A method of forming a three-dimensional object comprising: a) providing a highly viscous pseudoplastic flame retardant material having a first viscosity and agitating the material to shear the pseudoplastic flame retardant material thereby decreasing viscosity to a second viscosity and to cause it to flow through a delivery system to an extrusion unit; b) employing an extrusion unit to extrude a first portion of the pseudoplastic flame retardant material in image-wise manner, the first portion having a cross section with a diameter; c) illuminating the first extruded portion to harden the pseudoplastic flame retardant material; d) extruding a second portion of the pseudoplastic flame retardant material adjacent to the first portion and contacting the first portion at at least one contact point, wherein a cross section of the second portion is shifted in an axis perpendicular to gravitational force compared to the cross section of the first portion; e) obtaining a common contact section between surfaces of the first and second extruded portions by forming an envelope into which a segment of the first portion protrudes by sliding, due to the gravitational force, of the second portion along the circumference of the surface of the first portion hardened in step c), wherein the surface of the second portion wets the surface of the first portion at the common contact section; f) illuminating the extruded second portion to harden the pseudoplastic flame retardant material and to form a bond between the first and second portions of pseudoplastic flame retardant material at the common contact section; g) adjusting the relative position between extrusion unit and extruded second portion such that the second portion obtains the location of the extruded first portion of step b); and repeating steps d) to g) until the three-dimensional object has been formed, wherein the flame retardant material is at least one of a group of flame retardants consisting of brominated polymers, oligomeric phosphate ester, e.g. Resorcinol bis(diphenyl phosphate), or aromatic phosphate ester, nitrogen flame retarders and a mix of the above. a) providing a highly viscous pseudoplastic flame retardant material having a first viscosity and agitating the material to shear the pseudoplastic flame retardant material thereby decreasing viscosity to a second viscosity and to cause it to flow through a delivery system to an extrusion unit; b) employing an extrusion unit to extrude a first portion of the pseudoplastic flame retardant material in image-wise manner, the first portion having a cross section with a diameter; c) illuminating the first extruded portion to harden the pseudoplastic flame retardant material; d) extruding a second portion of the pseudoplastic flame retardant material adjacent to the first portion and contacting the first portion at at least one contact point, wherein a cross section of the second portion is shifted in an axis perpendicular to gravitational force compared to the cross section of the first portion; e) obtaining a common contact section between surfaces of the first and second extruded portions by forming an envelope into which a segment of the first portion protrudes by sliding, due to the gravitational force, of the second portion along the circumference of the surface of the first portion hardened in step c), wherein the surface of the second portion wets the surface of the first portion at the common contact section; f) illuminating the extruded second portion to harden the pseudoplastic flame retardant material and to form a bond between the first and second portions of pseudoplastic flame retardant material at the common contact section; g) adjusting the relative position between extrusion unit and extruded second portion such that the second portion obtains the location of the extruded first portion of step b); and