With roots in the Bronze Age, turning is one of the oldest manufacturing processes. The materials used were wood, ivory and, since the Middle Ages, metal. The first more advanced lathes were used by precision mechanics and watchmakers from the 17th century onwards, before they became widespread in factories in the course of industrialization. The basic principle of turning has not changed over the millennia to the present day: A workpiece is rotated by a turning spindle, and contact with a turning tool produces a cutting motion. The tool in turn makes a feed motion so that the workpiece is machined over a machine-dependent longitudinal travel or turning diameter. Modern lathes far exceed this simple principle and are considered increasingly flexible wonders of precision.
Even the basic concept of turning allows for very different machining operations on the cylindrical workpieces. In face turning, the face of the cylinder is machined – either to create a flat surface or also to cut off a workpiece. The latter is common, for example, when machining multiple turned parts from a bar. Round turning, on the other hand, is done on the cylinder's lateral surface and produces a circular surface on it. Threads, for example, are produced by what is known as thread turning.
Development into a versatility marvel
Turn & Mill machines combine the 6-sided complete machining of the lathes with the 5-axis machining of the milling machines.
The fact that there are many other turning processes proves the flexibility of modern lathes. For the machining of rotationally symmetrical components, turning is still by far the most efficient technology. The combination of speeds of several thousand revolutions per minute and precision tools with long tool lives ensures maximum efficiency and extremely accurate production. Lathes became even more productive by using turrets or linear carriers to hold multiple tools. In conjunction with a Y-axis, off-center machining of very complex workpieces is made possible.
The highlight is certainly the 6-sided complete machining reserved for lathes. In addition to the main spindle, the lathes have a counter spindle in this case. This means that the workpiece can also be machined from the rear. In other words, from all six sides.
More productivity is achieved on the one hand by using several tool carriers, which allows several machining steps to run in parallel, and on the other hand by using several turning spindles in parallel. The top class of lathes, the multi-spindle automatic lathes, have up to eight main spindles and several counter spindles for backside machining. In principle, the entire machining process is distributed among the main and counter spindles, which all work in parallel. This massively reduces the machining time.
Automation has been an issue since the 1960s. Initially by means of bar feeders. Here, the raw material is automatically fed by the turning spindle. In the meantime, gantry loaders or jointed-arm robots are also used here to handle the raw and finished parts. The advent of NC-controlled lathes in the 1980s finally ushered in the current era of turning.
The increasing complexity of workpieces has ensured that turning and milling – once strictly separate disciplines – are increasingly merging. Turrets have long been equipped with driven tools so that milling operations can also be performed on rotationally symmetrical components. As a result, users avoid having to use a second machine. On the one hand, this saves time. On the other, it eliminates inaccuracies that can result from manual reclamping.
This development has resulted in versatile turning-milling centers that have a swiveling milling spindle, analogous to a 5-axis milling machine – creating a unique combination: The turn & mill machines combine the 6-sided complete machining of the lathes with the 5-axis machining of the milling machines. Today, this is the measure of all things in the production of highly complex workpieces. And they no longer have to be round.
DMG MORI with turning expertise for 150 years
With more than 150 years of experience in turning, DMG MORI has an almost unique know-how, which is reflected in about 20 series for almost all segments of this machining technology. For example, the technology leader enables 6-sided complete machining already in the entry-level segment of universal turning on the CLX series, followed by the high-tech CTX and NLX turning centers. Likewise, the segment of turn & mill machines is fully covered by the CTX TC, NT and NTX machines. In production turning with multiple tool carriers, for example, the CTX 4A and NZX machines can be used. The segment of automatic turning is also covered. The range includes the SPRINT series as well as the multi-spindle automatic lathes of the GM and MULTISPRINT series. To ensure that this variety of models guarantees long-term competitiveness for all users, all lathes are designed for digitized and automated production.