Double spindle construction increases accuracy and precision A novel double spindle arrangement on the Tsugami-Mori BS 20/26/32 CNC sliding head automatic lathes meets the higher working precision and tolerances demanded by its customers, says Pollard Mori Seiki. Industries already benefiting from these machines are the producers of telecommunications equipment, digital cameras, car navigation systems components, DVD player parts, and watch and optical instrument manufacturers. In these industries, accuracy and precision are crucial.

Growing competition demands too that component piece-part costs have to be reduced.

The Tsugami-Mori BS series of CNC sliding head automatics are able to machine more accurate work pieces with quicker machining time.

The novel Tsugami-Mori Double spindle construction has the rotary guide bush assembly and main spindle integrated together and therefore are completely synchronised in operation.

It results in higher accuracy combined with heavy duty machining capabilities.

This type of arrangement has low noise and vibration characteristics that provide better surface finishes when compared with the more traditional arrangement of machining spindles in competing machines.

(see diagram) The efficiency of the double spindle is increased by three times.

The BS series machines are able to take larger cuts, with greater positioning repeatability, without loosing accuracy.

The reason is that the bearing load capacity is three times larger and the bearing span three times wider when compared with more traditional sliding head construction.

Consequently, the Tsugami-Mori sliding head automatic will maintain dimensional tolerances in the order of 8 microns (Cp1.33), roundness of 1.5 microns and surface finish 1.5 microns Ra (depending upon material, these figures are for medium carbon steels).

Contributing to the achievement of this high quality working specification is the machines1 greater structural stability and rigidity.

The BS cast bed structure is heavier than comparable competing machines.

For example, the 20mm bar BS machine weighs 2.8 tons compared with competing machines which are at around 500kg lighter.

Therefore the capacity of the BS machines1 for absorbing and damping vibration is much higher.

Another big advantage with the BS sliding head design is that the remnant length is shorter than usual.

Tsugami-Mori has designed the arrangement of the front spindle guide bush cartridge and carrier and the main spindle collet chuck such that the collet can approach right up to the rear of the guide bush, so allowing very short components to be machined.

Also bar offcut scrap is minimised.

(see diagram) In addition to these features, Tsugami-Mor has also increased the number of back end working tools to eight stations, including two driven tool stations.

Opposed gang type tooling platens, as used on the BS series, enable the user to maximise the number of tools fitted on the tool platen.

The selected tool can arrive at the cutting position quicker when compared with the vertical arrangement used by competitors.

It is worth noting that in the BS design the tooling is on same centre line as the spindle when cutting.

In order to reduce the thermal growth Tsugami-Mori uses the double platen, which will achieve 2-3 microns thermal displacement.

In all, up to 18-24 tools, with up to six driven tools, can be set up in a BS machine.

Such an extensive set-up allows the machining of complex parts, such as hydraulic valve spools, or a variety of simpler components without having to change tooling.

All driven tooling spindles have a Y axis function allowing eccentric drilling, PCD drilling and milling.

Set-up times have been considerably shortened as a guide bushing and a main spindle collet chuck can be quickly drawn out into the tooling zone.

So a short set-up time of 5min can be realised.

The guide bushing holder cartridge can be changed, so a replacement can be adjusted away from the machine.

Users of sliding head automatics can specify a Tsugami-Mori BS machine to be multi-functional in nature, or to be more narrowly dedicated to a specific number of operations.

There are 18 different machine and tooling layout specifications to choose from.

Machine types cover a range of bar sizes from 6-32mm.

The CNC is based on a GE Fanuc 18i-TA running Tsugami-Mori 'Meister-Pro' automatic programming software.