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

richard_earl

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.

jelte_steur814

yes, using parameters within a sketch or feature without bloating the feature tree with parameter features would be useful indeed. how can we vote this one up?

steve_shubin

@richard_earl

Here in the forum, seems I recall someone requesting this before. That is, the ability to use a dimension from one sketch in another sketch. So someone may have already made a post where you could vote this up. And the more votes, the more likely this is to be incorporated

In the mean time, here is a GIF, showing how I used the EQUAL constraint, between a line on Sketch 1, and a different line on Sketch 3. I changed the length of the line in Sketch 1, and the line in Sketch 3 changed. And then I selected a line on Sketch 2, and changed the dimension, and it changed the length on one side of the rectangle in Sketch 3

Now you may come up against a situation where you want to use the distance between a line and a point, or the distance between two points on one sketch — and you want to have this distance linked to another sketch. For that you can use Measure Value, which will save you a few steps in comparison to using a variable

If you need to use the distance in one sketch in some kind of a formula that could be used in whatever following sketch, then you could get that distance again, using Measure Value

Here’s where you can get the Measure Value featurescript

https://cad.onshape.com/documents/77baa8153589a7fc5f289829/v/33ba34fba75bf5f4ba08ed63/e/d3174bf5315e6aafcb889367

If the holes for the ATX power supply, are dimensioned from the outline of the power supply, then even if the sheet metal size changes, those holes will be in the proper place for that power supply

anjali_parikh540

Can variables be used to accomplish this?

steve_shubin

anjali_parikh540 said:

Can variables be used to accomplish this?

Yes - You could insert a variable into many dimensions throughout numerous sketches within a document

In fact now, I think there is some type of global variable that could be used across different documents

richard_marcus

I would love this as well. As mentioned, you can do this with variables. But for my preferred workflow, only important variables should be given the status as a row of the feature tree, anything more is clutter. I would love to be able to reference sketch dimensions even within the same sketch. on dimension is 1/2 another for example. Having this ability to reference sketch dimensions in future sketches would be icing on the cake. I am used to this ability from Solidworks. 

I have created an improvement request for this: https://forum.onshape.com/discussion/19053/use-existing-sketch-dimensions-in-another-dimension-within-the-sketch-and-other-sketches-in-ps/p1?new=1