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The ability to use other existing sketch dimensions in another dimension within the sketch.

richard_earlrichard_earl Member Posts: 1
I am not a professional CAD designer, I use CAD software for hobby purposes, I have until recently been using Inventor under an academic licence, as my situation has changed I can no longer use Inventor, and I cannot justify the expense for hobby purposes. Hence I have moved to Onshape as it looks to be the best alternative for me, however the inability to use existing sketch dimensions within another sketch dimension is almost a deal breaker.

I would like to see the ability to use an existing dimension within a sketch (d1) within another dimension (d2), either as a simple reuse of that dimension (d1) value, or more usually as part of a formula for determining the value of the dimension (d2).

An simple example use would be placing a rectangular cutout in the centre of the face of a solid/sheet metal part, I have the driven dimensions of face width and height (these will change if the part dimensions are changed) and the rectangle width and height (these are fixed as they have to fit a display for example) the dimensions for the distance from the part edge to the rectangle edge determine if the rectangle is in the centre, these should be a formula, for example to center across the width the formula would be "(part_width - rectangle_width)/2", then if either width dimension changes the rectangle remains centered.

I appreciate that using constraints would achieve the same result in the above example, but if you are working with for example the hole pattern for an ATX power supply, and you want the power supply to be centered across the face width, constraints will not work in this situation, as the holes are not symmetrically placed. Or when working with a series of dimensions whose values are based on a formula using a value from another dimension or dimensions, the ability to use the existing dimensions in a sketch is for me what makes the difference between a computer aided drawing program and a computer aided design program.

When creating a drawing all the dimensions have already been worked out and it is basically documenting the design, the current approach in Onshape is this, when creating a design it is more of a "trial and error" approach, I might know some things must be this shape and/or in this position but mostly I rough out the design and then refine it, I have found this approach extremely easy in Inventor as I could use dimensions that are relative to other geometry sizes and automatically adjust if the other geometry changes, in Onshape the workflow is tedious and time consuming, I discover that a dimension should be referenced, I exit the sketch create a variable, find and change the sketch where the reference dimension is first used to use the variable,  then go back to the sketch change the reference dimension to use the variable, then add the driven dimension using the reference, this takes a lot more time, and reduces productivity.

I guess I am asking for Onshape to be changed from a Computer aided drawing program to a Computer aided design program.
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