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Method and apparatus for making products by sintering and/or melting

Method and apparatus for making products by sintering and/or melting description/claims

The invention relates to a method for making metallic and/or non-metallic products, in particular dental products, by freeform sintering and/or melting, in which the products are fabricated layer by layer from a material that is applied layer by layer by means of a computer-controlled high-energy beam, in particular a laser or electron beam.

The invention also relates to an apparatus for performing such a method, said apparatus comprising: a beam source for generating said beam, a platform for receiving a material that can be applied in layers, and a controller for controlling the beam, by means of which the beam can be guided by computer control to fabricate the products layer by layer from the material.

Such methods and apparatus are known. They are used, inter alla, to make dental products such as crowns, bridges, implants, etc., but they are also used in other fields of application.

However, due to the high degree of precision required for the products being made, these known devices are very complex in design and therefore very costly, but the unit costs for the products can be reduced if the time required to make a product is shortened. In this way, it is possible to increase the efficiency of such a device.

The invention is therefore focused on the technical problem of reducing the production time required to make products by freeform sintering and/or melting.

The invention solves this problem with a method of the kind initially specified by configuring the control unit in such a way that by means of said control unit the beam irradiates predetermined positions of a material a plurality of times in each case, namely m times, where m is a whole integer greater than 1, wherein each of said positions is initially heated during the first irradiation to a temperature below the melting point of the material and during the m-th irradiation to a temperature above said melting point so that it is completely melted over the entire thickness of the layer in such a way that the material fuses at said position to the layer thereunder.

The invention also solves the problem by means of an apparatus of the kind initially specified, in which the controller is configured in such a way that the beam can be controlled by means of said controller in the manner described in the foregoing.

The invention is based on the realization that the production time can be reduced when the energy of the high-energy beam is coupled into the material in a plurality of steps. In the first step, the energy is coupled into a certain position in the layer of material until the respective portion of the layer at said position has been heated to a temperature just below its melting point. In the final step of coupling in energy, the beam then heats said portion above the melting point, thereby fusing the material to the layer below it. In this way, the product being made is formed.

When melting and/or sintering using a high-energy beam, it is important that every portion covered by the beam is brought to the melting point of the material, but without exceeding the vaporization point, since otherwise the material would merely vaporize without forming the product being made.

However, the beam reaches only a surface portion of the layer of material being irradiated. For this reason, only the surface of the irradiated portion is heated at first. The side of said portion facing away from the beam is not reached, however. Thus, the side facing away from the beam is heated solely by heat transfer within said portion. This limits the maximum processing speed.

The invention overcomes this limitation by irradiating each position several times so that heat transfer from the hot to the cold side can occur within the respective portion of the layer of material during a period in which the surface of said portion is not being irradiated. Said duration can then be used to heat another portion of the layer. After said other portion has been heated, the beam returns to the former portion and can continue or complete the heating process.

Such alternating irradiation means there is no need to wait during irradiation for time-consuming temperature equalization to occur within the irradiated portion. Instead, these temperature equalizations can occur after an irradiation step has temporarily ended and another irradiation step is started or continued elsewhere.

In this way, the durations of irradiation at separate positions or portions of the material are significantly reduced. This alternating irradiation also allows the beam source, e.g. a laser or electron beam source, to be higher powered, thus allowing a greater amount of energy to be delivered to the respective position. The risk of explosive vaporization of these particles of material is considerably reduced by directing the beam to a different position after a short period.

In one particularly preferred embodiment, the positions in a layer of material to be irradiated are irradiated twice. Each of these positions is initially irradiated for a first duration, then not irradiated for a second duration. The second duration, of non-irradiation, is at least exactly as long or twice as long as the first duration of irradiation.

In another preferred embodiment, the positions in a layer of material to be irradiated are irradiated three times. In this case, each of these positions is initially irradiated for a first duration, then not irradiated for a second duration. This process is then repeated at that position. Finally, a third irradiation step of the first duration is performed. In each case, the second duration, of non-irradiation, is at least exactly as long, twice as long or four times as long as the first duration of irradiation. in one particularly preferred embodiment, the beam is guided backward and forward with a first substantially linear movement, with the forward movement extending over a longer path than the backward movement. This results in simple alternation between irradiation and non-irradiation of adjacent positions.

It is preferred that a second, meandering movement be superimposed upon the first movement. In this way, surface portions of the product being made are formed very uniformly.

In yet another preferred embodiment, an ensuing or completed contour of the product (2) is optically measured during andlor after a layer is irradiated. The measuring data thus obtained are compared with specified data, and if a deviation is discovered the beam is adjusted to take account of the deviation. In this way, the precision and dimensional accuracy of the products being made can be further improved.

Other preferred embodiments derive from the embodiments that are described In detail with reference to the enclosed drawings. In the drawings,

FIG. 1 is a schematic sectional view of an apparatus for making products by freeform laser sintering and/or melting in accordance with one embodiment of the invention;

FIG. 2 is a schematic view illustrating the coupling in of heat and the temperature equalization process inside a grain of the powdery material during laser sintering or melting;

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