Mill/turn centre has HMC capability

Turning and milling are combined on an equal footing by essentially marrying a CNC lathe structure to a vertical machining centre structure for higher milling performance.

At EMO Hannover 2005 Mori Seiki presented the new NT Series that combines milling and turning at their maximum performance.

Eight machines from these series will be demonstrating the extensive variants of this integrated milling and turning center that has taken a huge leap in productivity to set new standards in complete machining.

One of the world's leading machine tool manufacturers, Mori Seiki regularly analyzes the needs of its customers in order to provide the perfect solution each and every time.

The latest studies have shown that there is an ever growing demand for multi-axis simultaneous complete machining on so-called hybrid machines.

These machines combine various machining methods, for example turning and milling, in the one system.

Many short production runs in the aviation and power industries, prototype parts in automotive engineering, and mold inserts are ideally finished by turning and milling in the one chuck.

This serves to minimize rechucking times and errors, which in turn benefits quality and profitability.

Now integrated milling and turning centers are nothing new and have been on the market for over ten years.

Nevertheless, compromises had to be made in performance.

In most instances the one machining method was given priority, the second was merely 'docked on'.

With the new NT Series Mori Seiki is not making any compromises, but is setting standards in performance and precision like its current NL, NH, and NV Series turning and milling centers.

Consequently its engineers have developed a new concept for the NT Series that has managed to combine turning and milling on an equal footing and at their maximum performance in the one machine.

Top technology in turning and milling So that they did not have to reinvent the wheel from scratch, the developers fell back on the now established highlights of the current Mori Seiki turning and milling machines, not least because the NH Series horizontal machining centers have taken a world-leading role in milling technology covering a wide range of applications from high-speed machining to high-performance cutting - effectively for all materials.

The carefully conceived box-in-box machine layout based on the DCG principle (driven at the center of gravity - provides for high precision and reproducible high quality.

The NL Series lathes from Mori Seiki are characterised by particularly high stability that above all benefits high-performance cutting.

The stability of the spindle head axis, the large spindle head mount, the innovative tool turret, and other details featured on the NL machines are setting the present standards on the lathe sector.

* Merging highlights, not compromising - with its new hybrid NT Series Mori Seiki is setting new productivity and precision standards that other integrated turning and milling centers have to measure up against.

A machine bed of high-grade cast, a new development that ups the gross weight of NT 4200 DCG to eighteen tons, not only provides for extremely high rigidity, its structure minimises in addition heat-induced distortion.

Also the symmetrical arrangement of the spindle head and bottom tool turret accommodates the optimal thermal behavior.

As a result, the machines are able to manufacture a consistently high quality.

Like in the NH Series the milling unit is designed as a frame construction and boasts a double drive along the X and Z axes in accordance with the DCG principle.

In maximizing the rigidity and smooth running along the Y axis as well (unit with integrated b axis and tool spindle) Mori Seiki developed a special octagonal shape facilitating guidance towards the center.

The distance between opposite sides is 400mm.

* Values equivalent to pure machining centers - owing to the DCG principle and the box-in-box design that guides the compound rest via double axis drives, guidance and drive undergo essentially less vibration than on conventional designs, in turn enhancing speed and acceleration.

The frame column structure together with the double drives gives the machine its high stability (and renders large counterweights superfluous).

The DCG technology minimises vibrations and hence enhances reproducible surface qualities and concentricity.

With 750mm along the X, 420mm along the Y, and 1120mm along the Z axis of the NT 4200 DCG, the travels in the frame column need not fear comparisons with the classical machining centers.

Also the max speeds and accelerations of 50m/min (0.8G), 30m/min (0.4G), and 50m/min (0.6G) along the X, Y, and Z axes respectively hold their ground undaunted.

Powerful milling is ensured by the direct-drive motor spindle that masters all fields of applications from high-speed machining to high-performance roughing - at speeds up to 12,000 rev/min (NT 4200 DCG/1000).

