

I am only asking about converting a square's side to a read-only variable which is dependent on the existing variable representing the diagonal size.
This should not be a problem, should it?

andrew_troup

alexander_potochkin said:

I am only asking about converting a square's side to a read-only variable which is dependent on the existing variable representing the diagonal size.
This should not be a problem, should it?

It shouldn't be, but it seems it is currently not possible. You can currently define such a variable using trig, but not solve it using a sketch. I expect this will be addressed.

shashank_aarya

alexander_potochkin said:

I am only asking about converting a square's side to a read-only variable which is dependent on the existing variable representing the diagonal size.
This should not be a problem, should it?

Yes I agree. To convert square side dimension to read only dimension we can select the dimension, right mouse button and select "change to driven dimension".
But after changing the diagonal the result will not be a square which has all sides equal to each other. It will be a rectangle with two opposite equal sides. We can put the length of rectangle side (driving dimension) as variable in extrude also.
See the below video. I hope this could be one of your requirements.

lougallo

This is something we will add but was not in the first build of the feature.  Currently you will need to use a variable to define the dimension you want to reference.  More iterations to come.

jrs_spedley

I know it is an old post but I've search and can't find it.  Has this been implemented yet?

NeilCooke

@jrs_spedley no - you will have to use the measure FS for now - https://cad.onshape.com/documents/572b968ce4b07aad125dbaaf/v/08093fef6c4d4f330f24dd19/e/b40df94c5081948fe8195e81

Kyler_Walker

The ability to use dimensions to define variables would be very helpful.

EvanReese

here's the custom feature I use for this a lot: https://cad.onshape.com/documents/77baa8153589a7fc5f289829/v/ceb4a03e4ac77173bf6d0074/e/181cb871f3008e6b885df46a

tom_auger

I've come across use cases for this a number of times. I feel allowing "calculated" dimensions from a sketch to become used as variables to drive other parameters or dimensions could be a great time-saver in many situations.