How Hypodermic Tubing is Manufactured
When dealing with hypodermic tubing people will ask, and rightly so, "How do they make tubing with such a small opening". In the greater scheme there are more impressive metal tubing manufacturing feats such as 0.062"OD stainless capillary tubing with a 0.005"ID or the 316 Stainless Steel tubing with 2 micron (0.0000787") orifice. But hypodermic tubing is more common and widely known in and out of the medical device community.
This is a brief overview of the manufacturing processes of hypodermic tubing. While this will give a description of methods it does not cover all the details and methodology that go into producing these tubes. There are a number of manufacturers out there and plenty of information available to do more research.
Hypodermic tubing is always welded and is always drawn. It is not seamless tubing. Most of the welds are not easily detectable, particularly on the smaller gauge sizes. But either way it is not seamless tubing. Hypodermic can be roll-formed or it can be die and plug drawn or just die drawn.
Roll forming is typically used for the larger gauge sizes. This is a process where strip stock is roll formed and the seam is TIG welded. The more standard sizes that everyone thinks about when it comes to hypodermic tubing the other two processes are used. With die drawn tubing, the material is drawn through an external die and the seam is welded. For the smaller gauge sizes the material is plug drawn, where the material is drawn with and external die and an internal plug. This process allows for tighter tolerances and a less noticeable weld seam on both the outside diameter and the inside diameter.