US 5597589 A——SLS基本专利学习（中文翻译） - 3D小蚂蚁工作室

An apparatus for selectively sintering a layer of powderto produce a part made from a plurality of sintered layers. The apparatusincludes a computer controlling a laser to direct the laser energy onto thepowder to produce a sintered mass. The computer either determines or isprogrammed with the boundaries of the desired cross-sectional regions of thepart. For each cross-section, the aim of the laser beam is scanned over a layerof powder and the beam is switched on to sinter only the powder within theboundaries of the cross-section. Powder is applied and successive layerssintered until a completed part is formed. Preferably, the powder dispensingmechanism includes a drum which is moved horizontally across the target areaand counter-rotated to smooth and distribute the powder in an even layer acrossthe target area. A downdraft system provides controlled temperature air flowthrough the target area to moderate powder temperature during sintering.

这是通过选择烧结一层粉末，层层烧结粉末最终生产出零件的一种装置。里面有一个电脑，用来控制激光，使激光能量作用在粉末上烧结。计算机还决定或规划零件要求的截面区域的边界。对每一个截面，激光束按打印目标的层信息，在一层粉末上烧结截面区域内的粉末。一层层供应粉末，每一层完成烧结，直到零件成型。推荐的办法是，粉末分发装置用一个滚轮水平地从打印区域穿过，再反向旋转回来，使分发的粉末表面的一层光滑而平整。用一个抽风系统提供打印件表面的高温气流控制，约束粉末温度在烧结范围内。

The present application is a continuation of application Ser. No.07/911,879, filed Jul. 10, 1992 now U.S. Pat. No. 5,376,580, which is adivisional of application Ser. No. 541,788, filed Jun. 21, 1990 now U.S. Pat.No. 5,132,143, which is a divisional of application Ser. No. 105,316, filedOct. 5, 1987 now abandoned, which is continuation-in-part of Ser. No.06/920,580, filed Oct. 17, 1986, now U.S. Pat. No. 4,863,538.

此项申请是接续Ser. No. 07/911,879的申请。申请于 Jul. 10, 1992，现在是U.S. Pat. No. 5,376,580,是Ser. No. 541,788申请的分支。Ser. No. 541,788申请于Jun. 21, 1990，现在是U.S. Pat. No. 5,132,143，是Ser. No. 105,316的分支，Ser. No. 105,316申请于Oct. 5, 1987，现在已经公开，是Ser. No. 06/920,580的接续部分，申请于Oct. 17, 1986，现在是U.S. Pat. No. 4,863,538。

This invention relates to a method and apparatus which uses a directedenergy beam to selectively sinter a powder to produce a part. In particular,this invention relates to a computer aided laser apparatus which sequentiallysinters a plurality of powder layers to build the desired part in alayer-by-layer fashion. The present application is particularly directedtowards a mechanism for dispensing a layer of powder and a mechanism fordirecting air flow to the target area to moderate powder temperature.

这个发明是关于一种方法和装置，使用一个定向的能源束选择性地烧结粉末生成部件，此发明尤其关于一个计算机辅助激光装备，可连续烧结多层粉末，一层一层地制造所需的部件。目前的应用特别针对一个分发一层粉末的机械，和引导气流到目标物体区域来调节粉末温度的机械。

The economies associated with conventional part production methods aregenerally related directly to the quantity of parts to be produced and thedesired material characteristics of the finished parts. For example, largescale manufacture casting and extrusion techniques are often cost effective,but these production methods are generally unacceptable for smallquantities--i.e. replacement parts or prototype production. Many suchconventional part production methods require expensive part specific tooling.Even powder metallurgy requires a die for shaping the powder, making powdermetallurgy unattractive as a method for producing a small number of parts.

传统部件生产方法相关的经济，一般直接与所生产的部件数量和成品所需的材料特性有关。例如：大规模制造的铸造和挤压技术往往是低成本的，但是这些生产方法对小规模制造通常无法接受。比如：替代部件或原型产品。很多这种传统部件的生产方法需要昂贵的部件特定工具。即使粉末冶金也需要塑模进行粉末成型，使粉末冶金对生产小批量部件也没有吸引力。

Where only a small number of parts are desired, conventional productionmethods involving a subtractive machining method are usually used to producethe desired part. In such subtractive methods, material is cut away from astarting block of material to produce a more complex shape. Examples ofsubtractive machine tool methods include: milling, drilling, grinding, lathecutting, flame cutting, electric discharge machine, etc. While suchconventional machine tool subtractive methods are usually effective inproducing the desired part, they are deficient in many respects.

