Laser pulse shaping for additive manufacturing

Patent metadata

Field	Value
Publication number	US-2017216966-A1
Application number	US-201615010107-A
Country	US
Kind code	A1
Filing date	Jan 29, 2016
Priority date	Oct 14, 2015
Publication date	Aug 3, 2017
Grant date	—

Abstract

A system for melting powdered material and bonding it to the substrate below such as could be used for the additive manufacturing of a product includes a substrate, powder particles on the substrate, a pulsed laser that produces a pulsed laser beam with one or more low flux components on the order of kW/cm̂2, and one or more high flux components on the order of MW/cm̂2 during the duration of the pulse. The pulsed laser beam is directed onto the powder particles on the substrate thereby melting the powder particles and melting the substrate at the interface layer between the powder and the substrate such that the powder particles bond to the substrate. The laser further can be spatially patterned through the use of a mask such that portions of the laser pulse can be transmitted to the powder to be melted, and other portions can be rejected to prevent melting of the powder in desired locations. The system enables the conversion of powder to solid material in a layerwise fashion where the powder can be bonded to the substrate layer (or previous layer) such as is desired in the process of additive manufacturing. This is accomplished by using low power (and low cost) lasers to do the majority of the energy transfer, and using high power (and higher cost) lasers to complete the melting process, overcoming the kinetics of powder agglomeration through surface tension forces by partially melting the powder-substrate interface layer before surface tension can take effect on the molten powder particles.

First claim

1 . A method of melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing as a method of producing a product, comprising the steps of:
providing a substrate, positioning a layer of powder particles on said substrate producing an interface between said layer of powder particles and said substrate, providing a temporally varying photon flux as produced by a laser that has at least one low power flux component (on the order of kW/cm̂2 depending on the type of powdered material), and on high power flux component (on the order of MW/cm̂2 depending on the type of powdered material), providing at least one processor for controlling the output of the one or more lasers generating the low and high flux components, directing said temporally varying pulse of laser beam having on said substrate, heating said powder particles to just before, or above their melting point with the low power flux portion of the beam and using either the high powder flux component of the beam, or a combination of low and high power flux components of the beam to melt the interface layer of the substrate and said powder particles before surface tension forces can act on the molten powder particles to prevent an contiguous layer of powder to be melted and bonded to the substrate.

2 . The method of melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 1 wherein a mask is introduced into the system such that a first portion of the temporal photon flux is transmitted to the powder in a 2D pattern, and a second portion is not where either the low power photon flux, high power photon flux, or both components of the temporal photon flux are spatially patterned generating a spatial pattern in a 2D layer in the powder such that a pre-defined 2D image is formed by melting the powder in a 2D pattern.

3 . The method of melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 2 where the mask introduced in claim 2 is a static mask such as one carved from a thin sheet of reflective material.

4 . The method of melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 2 where the mask introduced in claim 2 is a dynamic a mask for receiving the optical signal generated by the lasers, the mask forming a liquid crystal polarization rotator, the liquid crystal polarization rotator including a liquid crystal module and a polarizer, wherein the liquid crystal module operates to receive and to rotate a first portion of the optical signal passing therethrough while allowing a second portion of the optical signal to pass therethrough without being rotated, and wherein the polarizer operates to reject one of the first or second portions of the optical signal received from the liquid crystal module, and thus to prevent the one of the first or second portions from reaching the substrate, while the polarizer allows the other one of the first or second portions of the optical signal to reach the substrate, the liquid crystal module of the mask module having a plurality of effective pixels arranged in a two dimensional pattern that are individually controlled to enable the mask to mask off one or more selected areas of a specific layer of the powdered material of the substrate, and wherein the mask absorbs substantially no optical energy from the optical signal; and
at least one processor controlling an output of the laser generating the photon flux and assisting in controlling operation of the mask such that only selected pixels are controlled to enable portions of the optical signal passing through the liquid crystal polarization rotator to be rotated to thus form the first portion of the optical signal.

5 . The method of melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 1 where the low power photon flux is created by generating an optical signal from diode lasers, the high power flux is created by generating an optical signal from solid state q-switched lasers such as Nd:YAG or Nd:YLF crystals, or by modulation of either individual high or low power flux from any laser type such that the beam contains two components in time consisting of low power and high power components.

6 . An apparatus for the of melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing as a method of producing a product, comprising of:
a substrate, a layer of powder particles on said substrate producing an interface between said layer of powder particles and said substrate, one or more laser sources capable of providing a temporally varying photon flux that has at least one low power flux component (on the order of kW/cm̂2 depending on the type of powdered material), and on high power flux component (on the order of MW/cm̂2 depending on the type of powdered material), one or more processors for controlling the output of the one or more lasers generating the low and high flux components, optical components for directing said temporally varying pulse of laser beam having on said substrate, enabling the heating said powder particles to just before, or above their melting point with the low power flux portion of the beam and using either the high powder flux component of the beam, or a combination of low and high power flux components of the beam to melt the interface layer of the substrate and said powder particles before surface tension forces can act on the molten powder particles to prevent an contiguous layer of powder to be melted and bonded to the substrate.

7 . An apparatus for melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 1 wherein a mask is introduced into the system such that a first portion of the temporal photon flux is transmitted to the powder in a 2D pattern, and a second portion is not where either the low power photon flux, high power photon flux, or both components of the temporal photon flux are spatially patterned generating a spatial pattern in a 2D layer in the powder such that a pre-defined 2D image is formed by melting the powder in a 2D pattern.

8 . An apparatus for melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 2 where the mask introduced in claim 2 is a static mask such as one carved from a thin sheet of reflective material.

9 . An apparatus for melting a powdered material and bonding it to the layer below such as could be used in additive manufacturing of claim 2 where the mask introduced in claim 2 is a dynamic a mask for receiving the optical signal generated by the lasers, the mask forming a liquid crystal polarization rotator, the liquid crystal polarization rotator including a liquid crystal module and a polarizer, wherein the liquid crystal module operates to receive and to rotate a first portion of the optical signal passing therethrough while allowing a second portion of the optical signal to pass therethrough without being rotated, and wherein the polarizer operates to reject one of the first or second portions of the optical signal received from the liquid crystal module, and thus to prevent the one of the first or second portions from reaching the substrate, while the polarizer allows the other one of the first or second portions of the optical signal to reach the substrate, the liquid crystal module of the mask module having a plurality of effective pixels arranged in a two dimensional pattern that are individually controlled to enable the mask to mask off one or more selected areas of

Assignees

• L Livermore Nat Security Llc

Inventors

• Demuth James A
• Bayramian Andrew J
• Duoss Eric B
• Kuntz Joshua D
• Spadaccini Christopher M

Classifications

• B29C64/282

  of the same type, e.g. using different energy levels · CPC title

• B29C64/286

  Optical filters, e.g. masks · CPC title

• B22F10/362

  for preheating · CPC title

• B22F10/366

  Scanning parameters, e.g. hatch distance or scanning strategy · CPC title

• B22F10/28

  Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM] · CPC title