CNC Turning Machining Services

Traditionally the term “turning” refers to a complex machining processes. In this machining process a lathe head spins (rotates), at a pre-specified rotational speed, turning either a part or a work piece with a part.  A stationary tool/tool-holder is used in combination with an special grade material insert to remove material from the part.  

The tool insert has varying characteristics of material, hardness, heat dissipation capability, density, and special surface coatings, which are used to remove chips from the surface of the part diametrically.  The various tools that are used provide an index, or better said, an appropriate angle of attack for removing chips, based upon the direction of surface contact, and the material to be machined.  Different materials use different parameters.   

While the description above implies that the tooling is moving or traveling on a parallel axis to the spinning work, the tool/tool-holder can also travel perpendicular to the part, turning the surface of the OD of the part to the ID, referred to as facing off.  If the tool is moved at an angle of 30, 45 or 60 degrees to the centerline of the part, a chamfer can then be achieved.  In short a Lathe can be used to contour a part to many different configurations.  Lathes are capable of turning, facing, boring, center drilling, drilling, threading, reaming, knurling, chamfering, cutoff, parting and taper cuts, among others processes.  

Parts can be quite complex.  One end may only require a light surface pass, while the other end may be at 1/5th of the original diameter, with numerous diametrical steps from one end to the other.  In this case, multiple cuts or passes are required to remove as much material as possible

A turning finish cut, usually specified by drawing surface tolerance, refers to the last one or two cuts which bring the part to its final size – within the specified tolerance. These cuts are typically very shallow and special attention should be paid to the parts final finish at this time. The final finish will be greatly affected by the condition of the cutting tool, the inserts radius or type, the feed rate, and speed at which the lathe is operating.  Lindstrom Machine works diligently to maximize the efficiency of tool usage and to eliminate wasted time in the manufacture of parts. 

Of special interest is the term no machine leads permitted.  This surface requirement generally applies to a surface interface that shall be in contact with a lip or oil seal.  On a micro scale, the tool insert will leave a micro-screw-like surface groove, which can be detected laying a piece of thread on the surface of interest.  As the part rotates, the thread will move like a stylist on a turntable with the spiral-screw-like micro grooves on the surface of the part.  Dependent upon the characteristics of these micro grooves, it may influence the overall life of the oil or lip seal.  Many utilize surface grinding tolerances to remove the grooving effect thereby ensuring overall seal life.  Others use wiper insert tolerances, to save on both machining costs and manufacturing lead times required for separate operations.

Most lathe applications do not use large production runs, where manual lathes are often used.  Prototypes are an example, but there are many production pieces that have low yearly usage as part of a large complex of parts.  Manual lathes are most cost effective when low usage is considered versus initial set up costs.  Large production runs of parts favor CNC machining.    

The addition of Computer numeric control (CNC) to lathes has enabled turning process to achieve new heights in productivity and in the creation of highly precise parts. CNC lathes are equipped with a computer consisting of one or more microprocessors and storage units, a user interface for programming and other interfaces that enable the CNC lathes to work in conjunction with CAD/CAM software systems. All of this enables a CNC machinist to instruct the CNC lathe to execute the exact movements necessary to create the precision turned part. Productivity has been further enhanced by the addition of live tooling and multiple spindles.  

CNC turning is an economical manufacturing process because it requires very little time or attention from a machinist once the machine, program and tools have been set up.  Operators only need to load materials and make any adjustments to the design parameters in order for a CNC turning operation to run unattended for a certain period of time.  CNC turning is an efficient and quick way to precisely produce detailed parts.

03.06.09