topic Re: Use power or multiplication with users parameters in Fusion Support Forum

Use power or multiplication with users parameters

remy.muller — Fri, 01 Jun 2018 16:08:16 GMT

Hello the community,

I'm disapointed ! I want to create an user parameters with power on a "model parameters" (d1) but I can't.

I try this expression :

Add User parameters >

Name : calcul

Unit : mm

Expression : 10 ^2

and it works !

But I would like to use this with model parameters :

Name : calcul

Unit : mm

Expression : d1 ^2

And it doesn't work !

Anybody have an idea ?

Rémy

Re: Use power or multiplication with users parameters

HughesTooling — Fri, 01 Jun 2018 17:08:56 GMT

You need to match the units, the input type needs to be unitless so (d1/mm)^2 will work. If you don't cancel the units the output would be square mm so you'd need to select an area unit type for the parameter.

Mark

Re: Use power or multiplication with users parameters

Phil.E — Fri, 01 Jun 2018 18:15:52 GMT

Hi,

The reason you can square 10 in your example is it produces a unitless result, which is given the units "mm" by the parameter. So 10^2 = 100, and the value of the parameter is shown as 100, with mm units. It is a linear value.

When you try to square d1, it already has mm units. The result is square mm which conflicts with your chosen units of "mm". d1 squared is an area value.

Assuming you just want the linear result (mm) and not area (mm^2), you just need to eliminate the squaring of "mm".

If that's what you need, try this:

If not, please let me know, or if you have any other questions of course just ask!

Re: Use power or multiplication with users parameters

remy.muller — Fri, 01 Jun 2018 21:29:55 GMT

Thanks a lot Mark and Phil ! I understand and It works 😃

Thank you for your rapidity !

Re: Use power or multiplication with users parameters

edburns000 — Wed, 11 Nov 2020 12:05:34 GMT

@Phil.E Powers handle units correctly but sqrt() or ^0.5 do not!

To do some simple length-of-hypotenuse sums I am having to convert dimensionless quantities before calculating, i.e. sqrt(((width/1mm)^2)/2). Not the worst workaround to implement if you know how to handle it, but the unit handling seems half-baked...

Re: Use power or multiplication with users parameters

Phil.E — Wed, 11 Nov 2020 16:36:59 GMT

Referring to the product documentation, sqrt is handled by: unit^1/2

http://help.autodesk.com/view/fusion360/ENU/?guid=GUID-76272551-3275-46C4-AE4D-10D58B408C20

Re: Use power or multiplication with users parameters

edburns000 — Fri, 13 Nov 2020 16:47:21 GMT

@Phil.E

Any idea why I can't enter "sqrt(2mm^2)" as a valid expression then? (sqrt(2^2) is valid) Am I missing something obvious?!

Re: Use power or multiplication with users parameters

Phil.E — Fri, 13 Nov 2020 16:55:40 GMT

2mm squared is an area measurement. You cannot take the sqrt of an area.

Re: Use power or multiplication with users parameters

edburns000 — Fri, 13 Nov 2020 17:22:49 GMT

In the example above, if length^2 = area (as it should) and length^3 = volume, then sqrt(area) = area^1/2 = length and cube-root(volume) = volume^1/3 = length

It's a perfectly valid calculation, and mathematically correct - if the square of a number squares the units, then sqrt of a number should sqrt the units.

I might want to calculate the length of the sides of a square face from its area. Or calculating the length of a hypotenuse on a triangle:

sqrt(side1[mm]^2 + side2[mm]^2) = side3

sqrt(length^2) = length

Re: Use power or multiplication with users parameters

Phil.E — Fri, 13 Nov 2020 19:35:02 GMT

You are correct, Fusion should allow you to use unit measures. At this time you must strip units out before using sqrt.

Re: Use power or multiplication with users parameters

Anonymous — Sat, 06 Nov 2021 13:31:47 GMT

You can divide it out.