DRYING PROCESS, DRYING DEVICE AND VACUUM CONVEYOR WITH DRYING

Abstract

A method and to a device for drying a powdered and/or granular material for additive manufacturing, in particular for drying a metal powder or a metal powder blend. The material to be dried is contained in an evacuable volume, in particular in a vacuum conveyor. The evacuable volume is fluidically connected to a vacuum pump arrangement. The vacuum pump arrangement is fluidically connected on the inlet side to the evacuable volume and on the outlet side to the surroundings of the evacuable volume. The vacuum pump arrangement on the outlet side comprises a sensor for recording the moisture in the fluid pumped out of the evacuable volume, with the sensor being used to record the residual moisture in the powdered and/or granular material as a function of the moisture in the fluid that is pumped out.

Claims

1. A method for drying a powdered and/or granular material for additive manufacturing, in particular for drying a metal powder or a metal powder blend, with the material to be dried being contained in an evacuable volume, in particular in a vacuum conveyor, the evacuable volume being fluidically connected to a vacuum pump arrangement, and the vacuum pump arrangement being fluidically connected on the inlet side to the evacuable volume and on the outlet side to the surroundings of the evacuable volume, wherein the pump arrangement comprises a positive-displacement pump for vacuum drying and a jet pump for vacuum conveying, in particular a single-stage or multiple-stage ejector pump for vacuum conveying, or a compressor, in particular a side-channel compressor, for vacuum conveying.

2. The method as claimed in claim 1, wherein the vacuum pump arrangement on the outlet side comprises a sensor for recording the moisture in the fluid pumped out of the evacuable volume, the sensor being used to record the residual moisture in the powdered and/or granular material as a function of the moisture in the fluid that is pumped out.

3. The method as claimed in claim 2, wherein it comprises a calibration of the sensor by means of a test medium.

4. The method as claimed in claim 2, wherein the pump arrangement comprises a positive-displacement pump, a jet pump, in particular a single-stage or multiple-stage ejector pump, and/or a compressor, in particular a side-channel compressor.

5. The method as claimed in claim 4, wherein the sensor is arranged on the outlet side of the positive-displacement pump, in particular on or in an outlet-side flow channel of the positive-displacement pump.

6. The method as claimed in claim 1, wherein a suction fluid flow, in particular suction air flow, is created in the evacuable volume by means of the pump arrangement, with the result that the powdered and/or granular material can be conveyed into the evacuable volume through a volume inlet by means of suction fluid flow, in particular suction air flow, and conveyed out of the evacuable volume through a volume outlet preferably by means of suction fluid flow, in particular suction air flow.

7. The method as claimed in claim 1, wherein at least one blocking device can be actuated between the pump arrangement and the evacuable volume.

8. The method as claimed in claim 2, wherein at least one reference moisture is recorded, which is preferably recorded in the surroundings of the evacuable volume.

9. The method as claimed in claim 2, wherein, for the determination of the residual moisture in the powdered and/or granular material, the sensor signal and the change in the sensor signal over time are taken into account.

10. The method as claimed in claim 1, wherein the evacuable volume is heated.

11. A device for drying a powdered and/or granular material for additive manufacturing, in particular for drying a metal powder or a metal powder blend, with the device comprising an evacuable volume which can be filled with the material (2) to be dried, a vacuum pump arrangement fluidically connected to the evacuable volume being provided, the vacuum pump arrangement being fluidically connected on the inlet side to the evacuable volume and on the outlet side to the surroundings of the evacuable volume, wherein the pump arrangement comprises a positive-displacement pump for vacuum drying and a jet pump for vacuum conveying, in particular a single-stage or multiple-stage ejector pump for vacuum conveying, or a compressor, in particular a side-channel compressor, for vacuum conveying.

12. The device as claimed in claim 11, wherein the vacuum pump arrangement on the outlet side comprises a sensor for recording the moisture of the fluid pumped out of the evacuable volume, the sensor being able to be used to record the residual moisture in the powdered and/or granular material as a function of the moisture in the fluid that is pumped out.

