Linear motor driven axes HMC halves cycle times

Operating at double the speed of conventional ball screw drive machining centres, this HMC uses linear motor drives and a low inertia main spindleto more than halve machining cycle times.

Operating at double the speed of conventional ball screw drive machining centres, the Pollard Mori Seiki HVM 630 horizontal machining centre uses linear motor drives and a low inertia main spindle to more than halve total cycle times, improve dimensional quality performance and reduce maintenance requirements.

The twin-pallet HVM 630 horizontal machining centre has rapid traverse rates of up to 80m/min with acceleration rates up to 1.5G.

Not only do these speeds substantially reduce non-cutting time, but also, together with the efficient vibration damping properties of the HVM machine structure, contribute to longer tool life.

The main spindle is rated at 56kW/45kW and runs up to 20,000 rev/min in 1.2sec.

Work pallet capacity is 630mm by 630mm and workpiece volume is 1000mm diameter by 1000mm high.

Toolchange time, cut-to-cut is 4sec and tool capacity is 60 tools as standard.

CNC is Mori Seiki1s MSG 501 CNC with the MAPPS operational management system, which allows very complex workpieces to be quickly programmed.

Novel structure and linear drives halve cycle times, improve quality performance - in more detail.

Pollard Mori Seiki is now distributing the Mori Seiki high speed, linear motor drive HVM horizontal machining centre.

Operating at double the speed of conventional ball screw drive machining centres, the Pollard Mori Seiki HVM 630 horizontal machining centre uses linear motor drives and a low inertia main spindle to more than halve total cycle times, improve dimensional quality performance and reduce maintenance requirements.

The twin-pallet HVM 630 horizontal machining centre has rapid traverse rates of up to 80m/min with acceleration rates up to 1.5G.

Not only do these speeds substantially reduce non-cutting time, but also, together with the efficient vibration damping properties of the HVM machine structure, contribute to longer tool life.

The main spindle is rated at 56kW/45kW and runs up to 20,000 rev/min in 1.2sec.

Work pallet capacity is 630mm by 630mm and workpiece volume is 1000mm diameter by 1000mm high.

Toolchange time, cut-to-cut is 4sec and tool capacity is 60 tools as standard.

Traverse movements are 940mm by 630mm by 600mm in X, Y and Z respectively.

In practice, it is possible that one high speed HNM 630 HMC will do the work of up to three conventional ballscrew drive HMCs and produce more consistently accurate work.

The Box-in-Box structure of the HVM 630 horizontal machining centre (HMC) provides a rigid box structure, in which is supported a substantial, double-column spindle head carrier.

Linear motors drive the X and Y lateral and vertical traverses up to 80m/min and with an acceleration of 10m/sec2.

A third linear motor drives the pallet indexing table, in the Z-axis cross traverse with an acceleration of 15m/sec2.

The structural arrangement lends itself to efficient heat dissipation and thermal compensation while providing a highly rugged and rigid structure to make full use of the higher metal cutting speeds and traverse speeds.

In addition, the low inertia spindle head, with its spindle running in hydrostatic bearings, and in combination with the box-in-box design and the smooth operational characteristics of the linear motor drives, absorb vibration.

The fast withdrawal of tools from cutting contact, coupled with vibration-free cutting, considerably lengthen tool life.

Additionally, the rigidity and vibration damping characteristics of the HVM 630 structure allow more dependable high speed machining of thin-walled workpieces, particularly for the aerospace structures industry and computer/electronics enclosures manufacture.

As regards accuracy, The HVM 630 is able to interpolation mill a circular path in aluminium, of 30mm diameter, using a 5mm diameter cutter within 1.5 microns.

This feat is aided by filtering software, adapted for high speed servo gain, and which eliminates the vibrational natural frequency of the HVM 630's machining system.

Without this, any vibration generated would effect the servo loop.

The interpolation milling used a cutting feed of 2000mm/min and spindle speed of 20,000 rev/min.

In the standard machine, a 60-tool chain-type magazine is located at the side of the machine.

Automatic tool change time is 1.4 sec or 4 sec chip-to-chip.

Tool capacities of 120 and 180 tools are optionally available.

Another timesaving bonus is the reduction in pallet change times.

The 630mm by 630mm pallet, with loads up to 1400kg, is changed in 10.7 sec.

The randomly indexing pallet table has an indexing speed of 180 deg/sec.

CNC is Mori Seiki's MSG 501 CNC with the MAPPS operational management system, which allows very complex workpieces to be quickly programmed.

It features dialogue type automatic programming with tools and cutting conditions displayed.

Features also include time studies, 3D part profile display and many other tool management and manufacturing data acquisition functions.

In practice, it is possible that one high speed HVM 630 HMC will do the work of up to three conventional ballscrew drive HMCs and produce more consistently accurate work For example, a US producer of FC250 grey cast iron, right angle power transmission gearboxes required cycle times of 2200 sec/part in a conventional ballscrew drive HMC.

Producing the gearboxes in the Mori Seiki HVM 630, reduced overall cycle time to 730 sec/part.

Nine machining operations are required and the user was able to save the cost of using three machining centres, which were required before.

In terms of saving tool life, because of the fast approach, vibration-free cutting, and subsequent fast removal of an 8.5mm diameter drill from workpiece, a user was able to realise a drill life of some 2.4 times that achieved in a conventional HMC.

This figure is possible, because of the high-speed response of the linear drive.

As soon as the drill depth is reached, the tool is immediately withdrawn, so the 'rubbing time' is minimised.

Also the smoother drilling action reduces wear on the drill1s cutting edges.

It is clearly time to consider the many production advantages to be gained by using a modern linear motor powered HMC: dimensional consistency in workpieces produced at up to three times the rate when compared with conventional HMCs.

In a worldwide marketing agreement with Ingersoll, US, and Mori Seiki, Japan, Pollard Mori Seiki is distributing the HVM 630 high speed, linear motor drive machining centres in the UK.

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