Parametric equation-driven curve

3D Design Volume Model
1

Hello

I've been using Solidworks for 8 years, but for the past few weeks I've been running into a problem: designing a pump lobe, more precisely a trilobe, for this we select a curve driven by parametric equation, which I succeeded! I found the equations, but I'm drying on the values of T1 & T2.

So I want to draw an epicyclic and a hypocycloid with 6 turnarounds

In advance, I thank you for the precious help you can give me

Gemona

2

Hello

Can you give us a screenshot of the problem so that we can get a better idea of the solutions to be proposed. 

3

Hello

Here is my data that was used to make the equations, equations that I found on the net.


note_lobe.pdf
4

Hello

Attached is a very short tutorial on parametric curves and the epicyclic

Good luck, you're almost there


epicycloide.pdf
5

Good evening,

Since then, I have seen your screenshot. You just have to fill in with the interval [t1, t2] of the values described by t (t varies from t1 to t2). I've never been able to make this work outside of  [0,1] contrary to what is said in the help.

But the main problem is the great instability of SW on this function. You change the formula or the interval and it doesn't work anymore and if you reset the initial values it doesn't work anymore. I have painful memories of involute of a spherical circle to model a bevel pinion. It's one of the bugs that persist from version to version and that don't seem to interest anyone, at least less than the color of the icons ...

3 Likes
6

Good evening Pierre

I have made significant progress thanks to your help, but I need to work on the equation manager! with SW2012 I don't have the same window as you, I'll try with SW2016.

If I may say so, what changes for the hypocycloid?

Very satisfied to reach the goal, thank you!

7

Glad I was able to help you a little.

I'm not a big hypocycloid but at first glance I'll say that what changes is the equation, see https://fr.wikipedia.org/wiki/Hypocyclo%C3%AFde

To make sure that the equations you write are correct, you can do them beforehand in Excel and draw a quick graph with a step of 0.1 rd for example (see attached file for the epicyclic). This way you will be able to differentiate between a writing error and a Solidworks crash.

Sincerely and enjoy the day, it's Sunday


epicycloide.xlsx
3 Likes
8

Good evening Pierre

I have managed to design my trilobe, I preciously keep all the calculations that allow them to be carried out

Good night


construction_trilobe.pdf
1 Like
9

Could you share the part file?

1 Like
10

Here is my example file but be careful SW bug quite a bit with these equations. Maybe Gemona's is doing better


epicycloide.sldprt
2 Likes
11

Thank you, I'll archive it may be useful one day.
We will try to debug it if necessary.

12

Good evening

I'd like a helping hand to draw a multilobe with 3 or even 4 lobes. I arrive for the root style lobe but I get stuck for the trilobe and quatrefoil. 63mm centre distance to drive the 2 lobes (pump).

Thank you