The metal spinning technique entails shaping sheet metal over a spinning mandrel using one or more stiff tools called rollers. This results in axisymmetric hollow pieces, typically with circular cross-sections. The procedure is similar to nett shape forming. Factors such as material type, blank size, product radii, and desired surface smoothness should be considered when choosing rollers. Rollers are available in various diameters, profiles, thicknesses, and materials, including plastic.
In metal spinning, the feeding motion of the roller or rollers causes a continual localised plastic deformation. Metal spinning has many benefits over deep drawing due to its local material deformation rather than its global deformation. These include a more versatile process, improved mechanical properties, low forming loads, high material utilisation, low production costs, and good dimensional accuracy and surface finish.
The wall thickness after spinning is the main differentiating factor among the three main metal spinning processes: shear spinning, conventional spinning, and flow forming.
Table of Contents
Brief History Of Metal Spinning
One way to transform flat sheet metal into a three-dimensional form is by metal spinning. To achieve the required shape, a flat disc, cone, or cylinder is rotated in conjunction with a form, and then the metal is worked against the form using blunt instruments to provide pressure.
A dent can be created when a harsh tool is used on a pliable metal surface. Rotating the metal about a centre while holding the tool against this dent will cause the dent to transform into a groove that surrounds the object. It may be called "spun" into a modified state.
Simply put, metal spinning involves pressing flat pieces of sheet metal onto forms that spin on a lathe to create various products, including saucers, trays, bowls, vases, and many more.
One way to transform flat sheet metal into a three-dimensional form is by metal spinning. To achieve the required shape, a flat disc, cone, or cylinder is rotated in conjunction with a form, and then the metal is worked against the form using blunt instruments to provide pressure.
A dent can be created when a harsh tool is used on a pliable metal surface. Rotating the metal about a centre while holding the tool against this dent will cause the dent to transform into a groove that surrounds the object. It may be called "spun" into a modified state.
Simply put, metal spinning involves pressing flat pieces of sheet metal onto forms that spin on a lathe to create various products, including saucers, bowls, trays, vases, and many more.
Although metal pressing and stamping have mostly supplanted metal spinning, the former will always have a place in production since there are numerous instances where the desired shape cannot be created in a single piece without spinning. They would need to be manufactured in sections and then joined via soldering, riveting, or welding if they were to be stamped or pressed. Thus, there are many ways to go when considering aesthetics and durability.
As we enter the space era, metal spinning—one of the earliest metalworking arts—contributes to its construction. Contemporary missiles, helium balloons, and nuclear power stations rely heavily on spun components. Spinning hot metal is a common technique in this field. As metallurgy has progressed, spinning has stayed up, and hydraulic-powered lathes meet our requirement for large, complex shapes in the missile age.
Spinning stainless, alloys, and chrome-molybdenum steel—essential materials for missile work—to tolerances and gauges that were previously impracticable is now possible with the use of automation, made possible by hydraulic power, which multiplies tool pressure while providing precise control.
Given the high cost of stamping equipment, the large number of products needed to cover that cost, and the low cost of spinning equipment, it is highly improbable that pressing and stamping will supplant spinning.
Different Types Of Metal Spinning Processes
Conventional Spinning
Finished spun components have wall thicknesses almost comparable to the flat blank in traditional spinning because the wall thickness is kept relatively constant during the spinning process. A rolling tool can apply localised pressure to a moving sheet metal blank, shaping it into a mandrel shape. The roller tool shapes the blank by pressing down on it in a sequence of predetermined passes. Gradually, the part is formed until its inside matches the shape of the mandrel. Depending on aspects including material type, complexity, part size, and quality requirements, it is sometimes possible to spin some components with a single roller pass.
In multipass conventional spinning, the final wall thickness is defined by the number of roller passes and the direction in which they occur. Rolling forward slightly loosens the material, while pulling back the roller displaces metal in the opposite direction, ensuring evenly thick walls and reducing spring back. The three-pass method—planishing, intermediate, and finishing—can enhance accuracy and polish. With planishing passes, the tangential flow is reduced using high feed rates, thus smoothing out the waves caused by the multiple winding phases. Finalising the roller pass entails reducing feed and speed while applying a relatively strong radial force to smooth off the surface.
Complex geometries combining various forms, such as domes, cylinders, and cones, can be generated using spinning. Despite sharing the same wall thickness as the blank, spun parts consistently end up with smaller diameters.
The producing pressures that cause yielding allow for the categorisation of spinning processes. The predominant tensile-compressive stresses are seen in the metal-forming processes of spindle bending, deep drawing, and conventional spinning.
