Early last year, the Japanese manufacturer Kitagawa introduced the first in a new range of compact general-purpose rotary tables — the MK series — for adding a rigid fourth CNC axis to a three-axis vertical machining centre.
One year later, the MK200 has been joined by a second model — the MK250 — with a significantly uprated performance; it is available in Britain and Ireland through the Salisbury-based sole sales agent 1st Machine Tool Accessories Ltd (
www.1mta.com/product/mk-series).
The most notable improvement is the 1,000Nm pneumatically actuated clamping torque, making the MK250 more than 80% stronger than the first model; and as with all Kitagawa tables, this torque is determined by the point at which the force on the worm wheel causes it to displace by 30µm. In contrast, some manufacturers quote the slipping torque as a maximum, which can cause inaccuracy.
If a Kitagawa TSR181A tail spindle with integral clamp (also available through 1st MTA) is added for securing a component or tooling column horizontally between centres, the clamping torque increases to 1,600Nm, allowing even faster heavier-duty — and more-productive — machining.
Moreover, because the table has a small footprint, the loss of bed area and working volume in a machining centre is minimised.
Kitagawa says that, while there are both stronger and more-compact rotary tables of similar capacity in its product ranges (such as the GT250 and CK250 respectively), the MK250 meets 90% of its customers’ requirements.
The unit on its own can support a load of 250kg horizontally; alternatively, it can be used to hold a component or column weighing up to 125kg in the vertical orientation.
The maximum positioning speed is 33.3rev/min, and the faceplate can be specified with either T-slots or pre-drilled holes, thereby allowing a chuck, trunnion or other work-holding device to be mounted directly on the rotary table (reducing the distance from the spindle bearing). The cutting torque is 480Nm, and the spindle through-hole diameter is 70mm.
Built-in 7MPa rotary joints can be selected from four-, five- and (6+1)-port types, the latter having a 12.5mm-diameter multi-purpose hole through the centre for additional hydraulic or pneumatic services to actuate work-holding.
1st MTA can also provide a high-pressure (25MPa) four-port or six-port rotary joint instead of the standard 7MPa variety, allowing a further reduction in fixture size as well as improved clamping speeds.