Process for producing a filter, in particular for a rotary separator
A filter, in particular for a rotary separator, is produced using an energy beam melting process, for example an electron beam, starting from powder made from the same material as a porous filtering portion to be formed, for example from a titanium alloy; on the basis of a three-dimensional model comprising a cell structure defining the porous filtering portion, subsequent layers of powder are applied and locally melted, so as to form successive sections of the porous filtering portion; at the end of the forming process, the residual powder is evacuated from the pores.
1. Process for producing a filter; the process comprising the steps of:
a) forming a three-dimensional mathematical model, which comprises a cell structure defining a filtering porous portion of said filter and has cells corresponding to respective pores to be obtained in said porous portion;
b) applying powder having the same composition as said porous portion and having a grain size lower than a porosity to be obtained, in order to define a horizontal layer of powder having a substantially constant thickness;
c) locally melting the powder of said layer by means of energy beam scanning in order to form a section of said porous portion according to a level of said three-dimensional model;
d) lowering the upper surface of the formed section to a predefined position;
e) repeating the steps from b) to d) until all the sections of said porous portion have been formed;
f) eliminating the residual powder from the pores of the formed porous portion;
wherein the process comprises the further step of forming at least one reinforcing ring together with said porous portion, by repeating the steps from b) to d) for a given number of times; said reinforcing ring being defined in said three-dimensional model, and being made from a solid and non-porous material integral with said porous portion and arranged along an edge of said porous portion.
2. Process according to claim 1 , wherein the cell structure of said three-dimensional model is formed by defining a basic module and repeating said basic module in exactly the same way until obtaining the shape and the dimensions that correspond, in said three-dimensional model, to those of said porous portion.
3. Process according to claim 1 , wherein the melting step is performed by means of an electron beam.
4. Process according to claim 3 , further comprising a step of pre-heating the powder of each layer that is applied, to a given temperature below that at which said powder is melted.
5. Process according to claim 4 , wherein the pre-heating step comprises a heating of said layer of powder by means of scanning by said electron beam, and in that the temperature reached by said layer of powder in the pre-heating step is adjusted by setting a number of passes of said scanning electron beam.
6. Process according to claim 1 , further comprising a cooling step using inert gas before removing said porous portion from a melting chamber in which said porous portion was formed.
7. Process according to claim 1 , wherein the melting step is performed while maintaining a vacuum in a melting chamber in which said porous portion is formed.
8. Process according to claim 1 , further comprising the additional steps of:
forming at least one anchoring portion on a starting platform repeating the steps from b) to d) for a given number of times, before forming the sections of said porous portion; said anchoring portion also being defined in said three-dimensional model;
separating the porous portion formed by said starting platform in correspondence with said anchoring portion.
9. Process according to claim 8 , wherein said anchoring portion is defined, in said three-dimensional model, by the same cell structure as said porous portion.
10. Process according to claim 8 , wherein said anchoring portion comprises a plurality of pedestals all having the same height and horizontally spaced in relation to one another.
11. Process according to claim 1 , wherein the powder has a grain size ranging from between 45 and 65 μm.
12. Process according to claim 1 , wherein said cell structure and/or at least one melting parameter is/are set so as to obtain a porous portion having an average pore diameter of between 500 μm and 1500 μm.
13. Process according to claim 1 , wherein the step of eliminating the residual powder is performed by means of a sandblasting process using sand having the same composition and grain size as said residual powder.
14. Process according to claim 1 , wherein said powder is made from a titanium alloy.
15. Process according to claim 1 , wherein a plurality of drive portions made from a solid material and protruding from said porous portion are formed, by repeating the steps from b) to d) for a given number of times; said drive portions also being defined in said three-dimensional model.
16. Filter, wherein it is produced according to the process of claim 1 .
17. Process according to claim 1 , wherein the step of forming at least one reinforced ring comprises forming two reinforcing rings together with said porous portion, by repeating the steps from b) to d) for a given number of times; said reinforcing rings being defined in said three-dimensional model, and being made from a solid and non-porous material integral with said porous portion and arranged along respective edges of said porous portion.
18. Process according to claim 1 , further comprising storing the mathematical model in a control unit.
19. Process according to claim 1 , wherein a size of the pores is larger than a grain size of the powder.