Additional types of spinning include those with and without mandrels, with and without opposing rollers, with and without heat and cold, and with and without computer numerical control.
Shear Spinning
Typically, a traditional spinning machine is used for shear forming or shear spinning, which involves shaping sheet metal over a conical mandrel that is in motion. The amount of purposeful reduction in wall thickness is determined by the angle between the part's wall and the axis of rotation.
There is a huge difference between this procedure and traditional spinning. The shear-spinning roller applies a compressive force as it moves, shaping the blank against the mandrel and stretching it over it in one pass. This process maintains a constant outside diameter for the completed item, which is identical to the blank diameter.
For the above stress values to cause metal flow, the shearing angle must be less than 80 degrees. Depending on the material properties, the minimum angle required for shear spinning could be anywhere from twelve to eighteen degrees. Shear spinning cannot be used to make cylindrical objects because the shear angle of the vertical walls is zero degrees.
The blank is compressed during shear spinning, which produces the same outcome as bulk shaping, extruding, and ironing.
Understanding The Shearing Process
A blade is often attached to a tool or machine to shear metal and cut the material into thin sheets. A squaring arm facilitates the accurate placement of a metal sheet, which controls the cut's location.
After positioning the sheet metal using the squaring arm, a precise cut is made by lowering the top blade, which compresses the metal against the bottom blade.
A bench shear is among the most used shearing instruments. Mounted on a workbench, bench shears are typically compact, light, and user-friendly.
The guillotine machine, often known as a power shear, is another tool for shearing. These devices require more work because they are powered by hydraulics or electricity. Power shears are more efficient and quicker than bench shears, although they are slightly more complicated. This is particularly true for manufacturers operating on a big scale.
Complex Shapes Can Be Made With Shear Forming
Some examples of common shapes are:
- Items such as cones, nozzles, chambers, flanges, and more.
Advantages
As indicated at the outset, shearing is now a standard procedure in the metalworking industry. To be sure, there are a lot of benefits to the procedure.
One thing to remember is that shearing metal does not require applying heat. Working with cold metal or at room temperature is common practice during the process.
The second advantage is that there is far less waste than other fabrication methods. Thanks to this, manufacturers can speed up the process and save money on cleanup.
Last but not least, shearing applies to many different types of metals. This includes but is not limited to, iron, bronze, and aluminium.
Disadvantages
Although shearing has many benefits, there are also some possible downsides that you should be aware of.
To begin, tungsten and other very hard metals cannot be sheared.
Second, stainless steel sheets can be distorted during shearing if the process is not executed carefully.
Flow Forming
The wall thickness is intentionally lowered in flow forming or tube spinning, depending on how much of an increase in workpiece length is needed.
Although they are changeable, metal spinning requires flow-forming equipment. This procedure consists of clamping a hollow component between a moving mandrel and tailstock to shape it so that it is symmetrical around its rotation. Typically, deformation is caused by the application of three rollers at the same time, which applies localised radial pressure. Within the mandrel, the metal's flow forms a shape.
Materials capable of low flow stress, high tensile elongation, high tensile strength-to-yield strength ratio, and high decrease in area are ideal for use in flow-forming procedures involving shaping tubes. They aren't necessarily required.
Some specialists liken it to the art of ceramics. The process begins with a certain amount of a pliable substance, in this example, clay, placed on a rotating turntable. Then, the artist uses their hands to delicately mould the clay into a useful and often aesthetically pleasing vessel, which initially appeared as a haphazard blob.
Similarities exist, with a few notable exceptions, in flow formation. Metal containers, instead of clay ones, can also be made using them. The growing workpiece is compressed by mechanical rollers rather than human hands, resulting in a more precise and stronger product than the best ceramic ever created.
Even non-vessel-shaped things can undergo flow formation. Tubes and cones with wall thicknesses ranging from as thin as a whisper to as thick as a billet may be made with this material, as you will see.
Flow Forming Benefits
Accuracy
Flow forming offers several significant advantages. The method first increases the strength and durability of the metal by stretching its grain structure lengthwise. Even extremely complicated geometries with large ratios of length to diameter are within the realm of possibility, provided that the wall thickness is 1 mm (0.039 in.) or thinner and that the average deviation is under 0.1 millimetre (0.0039 in.). Given the part's dimensions, shape, and material, it is common to achieve an accuracy of +/- 0.127 mm (0.005 in.). Walls that range from thick to thin, integrated weld flanges, and other comparable mounting elements are likewise within the realm of possibility.