在只需要小批量部件的地方，传统生产方式包括减材加工方法经常被用来生产需要的部件，这种方法通过把一块最初的材料切割成一个复杂的形状，减材加工的工具方法包括：铣，钻，磨，车床切割，火焰切割，电火花加工等。虽然这些传统的减材加工方法通常在生产所需的部件是有效的，但在很多方面存在缺陷。

First, such conventional machine tool subtractive methods produce a large amountof waste material for disposal. Further, such machine tool methods usuallyinvolve a large initial expense for setting up the proper machining protocoland tools. As such, the set-up time is not only expensive, but relies a greatdeal on human judgment and expertise. These problems are, of course,exacerbated when only a small number of parts are to be produced.

首先，减材加工方法产生大量的废料需要处置，而且，这种方法需要昂贵的初始花费，需要建立合适的加工原型和工具，这样，建立的时间不仅昂贵，而且很大地依赖人的判断和专业知识。这些问题，在只加工少量的部件时就更加恶化。

Another difficulty associated with such conventional machining techniquesinvolves tool wear--which not only involves the cost of replacement, but alsoreduces machining accuracy as the tool wears. Another limit on the accuracy andtolerance of any part produced by conventional machining techniques is thetolerance limits inherent in the particular machine tool. For example, in aconventional milling machine or lathe, the lead screws and ways aremanufactured to a certain tolerance, which limits the tolerances obtainable inmanufacturing a part on the machine tool. Of course, the tolerances attainableare reduced with age of the machine tool.

另一个传统加工技术的困难是刀具磨损——不仅包括替换成本，还降低加工精度。另外任何传统机床技术生产部件的精度和公差的限制是来自特殊机床的固有公差限制。比如，在传统的铣床和车床，丝杠和滑路是在一定的公差范围制造的，这限制了在机床制造零件的公差可获得性，老的机床还降低公差的可获得性。

The final difficulty associated with such conventional machine toolsubtractive processes is the difficulty or impossibility of making many partconfigurations. That is, conventional machining methods are usually best suitedfor producing symmetrical parts and parts where only the exterior part ismachined. However, where a desired part is unusual in shape or has internalfeatures, the machining becomes more difficult and quite often, the part mustbe divided into segments for production. In many cases, a particular partconfiguration is not possible because of the limitations imposed upon the toolplacement on the part. Thus, the size and configuration of the cutting tool donot permit access of the tool to produce the desired configuration.

传统制造方法的最后一个困难是,制造很多零件的结构很困难和不可能。因为传统的制造方法适合做对称形状的部件或只有表面结构的部件。而需要的部件往往有各种形状或者内部结构，导致必须把部件分成多个段来制造。很多情况，因为所使用的工具的限制导致特殊的部件结构无法制作，这样切割工具的尺寸和结构都不允许操作切割工具。

There are other machining processes which are additive, for example,plating, cladding, and some welding processes are additive in that material isadded to a starting substrate. In recent years, other additive-type machiningmethods have been developed which use a laser beam to coat or deposit materialon a starting article. Examples include U.S. Pat. Nos.4,117,302; 4,474,861; 4,300,474; and 4,323,756. These recent uses oflasers have been primarily limited to adding a coating to a previously machinedarticle. Often such laser coating methods have been employed to achieve certainmetallurgic properties obtainable only by such coating methods. Typically, insuch laser coating methods the starting article is rotated and the laserdirected at a fixed location with the coating material sprayed onto the articleso that the laser will melt the coating onto the article.

有另一种加工过程是增材制造，比如：电镀、覆层、焊接工艺是增材制造，材料被增加到一个基板上。近几年，其他的增材类型的加工方法已经开发出来，用一束激光通过涂覆或堆积材料到初始的制品上。例如U.S. Pat. Nos. 4,117,302; 4,474,861; 4,300,474; and 4,323,756.这些对激光的使用主要局限于增加涂层到预先加工好的制品上。这种激光电镀方法被用来达到特定的冶金性能，典型地，这种方法是，加工制品旋转，激光对准加工件一个固定的位置，在电镀材料喷涂到加工件时，激光熔化涂料黏贴到加工件上。

The problems outlined above are in large measure solved by the method andapparatus of the present invention. The present invention includes a directedenergy beam--such as a laser--and is adaptable to produce almost any threedimensional part. The method of the present invention is an additive process,with the powder being dispensed into a target area where the laser selectivelysinters the powder to produce a sintered layer. The invention is a layer-wiseprocess in which the layers are joined together until the completed part isformed. The method of the present invention is not limited to a particular typeof powder, but rather is adaptable to plastic, metal, polymer, ceramic powders,or composite materials.

