Up to five axis machining on one or two spindle positions is available with the new Index G400 mill-turning centre from Geo Kingsbury Machine Tools, Gosport. The machine is a modular design whose basic implementation is as a two-axis lathe. However the concept has been developed to allow complete machining of highly complicated components in a single set-up.
All versions make use of a massive 'torque tube' bed.
This is basically a heavily ribbed, thick wall cylindrical casting designed to offer maximum torsional and bending stiffness.
It is provided with two separate sets of guideways; the lower set accommodate the main and counter spindles (or tailstock where fitted), a lower turret option and any steady rests that may be employed.
The upper set of guides support the tooling carriers.
Maximum between-centres length is 2,000 mm whilst chucks up to 500 mm diameter can be fitted.
Both the main and counter spindles have identical 53 kW drives offering torque of up to 900 Nm and speeds up to 3,000 rpm.
A planetary drive option can be specified to increase available torque to 2,000 Nm.
There are a vast number of configuration possibilities for the Index G400, allowing the machine to be customised for a wide range of applications.
The tooling carriers are themselves massive structures, not dissimilar in format to side mounted ram boring machines.
A 12-station servo driven turret which uses the same motor for indexing and rotary tool drive is the basic tool system, and this can be provided with quill-type Y-axis (offering ñ 100 mm of movement) and B-axis facilities, along with C-axis on the spindle.
For two-axis turning, the Y-axis is fully retracted and locked by a Hirth coupling for maximum rigidity.
To allow this, the machine references to a vertical X-Z plane for live tool machining operations, but switches to a second plane at around 20 degrees from the vertical for fixed turning operations.
Alternatively, a multi-function milling spindle and 32-position tool carousel can replace the turret to enable heavier or more complex milling/drilling operations, providing true machining centre capabilities.
The combined unit comprises a separate milling spindle and a twelve station turret exclusively for fixed tooling, which is mounted on the Y-axis quill.
The 17 kW milling spindle is itself mounted on a pivoting arm, offering capability to extend Y-axis movement to ñ 175 mm, and can also be used in fixed position mode for turning or boring operations.
The main spindle/turret arrangements can either be replicated at the counter spindle or a simpler configuration can be adopted, depending on the complexity of the work being undertaken.
The counter spindle can be replaced by a servo driven tailstock if required.
Tailstock position and thrust are controlled electronically, eliminating the need for a quill, and it is interesting to note that the counter spindle can also be controlled in the same way.
When the machine is supplied as a twin spindle system with twin machining facilities, a dividing 'wall' with a pass-through port can be inserted.
This creates separate work areas with separate access to allow independent load/unload operations at either spindle.
Indeed, it is possible to operate the spindles fully independently, in which case the G400 constitutes two machines in one.
Control of the machine, which can have up to twelve machining axes, is by the Siemens hardware-based C200-4D control.
This provides full five axis interpolation capability at either spindle as well as automatically performing the geometric transformations required when the machine is operating in machining centre mode.
Feedback from all axes is by rotary encoder, apart from the X1, X2 and X3 axes which are equipped with glass linear scales.