ances attainable are reduced with age of the machine
SELECTIVE LASER SINTERING WITH ASSISTED tool.
POWDER HANDLING The final difficulty associated with such conventional
machine tool subtractive processes is the difficulty or
BACKGROUND OF THE INVENTION 5 impossibility of making many part configurations. That
.. .. i: . ^ c is, conventional machining methods are usually best
The present application is a continuation-in-part of .. _, r . . * . , . . . .
„ VT r„,/mn„„ 1.1 , _ ^ ,„., T* _ ^ suited for producingsymmetncal parts and parts where
N f" e*terior P^^hined. Howeviri where a
• > > • desired part is unusual in shape or has internal features,
1. FIELD OF THE INVENTION 1° the machining becomes more difficult and quite often,
_ . . ... the part must be divided into segments for production.
This invention relates to a method and apparatus fo caseS) a particular part configuration is not
which uses a directed energy beam to selectively sinter of ^ upon the
a powder to produce a part. In particular, this invention tool placement on the part. Thus, the size and configu
relates to a computer aided laser apparatus which se- 15 ration of ^ cutting tool do not permit access of the
quentially sinters a pluraUty of powder layers to build tool t0 produce the desired configuration.
the desired part in a layer-by-layer fashion. The present There are other machining processes which are addi
application is particularly directed toward a device and tive, for example, plating, cladding, and some welding
method for dispensing a layer of powder to attain a high processes are additive in that material is added to a
bulk density of the powder in each layer during sinter- 20 starting substrate. In recent years, other additive-type
ing. machining methods have been developed which use a
... Ac Toe Dcicv»mt Adt laser beam to coat or deposit material on a starting 2. DESCRIPTION OF THE RELEVANT ART Examples Pat Nos. 4,117,302;
The economies associated with conventional part 4,474,861; 4,300,474; and 4,323,756. These recent uses of production methods are generally related directly to the 25 lasers have been primarily limited to adding a coating to quantity of parts to be produced and the desired mate- a previously machined article. Often such laser coating rial characteristics of the finished parts. For example, methods have been employed to achieve certain metallarge scale manufacture casting and extrusion tech- lurgic properties obtainable only by such coating methniques are often cost effective, but these production ods. Typically, in such laser coating methods the startmethods are generally unacceptable for small quan- 30 ing article is rotated and the laser directed at a fixed tities—i.e. replacement parts or prototype production. location with the coating material sprayed onto the Many such conventional part production methods re- article so that the laser will melt the coating onto the quire expensive part specific tooling. Even powder article.
metallurgy requires a die for shaping the powder, mak- Additionally a process for compressing a powder
ing powder metallurgy unattractive as a method for 35 based material into a coherent mass prior to sintering
producing a small number of parts. ^ heen suggested. An example includes U.S. Pat. No.
Where only a small number of parts are desired, con- 4,752,352.
ventional production methods involving a subtractive SUMMARY OF THE INVENTION
machining method are usually used to produce the de- _ .. . , . .
sired part In such substractive methods, material is cut 40 ^ Pr°!>lems TM*hned above are in large major
c . .. . e . . \ . . solved by the method and apparatus of the present ui
away from a starting block of material to produce a 'L . . . . , „ ,
', . % , * u * i-- vention. The present invention includes a directed en
f1°f "SS^^Tr ^ f-ergy beam-such as a laser-and is adaptable to protool methods include: milling, dnlhng, grading, lathe d^ three ^^0^ part. The method of cuttrag, flame cutting, electric discharge mactoe, etc. 4J ^ nt mvention ^ ^ ocess> with the WMe such conventional machine tool substractive ^ ^ dispensed mto a ^ where the methods are usually effective m producing, the desired laser xlectiveiy sinters the powder to produce a sinpart, they are deficient m many respects tered k ^ mvention h a iayer.wise process in First, such conventional machine tool substractive whicn the k ,«jdlied together untU the completed methods produce a large amount of waste material for 50 part is formed. The method of the present invention is disposal. Further, such machine tool methods usually not limited to a particular type of powder, but rather is involve a large initial expense for setting up the proper adaptable to materials including but not limited to plasmacmning protocol and tools. As such, the set-up time tic> metai( polymer, ceramic powders, or composite is not only expensive, but relies a great deal on human materials.
judgment and expertise. These problems are, of course, 55 Broadly speaking, the apparatus includes a laser or exacerbated when only a small number of parts are to be 0ther directed energy source which is selectable for produced. emitting a beam in a target area where the part is proAnother difficulty associated with such conventional duced. A powder dispenser system deposits powder machining techniques involves tool wear—which not into the target area. A laser control mechanism operates only involves the cost of replacement, but also reduces 60 to move the aim of the laser beam and modulates the machining accuracy as the tool wears. Another limit on laser to selectively sinter a layer of powder dispensed the accuracy and tolerance of any part produced by into the target area. The control mechanism operates to conventional machining techniques is the tolerance selectively sinter only the powder disposed within delimits inherent in the particular machine tool. For exam- fined boundaries to produce the desired layer of the pie, in a conventional milling machine or lathe, the lead 65 part. The control mechanism operates the laser to selecscrews and ways are manufactured to a certain toler- tively sinter sequential layers of powder, producing a ance, which limits the tolerances obtainable in manufac- completed part comprising a plurality of layers sintered ruling a part on the machine tool. Of course, the toler- together. The defined boundaries of each layer corre