Additive manufacturing method depositing material within a granular constrained medium
An additive manufacturing process and device implement the deposition of a material to form a three-dimensional object. The process includes depositing the material in suspension within a stressed granular medium that comprises a granular phase and a gaseous interstitial phase. The granular phase consists solely of a material taking the form of discrete, solid elements that interact in regions of contact therebetween.
1 . An additive manufacturing process including the deposition of a material to form a three-dimensional object, wherein at least one step is carried out by a printing nozzle movable relative to a plate in such a way that an end of the printing nozzle is able to occupy any point in a useful printing volume defined by a printing tray that is fastened to the plate, the at least one step comprising depositing the material in suspension within a dry stressed granular medium contained in the printing tray, the depositing comprising moving the printing nozzle within the dry stressed granular medium and depositing the material during the moving, the dry stressed granular medium comprising:
a dry granular phase consisting solely of a material taking the form of discrete, solid elements that interact in regions of contact therebetween; and
a gaseous interstitial phase,
wherein the nozzle is introduced into the dry stressed granular medium via a displacement of the discrete elements around the nozzle.
2 . The process as claimed in claim 1 , wherein the dry granular phase has an angle of repose smaller than 40°.
3 . The process as claimed in claim 1 , wherein the dry granular phase has a compressibility lower than 200 m/N.
4 . The process as claimed in claim 1 , wherein the dry granular phase has a Carr index lower than 25.
5 . The process as claimed in claim 1 , wherein the ambient conditions under which the dry stressed granular medium is placed are present between the discrete elements.
6 . The process as claimed in claim 1 , wherein the dry granular phase is a single-phase material, which is cross-linked or amorphous or crystallized.
7 . The process as claimed in claim 1 , wherein the dry granular phase is a powdered polymer.
8 . The process as claimed in claim 1 , wherein the dry granular phase is a powdered dehydrated silica gel.
9 . The process as claimed in claim 1 , wherein the dry granular phase is a powdered polyvinyl acetate.
10 . The process as claimed in claim 1 , wherein the dry granular phase is a powdered polymethyl methacrylate.
11 . The process as claimed in claim 1 , wherein the dry granular phase is composed of sodium bicarbonate.
12 . The process as claimed in claim 1 , wherein the dry granular phase is composed of sand.
13 . The process as claimed in claim 1 , wherein the deposited material has a viscosity comprised between 10 −1 mPa·s and 10 7 mPa·s, wherein the viscosity is a dynamic Newtonian viscosity at 25° C.
14 . The process as claimed in claim 1 , further comprising a step of adjusting the pressure of the dry stressed granular medium.
15 . The process as claimed in claim 1 , further comprising a step of controlling the temperature of the dry stressed granular medium.
16 . The process as claimed in claim 1 , wherein the gaseous interstitial phase comprises an inert gas.
17 . The process as claimed in claim 1 , wherein the gaseous interstitial phase comprises air.
18 . The process as claimed in claim 1 , wherein the dry granular phase is composed of granules of ground silicone.
19 . The process as claimed in claim 1 , further comprising the dry stressed granular medium holding printed material in position for as long as required for the printed material to set via a thermal treatment.
20 . The process as claimed in claim 1 , wherein the dry granular phase is composed of cenospheres.
21 . The process as claimed in claim 20 , wherein the average diameter of the cenospheres is 100 to 200 μm.
22 . The process as claimed in claim 20 , wherein the density of the material from which the cenospheres are made is 0.6 to 0.8 g/cm 3 .
23 . The process as claimed in claim 20 , wherein the bulk density of the cenospheres is 0.3 to 0.5 g/cm 3 .