Laser-sintering
of Croning®-molding material
In 1994, the underlying patent entitled “Procedure to produce 3D molds of age-hardenable molding material“ by Dr. Florian Wendt. In the interim, the patent has been granted worldwide. ACTech in cooperation with the EOS GmbH has developed methods and plants to implement the procedure in practice. In this technique, Croning®-sand usable in foundries is deposited layer by layer to mold segments and cores in layers. This way, the sand casting-molds for prototypes are produced without the need for modeling equipment.
Series-oriented prototypes
These molds are characterized by minimal tolerances and are ideal for making first prototype-castings, without the necessity to invest in modeling equipment. Almost all materials commonly used for sand casting, from magnesium- or aluminum alloys to highly temperature-resistant steels, can be poured with this method.
Different from all the other rapid prototyping technologies, this procedure does not intend to make a component of a substitute material and with a rapid prototyping technology not to be used for series production. The only “assignment” for rapid prototyping is to build the required mold segments layer by layer. Afterwards, these molds are processed in gravity- or low-pressure sand casting, as is the case in any foundry.
Unlimited opportunities
The building procedure layer by layer means that even fine filigree contours which cannot be fabricated with conventional sand casting may be generated. It even makes it possible to fabricate undercuts without any problems. The otherwise common draft angles may become inapplicable, since this building procedure layer by layer works without any molding.
“Laser-sintering of Croning®-molding material” - the procedure
The building chain is subdivided into the following steps: Layering, exposing, lowering. These operations are repeated until the mold has been completed. Coating layer by layer is controlled exclusively by the component’s 3D-CAD data.
Even the finest filigree contours, which can only be produced with great difficulty, if at all, using other conventional methods like sand casting, may be generated layer by layer. It is also possible to create undercuts without any problems. The procedure itself relies on the mold segments and cores generated in the preceding CAD process, which are subsequently fully automatically built layer by layer.
After the building platform is lowered (Base: 720 x 380 mm, Maximal building height: 380 mm), it is coated with fresh molding material. Afterwards, two lasers expose the upper molding material layer simultaneously (double-laser-sintering). This way, the exposed top region is not only solidified, but also bound to the layer beneath. Finally, after the generated mold segments and cores are cured in an industrial furnace, they are ready for mold assembly and pouring. The binder content, which is higher than the Croning®-sand used in the series, may be safely emitted by ventilation.
Advantages
- Time and cost saving procedure
- Molds suitable for pouring all alloys usual for casting
- Obtainable quality commensurable with that of the series parts
Tolerances
The accuracy of the mold segments and cores generated by the lasers lies within the few tenths of a millimeters range. Laser-sintering of Croning®-molding material makes it possible to fabricate castings with greater accuracy than under series conditions without difficulty. In the event that individual measures of the casting blank are particularly significant for the total function, then it is also possible to individually measure and, if necessary, to correct them, during mold assembly.
Characteristics
With laser-sintering of Croning®-molding material, a time- and cost saving solution to fabricate sand casting series-oriented prototypes, the users of castings are offered all the advantages of a rapid prototyping method. The molds and cores produced this way are appropriate for pouring of all the alloys usual for sand casting. Here, the materials to be poured range from magnesium- and aluminum alloys to highly alloyed steels or grey- and spheroidal cast irons.
The quality achievable is identical to that of the series parts. As a result, truly 'technical prototypes', which allow for tests of mechanical and thermal characteristics whose results can be analyzed and generalized, are produced.
Since laser-sintering of Croning®-molding material works without the modeling equipment that would be necessary in conventional casting, we need only a small investment into the first prototypes. Initial prototypes can be made available after as little as a few days. The 3D-CAD data required may be processed without rounding and drafting angles. This way, modifications for the use of modeling equipment which would be necessary otherwise are rendered inapplicable.
Laser-sintering equipment (EOS)
- 7 EOSINT S - plants
- 16 curing furnaces
- 300 m² production area
- Double-laser-sintering system for the direct, tool-free production of sand cores and -molds for metal castings
- Fastest system of this type worldwide
- Enables quick fabrication of castings with sophisticated core geometry
- Cores and molds for sand casting are produced fully automatically with DirectCast® technology, directly from CAD data
- Building volume: 720 mm x 380 mm x 380 mm; building speed: up to 2,500 cm³ / h
EOSINT S 750
Data sheet “EOSINT S 750.pdf (German 94KB)
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