Kistler Instruments has introduced two new electro-mechanical NC press-fit systems that offer significant advantages over hydraulic systems. With only two multi-pin plug connections, the new actuators are simple to install and offer flexibility, precise positioning, high repeatability as well as accurate monitoring and control of the joining force plus minimum maintenance requirements. Kistler claims that its piezoelectric sensor expertise enables the range of press force up to 60kN to be covered by just two modules.
These new products are based on a range of seven press-fit actuators manufactured by Staiger Mohilo that were sold mainly to the German auto manufacturing industry. When Kistler acquired Staiger Mohilo during 2006, the actuators were developed further with the integration of Kistler piezoelectric force sensors, thus reducing the range from seven modules to only two to cover the range from 1kN to 60kN. This was made possible by the switchable measurement range, overload tolerance and consistent accuracy of the piezoelectric force sensors.
The actuators are based on a hollow shaft servomotor assembled directly around the threaded drive spindle to eliminate the need for gearing and provide highly responsive operation and compact dimensions. Although the length of the two modules is only 475 and 795mm, the stroke is 200 and 400mm respectively, making the units suitable for under-bench mounting and capable of extended end-point operations such as bearing installation in transmission half shells. The high-stroke speed of 300mm/s minimises machine cycle time to maximise productivity.
The force being applied by the actuator is constantly measured by the integrated piezoelectric sensors and, combined with a displacement signal by the monitoring system to avoid any deviation from predetermined parameters, it causes a reject signal to be generated.
Both modules are fitted with a standard holding brake to prevent the ram from dropping when the power is switched off, even when heavy tools are used.
The compact size, simple installation, long stroke and high speed provide great flexibility. The elimination of the need to pump and pipe hydraulic fluid reduces the cost of installation and delivers significant environmental benefits.