Variables and math

mark_wallström

Hi,

First; Onshape is the best thing since sliced bread, period. What you have done is extraordinary, thank you.

I'm a "make variables for everything"-kinda guy. Is there a reason we can't do math with variables? For example, I have variable #pistondiameter and I want to make a dimension be #pistondiameter+2, which can't be done.

Can it be so that I am doing something wrong?

viru

@mark_wallström, You can do math with variables. Currently you are facing problem in your dimension having varible because your variable expression is not Valid ( Not consisting with bracket before unit ). Please add bracket in your dimension it will definitely work. You should write (#pistondiameter+2) before unit
Please refer below video for more detail,

mark_wallström

Fantastic, thank you viru. I also think I made an error in putting in the value for the variable as [mm] and added a dimensionless number to it (+2 instead of +2mm) in the expression.

bradley_sauln

@mark_wallström you should also take a look at the integrated cloud app Swift Calcs. I think you will enjoy it
https://www.swiftcalcs.com/#product

ilya_baran

@mark_wallström

Thanks for the kind words!  Onshape supports all kinds of math in variables, other feature parameters, and dimensions (see https://cad.onshape.com/help/#numeric-fields.htm) and you can even write you own functions using FeatureScript.

Your diagnosis is correct -- Onshape is strict about not mixing units (you can add an inch to an inch or a meter, but not to an angle or a unitless number) so if #pistondiameter is a length, then you should add 2mm to it.

The parenthesis (bracket) is not necessary.

john_david_dunson

This should be added to the Variable page in the help library.  I was ripping my hair out trying to add numbers to variables.  I'm a beginner, but nowhere else that I've encountered have I had to specify units in dimensions.  So it's easy to multiply variables, but it's not at all obvious that specifying units would be required for that one thing.  To me anyway.
Thanks bunches

john_david_dunson

ilya_baran said:

@mark_wallström

Thanks for the kind words!  Onshape supports all kinds of math in variables, other feature parameters, and dimensions (see https://cad.onshape.com/help/#numeric-fields.htm) and you can even write you own functions using FeatureScript.

Your diagnosis is correct -- Onshape is strict about not mixing units (you can add an inch to an inch or a meter, but not to an angle or a unitless number) so if #pistondiameter is a length, then you should add 2mm to it.

The parenthesis (bracket) is not necessary.

This should be added to the Variable page in the help library.  I was ripping my hair out trying to add numbers to variables.  I'm a beginner, but nowhere else that I've encountered have I had to specify units in dimensions.  So it's easy to multiply variables, but it's not at all obvious that specifying units would be required for that one thing.  To me anyway.
Thanks bunches