Patent Description:
The present disclosure relates according to a second aspect to a method for producing an object by means of additive manufacturing using an apparatus.

3D printing or additive manufacturing refers to any of various processes for manufacturing a three-dimensional object in which material is joined or solidified under computer control to create a three-dimensional object, with material being added together, typically layer by layer.

A known apparatus for printing a three-dimensional object comprises:.

One of the challenges is how to realize an object using an apparatus for printing three-dimensional objects having a relative high product quality.

It is an object of the present disclosure to provide an apparatus and a method for producing an object, by additive manufacturing, that allows to manufacture objects having a relative high product quality.

This objective is achieved by the apparatus according to the appended claim <NUM> and a method according to the appended claim <NUM>.

By providing the control device a relative high product quality may be realized. Controlling the energy density allows to realize a manufacturing process that is relative stable as regards solidification of the powdered material. The present disclosure relies at least partly on the insight that a relative large variation of energy density during manufacturing of an object may result in a relative low product quality. The relative low product quality may be due to variations of the solidification process of the powdered material for manufacturing the object. A relative low energy density may for instance result in inclusions of powdered material in the object. Alternatively a relative high energy density may result in evaporation and/or ablation of powdered material thereby affecting the quality of the object. Moreover, relative small variations of energy density may result in variations of mechanical characteristics of the solidified powdered material due to temperature differences during the solidification and the subsequent cooling of the powdered material.

The present disclosure relies further at least partly on the insight that characteristics of the beam of electromagnetic radiation may be different for different positions at said surface level. The control device comprised by the apparatus according to the present is arranged for taking into account the position of the beam of electromagnetic radiation at the surface level for controlling the energy density of the electromagnetic radiation. A dimension of the beam of electromagnetic radiation, being a characteristic of the beam of electromagnetic radiation, may vary along the surface level for instance due to the optics provided between the solidifying device and the surface level for shaping and displacing said beam of electromagnetic radiation along said surface level.

In particular, when using a scanning mirror device for deflecting the beam of electromagnetic radiation along the surface level, a dimension of the beam of electromagnetic radiation may vary due to a change of an angle of incidence of the beam of electromagnetic radiation on the surface level due to movement of said beam of electromagnetic radiation along the surface level.

Moreover, by changing the position of the beam of electromagnetic radiation along the surface level, the optical path of the beam of electromagnetic radiation may differ thereby resulting in a difference between a focal plane of the beam of electromagnetic radiation and the surface level. A correction of a difference between the focal plane of the beam of electromagnetic radiation and the surface level may contribute to a variation of a dimension of the beam of electromagnetic radiation.

A further advantage of the apparatus according to the first aspect is that by providing the control device a feed-forward compensation may be realized for controlling the energy density of the electromagnetic radiation, during solidification of said selective part of said powdered material, taking into account a position of said beam of electromagnetic radiation at said surface level.

The control device may comprise a lookup table provided with settings related to a position of said beam of electromagnetic radiation along said surface level for controlling said energy density of said beam of electromagnetic radiation along said surface level.

In this regard, according to the appended claims, said control device is arranged for controlling said energy density of said electromagnetic radiation at said surface level taking into account said position of said beam of electromagnetic radiation at said surface level.

Within the context of the present disclosure, the energy density may be defined in terms of the power of the beam of electromagnetic radiation, a surface area or diameter of the beam of electromagnetic radiation at the surface level, a movement speed of the beam of electromagnetic radiation at the surface level and a hatch distance of the beam of electromagnetic radiation at the surface level, wherein the hatch distance is a distance between neighbouring scan lines of the beam of electromagnetic radiation at the surface level. The energy density is expressed in terms of Joule/cm<NUM>.

Controlling the energy density of the electromagnetic radiation at the surface level is beneficial for realizing a relative large power input of electromagnetic radiation in said powdered material while realizing a relative high product quality. It is noted that a relative high energy density at the surface level may result in evaporation and/or ablation of powdered material at the surface level, whereas a relative low energy density may result in a relative slow manufacturing process or may result in inclusions of powdered material in the object.

The energy density of the electromagnetic radiation at the surface level is maintained within a predetermined range. The predetermined range may take into account the material characteristic such as for instance particle size and/or the type of metal of the powdered material. This is beneficial for realizing a relative high product quality while allowing a relative short time for manufacturing the object.

It is advantageous if said control device is arranged for controlling said energy density of said beam of electromagnetic radiation at said surface level by controlling a dimension of said beam of electromagnetic radiation at said surface level and a power of said beam of electromagnetic radiation at said surface level. Controlling a dimension of said beam of electromagnetic material may involve changing a dimension of said beam of electromagnetic radiation.

According to the appended claims, said control device is arranged for controlling an energy density of said electromagnetic radiation at said surface level, by controlling a dimension of said beam of electromagnetic radiation at said surface level, during solidification of said selective part of said layer of said powdered material of said bath of powdered material, taking into account a position of said beam of electromagnetic radiation at said surface level such that at a constant power of said beam of electromagnetic radiation said energy density of said electromagnetic radiation at said surface level (L) is maintained within a range of <NUM>%, <NUM>%, <NUM>% or <NUM>% of a nominal energy density, along said surface level. This is beneficial for realizing a relative high product quality.

Preferably, said control device is arranged for maintaining said energy density at said surface level along said surface level within a range of <NUM> % of a nominal energy density at said surface level.

Within the context of the present disclosure a nominal energy density may be understood as a predetermined set energy density. A nominal energy density at said surface level is therefore to be understood as a predetermined set energy density at said surface level.

It is beneficial if said control device is arranged for maintaining said energy density at said surface level constant along said surface level.

Said control device is arranged for controlling said energy density of said electromagnetic radiation in a volume of said bath of powdered material taking into account said position of said beam of electromagnetic radiation at said surface level, preferably wherein said energy density at any position in said volume is larger than zero.

Preferably, said control device is arranged for controlling said energy density of said electromagnetic radiation in a volume of said bath of powdered material, by controlling said dimension of said beam of electromagnetic radiation, taking into account said position of said beam of electromagnetic radiation at said surface level such that at said constant output power of said beam of electromagnetic radiation said energy density in said volume of said bath of powdered material of said electromagnetic radiation is maintained within a range of <NUM>%, <NUM>%, <NUM>% or <NUM>%, along said surface level, wherein said energy density at any position in said volume is larger than zero. This is beneficial for realizing a relative high product quality.

The energy density of the electromagnetic radiation in a volume of said bath of powdered material may also be referred to as volumetric energy density. The volumetric energy density may be defined in terms of the power of the beam of electromagnetic radiation, a layer thickness of said powdered material, a movement speed of said beam of electromagnetic radiation along the surface level and a hatch distance of the beam of electromagnetic radiation at the surface level, wherein the hatch distance is a distance between neighbouring scan lines of the beam of electromagnetic radiation at the surface level. The volumetric energy density is expressed in terms of Joule/cm<NUM>.

It is noted that due to absorption of the electromagnetic radiation, by the powdered material, and/or the caustic of the beam of electromagnetic radiation the volumetric energy density may vary in said volume of said bath of powdered material. In this regard, the volumetric energy density may be defined as an average energy density of said electromagnetic radiation in the volume of the bath of material, wherein said energy density in any position of said volume is larger than zero.

Within the context of the present disclosure, said volume of said bath of powdered material is to be understood as a part of said bath of powdered material wherein said energy density is larger than zero.

Preferably, the average energy density of the electromagnetic radiation in the volume of the bath of material is maintained within a predetermined range. The predetermined range preferably takes into account the material characteristic such as for instance particle size and/or the type of metal of the powdered material. This is beneficial for realizing a relative high product quality while allowing a relative short time for manufacturing the object.

In this regard, it is beneficial if said control device is arranged for controlling said energy density of said beam of electromagnetic radiation in said volume of said bath of powdered material by controlling:.

In an embodiment of the apparatus according to the first aspect of the present disclosure, said control device is arranged for changing said dimension of said beam of electromagnetic radiation at said surface level by controlling at least one of:.

Preferably, said control device is arranged for controlling said power of said beam of electromagnetic radiation at said surface level by controlling at least one of:.

It is advantageous if said control device is further arranged for controlling a hatch distance at said surface level of said beam of electromagnetic radiation taking into account said dimension of said beam of electromagnetic radiation.

Preferably, the control device is communicatively coupled to said solidifying device.

Preferably, the apparatus according to the first aspect of the present disclosure comprises a beam shaping device for changing a focus setting and/or a beam shape of said beam of electromagnetic radiation, wherein said control device is communicatively coupled to said beam device for changing, by said control device, said focus setting and/or said beam shape of said beam of electromagnetic radiation.

