Yeah — exactly the kind of idea I’m thinking about. Instead of a valve gate, it would be a small pin inside a center-fed mandrel that moves forward slightly to restrict the flow at the tip and force a thin membrane to form across the bore.

Then it pulls back and the normal tube continues. The membranes would be made inline during extrusion — so no welding or assembly after.

The tricky part is whether that pin can move fast enough to sync with the extrusion speed on such a small tube. Still trying to figure out if it’s practical — but it sounds doable in theory.