上述的问题很大程度上用这个发明的方法和装置所解决。这个发明包括一个定向能量束——比如激光，可以用来生产几乎所有的三维部件。它是一种增材工艺，把粉末分配到目标区域，激光选择性烧结粉末形成烧结好的一层。此发明用逐层的方式，每层粘到一起形成完整的部件。此发明不局限于特殊的粉末类型，可以适用于塑料、金属、橡胶、陶瓷粉末或复合材料。

Broadly speaking, the apparatus includes a laser or other directed energysource which is selectable for emitting a beam in a target area where the partis produced. A powder dispenser system deposits powder into the target area. Alaser control mechanism operates to move the aim of the laser beam andmodulates the laser to selectively sinter a layer of powder dispensed into thetarget area. The control mechanism operates to selectively sinter only thepowder disposed within defined boundaries to produce the desired layer of thepart. The control mechanism operates the laser to selectively sinter sequentiallayers of powder, producing a completed part comprising a plurality of layerssintered together. The defined boundaries of each layer correspond torespective cross-sectional regions of the part. Preferably, the controlmechanism includes a computer--e.g. a CAD/CAM system--to determine the definedboundaries for each layer. That is, given the overall dimensions andconfiguration of the part, the computer determines the defined boundaries foreach layer and operates the laser control mechanism in accordance with thedefined boundaries. Alternatively, the computer can be initially programmedwith the defined boundaries of each layer.

广义上讲，此装置包括激光或其他定向能量源，能够选择地发射光束到部件产生的目标区域。粉末分发系统分发粉末到目标区域。一个激光控制机械移动激光束的方向，并且调整激光选择性地烧结一层粉末到目标区域。控制设备只选择性地烧结定义边界内的区域。控制设备一层层烧结粉末，生成完整的部件，定义的边界对应到部件的横截面。控制设备最好包括一个计算机，比如：一个CAD/CAM系统——决定每层的定义边界。计算机为每层决定定义边界并操作激光控制器依照边界操作。更进一步，计算机可以一开始就定义好每层的边界。

In a preferred form, the laser control mechanism includes a mechanism fordirecting the laser beam in the target area and a mechanism for modulating thelaser beam on and off to selectively sinter the powder in the target area. Inone embodiment, the directing mechanism operates to move the aim of the laserbeam in a continuous raster scan of target area. The modulating mechanism turnsthe laser beam on and off so that the powder is sintered only when the aim ofthe laser beam is within the defined boundaries for the particular layer.Alternatively, the directing mechanism aims the laser beam only within thedefined boundaries for the particular layer so that the laser beam can be lefton continuously to sinter the powder within the defined boundaries for theparticular layer.

激光控制器最好包含一个装置控制激光束的方向，和另一个装置控制激光束的开关。在一个实例中，方向控制装置移动激光束方向在目标区域连续进行光栅扫描激光束调节装置开关激光束，使得只有激光束对准到区域内后再打开激光连续地烧结粉末。

In a preferred embodiment, the directing mechanism moves the laser beam ina repetitive raster scan of the target area using a pair of mirrors driven bygalvanometers. The first mirror reflects the laser beam to the second mirrorwhich reflects the beam into the target area. Shifting movement of the firstmirror by its galvanometer shifts the laser beam generally in one direction inthe target area. Similarly, shifting movement of the second mirror by itsgalvanometer shifts the laser beam in the target area in a second direction.Preferably, the mirrors are oriented relative to each other so that the firstand second directions are generally perpendicular to each other. Such anarrangement allows for many different types of scanning patterns of the laserbeam in the target area, including the raster scan pattern of the preferredembodiment of the present invention.

一个推荐的实例：方向控制装置使用一对电流计驱动的振镜，移动激光束在目标区域重复光栅扫描。第一个振镜反射激光束到第二个振镜，第二个振镜反射激光束到目标区域。通过电流计移动激光束在目标区域到一个方向，来移动第一个振镜，同样的，通过电流计移动激光束在目标区域到第二个方向，来移动第二个振镜，最好振镜的方向会互相关联，第一个方向和第二个方向通常互相垂直。这样的设计允许目标区域的激光束有很多不同类型的扫描模式。包括光栅模式——本发明推荐的实例。

The method of part production of the present invention includes the stepsof depositing a first portion of powder onto a target surface, scanning the aim of a directed energy beam (preferablya laser) over the target surface, and sintering a first layer of the firstpowder portion on the target surface. The first layer corresponds to a firstcross-sectional region of the part. The powder is sintered by operating thedirected energy source when the aim of the beam is within the boundariesdefining the first layers. A second portion of powder is deposited onto thefirst sintered layer and the aim of the laser beam scanned over the firstsintered layer. A second layer of the second powdered portion is sintered byoperating the directed energy source when the aim of the beam is within theboundaries defining the second layer. Sintering of the second layer also joinsthe first and second layers into a cohesive mass. Successive portions of powderare deposited onto the previously sintered layers, each layer being sintered inturn. In one embodiment, the powder is deposited continuously into the target.

