I dunno if they have a proper name, but I’ve always called 'em “bendy straws”: you know, the straws with the “bellows” section about a quarter of the way from one end. The bellows lets you bend the straw this way and that, the better to feed soda pop at the exact right angle into your mouth.
So, anyway: how are these things made? I assume a straw is extruded straight, and then some kind of secondary operation is performed? Vacuum forming? Anyone got the straight dope?
Well, a partial answer is that they use a straw bending machine.
So it is indeed a secondary process. I don’t know how the SBM works internally.
The straw making machine on that site shows the vacuum forming system, but this would presumably be part of the straw making cycle itself rather than a secondary operation. Having a separate straw bending machine implies that the completed straight straws are reheated in a mold with the corrugations then vacuum-formed, or perhaps blow-formed. The 12-straw batch feeder mechanism shown suggests blow-forming.
Why do you think blow-forming, Elvis? Is it easier to use pressure in a multiple-piece mechanism than vacuum? Are there any other alternative forming methods? I assume at least that the “one-machine” operation implies that all the forming is done hot, rather than any sort of cold operation.
I’m guessing blow-forming, not vacuum, because of the small area of the corrugations. A vacuum process would require withdrawing air from completely around the straw through a hole located directly over the corrugations; however, the bendy straws I’ve seen do not show any mark that such a hole would create.
Blow-forming would produce the axisymmetric shape required with no witness marks, and would be rapid and practical for such a small pressurized volume.
Sorry for chiming in 12 years late, but here it is:
A rod is inserted into the almost-finished straw. The rod has the crimped shape on it, and fits pretty snug. Jaws that match that shape clamp down on it and release. Then the straw is compressed from end-to-end, accordion-ing it to it’s pre-use form. The reason why the crinkles always face the same angle has to do with the way the angles on the rod/jaws are designed, combined with the compression that also shunts the straw out in the direction so those angles fold down towards the end of the straw and clears that part of the machine for the next straw.
The original bendy straw was designed by a guy in the 1930’s. His little daughter had trouble reaching the straw with her mouth when they were sitting at a soda fountain drinking milkshakes. He stuck a screw down the inside of the wax-paper straw, and used dental floss to wrap around the straw and make ridges that conformed to the screw and allowed the straw to bend. He filed a patent, and now we have bendy straws!
Whoa. 
dubious::(:smack:
The dope comes through! (Eventually)
I’m glad it did, though. Thanks MinuteWalt!
No need to apologize! Anytime somebody has something interesting to share, it’s worth reviving a thread.
But I just have to ask: How and Why did you happen to stumble across a 12 year old thread like this? 
Did “bendy straws” come up in a trivia contest?
Are you a “bendy straw” professional in the plastics industry?
Did “bendy straws” get mentioned in a bar bet?
Did your lover scream out “BENDY STRAWS!!!” at the moment of orgasm?
Or are you just a typical Doper, truly dedicated to fighting ignorance in all fields-- and you chose to fight the good fight on the battlefield of bendy straws ?
Hey, now how do they make bigger tubes like air conditioner exhaust and vacuum cleaner hoses?
Very interesting! And NOW I know.
Be interesting to get an answer about the vacuum cleaner hose. I suspect that exhaust pipes are made similarly to the ‘bendy straw’.