Newbie question: Special user defined parameter problem

[since1954]

Hi! I started learning Fusion 360 two weeks ago. Today I tried to construct a new stand for my new old workbench. I need some squared timbers consisting of 4 layers glued together. To define the depth of each layer I entered a user defined parameter "depth" with 21 mm. All four layers were arranged side-by-side, so my squared timber had a width of 84 mm.

Changing "depth" to 18 mm, I expected that my squared timber width would shrink to 4 * 18 = 72 mm, all layers side-by-side without any gap. The result was 81 mm with 3 gaps of 3 mm.

What was wrong? Can somebody help me?

TIA - Hans from the south of Germany

[TheCADWhisperer]

File>Export and then Attach your *.f3d file here.

[since1954]

Here´s my upload ...

[etfrench]

See the attached file for one way to do this.

[laughingcreek]

at least part of your problem is using the move/copy command to place components.  this command isn't parametric, so it doesn't adjust when dimensions change. if you want a component that has been created with move/copy to stay put. you have to use a joint.

You also have things in your timeline that are in an error state (yellow and red).  those should be corrected as they come up.

I suspect you don't have a grasp of how to use the timeline, and how to go back in the timeline to make changes. that wouldn't be surprising since you just started 2 weeks ago.

for models like this I prefer to use a master skeleton sketch for the entire thing being built, and extrude components in place off that.  I will generally just put them on the origin planes.  Attached is an example oh how I would do this.  there are 27 components in 1 leg assembly, but only 8 unique components.   to create copies I used the pattern tool, which is parametric.  everything is driven off the first 3 sketches.  click on any dimension with out an fx in front to adjustments (I didn't use any user defined parameters).  if the dimension has an fx in it, that means I am referencing 1 or more other dimensions to figure that value.  you don't want to change those. 

step through the timeline and see if you have questions.

[since1954]

Thanks etfrench, it works, but only for identical layers. what about layers that are structured differently?

[since1954]

Thank you laughingcreek for the effort you have made. It's my turn, but I can not continue until next week. I'll get back!

[etfrench]

Create a formula for each structure. 

[since1954]

Hi etfrench, I´m back again. I don't understand your advice "Create a formula for each structure.". Do you have an example?

TIA since1954

[g-andresen]

Hi,

no higher mathematics:

calculate dimension

Set: P 1; P2; P3 and total lenght > Fusion calculates P 4

günther

[etfrench]

See my previous post.  It has formulas for each part of one structure.  Simply reuse the parts of those formulas that are valid for other structures in the formulas for each part of those structures. 

In other words, create user parameters for the dimensions that are common and user parameters for each unique dimension.  Each of those parameters can be formulas. 

[since1954]

Hallo Günther,

thanks for the little video. My problem is (and maybe I didn't explained it right) this: Assumed we have 4 layers with the same or a different thickness. Layers 1 and 4 are solid bodies, layers 2 and 3 have the same outer dimensions as Layers 1 and 4. However, each of Layers 2 and 3 is divided into 3 bodies, each with a gap in between.

Is there a way to stick the 4 layers to each other directly, if I change the material strength (user defined parameter). There have always been gaps in my attempts.

[laughingcreek]

Did you see the model I posted?

If you want components to stick together in a certain relationship, you have to either model them that way, or use positioning joints between them.   There are a number of way to achieve this, but none of these methods will involve the point to point move command.

[since1954]

Hi laughingcreek,

I´m still studying your model (thanks again) and things are getting clearer - no more point to point moving - I promise! 😉

Now I´m trying this again building relationships all over and the first few steps are working.

I announce myself with results again and in the meantime I say "thank you" to all who have taken care of my problem!

since1954