本发明的部件生产方法包括堆积第一部分粉末到目标表面的步骤。扫描能量束（推荐激光）定向到目标表面，烧结第一部分粉末的第一层到目标表面。第一层对应第一个部件横截面。通过操作定向能量源，当激光束对准在第一层定义的区域内时进行粉末烧结。第二部分粉末被放入第一个烧结后的层表面，然后激光束扫描过第一个烧结层上，第二层的第二部分粉末通过操作定向激光束在第二层的定义边界内烧结粉末。第二层烧结同时沾粘了第一层和第二层。连续不断地分发粉末到前一个烧结好的层，每一层依次烧结，直到粉末连续地层层堆积形成部件。

In a preferred embodiment, the laser beam is modulated on and off duringthe raster scan so that the powder is sintered when the aim of the beam isdirected within the boundaries of the particular layer. Preferably, the laseris controlled by a computer; the computer may include a CAD/CAM system, wherethe computer is given the overall dimensions and configuration of the part tobe made and the computer determines the boundaries of each cross-sectionalregion of the part. Using the determined boundaries, the computer controls thesintering of each layer corresponding to the cross-sectional regions of thepart. In an alternative embodiment, the computer is simply programmed with theboundaries of each cross-sectional region of the part.

在推荐的实例中，激光束在光栅扫描中进行开关控制，所以当激光束定向到一层的粉末上后烧结粉末。激光推荐用计算机控制。计算机安装有CAD/CAM系统以便预先给计算机完整的部件结构尺寸，用这些确定的边界，计算机控制烧结每一层对应的横截面区域。或者按另一个实例方法，计算机只简单地给定部件横截面的边界。

Additionally, another embodiment of the present invention includes adevice for distributing the powder as a layer over the target area or region.Preferably, the distributing device includes a drum, a mechanism for moving thedrum across the region, and a mechanism for counter-rotating the drum as it ismoved across the region. The drum moving mechanism preferably keeps the drum adesired spacing above the region to yield a layer of powder of a desiredthickness. The drum is operable when counter-rotated and moved across theregion to project powder forward in the direction of movement, leaving behind alayer of powder having the desired thickness.

另外，本发明的另一个实例包括一个设备用来分发粉末层到目标区域的表面。推荐的方法是，分发设备包括一个滚轮，一种机械用来移动滚轮穿过目标区域，还有一种机械用来反向旋转滚轮，滚轮移动装置最好让滚轮与目标区域表面保持所需的间距，以便产生所需的粉末层厚度。当滚轮反向旋转穿过粉末区域时是可以控制的，让滚轮一边移动一边留下一层所需厚度的粉末。

In still another embodiment, a downdraft mechanism for controllingtemperature of the powder is provided which includes a support defining thetarget area, a mechanism for directing air to the target area, and a mechanismfor controlling the temperature of the air prior to reaching the target area.The support preferably includes porous medium on which the powder is depositedand a plenum adjacent the porous medium. Thus, the controlled temperature airis directed to the powder in the target area and helps control the temperatureof the sintered and unsintered powder in the target area.

还有一个实例，一个向下通风装置用来控制粉末的温度，包括支撑限定的目标区域的粉末，一个装置用来引导空气到目标表面，另一个装置用来事先控制到达表面的空气的温度。支撑推荐包含多孔介质，粉末可以堆积在上面并且填满相邻的多孔介质。这样，恒温的空气被引到目标区域的粉末，帮助控制目标区域表面烧结和未烧结的粉末温度。

As can be appreciated from the above general description, the method andapparatus of the present invention solves many of the problems associated withknown part production methods. First, the present invention is well suited forprototype part production or replacement part production of limited quantities.Further, the method and apparatus hereof are capable of making parts of complexconfigurations unobtainable by conventional production methods. Further, thepresent invention eliminates tool wear and machine design as limiting factorson the tolerances obtainable in producing the part. Finally, with the apparatusof the present invention incorporated into a CAD/CAM environment, a largenumber of replacement parts can be programmed into the computer and can beeasily produced with little set-up or human intervention.

从上面的大体的描绘应该能感觉到，本发明的方法和装置解决了很多已知的部件生产方法的问题。首先，本发明很好地适用于原型部件生产，或替代部件小批量生产，而且，此方法和装置能够生产复杂结构的、用传统方法无法生产的部件。另外，本发明消减了刀具磨损和机床设计，对生产的部件公差可获得性的限制因素。最后，用本发明的装置结合CAD/CAM环境，大量的替代部件可以用计算机绘制，并且很容易地生产出来，而只用很少的建造成本和人工介入。

Turning now to the drawings, FIG. 1 broadly illustrates the apparatus 10in accordance with the present invention. Broadly speaking, the apparatus 10includes a laser 12, powder dispenser 14, and laser control means 16. In moredetail, the powder dispenser 14 includes a hopper 20 for receiving the powder22 and having an outlet 24. The outlet 24 is oriented for dispensing the powderto a target area 26, which in FIG. 1 is generally defined by the confinementstructure 28. Of course, many alternatives exist for dispensing the powder 22.

