It has come to our attention that some people who contact this website may not be familiar with the pilger mill manufacturing process. We hope the following information is helpful and you will learn more about how some tube manufacturing occurs.
Cold pilgering has been around for many years since being patented in the US in 1896. Cold pilger mill machines perform work on preexisting tubes produced by means of cast, welding or extrusion. Pilgered tube metal alloys include aluminum, copper, gold, silver, stainless steels, titanium, zirconium and a host of many other special materials that are derived from various metal alloys.
In general, the pilgering process has two primary purposes:
*One, and most importantly, pilgering is a cold working process that greatly improves the material grain structure.
*Two, it is a way of reducing large amounts of the outside diameter and inside diameter of a preexisting tube very quickly. Reduction rates can be as high as nearly 100% on some alloys.
There is also another major metal working process used today that also reduces the same types of tubing and alloys. The Cold Draw process performs similar work. This process does improve the grain structure but is limited to low reduction rates of generally 15 to 35%, depending on alloys. When producing large quantities of tubing, cold drawing is considered to be very slow, compared to the pilgering process. As an example, a cold drawn tube may have to be drawn 3-4 times to equal the same amount of work of a pilger mill. Each time a tube is cold drawn, the tube must be cleaned and annealed (softened) before drawing again. For producing very small quantities of tube alloys, cold drawing has the advantage with quick tool changes and low operational costs. Both metal working processes have their advantages depending on the manufacturing needs.
Pilgering is actually performed very quickly, the following photo shows the essences of the pilgering process. The saddle holds the top & bottom dies and forces the two dies over the tube material outside diameter. The mandrel is stationary but does rotate at a specific time in the process. The mandrel is tapered and maintains the tube inside diameter while the dies reduce the outside diameter. At a specific time in the cycling process, the incoming tube is fed into the dies and over the mandrel.
As the tube is reduced from a large diameter to a smaller diameter, the tube is elongated and therefore the finished tube becomes considerably longer.
Here are three additional videos that show the actual pilger process.
Pilger process in slow motion
Feed carriage in operation which provides the incremental feed of tube material into the dies
Actual speed of a pilger mill