13. The device as claimed in claim 12, wherein the pump arrangement comprises a positive-displacement pump, a jet pump, in particular a single-stage or multiple-stage ejector pump, and/or a compressor, in particular a side-channel compressor.

14. The device as claimed in claim 13, wherein the sensor is arranged on the outlet side of the positive-displacement pump, in particular on or in an outlet-side flow channel of the positive-displacement pump.

15. The device as claimed in claim 11, wherein a suction fluid flow, in particular suction air flow, can be created in the evacuable volume by means of the pump arrangement, with the result that the powdered and/or granular material can be conveyed into the evacuable volume through a volume inlet by means of suction fluid flow, in particular suction air flow, and conveyed out of the evacuable volume through a volume outlet, preferably by means of suction fluid flow, in particular suction air flow.

16. The device as claimed in claim 11, wherein it comprises at least one blocking device which is arranged between the pump arrangement and the evacuable volume.

17. The device as claimed in claim 11, wherein it comprises at least one heating means, by way of which the evacuable volume can be heated.

18. A vacuum conveyor for conveying a powdered and/or granular material for additive manufacturing, in particular for conveying a metal powder or a metal powder blend, wherein the vacuum conveyor comprises a device for drying the powdered and/or granular material as claimed in claim 11.

19. A vacuum conveyor for conveying a powdered and/or granular material for additive manufacturing, in particular for conveying a metal powder or a metal powder blend, wherein a method for drying the powdered and/or granular material (2) as claimed in claim 1 is carried out in the vacuum conveyor (4).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0020] In the drawing:

[0021] FIG. 1 shows a diagram of a drying arrangement.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0022] An arrangement 1 for drying a material 2 in an evacuable volume 3 can be derived schematically from FIG. 1. The evacuable volume 3 may be in the form of a vacuum conveyor 4 or comprise a vacuum conveyor 4. In the vacuum conveyor 4 there is located the powdered and/or granular material 2 that is to be conveyed (or is conveyed) and dried and that enters the volume 3 through a (blockable) intake 5 and can be conveyed out of the volume 3 through a (blockable) material outlet 6.

[0023] The vacuum conveyor 4 is fluidically connected to a pump arrangement 7, for instance via a (suction) line 8 or a (suction) pipe. A filtering means 9, which filters the fluid flow to the pump arrangement 7, is arranged in the volume 3 so that the fluid flow is free of powder or dust originating from the material 2 in the volume 3. The pump arrangement 7 comprises a first pump 10 and a second pump 11, which are operated one after the other in normal operation. First of all, the material 2 is conveyed into the container 3, 4 by means of the first pump 10. Then, the material 2 is dried by vacuum drying by means of the second pump 11. In order that the first pump 10 and then the second pump 11 can be operated one after the other, a respective fluidic blocking device 14 is provided in the region of the sides of the pump inlet. The blocking device 14 may comprise a valve or be formed by a valve.

[0024] The first pump 10 may be in the form of a pneumatic vacuum pump, for instance an ejector pump. The second pump 11 of the pump arrangement 7 may be in the form of an electric (positive-displacement) vacuum pump, for example a vane oil pump or rotary-vane pump.

[0025] A (capacitive) moisture sensor 13, which can be used to record the moisture in the fluid (air) conveyed out of the pump arrangement 7 by the pump 11, is arranged in the exit gas flow or in the exit gas line 12 of the second pump 11. A suitable calibration, for instance by means of a test medium, makes it possible to calculate the residual moisture in the powdered and/or granular material 2 in the vacuum conveyor 4. The sensor 13 detects absolute values of the moisture in the exit air. In the course of the sensor evaluation, it is also possible to take into account, in addition to the absolute values, a change in the sensor values over time.

TABLE-US-00001 LIST OF REFERENCE SIGNS 1 Drying arrangement 2 Material 3 Volume 4 Vacuum conveyor 5 Intake 6 Material outlet 7 Pump arrangement 8 Line 9 Filtering means 10 First pump, ejector pump 11 Second pump, positive-displacement pump 12 Exit air channel 13 Sensor 14 Blocking device, valve