Twin screw extruder modelling

[Ivan Silva]

I'm currently trying to reverse engineering an 3d scanned based screw model. The profile section cut are pretty straightfoward to model but I have no idea how to model the transaction between two diferent cross-sections with different pitches in an smoth way.

Someone have ever experience to model an extruder screw like that?

 

[ctopher]

Depends on your CAD software. In SolidWorks, there are probably a few ways: Different solid bodies merged with threads; Swept boss; Lofted cut, etc.

 

[JohnRBaker]

Those look like the screws out of a Baker Perkins MP Mixer.

 

[BEMPE16524]

Solidworks can do it easily.

 

[Brian Malone]

Ivan Silva, very interesting geometry - the screw profile transitions from a 'squared' profile to the round profile in one pitch length? I can work Solidworks fairly well and commonly model screw geometry with variable/changing pitches but I have never transitioned the profile. As ctopher suggests, using multiple bodies may be a method. But I envision this will entail having precise clocking cuts based on pitch to ensure correct pitch matching when the bodies are combined, etc. And this would create an abrupt transition zone. Possibly, model first the round profile screw full length then introduce a second helical cut for the squared profile that forms that shape and removes the 'extra' material of the round screw profile and use a guide curve follow to raise it out of the geometry in the half-pitch transition?

You may want to move this or repost in the Dassault forum. I'd love to see the guidance you receive from those who know!