Precision Turned Products
Precision-turned products are complex parts and components that are produced by controlled and careful machining, which normally involves CNC machining, multiple turning, or Swiss screw machine machining. The precision turning process ensures that components are consistent, reliable, and meet exacting manufacturing standards.
Precision turning involves rotating a workpiece as it is cut and shaped by sharp tools, a process that has been traditionally performed by a lathe that holds a workpiece in place as it is spun during the cutting process. There are few limitations to the types of metals that can be shaped into precision parts by the turning process, which is one of the major reasons for its use.
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Why Turning is Important
Precision turned products are used across a wide range of industries. The choice of turned parts is related to four basic factors, which are accuracy, precision, versatility, and productivity. The short amount of time it takes to produce high quality precision turned products is one of the main reasons that the turning process is so popular.
Precision and Accuracy – The primary reason for using turned parts is their exceptional accuracy. The turning process ensures that components are symmetrical and fall within design specifications.
Versatility – Any form of metal can be processed by turning to produce the most accurate and high tolerance precision turned products. Brass, steel, and aluminum can easily be formed by turning as well as certain plastics.
Efficiency – Through the use of modern technology, highly accurate parts can be produced in volume, quickly, for on time delivery for large projects.
Techniques Used to Produce Turned Parts
Advances and innovations in technology have further enhanced the ability to produce precision turned products. Computerization has removed the need for human involvement in calculations, tool placement, and manually manipulating workpieces. The improved precision of the turning process has rapidly grown such that every precision turned product exactly matches the parameters of its initial design.
Swiss Turning
The Swiss turning process was introduced near the end of the first industrial revolution and was used to produce the most accurate parts and components for Swiss watches, which could not be made manually. The process for Swiss turning is similar to the standard lathe with a fixed headstock that is spun and cut by shaping tools.
The key factor that differentiates Swiss turning from a standard lathe is the Swiss turning guide bushing, which supports a workpiece as close as possible to the cutting tool. The position of the guide bushing prevents a workpiece from deflecting and being gouged. The design makes the Swiss machines more flexible, productive, and precise.
The headstock on a Swiss machine has the same design as is found on a standard lathe with the workpiece being clamped on both ends. With a standard lathe, the workpiece is tightly held in place and immovable. To improve the precision of the cutting process, Swiss machines move and reposition the workpiece along the Z axis, which increases the precision of cutting and shaping.
The guide bushing of a Swiss machine supports the workpiece close to the cutting tools to avoid overhang and part deflection. This makes it possible for a Swiss machine to perform deeper and more accurate cuts in a single pass, rather than requiring multiple passes to perform multiple cuts.
A central feature regarding the use of Swiss machining for the manufacture of precision turned parts is the manufacturing cycle times in the production of complex and intricate geometries. While a typical lathe can cut along 2 to 5 axes during a single cycle, Swiss turning can cut along 7 to 13 axes, a factor that radically reduces cycle times.
Computer Numerical Control (CNC) Machines
One of the technological advancements that has made the greatest impact on the production of precision turned parts is CNC machining, a process that uses a set of codes to program cutting tools for part and component manufacturing. CNC machining has automated the movement and precision of cutting tools through the use of computer software. It is used to machine metals and plastics using mills, lathes, routers, drills, grinders, water jets, and lathes, the performance of which is programmed into the machine.
Every precision turned product is programmed into the machine using an internationally accepted computer language referred to as G-code. Every movement and cut completed in a CNC machine are entered into the machine in the same format as that is used to program computers, with the difference being the simplicity of G-code compared to computer language. The depth of cuts, workpiece movement and positioning, placement of cuts, number of tools, and other aspects of the process are covered by G-code. Along with the G-code language is M-code, which controls operations outside of the movement of the tools.
The design for precision turned products begins with the creation of a rendering using computer aided design (CAD) software, which has a diagram or drawing of the part that is translated into G-code. The completed programming is downloaded into a microcontroller where it is tested to ensure proper positioning of tools and the workpiece. After the test run, the CNC machine completes the production of high precision turned products.
As with Swiss turning, CNC turning happens rapidly and is capable of producing high volumes of exceptionally accurate turned products. The process reduces costs and waste, is safe, and is completed without the need for manual interference. Although the CNC process is expensive, it is one of the most efficient and accurate manufacturing processes.
Multiple Axis Turning
Multiple axis turning is used for its speed, efficiency, and accuracy. The process moves a workpiece in four or more directions to process exceptionally accurate and high tolerance parts and components. Complex and intricate precision turned products can be produced in a single cycle without the need to change tools or reposition the workpiece.
Modern lathes have been upgraded such that they have moved away from cutting along the X and Z axes to being able to shape components along multiple axes in a single cycle. Drilling, milling, and turning functions can all be performed at once, which removes the need for secondary finishing and processing.
Although multiple axis turning can be performed on a traditional lathe and completed by a highly trained expert, in the modern era, the majority of multiple axis operations are programmed into a CNC machine, which makes the process more efficient and quicker. CNC machines are capable of rapidly turning and repositioning workpieces to perform multiple cuts with different tools in a single cycle.
Turning Processes
The term turning covers several processes that involve the turning of a workpiece to achieve a particular shape or configuration. It can be performed on the exterior and interior of a workpiece that has been produced by casting, forging, extrusion, or drawing. The essence of turning is to achieve the requirements of a specific design by reshaping the surfaces of a workpiece.
Tapered Turning – The purpose of tapered turning is to achieve the shape of a cylinder by the controlled decreasing of the end of a workpiece. Tapering is completed by various sets of lathe tools positioned at one end of the workpiece.
Spherical Turning – Tools that produce spheres come in a variety of configurations with ball and radius attachments commonly used by CNC machines and lathes. The special tools for spherical turning have to be properly positioned in order to produce the spherical form.
Hard Turning – Hard turning is a reference to materials that are classified by the Rockwell C scale as having a hardness that is greater than 45, which requires the workpiece to be heated before being turned.
All of the various turning methods and procedures are designed to produce precision-turned products of the highest accuracy and tolerances with every product able to be used, without failure, in the application for which it was designed.