Arcam AB fka AMAVF

[charlie T colton]

New scan strategy patent application published

It took me a couple of minutes to understand what exactly made this different from what's been in use up to now. This is a huge improvement.

At the present time, all systems use a focused spot to make a weld pool. One advantage to Arcam's EBM technology is that the spot positioning is done electronically/electrically/magnetically. This is much faster than the mechanical systems that the laser technology uses. With this in mind, Arcam's EBM tech can redirect the beam very fast and essentially focus the energy in many spots enable multiple weld pools in any give instant. The product guides for the Arcam A1 and A2 machines Say "up to ~100" and "1 - 100" beam spots are possible simultaneously. Both of those machines have been out of production for quite a while. The guides for the machines available now just say that multi-beam "allows melting at multiple points simultaneously". The laser technology manufacturers have upped the number of melt pools by providing multiple lasers in some machines. The most I've seen is 4 pools produced by 4 individual lasers, each dependent on the speed and accuracy of the mechanical motion of the directing mirrors.

The present (new) invention describes using a directed line of energy to make a line of melted metal instead of a pool that is more or less round in shape. With the "melt line" idea it's possible to distribute a higher amount of energy over a larger section of the powder surface. With the technology in production today, if the energy delivered to the localized beam spot is too high, the metal evaporates instead of making a predictable weld pool.

The problem with the FastEBM that we've been waiting for is that the increased power density that the 10 KW guns produced blasted the metal powder rather than melting it. The new invention distributes the power over a line of powder enabling what should be much, much faster build times. This strategy should be available to existing production machines, not just the ones on the drawing board, albeit with the 3 KW guns. The machines already with customers will likely need improved beam focusing electromagnetic deflection coils to provide the astigmatism correction necessary.

It will be interesting to see how the technology advances and with it build speed driving faster production rates.

USPTO Applicaton #20170189964 - Apparatus, method, and computer program product for fusing a workpiece - Filed: March 22, 2017 - Published: July 6, 2017

Selected sections of the patent application:


BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0026] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0027] FIG. 1 depicts a schematic graph of a beam power as a function of scan speed;

[0028] FIG. 2 depicts a view from above of an additive manufacturing process with an enlarged view of the beam spot configuration;

[0029] FIG. 3 depicts an example embodiment of a freeform fabrication or additive manufacturing apparatus in which the method may be implemented;

[0030] FIG. 4A depicts a beam spot configuration according to prior art;

[0031] FIG. 4B depicts an example embodiment of a beam spot configuration according to the present invention;

[0032] FIG. 5A-5C depicts three different beam spot configurations for different beam power;

[0033] FIG. 6 depicts an example embodiment for accomplishing an appropriate beam spot shape in a laser beam based system,

[0034] FIG. 7 depicts an example embodiment for accomplishing an appropriate beam spot shape in an electron beam based system, and

[0035] FIG. 8 depicts a schematic flow chart of a method according to the present invention.

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[0054] FIG. 1 depicts a schematic graph 175 of a beam power as a function of scan speed. For beam power lower than a predetermined value an essentially circular beam spot may be used for fusing powder material or for welding pieces together. If increasing the beam power over a predetermined value, and thereby increasing the scan speed over a predetermined value, the material will start to boil instead of melt. The reason for this boiling of material is that the deflection or scan speed of the energy beam will be too fast so that the heat from the energy beam will not have sufficient time to penetrate into the material to be fused or welded. With a too high power and thereby a too fast speed of deflection of said energy beam, the surface temperature will become too high so that the material which is to be fused or welded is instead evaporated.

[0055] The invention solves this problem by protracting the spot, i.e., extending the spot dimension parallel to the scan direction and essentially keeping its dimension perpendicular to the scan direction. In FIG. 1 an essentially circular spot may be used for beam power and scan speed below P1 and S1 respectively. For beam power and scan speed above P1 and S1 respectively the beam spot is protracted in the direction parallel to the scan direction. By letting the beam spot being protracted parallel to the scan direction the surface temperature may be decreased since the power in said beam is distributed over a larger area. The heat from the beam spot may, because of this beam power distribution over a larger area, have sufficient time to penetrate into the material and thereby minimizing the radiated energy from the melt pool and thereby minimizing the boiling or evaporation of material. By protracting the beam spot in parallel to the scan direction, larger beam powers may be used compared to if a circular spot would have been used with a maintained resolution of the fusing or welding. The protracted beam spot may follow an intended scanning path so that the longer dimension of said beam spot follows the beam path, i.e., the dimension perpendicular to the scanning direction is smaller than the dimension parallel to the scanning direction irrespective of the direction of the intended beam path.

[0056] FIG. 2 depicts a view from above of an additive manufacturing process with an enlarged view 200 of the beam spot configuration. In FIG. 2 a cross section 270 of a three dimensional article is being built by melting powder material inside a build chamber 290 with an energy beam 210. The energy beam 210 is melting the material according to predetermined instructions stored in a control unit. The scan direction in FIG. 2 is denoted by an arrow 240. A number of scan lines 250 have already been provided onto the powder material in order to build the cross section of the three dimensional article. One scan line 220 is being provided onto the powder material and an enlarged view 200 of the beam spot 230 illustrates that the actual length L of the beam spot 230 in parallel to the scan direction 240 is larger than the dimension of the beam spot 230 perpendicular to the scan direction denoted by H.

[0057] FIG. 4A illustrates a beam spot shape when using beam power lower than a predetermined value. In FIG. 4A the horizontal size L1 of the beam spot in parallel to the scan direction is essentially equal to the vertical size H1 of the beam spot perpendicular to the scan direction.

[0058] FIG. 4B illustrates a beam spot shape when using a beam power higher than said predetermined value. In FIG. 4B the horizontal size L2 of the beam spot in parallel to the scan direction is substantially larger than the vertical size H1 of the beam spot perpendicular to the scan direction. As can be seen the vertical size H1 of the beam spot perpendicular to the scan direction is equal in FIGS. 4A and 4B. Any scan direction may be used, i.e. not only the horizontal scan direction as have been illustrated in the figures. The beam spot size for beam powers larger than a predetermined value may be larger in a direction in parallel to the scan direction than in a direction perpendicular to the scan direction for any scan direction.

[0059] FIG. 5A-5C depicts three different beam spot configurations for three different beam power. The first beam spot 510 in FIG. 5A has a first beam power. The second beam spot 520 in FIG. 5B has a second beam power which is higher than said first beam power. The third beam spot 530 in FIG. 5C has a third beam power which is higher than said second beam power. The first length L3 of said first beam spot 510 is shorter than said second length L4 of said second beam spot 520 which is shorter than the third length L5 of said third beam spot 530. The first, second and third beam spot have all the same size H1 perpendicular to the scan direction. In FIG. 5A-5C the shape of the beam spot is illustrated to be elliptical. However, any protracted shape of the beam spot may be used such as rectangular or polygonal or any other suitable mathematical function where the size of the beam spot is protracted in the scanning direction compared to the size perpendicular to the scanning direction.