E1 - KLM introduces a revolutionary Laser-Machining Center
Whether sintered cutting inserts, coins or small parts for watches – the result always requires the highest precision which has to last a long time. A challenge that the newly developed laser machining center "E1" by the startup KLM easily fulfills. The E1 provides extraordinary results even when working with the hardest materials, as demonstrated by various test customers. For example, the production time of sintered inserts was reduced from eight hours to two hours. Furthermore, the machine is also extremely easy to use and is available since February 2020. In 2017, the “E1” was still an idea by Ekkehard Alschweig - engineer, co-owner and former head of Kern Microtechnik. Two years later, he bundled his mechanical engineering knowledge with the know-how of the Dutch laser specialists from "Lightmotif B.V." and founded KLM Microlaser GmbH to realize his idea.
The KLM E1 is only available since the beginning of 2020, a modern high-tech laser machine that is particularly interesting for the mold and tool, watch and coin industries. When it comes to machining small parts, the KLM E1 is almost unbeatable in terms of productivity, long-term precision, freedom from wear, energy efficiency and usability. According to Alschweig, several key components in the KLM E1 are decisive for this: "We use the basic construction, including the axes and drives of the established Kern-Evo milling machine, use an fs laser source, a mirror-based laser beam guidance from Lightmotif and have developed a software , which makes operation extremely easy.” In order to penetrate new dimensions, particularly with regard to manufacturing accuracy, the young company has also developed two unique features: “ASPM” (Automatic Spot + Power Measurement) and “Adaptive Machining”.
High-end mechanical engineering and femtosecond laser
A mineral cast stand in monobloc construction and an X-Y cross table, which is manufactured by Kern, are the solid basis of the KLM-E1. They ensure the highest precision in the sub-µm range, which is important for positioning and measuring of the parts. The material is removed by a laser - more precisely a femtosecond laser, or fs laser for short. It emits light pulses, the duration of which is in the femtosecond range (1 fs = 10-15 sec.). The femtosecond laser is already used for eye operations (e.g. cataracts). Just this already provides an idea of the precision and accuracy which can be achieved with such a laser source. The KLM engineers use a mirror construction for the laser beam guidance.
Max Groenendijk, Managing Director of Lightmotif, explains: “Optical fibers are not suitable for guiding fs lasers. That is why we guide the laser beam with mirrors that are attached to the machine frame, from the laser source to the scanner.” The power of the laser source is 20 W. This means that the KLM-E1 can process a wide variety of materials. When the layers are removed, hardly any heat penetrates into the workpiece, because heat could cause a change in the material structure. As with all fs laser systems, the removal depth of the E1 is low and is usually between 0.3 µm and 2 µm per layer. This leads to an extremely high precision and accuracy. KLM uses all the advantages of this technology, in particular with two features.
Automatic calibration compensates external influences
"ASPM" stands for "Automatic Spot + Power Measurement". It is a system that makes the machine stable over the long term. Ekkehard Alschweig explains: "Every machine - including ours - is subject to certain thermal and other influences, which do not have an immediate but a creeping effect - that is, over a certain period of typically a few hours. As a consequence, workpieces are then produced with less precision. We are talking about minimal influences and minimal inaccuracies, but we are preventing them.” When working with fs laser machines two main challenges with an effect on precision over a long term may arise. First, the zero point of the laser spot can shift from its originally calibrated X-Y position, just in the µ range but this is enough to cause inaccuracies.
The reason for this is: The light guide mirrors for controlling the laser beam are mechanically attached to the machine frame. If heat is applied to the frame, the frame extends, the spot shifts and inaccuracies occur. As a result, the light guide mirrors have to be re-adjusted. Second, the power of the laser when it reaches the workpiece can vary. The output power of a laser is never really stable, and in the long term, contamination on mirrors and lenses can also cause small losses. This means that after a certain time, the laser power originally calculated is no longer available. As a result, the removal of material changes. With ASPM, the KLM-E1 has a simple and efficient solution for these two potential challenges. ASPM can be started automatically or just with a push of a button. ASPM then re-calibrates the entire system within just two minutes. Alschweig said: "If you rely on accuracy, just do the calibration every time production starts or even just once a day."
Depth accuracy of < +/-5 µm
Another highlight of the E1 is "Adaptive Machining". The fs laser removes material in the smallest layers of an average of 1 µm. The exact number is to be defined in individual cases. Adaptive machining optically measures the machined depth and compares the actual, measured values with the target values. The machine then adjusts the laser parameters accordingly and ensures that the target values are achieved. Without "Adaptive Machining" the depth accuracy depends on the total machining depth and is usually off between +/- 3% and 5% of the machining depth. At a typical depth of 0.5 mm, this results in an expected inaccuracy of around +/- 25 µm. With "Adaptive Machining", the depth accuracy is simply independent of the machining depth. The E1 achieves accuracies better than +/- 10 µm. "We even achieved values of less than +/- 5 µm in many tests," adds Alschweig.
Simple transfer of CAD data and easy program start
"It is important that the CAD model covers 100%," Alschweig emphasizes: "If individual points in the model are not connected, of course our machine cannot implement them. We recommend that users always check their customers' CAD programs.” If the 3D models fit, the volume to be removed is generated in CAD - this only takes a few minutes – and then the machine only has to be set up and only a few steps later the fully automated production can begin. Of course, this set-up process only needs to be done once per CAD model. Compared to creating an NC program for milling, the process is simple and very fast.
Results of test customers: Production times reduced by 75%
Several test customers are already very satisfied with the result. For example, a manufacturer of cutting inserts used to work with an EDMing and a milling process. Now they have converted the traditional process for press punches to produce blanks in green state carbide. With the new KLM-E1 they only run one process. The result is clear: The pressing tools were previously produced within an average of eight hours, now only two hours are needed.