Metal Spinning

About Metal Spinning and Metal Spinning Services Including: Aluminum Spinning, Hydroforming, Metal Spinners, Stainless Steel Spinning, Tank Heads & Titanium Spinning.

Metal spinning is a "cold worked" metal fabrication technique using a flat round disc of sheet metal which is rotating on a spinning lathe. The metal spinner applies pressure to the rotating blank using several tools to shape the metal over a form called a chuck or mandrel. This pressure can be applied by a single tool or by multiple levers hydraulically. The finished product, if produced correctly, should have no wrinkling or warble due to the high speed of rotation around the mandrel. The process is quick and cost efficient. An average metal piece will only take from five to 10 minutes, and to change the spinning shape, one must only replace the mandrel. Aluminum, stainless steel, copper, pewter, bronze, silver, and brass are preferable for metal spinning, but any metal that is available in sheet form may be spun.

Metal spinning and metal spinning services can be controlled by hand, but a CNC (Computer Numerically Controlled) machine, which produces a superior final product, most often controls it. Most shops no longer utilize full manual creation of parts. The technology allows for multiple accurate tool passes and a unified number of passes made for a particular part. This ensures quality and consistency from part to part. When the forming of the part is controlled by hand, it can be a physically demanding process requiring a great deal of practice by metal spinning services. Due to the high speed at which the metal is spinning and the large amount of human force used in the forming of a piece, extensive training and safety precautions are implemented.

Metal spinning services have recently become competitive with stamping and deep drawing with the birth of CNC machining. Another cost-effective alternative is hydroforming. This process sends flowing metal around a punch instead of stretching it with dies, so the material has a more consistent thickness, and is advantageous because it can perform in one operation what takes other methods three operations. Everything from household pots and pans to the jet engine cowling on a plane is made by spinning sheet metal to a desire shape. The metal spinning process is limited, however, to the making of concentric shapes. These shapes include those that are hollow dished, conical, hemispherical and elliptical. Soda cans are often formed via metal spinning as well as deeper cooking pots and pans. Tanks that store agricultural and chemical substances have heads that are created almost exclusively using metal spinning. Many metal spinning shops create solely tank heads and serve the agricultural/grain storage markets.

When using metal spinning it is important to note the supplier's output capability. Some metal spinning shops are not capable of short run orders and may have limitations as to the diameter and thickness of final product desired. However, many suppliers offer sizes from a fraction of an inch to over 6 feet in diameter. Sometimes, a metal spinning manufacturer will only have the capacity to spin a certain type of metal, such as stainless steel or aluminum. Though not all manufacturers can offer every type of spinning service, metal spinning can mean lower tooling costs, because spinner dies are simpler and cheaper. Spinning tooling can also be made in-house by many spinning shops, meaning shorter lead times. The spinning process often work-hardens the metal product as it is being shaped, providing a stronger end product. The metal spinning business continues to grow as the process becomes better through technological advances.

Metal Spinning and Metal Spinning Services Images Provided by Acme Metal Spinning, Inc.

Types of Metal Spinning

• Aluminum metal spinning fabricates metal parts by rotating aluminum sheet metal on a spinning lathe.
• CNC machine spinners (computer numerical controlled) and related technology are most often used during the metal spinning process. Today's modern CNC technology has made it possible to produce high volume, close tolerance, concentric metal parts quickly and economically. CNC machine spinners are also used for the fabrication of other sheet metal parts.
  
• Custom metal spinners are what the majority of metal spinning shops use. Because of flexible rapid tooling and the short set up times associated with the technique, the costs of metal spinning can be much lower than other metal fabrication techniques.
  
• Hand metal spinners are still used by some manufacturers but are increasingly rare. The spinning of the metal is machine controlled but the appliance of pressure is done by hand, making for a very hard and cumbersome process; the results sometimes lack uniformity from piece to piece.
  
• Hydroforming is a tool and die process that uses hydraulic fluid to make components, often for the automotive industry.
• Metal spinners rotate metal circles.
• Stainless steel spinning is the most prominent type done by metal spinning shops. Most, however, are capable of spinning a wide range of common to exotic metals, including aluminum, brass, copper, hastelloy and titanium.
  
• Tank heads are circular, pressed ends to cylindrical tanks.
  
• Titanium spinning is a way to create light yet strong spun products that are resistant to corrosion and offer a lustrous appearance.

Metal Spinning Terms

Alloy - A substance that has metallic properties and is composed of two or more chemical elements of which at least one is an elemental metal.
 
Buckling - An uncontrolled deformation pattern perpendicular to the surface of a sheet caused by compressive stresses.
 
CNC - Computer Numeric Controlled.
 
Camber - The sheering tendency of sheet metal material which occurs via the bending of the same plane.
 
Cold Working - The reforming of metal usually, but not necessarily, conducted at room temperature.  Also referred to as cold forming or cold forging. Contrast with hot working.
 
Concentric - Having the same center, as concentric circles; having the same axis, as concentric cylinders.
 
Deep Drawing - The drawing of deeply recessed parts from sheet material through plastic flow of the material when, the depth of the recess equals or exceeds the minimum part width.
 
Die - A tool, usually containing a cavity, that imparts shape to solid, molten, or powdered metal primarily because of the shape of the tool itself. 
 
Draw Plate - A circular plate with a hole in the center contoured to fit a forming punch; used to support the blank during the forming cycle.
 
Elongation - The amount of permanent extension of the material before it fractures. 
 
Hemming - The bending of a piece 180 usually done in two steps after a piece has been created via spinning. First a sharp angle is created then closed via a flat punch and die.
 
Hold Down - A device used to secure a workpiece.
 
Lathe - Machine tool for shaping metal or wood; the workpiece turns about a horizontal axis against a fixed tool.
 
Mandrel - A tapered steel form used to support metal as it is being formed. Also called a Chuck.
 
Necking - The reduction of the cross-sectional area of metal in a localized area by uni-axial tension or by stretching.
 
Orange Peel - Texture of steel that appears like an orange, either from the steel mill or after forming.
 
Overbending - Bending metal a greater amount than called for in the finished piece to allow for springback.
 
Reset - The realigning or adjusting of dies or tools during a production run; not to be confused with the operation setup that occurs before a production run.
 
Stamp - This is a general term used to describe most press workings.
 
Support Plate - Used most often as a spacer within the spinning machine.
 
Tooling - The form to which the sheet metal is formed to simulate.

Metal Spinning from Wikipedia, the free encyclopedia

Metal spinning, also known as spin forming or spinning, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe.

Metal spinning ranges from an artisan's specialty to the most advantageous way to form round metal parts for commercial applications. Artisans use the process to produce architectural detail, specialty lighting, decorative household goods and urns. Commercial applications include rocket nose cones, cookware, gas cylinders, brass instrument bells, and public waste receptacles. Virtually any ductile metal may be formed, from aluminum or stainless steel, to high-strength, high-temperature alloys. The diameter and depth of formed parts are limited only by the size of the equipment available.

A brass vase spun by hand. Mounted to the lathe spindle is the mandrel for the body of the vase a shell sits on the "T" rest. The foreground shows the mandrel for the base. Behind the finished vase are the spinning tools used to shape the metal.

Process

The spinning process is fairly simple. A mandrel, also known as a form, is mounted in the drive section of a lathe. A pre-sized metal disk is then clamped against the mandrel by a pressure pad, which is attached to the tailstock. The mandrel and workpiece are then rotated together at high speeds. A localized force is then applied to the workpiece to cause it to flow over the mandrel. The force is usually applied via various levered tools. Simple workpieces are just removed from the mandrel, but more complex shapes may require a multi-piece mandrel. Extremely complex shapes can be spun over ice forms, which then melt away after spinning. Because the final diameter of the workpiece is always less than the starting diameter the workpiece must thicken, elongated radially, or buckle circumferentially.

A more involved process, known as reducing or necking, allows a spun workpiece to include reentrant geometries. If surface finish and form are not critical, then the workpiece is "spun on air"; no mandrel is used. If the finish or form are critical then an eccentrically mounted mandrel is used.

Tools

The basic hand metal spinning tool is called a spoon, though many other tools (be they commercially produced, ad hoc, or improvised) can be used to effect varied results. Spinning tools can be made of hardened steel for using with aluminium or solid brass for spinning stainless steel or mild steel.

Some metal spinning tools are allowed to spin on bearings during the forming process. This reduces friction and heating of the tool, extending tool life and improving surface finish. Rotating tools may also be coated with thin film of ceramic to prolong tool life. Rotating tools are commonly used during CNC metal spinning operations.

Commercially, rollers mounted on the end of levers are generally used to form the material down to the mandrel in both hand spinning and CNC metal spinning. Rollers vary in diameter and thickness depending the intended use. The wider the roller the smoother the surface of the spinning; the thinner rollers can be used to form smaller radii.
Cutting of the metal is done by hand held cutters, often foot long hollow bars with tool steel shaped/sharpened files attached. In CNC applications, traditional carbide or tool steel cut-off tools are used.

The mandrel does not incur excessive forces, as found in other metalworking processes, so it can be made from wood, plastic, or ice. For hard materials or high volume use, the mandrel is usually made of metal.

Advantages & Disadvantages

Several operations can be performed in one set-up. Work pieces may have re-entrant profiles and the profile in relation to the center line virtually unrestricted.

Forming parameters and part geometry can be altered quickly, at less cost than traditional metal forming techniques. Tooling and production costs are also comparatively low. Spin forming is easily automated and an effective production method for prototypes as well as high production runs.

Other methods of forming round metal parts include hydroforming, stamping and forging or casting. Hydroforming and stamping generally have a higher fixed cost, but a lower variable cost than metal spinning. Forging or casting have a comparable fixed cost, but generally a higher variable cost. As machinery for commercial applications has improved, parts are being spun with thicker materials in excess of 1" thick steel. Conventional spinning also wastes a considerably smaller amount of material than other methods.