Laser cell uses latest positioning technology

Launched at the Hanover Fair in April 2006, the MR J3 series is Mitsubishi Electric's latest generation of servo amplifiers and motors. Designed to be easy to install and configure, with vibration suppression and advanced autotuning, a high-resolution absolute position encoder is fitted as standard.

TEC's laser marking cell was initially designed for applying data matrix codes (two-dimensional barcodes) to computer peripherals during manufacture, but was then further developed with a range of options so that it can be adapted to different users' precise needs.

In operation, parts to be laser marked are loaded onto a pallet that indexes beneath the laser head for individual marking. The X-Y indexing of the pallet needs to be programmable, as parts can be of different sizes and the dwell time required between movements will vary with the complexity of the mark being applied.

One of the options TEC offers for the cell is a vision system mounted on the laser head for verifying the mark as soon as it is made. This will increase the dwell time slightly, and the motion system's programme has to be able to adapt to this. Laser marks are generally precision applied, so TEC used the MR-J3's vibration suppression to ensure that each part is presented efficiently and stably to the laser head.

During machine build the real-time autotuning and fully-automatic controller configuration makes installation of the motion system simple and fast.

SSCNET III servo network

TEC uses the MR J3 servos in combination with Mitsubishi Electric's high-speed optical SSCNET III (Servo System Controller Network). This supports data transfer rates of up to 50 megabits per second, with a bus cycle period of just 0.44 milliseconds. Importantly for TEC, installation is plug-and-play, so build and commission time are kept to a minimum.

In use, the MR-J3's real-time autotuning continually adjusts and optimises the control parameters for the current operating conditions. This ensures the cell operates flawlessly for extended periods without any degradation of the quality of the laser mark.

The MR-J3 motors are brushless and feature high-quality neodymium-iron-boron magnets and modern winding technologies for extremely high power density. Also contributing to the motors' performance capability is the integral 18-bit absolute position encoder, which provides more than 260,000 absolute values per rotation.

Tony Jones of TEC acknowledges the value of the new servos: "When we embarked on this development we expected it to be a one-off design for a particular customer. But when we heard that Mitsubishi was developing a new generation of servo technology we realised that it would allow us to expand the scope of the design to give us a customisable concept that could be adapted to many applications."