In a practical embodiment of the apparatus according to the first aspect the control device is arranged for controlling said energy density of said electromagnetic radiation at said surface level taking into account said position of said beam of electromagnetic radiation at said surface level and for controlling said energy density of said electromagnetic radiation in said volume of said bath of powdered material taking into account said position of said beam of electromagnetic radiation at said surface level, wherein said energy density at any position in said volume is larger than zero.

Controlling both the energy density at said surface level and the volumetric energy density allows for realizing a relative large energy input in the layer of powdered material while realizing a relative high product quality. The present disclosure relies at least partly on the insight that both the energy density at said surface level and the volumetric energy density may be controlled separately, preferably by a single control device, and are preferably both controlled within a predetermined range.

According to the second aspect, the present disclosure relates to a method for producing an object by means of additive manufacturing according to the appended claim <NUM>.

Embodiments of the method according to the second aspect correspond to embodiments of the apparatus according to the first aspect of the present disclosure. The advantages of the method according to the second aspect correspond to advantages of the apparatus according to first aspect of the present disclosure presented previously.

Preferably, during said step of controlling, by said control device, said energy density of said beam of electromagnetic radiation at said surface level is controlled by controlling a dimension of said beam of electromagnetic radiation at said surface level, taking into account a position of said beam of electromagnetic radiation at said surface level such that at a constant output power of said beam of electromagnetic radiation said energy density of said electromagnetic radiation at said surface level is maintained within a range of <NUM>%, <NUM>%, <NUM>% or <NUM>%, along said surface level. This is beneficial for realizing a relative high product quality.

In this regard, it is beneficial if said control device is arranged for controlling said energy density of said beam of electromagnetic radiation at said surface level by changing a dimension of said beam of electromagnetic radiation at said surface level and/or a power of said beam of electromagnetic radiation at said surface level and wherein during said step of controlling, said control device changes at least one of said dimension of said beam of electromagnetic radiation at said surface level and said power of said beam of electromagnetic radiation at said surface.

Preferably, said control device is arranged for maintaining said energy density at said surface level along said surface level within a range of <NUM> % of a nominal energy density at said surface level and wherein, during said step of controlling, said control device maintains said energy density at said surface level along said surface level within a range of <NUM> % of a nominal energy density at said surface level.

Preferably, said control device is arranged for controlling said energy density of said electromagnetic radiation in a volume of said bath of powdered material taking into account said position of said beam of electromagnetic radiation at said surface level, wherein said energy density at any position in said volume is larger than zero and wherein during said step of controlling said control device is controlling said energy density of said electromagnetic radiation in said volume of said bath of powdered material taking into account said position of said beam of electromagnetic radiation at said surface level.

Preferably, said control device is arranged for controlling said energy density of said electromagnetic radiation in a volume of said bath of powdered material, by controlling said dimension of said beam of electromagnetic radiation, taking into account said position of said beam of electromagnetic radiation at said surface level such that at said constant output power of said beam of electromagnetic radiation said energy density in said volume of said bath of powdered material of said electromagnetic radiation is maintained substantially constant along said surface level, wherein said energy density at any position in said volume is larger than zero, and wherein during said step of controlling said control device is controlling said energy density of said electromagnetic radiation in said volume of said bath of powdered material, by controlling said dimension of said beam of electromagnetic radiation, taking into account said position of said beam of electromagnetic radiation at said surface level such that at said constant output power of said beam of electromagnetic radiation said energy density in said volume of said bath of powdered material of said electromagnetic radiation is maintained substantially constant, preferably constant, more preferably within a range of <NUM>%, <NUM>%, <NUM>% or <NUM>%, along said surface level. This is beneficial for realizing a relative high product quality.

In this regard, it is beneficial if said control device is arranged for controlling said energy density of said beam of electromagnetic radiation in said volume of said bath of powdered material by controlling at least one of:.

and wherein during said step of controlling, said control device is controlling said energy density of said beam of electromagnetic radiation in said volume of said bath of powdered material by controlling at least one of:.

Preferably, said control device is arranged for controlling said dimension of said beam of electromagnetic radiation at said surface level by controlling at least one of:.

wherein during said step of controlling said control device controls said dimension of said beam of electromagnetic radiation at said surface level by controlling at least one of:.

wherein during said step of controlling said control device changes said power of said beam of electromagnetic radiation at said surface level by controlling at least one of:.

Preferably, said control device is further arranged for controlling a hatch distance at said surface level of said beam of electromagnetic radiation taking into account said dimension of said beam of electromagnetic radiation and wherein said control device controls said hatch distance at said surface level of said beam of electromagnetic radiation taking into account said dimension of said beam of electromagnetic radiation.

The apparatus and method according to the present disclosure will next be explained by means of the accompanying schematic figures. In the figures:.

<FIG> shows an overview of an apparatus <NUM> for producing an object <NUM> by means of additive manufacturing. The apparatus <NUM> is built from several frame parts <NUM>, <NUM>, <NUM>. The apparatus comprises a process chamber <NUM> for receiving a bath of material <NUM> which can be solidified. The material of said bath of material <NUM> is provided from a supply container <NUM>. In a lower frame part <NUM>, a shaft is formed, wherein a support <NUM> is provided for positioning the object <NUM> (or even objects) in relation to the surface level L of the bath of material <NUM>. The support <NUM> is movably provided in the shaft, such that after solidifying a part of a layer <NUM>, the support <NUM> may be lowered, and a further layer of material may be applied and at least partly solidified on top of the part of the object <NUM> already formed. In a top part <NUM> of the apparatus <NUM>, a solidifying device <NUM> is provided for solidifying a selective part of the material <NUM>.

In the embodiment shown, the solidifying device <NUM> is a laser device, which is arranged for producing electromagnetic radiation in the form of laser light, in order to melt powdered material <NUM> provided on the support <NUM>, which then, after cooling, forms a solidified part of the object <NUM> to be produced. However, the invention is not limited to the type of solidifying device. As can be seen, the electromagnetic radiation <NUM> emitted by the laser device <NUM> is deflected by means of a displacement unit comprising a deflector unit <NUM>, which uses a rotatable optical element <NUM> to direct the emitted radiation <NUM> towards the surface L of the layer of material <NUM>. Depending on the position of the deflector unit <NUM>, radiation may be emitted, as an example, according to rays <NUM>, <NUM>.

Apparatus <NUM> further comprises a control device <NUM>. Control device <NUM> is arranged for controlling an energy density of said electromagnetic radiation at said surface level L, , during solidification of said selective part of said layer <NUM> of said powdered material of said bath of powdered material <NUM>, taking into account a position of said beam of electromagnetic radiation <NUM>, <NUM> at said surface level L. The control device <NUM> is communicatively coupled to the solidifying device <NUM> and the deflector unit <NUM>. The control device <NUM> may control the energy density at said surface level L by changing a duty cycle of the solidifying device <NUM> and/or by changing an output power of the solidifying device <NUM>. Communicatively coupling the control device <NUM> to the deflector unit <NUM> allows for controlling the energy density by changing a speed of moving said beam of electromagnetic radiation <NUM>, <NUM> along said surface level L and/or controlling the energy density by changing a hatch distance h at said surface level L of said beam of electromagnetic radiation <NUM>, <NUM> taking into account a dimension d1, d2 of the beam of electromagnetic radiation <NUM>, <NUM> at the surface level L. Dimension d1 corresponds to the size of the beam of electromagnetic radiation at the surface level L in a first direction X, and d2 correspond to the size of the beam of electromagnetic radiation at the surface level L in a second direction Y. The first direction X and the second direction Y are mutually perpendicular and directed parallel to the surface level L. During manufacturing of the object <NUM>, the beam of electromagnetic radiation is moved along the surface level L for solidifying the part of the layer <NUM> for forming a layer part of object <NUM>. Solidification of the part of layer <NUM> that forms a layer part of object <NUM> may be done by repeatedly moving said beam in direction m1 and subsequently in direction m2, wherein said beam is displaced in a direction perpendicular to m1 and/or m2 by the hatch distance h.

In addition, the control device <NUM> is communicatively coupled to beam shaping optics <NUM> for changing a focus setting and/or a dimension d1, d2 of the beam of electromagnetic radiation <NUM>, <NUM> at the surface level L such that at a constant power of said beam of electromagnetic radiation said energy density of said electromagnetic radiation at said surface level L is maintained substantially constant, preferably constant, along said surface level L. The control device <NUM> is further arranged for moving the support <NUM> and thereby controlling a thickness t of the layer <NUM> of the powdered material of the bath of powdered material <NUM>.

The control device <NUM> is arranged for controlling said energy density of said electromagnetic radiation at said surface level L taking into account said position of said beam of electromagnetic radiation <NUM>, <NUM> at said surface level L while simultaneously controlling said energy density of said electromagnetic radiation in a volume of said bath of powdered material <NUM>. The control device <NUM> takes into account said position of said beam of electromagnetic radiation <NUM>, <NUM> at said surface level L for maintaining said energy density at said surface level L along said surface level within a range of <NUM> %, preferably within a range of <NUM>% of a nominal energy density at said surface level and/or for maintaining the energy density of said electromagnetic radiation in the volume of the bath of powdered material <NUM> within a range of <NUM> %, preferably within a range of <NUM>% of a nominal energy density in said volume of said bath of material.

Method <NUM> comprises a step <NUM> of receiving, in the process chamber <NUM>, a bath of powdered material <NUM>, wherein a surface level L of the bath of powdered material <NUM> defines an object working area. A subsequent step <NUM> of method <NUM> is solidifying, by solidifying device <NUM>, a selective part of said layer <NUM> of said bath of powdered material <NUM> on said surface level L. A step <NUM> of controlling, by the control device <NUM>, is performed during said step <NUM> of solidifying. During step <NUM> of controlling, the energy density of the beam of electromagnetic radiation <NUM>, <NUM> is controlled taking into account a position of the beam of electromagnetic radiation <NUM>, <NUM> at said surface level L. The step <NUM> of controlling during the step <NUM> of solidifying may comprise controlling 107a the power of the beam of electromagnetic radiation <NUM>, <NUM> at said surface level L, controlling 107b a speed of moving the beam of electromagnetic radiation <NUM>, <NUM> along the surface level L, controlling 107c a dimension d1, d2 of the beam of electromagnetic radiation <NUM>, <NUM> at the surface level L and/or controlling 107d the hatch distance h at said surface level L of said beam of electromagnetic radiation <NUM>, <NUM> for maintaining said energy density at said surface level L along said surface level within a range of <NUM> %, preferably within a range of <NUM>% of a nominal energy density at said surface level and/or for maintaining the energy density of said electromagnetic radiation in the volume of the bath of powdered material <NUM> within a range of <NUM> %, preferably within a range of <NUM>% of a nominal energy density in said volume of said bath of material.

The step of controlling 107a the power of the beam of electromagnetic radiation may comprises a sub-step 111a of controlling a duty cycle of said solidifying device <NUM> and/or a sub-step 111b of controlling an output power of said solidifying device <NUM>. The step of controlling <NUM> a dimension d1, d2 of the beam of electromagnetic radiation may comprise a sub-step 113a of controlling a focus setting of said beam of electromagnetic radiation, a sub-step 113b of controlling a beam shape of said beam of electromagnetic radiation and/or a sub-step 113c of controlling expansion of said beam of electromagnetic radiation. During said step <NUM> of solidifying, said beam of electromagnetic radiation may be moved along said surface level L as is shown in <FIG>.

Claim 1:
Apparatus (<NUM>) for producing an object (<NUM>) by means of additive manufacturing, said apparatus (<NUM>) comprising:
- a process chamber (<NUM>) for receiving a bath of powdered material (<NUM>) which can be solidified by exposure to electromagnetic radiation;
- a support (<NUM>) for positioning a part of said object (<NUM>) in relation to a surface level (L) of said bath of powdered material (<NUM>);
- a solidifying device (<NUM>) arranged for emitting a beam of electromagnetic radiation on said surface level (L) for solidifying a selective part of a layer (<NUM>) of said powdered material of said bath of powdered material (<NUM>); and
characterised by a control device (<NUM>) arranged for controlling an energy density of said beam of electromagnetic radiation at said surface level (L), by controlling a dimension (d1, d2) of said beam of electromagnetic radiation at said surface level (L), wherein said dimension (d1, d2) corresponds to the size of the beam of electromagnetic radiation at the surface level (L) in a first direction (X) and/or second direction (Y) that are mutually perpendicular and directed parallel to the surface level (L), during solidification of said selective part of said layer (<NUM>) of said powdered material of said bath of powdered material (<NUM>), taking into account a position of said beam of electromagnetic radiation at said surface level (L) such that at a constant power of said beam of electromagnetic radiation said energy density of said electromagnetic radiation at said surface level (L) is maintained within a range of <NUM>%, <NUM>%, <NUM>% or <NUM>% along said surface level (L), preferably such that at a constant power of said beam of electromagnetic radiation said energy density of said electromagnetic radiation at said surface level (L) is maintained constant along said surface level (L).