Driven tool technology has changed the nature of CNC lathe machining

Driven tools have changed the nature of machining on CNC lathes. With multi-axis control, these lathes can produce more parts in a single clamping cycle.

The use of rotary tools, updated Y-axis and B-axis machining has expanded the capabilities and performance of CNC lathes to a new level. When the basic 2-axis lathe still accounts for more than half of the machine tools sold in the UK, the multi-axis turning center has turned to the ability to produce different types and complex parts in a single setup.

These machines are mostly fixed bed head boxes (turn-mill type) or sliding head box (cross-type) structures, which can be used for milling, drilling, tapping and turning in a single clamping cycle, which brings significant impact to the manufacturing industry. benefit. These two types of turning centers are theoretically applicable to complex workpieces that require multiple machining operations while requiring relatively tight tolerances between certain parts. One-time clamping capability of these turning centers reduces lead times, reduces the number of work-in-progress, improves accuracy, eliminates the transport of workpieces in the factory (to complete some secondary processing) and facilitates economic production in smaller batches. They also guide themselves to automation and can be left unattended for long periods of time.

The turning center has become a truly versatile machine tool, like a machining center, and some even use some of the basic components of a VMC (Vertical Machining Center). The Okuma Mac Tarn 50 from NCMT is one of these machines. It is configured like a column-mounted VMC with a turning spindle added to the workbench. Parts can be machined jointly with CNC5 axes X, Y, Z, C and B (turret rotary axes) and driven tools. A unit installed at BAE Systems Samksbury near Blackburn is a custom-built Mac Tarn 50 for multi-process machining of noisy wing parts (materials such as cast steel) (eg, turning, milling, drilling, boring) , thread, etc.).

This unit-based turning center brings many benefits to BAE, including a 71% reduction in the number of process steps; 82% savings in required fixtures; 68% reduction in the number of parts shipped between processes; and a reduction in processing cycle time from 84h 19h. The lead time for wing part machining is reduced by approximately 89%.

Another machine tool is the Tsugami TMA-8 car-milling center produced by Yamazen (UK). It has 7 moving axes, including: B (tool spindle rotation), Y, C and E (2nd spindle indexing) and a 30-position ATC (automatic tool changer as standard). The tool spindle is driven by a 5.5kW motor with a speed of 6000r/min. The TMA-8 is capable of turning, milling, drilling, boring and cutting in one-time and fully automatic clamping. The first model sold in the UK, Roussant Sherwood, located near Henley, proved extremely successful for precision parts subcontractors. Production of a complex family of valve bodies for use in respiratory equipment for the medical sector and firefighting equipment, which has enabled Roussant to increase production capacity by a factor of four without adding manpower and to operate virtually unmanned 24 hours a day. . These 35mm diameter brass pieces feature a large number of internal interconnects and channels as well as many beveled holes and features. One-time clamping process covers car, boring, drilling, tapping, thread cutting and engraving. The cycle time is 15 min and nearly 85% of the machining is milling.

Hitachi Seiki UK (Hitachi Seiki, UK) also has a top-of-the-line machine for turning and machining. The machine has a 3-axis turret and a 7.5 kW drive cutter, model Super Hicell250. Moreover, other models in the HiCell series are also favored for their one-shot machining. An example is the HiCell23 multi-axis turning center installed by John Crene, a seal manufacturer in Reading City, which allows the company to switch from a single machine tool to a one-model machine. This part is produced in a single setup.

This HiCell combines various processes, including milling and drilling, to reduce the lead time by at least 20% and shorten the clamping time by 40%. In fact, these are the advantages of a single clamping process. So two years later, John Crene invested in four HiCell machines, intended to spread a single clamping process onto the main part of its standard key cylinder seal. These multi-axis lathes run 24 hours a day, five days a week.

In addition, after the installation of two Mazak CNC turning centers, the manufacturer of woodworking machinery and accessories at Axminster has been guaranteed, and Styles&Brown continues to be competitive in the international market. “AxminsterPower Tool Centre” is a more well-known company that now uses two Mazak machines (one Quick Turn10M and one Super Quick Turn 250MSY) to produce a range of parts for its drive top clamps and chucks. .

The processing of a chuck body highlights the benefits derived from the Mazak lathe. After a single clamping, it is possible to perform end face machining, car, boring, car milling and slotting, drilling and tapping on the inner surface of the chuck member with a diameter of 100 mm. After the transfer to the 2nd spindle, turning, lateral milling, T-slot milling and final chamfer milling can be further performed. The total processing time is 15 min, and the level of surface finish and precision achieved eliminates the need for fine grinding.

Increasing the number of sliders, the CNC lathe has the ability to perform a single clamping process based on multi-axis machining, driven tools, counterspindles, and lateral, vertical and end-face machining slides. These multi-function machines are not suitable for small parts and slender parts. Deans Engineering, based in Livingston, now processes 32mm diameter brass connectors on a Citizen L32 sliding head CNC lathe supplied by NC Engineering.

It originally planned to use a fixed-head turning and milling center to produce telecommunications parts, but since the machining of these parts in one setup required many tools, exceeding the capacity of this 42mm machine, the company was persuaded that this activity should be in one Two-spindle configuration with 18 tools (5 of which can be driven) on the Citizen L32. This machine has the ability to overlap multiple machining cycles, making cycle times actually 30% less than on a turn-mill machine.

Mirror finish

The comprehensive flexibility and performance of the modern sliding head CNC lathe is also highlighted by the activities of the Automatics Tooling company at Reahill. Regardless of their complexity, all diameters are less than 20mm, as the milled parts in the medical and other industries are machined in a single clamping cycle on the Star Micronics sliding head machine from A & S Precision. With the complete C-axis, Y-axis, drive tool and an opposed counter-spindle, these machines add more value to the part, especially for complex parts. When combining the benefits of these CNC lathes, the head of operations, Guy Lord, said: "We maintain a dimensional tolerance of 3μm for medical titanium stainless steel and even cobalt-chromium alloy, which can be compared with the best precision achieved anywhere in the world. We obtained an innocent, mirror-finish surface directly from the Star SV-20 machine. So, without manual polishing, we can often get the high-grade decorative look we need."

One of the latest developments, the result is a good complement to the driven tool and can continue to expand the role of the multi-axis lathe is the laser. Used by Traub to use a 50W yttrium aluminum garnet laser on the TNC30 turning and milling center (mounted on the upper tool turret), which can be used for contour machining, drilling holes, engraving, welding, segmented heat treatment of turned parts And deburring, etc. are all done in one setup.