EMO 2011 - Precision ensures Danobat’s VTC series - Hall 13, stand B36
Last modified 15-09-2011
Combining turning, milling and grinding operations in a single machine tool has generated considerable interest in Danobat’s VTC range of large vertical turning centres.
Demand for these versatile and extremely rigid machine tools is across the complete spectrum of manufacturing industry, from aerospace, power generation and transport to mining and oil & gas. This is because the modular design enables a wide variety of different configurations to be produced quickly, efficiently and cost-effectively. However, it is also a reflection of the design and manufacturing expertise gained since 1954 when Danobat first began manufacturing horizontal and vertical lathes.
The VTC-2500 on display at EMO 2011 has a table diameter of 2100 mm and is capable of turning a 2500 mm diameter on a workpiece weighing up to 20,000 kg and rotating at speeds up to 260 rev/min. This version has its table mounted directly on high precision crossed roller bearings, while heavier-duty H designation machines have the table supported radially and axially on hydrostatic bearings.
The VTC-2500 ram’s X axis traverse is 2870 mm and its Z axis stroke is 1500 mm. In comparison, the smallest model in the VTC range can turn a 1600 mm diameter on a 9000 kg workpiece, while the largest model can turn an 8000 mm diameter on workpieces weighing up to 150,000 kg.
The main elements of the VTC range – base, column and cross rail – are fully stress relieved ribbed castings that impart a high degree of stability to the assembled machine. This ensures the structure is able to absorb the stresses and dampen the vibrations induced by cutting forces under the heaviest of cutting conditions. Continuing this theme of rigidity coupled with precision is the 250 mm square ram that is manufactured from a normalised steel forging – hardened and precision ground.
The basic configuration is a two axis (X and Z) machine, although an optional C axis provides high positional accuracies and allows heavy-duty milling operations as well as interpolation operations. (C axis repeatability on the VTC-2500 is 1.04 arc-seconds with a positional accuracy of 2.57 arc seconds.) Positioning of toolholders and milling heads in the ram is by way of a Hirth gear system, guaranteeing accuracy and repeatability during tool changes. The automatic tool changer holds a maximum of 18 tools. However, the tool holding capacity can be increased up to 100 tools as it is possible to install ATCs on both side of the machine. Options also include automatic chucks; a second ram; live spindle; part probing; and tool pre-setting.
Danobat has designed several new heads for turning, drilling, milling, grinding and threading applications, each fitted with an integral bearing. This means that in the unlikely event of damage to the bearing due to possible collisions, only the head and not the vertical ram itself needs to be changed. The new B axis head is mounted at the bottom end of the ram and positioned via a Hirth coupling.
The new Y axis head has a fully-programmable stroke of ±200 mm with a working diameter of 600 mm (depending on the cutting tool). Using this particular design of head, it is possible to machine keyways in gears, machine offset faces on a component and drill holes that are not located in the X axis. A third new head takes four Capto tool holders located at 90º intervals and holding C5/C6/C8/C10 toolholders. Danobat has also introduced an alternative to the standard milling head with its live tool positioned in the same (Z) axis of the ram. In this new design the axis of the live tool is offset by 50 mm from the main spindle axis, and enables lateral milling and drilling operations for holes that are not located outside the center line of the part.