Retained self-aligning washer and nut assembly and method for fabrication by additive manufacturing

A fastening system with offset angle capability, said system comprising:

• a fastener receivable in a hole in a structure, said hole having an offset angle relative to a surface of the structure;
• an additively manufactured nut and washer assembly having
• a washer with a bottom surface received on the surface of the structure and an aperture to receive the fastener, said washer a having a retaining flange and a positioning cavity;
• a nut received in the washer and having a bore to receive said fastener, said nut having a shoulder received in the positioning cavity, a top surface of the shoulder engaging a lower surface of the retaining flange in a loose condition of the washer and nut, said nut further having an engagement surface and said washer having a receiving surface, a removable ceramic intermediary in contact locations between the receiving surface on the washer and the engagement surface of the nut during additive manufacturing, said engagement surface contacting the receiving surface in the washer in an engaged position of the washer and nut over a range of offset angle orientation after completion of additive manufacturing, said nut further having a peripheral surface, said peripheral surface engaging a blocking surface in the washer with the nut and washer in a maximum offset angle orientation between the washer an nut in the engaged position.

A method for producing a washer and nut assembly, said method comprising:

• printing microlayers using a metal powder and binder formulation for a washer and a nut, said nut retained within said washer wherein the washer has a retaining flange and a positioning cavity and the nut has a body with an extending shoulder, the shoulder received in the positioning cavity, a top surface of the shoulder engaging a lower surface of the retaining flange in a loose condition of the washer and nut, the retaining flange having an inner diameter assuring engagement of an outer diameter of the shoulder to retain the nut within the washer in the loose condition, said nut further having an engagement surface, said engagement surface contacting a receiving surface in the washer in an engaged position of the washer and nut, said nut further having a peripheral surface, said peripheral surface engaging a blocking surface in the washer with the nut and washer in a maximum offset angle orientation between the washer and nut in the engaged position;
• laying down a ceramic intermediary in contact locations between the receiving surface on the washer and the engagement surface of the nut at predetermined locations in the printing of each microlayer;
• curing the binder to solidify a metal matrix in the structure of the washer and nut;
• sintering the metal matrix;
• removing the binder by solvent wash or heat vaporization;
• consolidating the remaining metal matrix;
• and
• vaporizing the ceramic intermediary in an oven cure leaving the consolidated metal washer and retained nut with the positioning cavity.

A method for use of an additively manufactured self-retaining washer and nut assembly comprising:

• manipulating a washer having a retaining flange and a positioning cavity, said retaining flange having an inner diameter, and a captive nut having a cylindrical body with a maximum body diameter at a periphery, said maximum body diameter less than the inner diameter of the retaining flange whereby the periphery of the cylindrical body extends through the inner diameter, and said body having a shoulder extending from the cylindrical body to a peripheral surface having an outer diameter, the outer diameter larger than the inner diameter of the retaining flange, with an upper surface of the shoulder engaged by the retaining flange on the washer, a top surface of the shoulder engaging a lower surface of the retaining flange in a loose condition of the washer and nut, the inner diameter of the retaining flange being less than the outer diameter of the shoulder assuring engagement of the shoulder with the retaining flange to retain the nut within the washer in the loose condition, said nut further having an engagement surface, said engagement surface contacting a receiving surface in the washer in an engaged position of the washer and nut, wherein the engagement surface and the receiving surface have spherical profiles, said peripheral surface of the nut engaging a blocking surface in the washer with the nut and washer in a maximum offset angle orientation between the washer and nut in the engaged position;
• retaining the nut in a positioning cavity;
• engaging a fastener in the nut through a hole in a structure, the hole offset by an angle from a neutral axis;
• maintaining the engagement surface on the nut in spherically concentric contact with the receiving surface on the washer while a bottom surface of the washer remains in parallel contact with the surface of the structure;
• and
• contacting the blocking surface in the positioning cavity with the peripheral surface of the nut with the nut at a predetermined blocking angle relative to the washer.