看图纸，图1概要地描绘装置10，包括一个激光器12，粉末分发器14，和一个激光控制装置16。更详细地说，粉末分发器14包括一个漏斗20用来收集粉末20和一个出口24.出口24是为分发粉末到目标区域26，26被密封结构28所限制，当然有很多方法来分发粉末22.

The components of the laser 12 are shown somewhat schematically in FIG. 1and include a laser head 30, a safety shutter 32, and a front mirror assembly34. The type of laser used is dependent upon many factors, and in particularupon the type of powder 22 that is to be sintered. In the embodiment of FIG. 1,a Nd:YAG laser (Lasermetrics 9500Q) was used which can operate in a continuousor pulsed mode with a hundred-watt maximum outlet power in the continuous mode.The laser beam output of the laser 12 has a wavelength of approximately 1060nM, which is near infrared. The laser 12 illustrated in FIG. 1 includes aninternal pulse rate generator with a selectable range of about one kilohertz toforty kilohertz, and an approximately six nanosecond pulse duration. In eitherthe pulsed or continuous mode, the laser 12 can be modulated on or off toselectively produce a laser beam which travels generally along the path shownby the arrows in FIG. 1.

图1中，激光器12的组件包括一个激光头30，一个安全快门32，和一个前反射镜组件34。所使用的激光类型依赖很多因素，特别依赖粉末22，在图1的实例中，使用一个Nd:YAG激光器(激光计量器 9500Q)，可以在连续或脉冲模式操作，连续模式的最大输出功率为100W。激光器12发出的激光束波长大约1060nM，接近红外线波长。激光器12包括一个内部脉冲率，脉冲触发的可选择范围是大约1KHZ 到40KHZ，脉冲周期大约6nS，在脉冲或连续模式，激光器12都可以开关以便选择地产生激光束，激光束方向如图中的箭头方向。

To focus the laser beam, a diverging lens 36 and converging lens 38 aredisposed along the path of travel of the laser beam as shown in FIG. 1. Usingjust the converging lens 38, the location of the true focal point is not easilycontrolled by varying the distance between the converging lens 38 and the laser12. The diverging lens 36 placed between the laser 12 and converging lens 38creates a virtual focal point between the diverging lens 36 and the laser 12.Varying the distance between the converging lens 38 and-the virtual focalpoint, allows control of the true focal point along the laser beam path oftravel on the side of the converging lens 38 remote from the laser 12. Inrecent years there have been many advances in the field of optics, and it is recognizedthat many alternatives are available to efficiently focus the laser beam at aknown location.

图1中，为触发激光束，发散透镜36和会聚透镜38设置在激光束的路径上，只用会聚透镜38的话，通过改变会聚透镜38和激光器12之间的距离，不容易控制实焦点的位置。发散透镜36放在38和12中间，产生一个虚焦点在38和12之间，能够控制在会聚透镜38一侧的实焦点，远离激光器12。近几年光学领域已经有很多进展，公认的说有很多方法可以有效地聚焦激光束到已知的位置。

In more detail, the laser control means 16 includes computer 40 andscanning system 42. In a preferred embodiment, the computer 40 includes amicroprocessor for controlling the laser 12 and a CAD/CAM system for generatingthe data. In the embodiment illustrated in FIG. 1, a personal computer is used(Commodore 64) whose primary attributes include an accessible interface portand a flag line which generates a nonmaskable interrupt.

激光控制装置16包括计算机40和扫描系统42，推荐的实例中，40包括一个微处理器用来控制激光器12，还有CAD/CAM系统产生数据，这里用了一个个人电脑（Commodore 64），主要包括一个访问接口和一个用来产生非屏蔽中断的标志线。

As shown in FIG. 1, the scanning system 42 includes a prism 44 forredirecting the path of travel of the laser beam. Of course, physical layout ofthe apparatus 10 is the primary consideration in determining whether a prism44, or a plurality of prisms 44, are needed to manipulate the path of travel ofthe laser beam. The scanning system 42 also includes a pair of mirrors 46, 47driven by respective galvonometers 48, 49. The galvanometers 48, 49 coupled totheir respective mirrors 46, 47 to selectively orientate the mirrors 46, 47.The galvanometers 46, 47 are mounted perpendicular to each other such that themirrors 46, 47 are mounted nominally at a right angle to each other. A functiongenerator driver 50 controls the movement of the galvanometers 48 (galvanometer49 is slaved to the movement of galvanometer 48) so that the aim of the laserbeam (represented by the arrows in FIG. 1) can be controlled in the target area26. The driver 50 is operatively coupled to the computer 40 as shown in FIG. 1.It will be appreciated that alternative scanning methods are available for useas the scanning system 42, including acusto-optic scanners, rotating polygonmirrors, and resonant mirror scanners.

