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Eli5: How are “hollow” objects extruded?

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72 utenti della rete avevano questa curiosità: Spiegami: How are “hollow” objects extruded?

Example: Penne pasta, metalwork such as non-welded pipes, etc.

Ed ecco le risposte:

You make a dire so the center part is supported from behind and the material is allowed to flow around the center part and form a single extruded part.

Here is 3D printed nozzle for pasta.

Here is an animation for the same for aluminum

I have to say that I am not sure how you do that for steel but I would assume the same thing and cooling the die made of a material that survives higher temperature.

Usually you have a pin that forms the hole that is attached to the extruding machine only at the back, therefore giving time for te material to flow around it and fill the gaps

I’m not sure they do that for non-welded pipes though

There is a plug in the center to make the interior hole. That plug is supported by a connection back in the extruder, but the concept of extrusion implies the substance being extruded is plastic enough to merge around the connection.

Don’t know if this is always the case but at least some pipes are made with centrifugal casting. Spin some liquid metal in a long barrel and let it cool.

Seamless steel tube is made by punching a hole through a solid round cylinder and then drawing the hollow cylinder through smaller and smaller dies.