In order to minimise the vibrations generated by such high spindle rotations and transferred directly to the tool, Mori Seiki has developed a new tool holding fixture that exerts a clamping force of 12kN.

A further contribution towards greater productivity is made by the B axis that is likewise directly driven in the NT Series.

The axis swivels through +/-120 deg at a maximum speed of 100 rev/min.

This benefits machining on freeform surfaces, yet also facilitates fast retooling (retooling time 1s; chip-to-chip time 3.4s).

The standard tool magazine takes twenty tools, but can be optionally expanded to forty or one hundred.

* Powerful spindles and a turret with integrated motor - for its turning unit in the NT turning and milling center, Mori Seiki has borrowed from its successful NL Series.

For example, the NT center features structurally identical lathe spindles, and on the NT 4200 DCG/1000 the spindle exhibits the following characteristics: 22kW output power, 456Nm torque, 5,000 rev/min max speed, and 73mm max workpiece diameter.

Likewise, the spindle can be used in the second, optional spindle head that can be operated simultaneously for machining long, thin workpieces.

The NL Series is also home to the innovative tool turret that is arranged vertically beneath the spindle head.

The special thing about this is the integrated motor that in contrast to external motors with drive belts minimises heat generation and vibrations and improves the transfer of forces.

This leads to greater machining precisions and higher cutting performance.

* Heat generation under control - Mori Seiki attaches great importance to compensating heat generation in the machine.

The motor integrated in the turret, the tool spindle, and the lathe spindles as well are permanently cooled.

This is ensured by intelligent cooling of the spindle jacket that draws off the generated heat.

In addition, two heat sensors on the lathe spindle register the actual temperature.

Based on these measured values the controller, when necessary, compensates accordingly.

The ball spindles are cooled via a through hole.

Located near the motor connection - on the bearing side - are additional cooling ducts that more than effectively prevent the heat generated by the driving servomotors from reaching the ball spindle at all.

* Easy to operate and service - all maintenance units for the hydraulics are arranged on a common site for minimising servicing time.

In addition, the front cover can be pulled open fully, allowing unobstructed access to the tool magazine as well.

In order to minimize replacement times for a damaged B axis - a vulnerable component - Mori Seiki has developed a system that allows the axis to be removed and replaced as a unit.

High user friendliness is ensured by the new high-performance operating system MAPPS III facilitating dialog programming specifically for integrated turning and milling.

Its functionality includes three-dimensional visualisation and extensive editing capabilities.

Also users that prefer to create machine programs on their PCs have not been forgotten by Mori Seiki: postprocessors are available for all customary CAM systems.

The NT Series from Mori Seiki provides nine models that differ in their Y traverses and their max distances between chucking points.

These models come in a great number of variants, e g, without tailstock (C), without tailstock but with turret (CZ), with counterspindle (S), with turret (Z), or with counterspindle and turret (SZ).

A total of 66 different machines are available, of which eight were presented at EMO Hannover.

* DCG - the recipe for higher speed and higher quality - moving machine parts, above all when accelerating and braking, generate vibrations that prove detrimental to machining.

To prevent these vibrations as far as possible Mori Seiki has developed the DCG principle, the abbreviation for 'driven at the center of gravity'.

This development was the outcome of considerations on machine dynamics.

Vibrations are generated in the first instance when the moving part is not driven at its center of gravity.

Superimposed torques give rise to small oscillating tipping motions that cause the machine's structure to vibrate.

However, not every drive in a machine tool can be positioned directly at the center of gravity, so Mori Seiki resorted to a trick: positioned on the linear axes are two parallel drives whose centers coincide with the moving part's center of gravity.

As a result vibrations are minimised, culminating ultimately in enhanced machining and contour precisions and surface qualities.

Greater accelerations become possible, in turn reducing machining times.

Furthermore, the tools' useful lives are hugely extended.

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