图1中，扫描系统42包括一个棱镜44用来改变激光束路径，当然，装置10的物理布局是主要的考虑因素，决定是否需要一个或多个棱镜44来处理光束。扫描系统42还包括一对镜面46和47，分别由检流器48、49驱动，48和49同他们各自的46和47一起，选择性地定向46、47，检流器48和49互相垂直地安置，46和47互相也按直角安装。一个函数发生器50控制检流计48（49随48的运动而运动）的运动，所以激光束的方向（图1中的箭头所示）可以被控制在目标区域26。如图1，驱动器50结合计算机40一起操作，很感激的是有可替代的扫描方法供我们使用如扫描系统42，包括超声光扫描器、旋转多面镜和振镜扫描器。

Turning to FIG. 2 of the drawing, a portion of a part 52 is schematicallyillustrated and shows four layers 54-57. The aim of the laser beam, labeled 64in FIG. 2, is directed in a raster scan pattern as at 66. As used herein,"aim" is used as a neutral term indicating direction, but does notimply the modulation state of the laser 12. For convenience, the axis 68 isconsidered the fast scan axis, while the axis 70 is referred to as the slowscan axis. Axis 72 is the direction of part build-up.

图2中，部件52的一部分大体地描述和显示了4层54——57，图2中激光束的目标点标示为64，以光栅扫描的模式66所示移动，在这里，“目标点”是一个中性词表示方向，但不代表激光器12的调校的状态。为了方便，轴线68可以看做快扫描轴，轴线70代表慢扫描轴，轴线72是部件创建的方向。

Turning to FIGS. 9 and 10, an alternative form of powder dispenser 20 is illustrated.Broadly speaking, a support defines a target area 102 where the aim of the beam64 is directed (see FIG. 1). A hopper 104 dispenses the powder 106 throughopening 108 into the target area 102. A metering roller (not shown) is disposedin the opening 108, such that when rotated the metering roller deposits ametered mound of powder in a line at end 110 of the target area 102.

图9和10中，描述了一个可代替的粉末分发形式20。概括地说，支撑定义一个目标区域102，也是图1中激光束64所指的方向，一个漏斗104通过打开108，分发粉末106到目标区域102，一个带测量的滚筒（没显示）安置在出口108，这样当旋转滚筒，滚筒留下一定量的粉末依次排列到目标区域102的一头110。

A leveling mechanism 114 spreads the mound of powder 106 from end 110 tothe other end 112 of the target area. The leveling mechanism 114 includes acylindrical drum 116 having an outer knurled surface. A motor 118 mounted on bar120 is coupled to the drum 116 via pulley 122 and belt 124 to rotate the drum.

The leveling mechanism 114 also includes a mechanism 126 for moving the drum116 between end 110 and end 112 of the target area. The mechanism 126 comprisesan X/Y table for moving the bar 120 horizontally and vertically. That is, table128 is fixed while plate 130 is selectively moveable relative thereto.

标准的装置114还包括装置126，用来让滚筒116在一端110和另一端112之间区域内移动。装置126包含一个X/Y平面的面板，用来纵向和横向地移动柱子120，所以当平板130选择性地相对往那儿移动时，面板128是固定的。

Still another embodiment is shown in FIG. 11 for controlling thetemperature of the article being produced. Undesirable shrinkage of the articlebeing produced has been observed to occur due to differences between thetemperature of the particles not yet scanned by the directed energy beam andthe temperature of the previously scanned layer. It has been found that adownward flow of controlled-temperature air through the target area is able tomoderate such undesirable temperature differences. The controlled-temperatureair downdraft system 132 of FIG. 11 reduces thermal shrinkage by providing heattransfer between the controlled-temperature air and the top layer of powderparticles to be sintered. This heat transfer moderates the temperature of a thetop layer of particles to be sintered, controls the mean temperature of the toplayer, and removes bulk heat from the article being produced, thereby reducingits bulk temperature and preventing the article from growing into theunsintered material. The temperature of the incoming air is adjusted to beabove the softening point of the powder, but below the temperature at whichsignificant sintering will occur.