It should be no surprise flow forming is most effective on pliable metals like copper and aluminium, but even extremely tough materials can be fluid-formed. Some examples of materials that could be processed using this new method include stainless steels AISI 304 and 321; aluminium alloys 15-5 and 17-4 PH; nickel-based superalloys such as Inconel and Hastelloy; Maraging steels; and hardened and tempered alloys made of steel up to 52 HRC. Because of their exceptional strength-to-weight ratio, these materials find widespread use in aerospace and aviation components.
Wide Variety Of Applications
Aerospace, nuclear, defence, and even certain high-performance car components can be made using flow forming. With precise dimensions and smooth surfaces, these can be anything from a Coke can to a missile casing several metres long. Thanks to the compressive actions of the rollers, which stretch and align the material grains during processing, the metallurgical qualities of flow-formed components are also greatly improved. In the end, this helps conserve both weight and resources.
Cost Efficiency
As key features, many components have cost, lead time, surface polish, and strength. Regardless of the batch size, flow forming's rapid turnaround times and cheap piece pricing are because it only requires one specialised tool—the mandrel—and can frequently create entire, even extremely complicated, workpieces in a single operation.
Conclusion
Metal spinning uses stiff tools called rollers to turn flat sheets of metal into three-dimensional shapes. To do the process, a flat disc, cone, or cylinder with a shape is turned and blunt tools are used to apply pressure to it. This makes hollow pieces that are axisymmetric and have circle cross-sections. Metal spinning is better than deep drawing in many ways, such as having better mechanical qualities, low forming loads, high material utilisation, low production costs, and good surface finish and accuracy of dimensions.
Shear spinning, standard spinning, and flow forming are the three main ways to spin metal. In traditional spinning, a moving sheet of metal is shaped into a mandrel form by applying pressure to a small area of it. The end wall thickness is set by the number of roller passes and the direction in which they happen in multipass conventional spinning. Planishing, middle, and finishing are the three steps in the three-pass method that can improve accuracy and polish.
Spinning can be used to make complex designs that combine different shapes. The main tensile and compressive forces are caused by spindle bending, deep drawing, and normal spinning. Some other types of spinning are those with and without mandrels, wheels that move against each other, heat and cold, and computer numerical control.
Shear spinning is an old method of working with metal that includes moving a conical mandrel and shaping sheet metal over it. How much of a decrease in wall thickness is planned depends on the angle between the part's wall and its axis of rotation. It is important that the cutting angle is less than 80 degrees. The lowest angle needed for shearing is between 12 and 18 degrees. The end result of shear spinning is the same as that of mass shaping, extruding, and ironing.
Shapes like cones, needles, chambers, flanges, and more can be made by shear spinning. Shearing has many benefits, such as not needing heat, less waste, and the ability to be used on many types of metals. But it has some problems, like not being able to cut tungsten and stainless steel pieces.
Flow making is another way to lower the wall thickness of a material on purpose, which makes it useful in many situations. It works best on metals that are easy to shape, like copper and aluminium, but it can be used on very tough materials too. This new method can be used to work with stainless steels AISI 304 and 321, aluminium alloys 15-5 and 17-4 PH, nickel-based superalloys like Inconel and Hastelloy, Maraging steels, and steel alloys that have been hardened and ground up to 52 HRC.
The cost of flow-making is also low because it only needs one special tool (the mandrel) and can make whole pieces in one step. On the whole, flow forming has a lot of benefits in the metalworking business.
Content Summary
- Metal spinning shapes sheet metal into hollow, axisymmetric pieces, often with circular cross-sections, using a spinning mandrel and rollers.
- The choice of rollers, varying by diameter, profile, thickness, and material, affects the outcome of the spinning process.
- Metal spinning benefits include versatility, improved mechanical properties, low forming loads, and high material utilisation.
- The three main metal spinning processes are shear spinning, conventional spinning, and flow forming, which are differentiated by wall thickness changes.
- Metal spinning transforms flat sheet metal into three-dimensional shapes using a lathe, achieving diverse products like saucers and vases.
- The technique allows for creating shapes that might otherwise need to be assembled from multiple pieces, enhancing aesthetics and durability.
- Metal spinning has evolved with technology, now incorporating hydraulic-powered lathes for complex shapes in fields like aerospace.
- Automation in metal spinning allows for working with tough materials like stainless steel and alloys to precise tolerances.
- The cost-effectiveness of metal spinning compared to stamping makes it a preferred choice for many manufacturing needs.
- Conventional spinning maintains the wall thickness of the original blank, gradually shaping the metal to match a mandrel.
- The process can achieve complex geometries, with the final wall thickness and diameter affected by the number of roller passes.
- Shear spinning involves shaping metal over a conical mandrel, aiming for a constant outside diameter with reduced wall thickness.
