Incoming material and inspection
The process starts before a single tube is cut: incoming copper coil is checked against mill certificates for alloy, temper and dimensional tolerance, and a sample is usually pulled for an internal cleanliness and wall-thickness check. Any variance here carries through the entire batch, so this step is treated as a gate, not a formality.
Forming and cutting
Straight lengths are cut to size on automated cut-off machines; coiled tube destined for coils or capillary applications is uncoiled and fed into bending or coiling equipment. This is also where U-bends, hairpins and other formed shapes are produced, using tooling that controls wall thinning at the bend so the tube doesn't weaken at exactly the point it needs strength.
Joining and assembly
Sub-components — headers, U-bends, connectors — are brought together and brazed, typically with a silver-bearing filler and, for critical joints, under a nitrogen purge to prevent internal oxide scale from forming inside the tube during heating. Assemblies with multiple joints are built up in a controlled sequence so earlier joints aren't re-heated and weakened by later brazing operations.
Testing and finishing
Every assembly goes through a pressure or helium leak test before it's accepted. Depending on the part, this is followed by dimensional checks, deburring, and packaging steps designed to prevent damage or moisture ingress in transit. The goal at this stage is simple: nothing ships that hasn't been verified against the same specification the customer ordered against.