图11中是另一个实例用来控制制造物品时的温度。从观察中知道，由于还未被激光束扫描到的颗粒和已经被扫描到的层的颗粒之间的温度差，导致制造物品的不良收缩，而且已经发现，通过目标区域的下行恒温气流可以调节这种不良温度差异。控制温度的下拽气流系统132可以减少热收缩，它提供给定温度的空气与打印件表面一层将被烧结的粉末颗粒之间的热交换，这种热交换调节了打印件表面粉末的温度，控制最上层的平均温度，带走了打印件刚打印的表面热量，降低打印件的体温，避免打印件“增长”到未烧结的材料里。进入气体的温度被调节到粉末软化点之上，但要在有效地烧结温度之下。

The downdraft system 132 broadly includes a support 134 defining targetarea 136, means for directing air to the target area, and a mechanism forcontrolling the temperature of the incoming air, such as resistance heater 142.The air directing means includes chamber 138 surrounding support 134, fan 140and/or vacuum 141. A window 144 admits the aim of the beam 64 (FIG. 1) to thetarget area 136. A powder dispensing mechanism (not shown), such as illustratedin FIGS. 1 or 10 is disposed at least partially in the chamber 138 to dispensepowder onto target area 136.

下拽气流系统132主要包括一个支撑系统134支撑目标区域136，引导气流到目标区域的工具和控制进入空气温度的装置，比如电阻加热器142。气流引导装置包括构建仓138（包围了134），风扇140和（或者）真空装置141。一个窗口144允许光束64（图1）到目标区域136。一个粉末分发装置（未显示），比如在图1或图10里，至少部分地安置在构建仓138里。

Support 134 preferably comprises a filter medium 146 (such as a small-porepaper) on top of a honey-comb porous medium 148. A plenum 150 is disposed forgathering air for passage to outlet 152. Of course, the outlet 152 is connectedto vacuum 141 or other air handling mechanism.

A fundamental concept of the present invention is the build up of a partin a layer-by-layer manner. That is, a part is considered a plurality ofdiscrete cross-sectional regions which cumulatively comprise thethree-dimensional configuration of the part. Each discrete cross-sectionalregion has defined two-dimensional boundaries--of course, each region may haveunique boundaries. Preferably, the thickness (dimension in the axis 72direction) of each layer is constant.

本发明的基本概念是一层层的方式创建部件，就是说，一个部件被看做分离的横截面的集合，逐渐累积组合成部件的三维结构。每一个分离的横截面被定义为二维边界，当然每个横截面有唯一的边界，每层的厚度（在轴线72方向的尺寸）最好是固定的。

In the method, a first portion of powder 22 is deposited in the targetarea 26 and selectively sintered by the laser beam 64 to produce a firstsintered layer 54 (FIG. 2). The first sintered layer 54 corresponds to a firstcross-sectional region of the desired part. The laser beam selectively sintersonly the deposited powder 22 within the confines of the defined boundaries.

用这个方法，粉末22的第一个部分被堆积在目标区域26，并被选择地烧结——激光束64完成第一层54（图2）烧结.第一个被烧结的层对应部件的第一层横截面，激光束只选择地烧结定义的、边界内的堆积的粉末22.

There are, of course, alternative methods of selectively sintering thepowder 22. One method is for the aim of the beam to be directed in a"vector" fashion--that is, the beam would actually trace the outlineand interior of each cross-sectional region of the desired part. Alternatively,the aim of the beam 64 is scanned in a repetitive pattern and the laser 12modulated. In FIG. 2, a raster scan pattern 66 is used and is advantageous overthe vector mode primarily in its simplicity of implementation. Anotherpossibility is to combine the vector and raster scan methods so that thedesired boundaries of the layer are traced in a vector mode and the interiorirradiated in a raster scan mode. There are, of course, trade-offs associatedwith the method chosen. For example, the raster mode has a disadvantage whencompared to the vector mode in that arcs and lines which are not parallel tothe axes 68, 70 of the raster pattern 66 of the laser beam 64 are onlyapproximated. Thus, in some cases resolution of the part can be degraded whenproduced in the raster pattern mode. However, the raster mode is advantageousover the vector mode in the simplicity of implementation.

当然有替代烧结粉末方法22的方法，一个方法是光束以“矢量”的形式引导，就是说光束需要追踪部件的每个横截面内部的轮廓，替代地，光束64的目标重复地扫描，激光器12也被调整。在图2中，使用了光栅扫描模式66.有利于使用矢量模式，主要是实现简单。另外一种可能的方法是，结合矢量和光栅扫描方法，这样可以在矢量模式和光栅扫描内照射模式追踪每层的所需边界，这当然要权衡选择的方法，比如，光栅模式跟矢量模式比较就没有优势，弧形和轴线（与光栅模型66的轴线68、70不平行）只是相近的。在有些情况，在光栅模式生产，部件精度可能会降低。然而，光栅模式的优点是简单和容易实现。

Turning to FIG. 1, the aim of the laser beam 64 is scanned in the targetarea 26 in a continuous raster pattern. Broadly speaking, the driver 50controls galvanometers 48, 49 to made the raster pattern 66 (see FIG. 2).Shifting movement of the mirror 46 controls movement of the aim of the laserbeam 64 in the fast scan axis 68 (FIG. 2), while movement of the mirror 47controls movement of the aim of the laser beam 64 in the slow scan access 70.

