In the old-fashioned sense, a tube Mills is simply a type of welded roll forming machine; but not every welded roller form machine is actually a tube Mills. Tube Mills is often welded roller form machines that are fine-tuned in order to operate within a certain diameter range, usually at very high speeds (Figures 1 and 2). There are also other types of welders such as sheet metal roll mills (also known as flat bottom or fan milling machines), as well as belt conveyor units. The main difference between these types of welders is in the manner in which the filler metal (such as aluminum or lead) or any other material is fed into the machine.
Most tube mills operate with the assistance of a combination of guiding rolls or discs. These are typically used along with a large variety of cutting tools for precise and consistent results. The most common materials that are fed into the machine are metals of various shapes. Commonly these materials include (but are not limited to) brass, steel, aluminum, tin, steel, lead, and copper. Depending on the shape and grade of the metal, the diameter of the pipe or the part it is made from may differ.
Tube Mills can be either directed feed or indirect feed. Indirect feed tubes mill material directly into the machine from a lower chamber through a succession of holes. Alternatively, direct feed tube mills feed items into the machine from an injection tray placed directly above the work area. Because of the differences in the two different feeding procedures, the efficiency of both methods is different and dependent upon the qualities of the materials being fed. This leads to a trade-off between efficiency and cost; where the cost is generally higher in indirect feed systems, where the precision of the forming process is dependent on precise feeding of work pieces into the machine.
Tube forming is sometimes used for cold forming as well as hot rolled tubing. Some tube manufacturers offer both pre-punching and welded tube mills, where pre-punching operations are performed before the actual tube forming starts. Welded tube mills, which employ thermal closing devices for welding the tube edges together, are not widely used in manufacturing, but are sometimes seen in machine shops.
Tube forming machines must be able to produce tubes of different diameters, including both precision and half-diameter varieties. It is important that the machine be designed to meet the varying needs of the customer. For example, while some customers will require a very small diameter, other customers will want a much larger diameter. If the machine has a very small diameter range but is also designed for large volume forming, the overall cost will be much greater than if it is designed for smaller volume but a much larger diameter range.
Cylindrically shaped grinding balls can be installed inside tube mills, or in any other grinding system. Cylindrically shaped grinding stones produce more polished surfaces than do spherical grinding stones. The ball milling system that includes a ball and diamond contact can produce a fine finish on many types of metals. Tube forming equipment is primarily used to perform abrasive grinding, which includes removing minute amounts of material from an alloy without removing large amounts of the metal itself.