Precise positioning in the laser application laboratory

VONJAN Technology GmbH is a supplier and solution consultant for laser system manufacturers. Its core area is to provide the optimum laser sources, deflection units and laser optics for industrial laser systems to ensure smooth system integration. The company procures the components from suppliers worldwide and customises them to the individual needs of its customers.

In order to be able to offer not only the products but also the appropriate advice, an application laboratory was set up in 2020 in which tests are carried out for customers. Laser sources, scan heads, optics and process parameters can be tested on sample material. This ensures that the desired process with the respective components actually works reliably for the customer. VONJAN can also recommend optimisations if the measurement results suggest a slightly different setup from what the customer initially had in mind.

The application device that is set up for this always consists of a laser, a deflection unit and focussing optics that have a fixed focal distance to the workpiece - but which must be precisely adjusted first. VONJAN was looking for a suitable linear axis with motor and control system.

The linear unit should make it possible to identify the ideal position for the laser head for the customer's application with relatively little effort. The laser head is mounted in the fixture and then moves along the axis to various positions until the laser spot focuses on the surface to be processed with an accuracy of 1/10th of a millimetre. Because the adjustment must be so precise - and this with a weight of the laser beam sources of up to 35 kilograms and a stroke of 800 millimetres - the system must have a high degree of stiffness.

In addition to high accuracy and stiffness, it was important for VONJAN to find a system that was as easy to configure and installation-friendly as possible.

igus had the perfect solution: a drylin SLW-25120 linear module with a TR24x5 lead screw. The SLW series has highly torsion-resistant aluminium double-shaft profiles and is suitable for electric adjustments both manual and with a motor like VONJAN's. The axis is controlled by a drylin D1 motor control system, which is suitable for stepper, DC and EC/BLDC motors. The VONJAN application uses a NEMA 24 stepper motor with encoder and a 3:1 gearbox.

The system was configured at igus using the data specified for VONJAN. The SLW-25120 is radially suitable for 2500N. Although the centre distance of 435 millimetres reduces the maximum permissible force, the torsion-resistant aluminium double shaft profile means that the VONJAN system has more than enough reserves. With the help of the igus online tool, the calculations and design of the motor and gearbox can be carried out easily. VONJAN was able to install the pre-assembled linear module with gearbox and motor as well as the programming and sensor connections without any problems.

The lead screw drive not only enables very high forces to be transmitted, but the lead screw also acts as a safety device in the event of a power or motor failure, so that the axis cannot slide down and destroy the laser. The fact that VONJAN sometimes assembles pico lasers worth 100,000 euros for adjustment shows its confidence in the system. A stepper motor was chosen because it can deliver its maximum torque even at low speeds and the step value can be set to 0.72 degrees using the D1 control system. And because the motor has an encoder, the D1 knows where the carriage is at all times. This is very important for programming the tests. For example, a customer has ordered a replacement laser for his system. VONJAN adjusts it, sets the exact focal point and then sends it abroad by express shipment. Everything has to be right before it goes out, the customer just has to install it and then his system has to run again.

For the correct setting, the laser head is assembled on the axis and a reactive material is irradiated with low laser power. The axis runs through a stored movement programme and the start and end of the reaction can be measured on the reactive material. As the stepper motor records the exact position via the encoder, VONJAN can determine the exact centre between the start and end of the reaction, the spot, on the web interface. CEO Tobias von Jan summarises: