Depowdering device and depowdering method

Abstract

Device (200) for depowdering parts obtained by additive manufacturing, said device comprising: - a vibrator (203); - a support plate (202) attached to a part to be depowdered (201); said device (200) being characterised in that it comprises a first damper (204) and a connecting plate (205) connecting the vibrator (203) and the support plate (202), said first damper (204) being in contact with the connecting plate (205) and having a cutoff frequency fc lower than fp, where fp is a first natural frequency of the part to be depowdered (201).

Description

DESCRIPTION TITLE: Depowdering device and depowdering method TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of additive manufacturing and in particular that of the depowdering of parts obtained by additive manufacturing on a powder bed.

[0002] An object of the present invention relates to a device for depowdering parts obtained by additive manufacturing on a powder bed. Another object of the invention relates to a method for depowdering parts obtained by additive manufacturing on a powder bed. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Parts obtained by powder bed additive manufacturing often require post-processing to remove excess powder, particularly when the parts have internal cavities or complex geometry. One solution known to those skilled in the art is to use vibrations to detach excess manufacturing powder. To this end, the integral assembly consisting of the melting plate and the part is removed from the machine after cooling, then placed in a depowdering device to carry out a part depowdering step.

[0004] An example of a prior dedusting device is described in US application 2022 / 314546 A1.

[0005] However, cracks can occur during vibration depowdering, and this has been observed for various types of parts and materials. In these cases, the vibration level experienced by the parts at their natural frequency is too high. Furthermore, the operation of the vibrator used during depowdering does not allow for modulation of the vibration level or the frequency used. SUMMARY OF THE INVENTION

[0006] The invention provides a solution to the problems mentioned above by describing a vibration depowdering device capable of controlling the vibrations applied to the part to be depowdered, so as to eliminate the formation of cracks in the part to be depowdered.

[0007] A first aspect of the invention relates to an assembly comprising a device for depowdering parts obtained by additive manufacturing on a powder bed and a part to be depowdered obtained by additive manufacturing on a powder bed, said device comprising: a vibrator; a support plate secured to the part to be depowdered; said device further comprising a first damper and a connecting plate connecting the vibrator and the support plate, said first damper being in contact with the connecting plate and having a cut-off frequency fc less than f P , f P being a first natural frequency of the part to be depowdered.

[0008] A vibrator is a device capable of generating vibration at a given frequency or at a plurality of given frequencies.

[0009] A support plate is a plate that is integral with a part obtained by powder bed additive manufacturing. An example of a support plate is a tray for powder bed additive manufacturing.

[0010] A damper is a device that has a resonant frequency and can transmit the vibrations produced by the vibrator. For example, the vibrator is made of elastomer material.

[0011] The cutoff frequency fc of the first damper is the frequency at which the vibrations generated by the vibrator are attenuated. In other words, a cutoff frequency refers to the frequency at which the impulse response of a filter begins to fall. Thus, for low-pass filters, frequencies below the cutoff are retained and frequencies above the cutoff are attenuated.

[0012] Advantageously, the depowdering device according to a first aspect of the invention makes it possible to apply a sufficiently high level of vibration to remove excess powder, while avoiding damage to the parts obtained by additive manufacturing on a powder bed.

[0013] Advantageously, the dedusting device according to the first aspect of the invention applies vibrations having a frequency lower than the first natural frequency fp of the part to be depowdered, which limits the level of acceleration to which the part to be depowdered is subjected while ensuring efficient depowdering.

[0014] Advantageously, the first damper has a cut-off frequency fc lower than the first natural frequency fp of the part to be powdered. The damper therefore makes it possible to attenuate vibrations at frequencies close to the first natural frequency fp of the part to be powdered and to limit the level of acceleration seen by the part to be powdered, which makes it possible to eliminate the risk of cracking of the part to be powdered.

[0015] In addition to the characteristics which have just been mentioned in the preceding paragraphs, the assembly according to the first aspect of the invention may have one or more additional characteristics among the following: the first damper is made of elastomer material; the difference between the first natural frequency f P of the part to be depowdered and the cut-off frequency f cof the damper is greater than 50 Hz; advantageously, this characteristic makes it possible to subsequently reduce the risk of cracking of the part to be depowdered; the first damper is arranged between the vibrator and the connecting plate; advantageously, this location of the vibrator makes it possible to limit the weight supported by the first damper; the device further comprises a lower plate, the lower plate and the connecting plate being separated by a set of second dampers; advantageously, the second dampers make it possible to attenuate the vibrations by preventing them from being transmitted to the ground; the first damper is arranged between the connecting plate and the support plate; the device comprises a plurality of first dampers, said plurality of first dampers comprising a number of first dampers greater than or equal to one; the support plate is a fusion plate for additive manufacturing on a powder bed.

[0016] A second aspect of the invention relates to a method for depowdering parts obtained by additive manufacturing on a powder bed, said method comprising the following steps: determining the first natural frequency of a part to be depowdered; placing a first damper configured to transmit the vibrations of a vibrator to a support plate, said support plate being integral with the part to be depowdered, the cut-off frequency of the first damper being lower than the first natural frequency of the part to be depowdered; setting the vibrator into vibration at a vibration frequency lower than or equal to the cut-off frequency of the first damper.

[0017] Advantageously, the method according to a second aspect of the invention makes it possible to choose a vibration frequency lower than the first natural frequency of the part to be depowdered, which prevents the formation of cracks in the part while allowing it to be depowdered effectively.

[0018] In addition to the characteristics which have just been mentioned in the preceding paragraphs, the method according to the second aspect of the invention may have one or more additional characteristics among the following: the step of setting the vibrator into vibration is followed by at least one other step comprising setting it into vibration at another vibration frequency less than or equal to the cut-off frequency of the first damper; the step of setting up a first damper further comprises the positioning of a set of first dampers. BRIEF DESCRIPTION OF THE FIGURES

[0019] The figures are presented for information purposes only and in no way limit the invention: [figure 1a] illustrates the transfer function of an elastomer damper used in the depowdering device according to a first aspect of the invention; [Figure 1 b] illustrates the Bode diagram of an elastomeric damper used in the depowdering device according to the first aspect of the invention; [Figure 2] illustrates an embodiment of the assembly according to the first aspect of the invention; [Figure 3] illustrates another embodiment of the assembly according to the first aspect of the invention; [Figure 4] illustrates the depowdering method according to a second aspect of the invention. DETAILED DESCRIPTION

[0020] The figures are presented for information purposes only and in no way limit the invention.

[0021] [Figure 1a] illustrates the frequency response or transfer function H of an elastomeric damper used in the depowdering device according to a first aspect of the invention. The abscissa represents the natural pulsation of the vibrating system, equal to 2 times PI multiplied by the natural frequency. The ordinate represents the gain of the transfer function of the damping system, reflecting the amplification (>1) or the attenuation of the system (<1).

[0022] The resonant frequency wo of the damper is indicated by the dashed vertical line.

[0023] The behavior of an elastomeric damper is described below: before its resonance frequency wo, the damper does not filter the acceleration and transmits it entirely to the melting plate; at its resonance frequency, the damper amplifies the acceleration with a factor between 5 and 10; after its resonance frequency, it attenuates the acceleration with a slope, for example in -20DB / decade, as illustrated by the Bode diagram shown in [Figure 1 b].

[0024] [Figure 2] illustrates an embodiment of the assembly comprising a dedusting device 200 according to a first aspect of the invention. The assembly comprises a part to be depowdered 201 obtained by additive manufacturing. It further comprises a support plate 202 secured to the part 201. For example, the support plate 202 is a fusion plate for additive manufacturing on a powder bed, secured to the part 201.

[0025] The device 200 according to the first aspect of the invention further comprises a vibrator 203 and a first damper 204. According to the embodiment illustrated in [Figure 2], the device 200 comprises a plurality of first dampers 204.

[0026] According to one embodiment, the first dampers 204 are made of elastomer material.

[0027] The device 200 illustrated in [Figure 2] further comprises a connecting plate 205 connecting the vibrator 203 and the support plate 202. The first dampers 204 are placed between the connecting plate 205 and the support plate 202 so as to transmit the vibrations of the vibrator 203 to the support plate 202 and to the part to be depowdered 201, while attenuating the vibrations having frequencies higher than the cut-off frequency of the dampers 204.

[0028] The cut-off frequency of the first dampers 204 is lower than the first natural frequency of the part to be depowdered 201. Advantageously, this makes it possible to reduce the level of acceleration seen by the part to be depowdered 201, while guaranteeing the depowdering of the part.

[0029] According to an embodiment of the device 200 according to the first aspect of the invention, the difference between the cut-off frequency of the first dampers 204 and the first natural frequency of the part to be depowdered 201 is greater than or equal to 50 Hz. Advantageously, this difference between the cut-off frequency of the first dampers 204 and the first natural frequency of the part to be depowdered 201 makes it possible to reduce the risk of cracking of the part to be depowdered.

[0030] The device 200 according to the first aspect of the invention further comprises a lower plate 206 as well as a set of second dampers 207, said second dampers 207 being arranged between the connecting plate 205 and the lower plate 206.

[0031] Advantageously, the second dampers 207 make it possible to reduce the transmission of vibrations from the vibrator to the ground.

[0032] [Figure 3] illustrates another embodiment of the assembly comprising a device 200 according to the first aspect of the invention. In this case the first dampers 204 are in contact with the vibrator 203 and placed between the vibrator 203 and the connecting plate 205.

[0033] Advantageously, the first dampers 204 used in this embodiment must support only the weight of the vibrator 203, which reduces the mechanical constraints in the manufacture of said first dampers 204.

[0034] [Figure 4] schematically illustrates the steps of the process 300 for depowdering parts obtained by additive manufacturing on a powder bed.

[0035] The method 300 according to a second aspect of the invention comprises a step 301 of determining the first natural frequency of the part to be depowdered.

[0036] The method 300 according to the second aspect of the invention further comprises a step 302 of placing a first damper configured to transmit the vibrations of a vibrator to a support plate, said support plate being integral with the part to be depowdered, the cut-off frequency of the first damper being lower than the first natural frequency of the part to be depowdered.

[0037] Advantageously, this step allows the use of a first damper having a chosen cut-off frequency in order to attenuate vibrations at a natural frequency of the part and which could damage the part during depowdering.

[0038] According to one embodiment of the method 300, the step 302 of placing a first shock absorber further comprises the positioning of a set of first shock absorbers.

[0039] The method 300 according to the second aspect of the invention further comprises a step 303 of setting the vibrator into vibration at a vibration frequency less than or equal to the cut-off frequency of the first damper.

[0040] According to one embodiment, step 303 is followed by at least one other step comprising vibrating at another vibration frequency less than or equal to the cut-off frequency of the first damper.

Claims

CLAIMS

1. Assembly comprising a device (200) for depowdering parts obtained by additive manufacturing on a powder bed and a part to be depowdered (201) obtained by additive manufacturing on a powder bed, said device comprising: a vibrator (203); a support plate (202) secured to the part to be depowdered (201); said device (200) being characterized in that it comprises a first damper (204) and a connecting plate (205) connecting the vibrator (203) and the support plate (202), said first damper (204) being in contact with the connecting plate (205) and having a cut-off frequency fc less than f P , f P being a first natural frequency of the part to be depowdered (201).

2. Assembly according to the preceding claim characterized in that the first shock absorber (204) is made of elastomer material.

3. Assembly according to one of the preceding claims, characterized in that the difference between the first natural frequency of the part to be depowdered (201) and the cut-off frequency of the first damper (204) is greater than or equal to 50 Hz.

4. Assembly according to one of the preceding claims, characterized in that the first damper (204) is arranged between the vibrator (203) and the connecting plate (205).

5. Assembly according to one of claims 1 to 3 characterized in that the first shock absorber (204) is arranged between the connecting plate (205) and the support plate (202).

6. Assembly according to one of the preceding claims, characterized in that the support plate (202) is a fusion plate for additive manufacturing on a powder bed.

7. Method (300) for depowdering a part obtained by additive manufacturing on a powder bed, said method (300) comprising the following steps: determining (301) the first natural frequency of the part to be depowdered; placing a first damper (302) configured to transmit the vibrations of a vibrator to a support plate, said support plate being integral with the part to be depowdered, the cut-off frequency of the first damper being lower than a first natural frequency of the part to be depowdered; vibrating (303) the vibrator at a vibration frequency lower than or equal to the cut-off frequency of the first damper.

8. Method (300) according to the preceding claim characterized in that the step of vibrating (303) the vibrator is followed by at least one other step comprising vibrating at another vibration frequency lower than or equal to the cut-off frequency of the first damper.

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