topic Re: Creating a relation between 2 junctions based on a math function in Fusion Support Forum

Creating a relation between 2 junctions based on a math function

miguelon1602 — Fri, 28 Jul 2023 19:38:36 GMT

Hi everyone. I'm developing a scissor mechanism (see image), and I want to start with the junctions' movement relations to get it to work. However, I haven't found any way to create a junction that's based on a math function. I have the function on paper, but I don't know how to apply it. it would be between the rotation and prismatic junction that are on the same point. How can I do this?

TIA

Re: Creating a relation between 2 junctions based on a math function

TheCADWhisperer — Fri, 28 Jul 2023 19:56:19 GMT

@miguelon1602

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

Also indicate your desired Equation.

Re: Creating a relation between 2 junctions based on a math function

jeff_strater — Fri, 28 Jul 2023 20:28:55 GMT

you can use an expression in a Motion Link between two joints. I assume here that you want to relate the two Revolute joints in the image with a Motion Link?

Re: Creating a relation between 2 junctions based on a math function

miguelon1602 — Fri, 28 Jul 2023 21:34:46 GMT

file attached. the formula I want to apply is d=-50*cos(theta), being d the movement of the lineal joint (negative to go closer to 0), and theta the angle on the rev joint that's on the same point

Re: Creating a relation between 2 junctions based on a math function

miguelon1602 — Fri, 28 Jul 2023 21:37:09 GMT

that's not what I'm asking about. I want to create a motion link between the lineal and the revolute joint that are on the same point, but with a non-linear relation (I want the distance travelled by the lineal joint to rely on the cosine of the angle of the revolution joint that's on the same point)

Re: Creating a relation between 2 junctions based on a math function

jeff_strater — Fri, 28 Jul 2023 21:48:19 GMT

OK, well, that was just a guess. No, I don't think that you can create that kind of a relationship in a Motion Link. Someone smarter may find a way, but I don't know of one. You can simulate it with Motion Study.

Re: Creating a relation between 2 junctions based on a math function

miguelon1602 — Fri, 28 Jul 2023 22:16:20 GMT

UPDATE: In the end, I applied a revolution joint with a 2:1 ratio link to another one of the existent revolution joints, and now the mechanism behaves as it should

Re: Creating a relation between 2 junctions based on a math function

jhackney1972 — Fri, 28 Jul 2023 22:50:50 GMT

That sure is a far cry from the formula of motion you posted in message #5!

Re: Creating a relation between 2 junctions based on a math function

miguelon1602 — Fri, 28 Jul 2023 22:56:29 GMT

The formula was to get the middle holes to move fully vertical, just so the mechanism behaved as expected (a scissor lifting mechanism). I ended up trying another route to see if I could get it to work, and I ended up getting the result with a different way of applying joints