- Shear spinning cannot produce cylindrical objects due to the zero-degree shear angle of vertical walls.
- Understanding shearing in metalwork involves cutting material into sheets with precise control, using tools like bench shears and power shears.
- Shear forming can create complex shapes like cones and nozzles, offering advantages like working with cold metal and minimal waste.
- Disadvantages of shearing include limitations with very hard metals and potential distortion of stainless steel sheets.
- Flow forming, or tube spinning, intentionally reduces wall thickness while increasing workpiece length.
- Flow forming involves clamping a hollow component and shaping it with rollers, ideal for materials with low flow stress.
- The process can create objects with varying wall thicknesses, from very thin to very thick, enhancing accuracy and strength.
- Flow forming benefits include improved strength and durability of metal, capable of creating complex geometries and precise dimensions.
- The technique is suitable for pliable metals as well as tough materials, finding applications in aerospace and defence industries.
- Flow-formed components offer improved metallurgical qualities due to the compressive actions of rollers during processing.
- Cost efficiency in flow forming is attributed to rapid turnaround times, low piece pricing, and the ability to create complex workpieces in a single operation.
- Metal spinning is a versatile manufacturing process suitable for creating a wide range of products of various shapes and sizes.
- The history of metal spinning illustrates its evolution from a traditional craft to a modern manufacturing technique.
- Metal spinning's adaptability to technological advancements ensures its continued relevance in contemporary manufacturing.
- The selection of the spinning process depends on factors like material type, desired final product characteristics, and manufacturing efficiency.
- The precision and control offered by modern metal spinning techniques enable the production of high-quality components.
- Metal spinning's role in the production of components for advanced applications highlights its importance in modern industry.
- The process of choosing the right spinning technique involves understanding the specific requirements of the product being manufactured.
- Advancements in metal spinning technology have expanded its applications beyond traditional products to high-tech components.
- The efficiency of metal spinning in terms of material utilisations and production costs makes it a competitive manufacturing method.
- The adaptability of metal spinning to different materials and product designs contributes to its widespread use in manufacturing.
- Metal spinning's contribution to industries like aerospace and defense underscores its capability to meet stringent quality standards.
- The continued innovation in metal spinning techniques and equipment drives improvements in product quality and manufacturing efficiency.
- The ability to create complex shapes with metal spinning offers designers and engineers greater flexibility in product development.
- The integration of automation and computer numerical control (CNC) in metal spinning enhances precision and repeatability.
- Metal spinning supports sustainable manufacturing practices through efficient material utilisation and minimal waste production.
- The process's capability to work with a variety of metals, from soft aluminium to tough stainless steels, demonstrates its versatility.
- Metal spinning plays a crucial role in the fabrication of custom and specialised components for various applications.
- The ongoing development of metal spinning techniques and tools opens new possibilities for manufacturing innovation.
- The choice between conventional, shear, and flow forming processes depends on the specific requirements of the application.
- Metal spinning's economic advantages, combined with its manufacturing capabilities, make it a valuable process in many sectors.
- The historical significance of metal spinning, from its traditional roots to its modern applications, highlights its enduring relevance.
- The process's ability to produce high-quality surface finishes and dimensional accuracy contributes to its appeal in precision manufacturing.
- Metal spinning's role in enabling the production of complex and durable components makes it a key technique in advanced manufacturing.
- The adaptability of the spinning process to changes in design and material requirements enhances its utility in custom manufacturing.
- Metal spinning's contribution to cost savings and efficiency in production processes benefits manufacturers and consumers alike.
- The technique's application in producing components for critical industries like aerospace and defence illustrates its reliability and precision.
- Metal spinning continues to evolve, offering new solutions for manufacturing challenges and supporting innovation in product design and development.
Frequently Asked Questions
Hand spinning and manual spinning processes are limited by the skill and physical capabilities of the operator, as well as the complexity and size of the parts being formed. They are generally slower and less precise than automated methods.
Automatic spinning offers increased production speed, consistency, and repeatability compared to manual methods. It also reduces the reliance on skilled labour and can be more cost-effective for large production runs.
A CNC spinning machine typically consists of a computer-controlled lathe, a spinning chuck or mandrel, tooling holders, cutting tools, and a control system that manages the spinning process according to programmed instructions.
Yes, CNC spinning machines are versatile and can handle a wide range of metal thicknesses and materials, including aluminium, stainless steel, copper, and brass. The machine parameters and tooling can be adjusted to accommodate different materials and thicknesses.
Factors such as production volume, part complexity, tolerances, material properties, and budget considerations should be considered when selecting the most appropriate metal spinning process for a specific application.