Tube Mill – A Brief Introduction
In the conventional sense, a tube mill is simply a type of sheet metal roll forming machine; but not every sheet metal roll forming machine is actually a tube mill. Tubemills are generally welded roller form machines that are fine-tuned to work at a particular diameter range, usually in high speed production operations. A normal tubemaker would call the resulting pipe the ‘tube.’ However, in non-woven industries, such as the jet engine market, there is more than one type of tube mill, and in fact many different kinds of welding processes, which might be performed at the same time. The Jet Propulsion Research Facility at Livermore, CA uses a variety of welding techniques to create both integral joints and parts for its various aircraft applications.
Common examples of tube mills include Cylinder Jetting and Scroll Shafting. Cylinder jetting involves feeding a piece of material through a hopper which pushes a succession of balls down a cylindrical channel. The balls then collide with a stationary grinding head on the lower face of the tube. The Cylinder Jetting machine can be set to work on either a sliding movement or a fixed position. Scroll Shafting works in a similar way, but the product is fed through a scroll or reciprocating motion rather than down a spiral path.
All tube mills essentially require one finishing stage: the Sizing Section Cut-off (SSCCA), which is where the material’s diameter is measured and the tube’s cross-sectional area is determined. The Sizing Section Cut-off, also called the SVCAD, is typically performed at the same time as the Sizing Step (SSC); however the two measurements must be performed in separate operations to avoid material crowding between stages. The Sizing Section Cut-off determines the size of the finished part. Cross-sectional diameters are used to determine the cross-sectional area, while frustometers and cutters are used for the actual cutting. Some tube mills have the ability to perform both operations simultaneously, though this is not generally the case.
The cutting machine uses two types of performance testing; namely, rotary and planetary brushing. Planetary brushing tests the strength of the tubes by using high-speed, high-energy drawings. Rotary testing is performed using an axial force component and determines if the performance is dependent upon the orientation of the cutting machine’s symmetry.
The most common sizes of tube mill products are; however, the manufacturer may provide other customized sizes, depending upon the application. Common product sizes range from; to 24 inches. Although the diameter range can vary, the width will remain consistent. The benefit of custom sizes is that they are often of a larger diameter than would be available, if a customer ordered a standard or round product.
Tube Mills is available in different construction materials, including iron, steel, cast iron, stainless steel, aluminum, brass, bronze, and nickel titanium. The quality of construction material will determine the lifespan and performance of the mill; therefore, prior to purchasing, the customer should ensure that the product is sturdy and long-lasting. Many tube mills are designed to withstand extreme temperatures; therefore, the appropriate type of temperature resistant flints should also be purchased.