doris schulz

Topic: CO2 snow-jet cleaning for laser machining and precision cutting

High-tech material processing with integrated cleaning process

Innovative technologies such as 3-D laser machining, laser precision-cutting and laser drilling offer material processing methods which fulfil the demands of the micro technology industry. To remove residues in the µ-range from highly filigree shapes, a leading manufacturer of laser processing machines has integrated the CO2 snow-jet technology into his systems.

Sauer GmbH | Lasertec, a company belonging to the Deckel Maho Gildemeister group, develops and manufactures machines for laser machining, laser precision cutting and laser drilling. Sauer also supplies three-dimensional laser machining systems. This form of material processing enables tiny, highly-filigree cavities and shapes to be produced. Such components are demanded by the computer industry, medical technology, automotive, aerospace as well as by other industries where the trend towards miniaturisation is advancing. Examples include injection moulds, electronic and semiconductor moulds, mould inserts, indexable inserts, extrusion dies and prototypes. As well as featuring shorter processing times and reduced staff time involvement, the technique also possesses a significant number of economical advantages over conventional methods. The main customers of the high-tech company include companies concerned with mould construction, tool manufacture and rapid tooling. “Unlike milling or die sinking, the idea of using 3-D laser machining to manufacture moulds isn’t very widespread. As a result, our customers want to see how the technology works and what a finished part looks like. In order to be able to demonstrate the process, we operate a range of machines at our test centre”, said Michael Kuhl, manager of laser technology development at Sauer.

Residues in the µ-range can lead to defective goods

The laser beam can be used to process a wide range of materials such as steel, aluminium, brass, carbide, ceramic, graphite and boron carbide. Extremely fine residues such as cinder and scale are generated during the machining process which are then removed by suction. In the case of highly filigree shapes, especially those with sheer walls, tiny particles of residue may settle on the surface and impair the effect of the laser beam, resulting in defective goods. “Therefore, it is essential that they are removed completely,” explained Michael Kuhl. About six years ago, the development manager began searching for a suitable solution for his machines and stumbled across the CO2 snow-jet technology from acp – advanced clean production GmbH. Because the carbon dioxide cleaning technique is a dry process and also because the system made by the Wiernsheim-based company requires a minimum of space and is easy to integrate, it was ideal for incorporating into laser-processing machines. “Back then, I also talked to other manufacturers of CO2 snow-jet cleaning systems, but the one made by acp is by far the best. The fact that the company is locally based also played a role in our decision because it is essential for people to cooperate closely on such a project - things are working out fine with acp“, commented Michael Kuhl.

Cleaning tests confirm suitability

Cleaning tests carried out on various components in the technical centre of the Wiernsheim-based company formed the basis of the decision. The tests confirmed that residues could be removed effectively. With this technique, liquid carbon dioxide - which is fed from cylinders at Sauer - is utilized as a jet medium. Through a combination of mechanical, chemical and thermal actions, the non-toxic, non-combustible CO2 snow removes solid and filmy contamination using a dry, residue-free process. On impacting on the surface to be cleaned, the snow crystals liquefy and then sublimate. The sublimation impulse detaches and removes the tiny particles of contamination adhering to the workpieces. In the liquid phase, the environmentally-safe carbon dioxide functions like a solvent and removes filmy coatings or contamination. The low degree of hardness of the tiny snow crystals ensures that the surfaces of the filigree workpieces do not become damaged.

The main reason behind the effectiveness of the snow crystals is the patented acp cleaning head which is equipped with a supersonic, two-component ring nozzle. Liquid carbon dioxide expands on exiting the nozzle to create a mixture of snow and gas which forms the core jet. Compressed air is also fed to the nozzle as a jacketed jet and this accelerates the CO2 snow crystals to supersonic speed. The acceleration with compressed air results in a significantly higher degree of cleaning efficiency than that attained with single-component nozzle systems - it also considerably reduces carbon dioxide consumption.

“To achieve good cleaning results, it is imperative that the quantities of carbon dioxide and compressed air are optimally matched“, said Michael Kuhl.

Interval cleaning using a system integrated into the laser machine

The laser-machining process takes up to several hours to complete. In order to be able to carry out the necessary cleaning steps during the process, Sauer integrated the CO2 cleaning system into its laser machines. Workpieces are processed on a guidance machine equipped with an x- and y-axis as well as a turntable. For the cleaning intervals, which take about 10 minutes each time, the guidance machine positions the component in front of the cleaning head in accordance with a program specific for each part. As a result of integrating the CO2 snow-jet cleaning system, our customers are now able to manufacture extremely filigree parts with maximum precision, even sheer walls up to 90 ° with a depth of up to 2 mm provided certain materials are used“, remarked the development manager. www.acp-micron.com.


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