图1中，激光束64的目标点扫描在目标区域26，在一个连续的光栅模式。大体地讲，驱动50控制检流计48、49，实现光栅模型66（见图2）。镜面46的移位运动控制激光束64的目标点在快速扫描轴线68（图2）时移动，同时镜面47的运动控制激光束64的目标点在慢扫描过程70的运动。

The present position of the aim of the beam 64 is fed back through thedriver 50 to the computer 40 (see FIG. 3). As described below, in more detail,the computer 40 possesses information relating to the desired cross-sectionalregion of the part then being produced. That is, a portion of loose powder 22is dispensed into the target area 26 and the aim of the laser beam 64 moved inits continuous raster pattern. The computer 40 modulates the laser 12 toselectively produce a laser beam at desired intervals in the raster pattern 66.In this fashion, the directed beam of the laser 12 selectively sinters thepowder 22 in the target area 26 to produce the desired sintered layer with thedefined boundaries of the desired cross-sectional region. This process isrepeated layer-by-layer with the individual layers sintered together to producea cohesive part--e.g. part 52 of FIG. 2.

激光束64的目标点的现有位置通过驱动器50反馈给计算机40（见图3）。如下面描述，计算机40处理与所需的部件横截面相关的信息，并且打印。就是说，松粉22的一部分被分发到目标区域26，激光束64的目标点连续地按光栅模式移动。计算机40调节激光器12，选择性地产生在光栅模型66中所需的所需间隔的激光束。在这个形式下，定向的激光束12选择性地烧结粉末22到目标区域26.这个过程一层层重复，单个的层被烧结在一起生成一个粘结在一起的部件。比如部件52（图2）

Because of the relatively low output power of the laser head 30illustrated in FIG. 1, the powder 22 consisted of a plastic material (e.g.ABS), based on the lower heat of fusion of most plastics, which is compatiblewith the lower power laser. Several post formation treatments are contemplatedfor the parts produced by the apparatus 10 of the present invention. Forexample, if such a produced part is to be used only as a prototype model or asa die for sandcast or lost wax casting, then post-formation treatment may notbe necessary. In some situations, certain surfaces of the parts produced may bedesigned for close tolerances, in which case some post-fabrication machiningwould be accomplished. Alternatively, some types of parts may require certainmaterial properties which can be achieved by heat-treating and/or chemicallytreating the part. For example, the granule size of the powder 22 could be suchto produce a part having an open porosity and epoxy or similar substanceinjected into the part could achieve the desired material properties--e.g.compression strength, abrasion resistance, homogeneity, etc.

因为激光头30（图1）的相对较低的输出功率，粉末22包括塑料材料（比如ABS），基于大多数塑料的低熔解热，与低功率激光兼容，用装置10生产的部件需要考虑部件的几个后成型处理。比如，如果这个部件只被用来做原型模型，或者作为沙铸法或失蜡制作的模子，那么后成型处理一般不需要，在有些情况，有些部件的表面可能设计为很小的公差，那么一些加工后再处理需要实施。代替地，一些类型的部件可能需要某些材料性质，需要通过热处理或化学处理才能达到。比如,粉末22的颗粒尺寸可能是这样的：能够生产出可开孔的、环氧的或者同类物质可注入部件的、能够达到所需材料的性质。比如：抗压强度、耐磨性、均一性等。

Several characteristics of powder 22 have been identified which improveperformance. First, energy absorption by the powder can be controlled by theaddition of a dye such as carbon black. Adjusting the concentration andcomposition of the additive controls the absorbtivity constant K of the powder.Generally, energy absorptivity is governed by the exponential decay relation:

粉末22的几个特性被识别出来以便提高性能，首先粉末的能量吸收率可以被附加的染料所控制，比如碳黑色。调节粉末附加的控制吸收率的常数K的浓度和组成，通常地，能量吸收率控制遵循指数衰减关系式：

where I(z) is the optical intensity (powder per unit area) in the powderat a distance z normal to the surface, Io isthe surface value of I (intensity at the surface), and K is the absorptivityconstant. Adjustment of the absorptivity constant K and adjustment of the layerthickness in which a given fraction of beam energy is absorbed gives overallcontrol of the energy absorbed in the process.

I(z)是表面垂直距离z上的粉末光强度（粉末单位面积），Io是I（表面强度）的表面变量，K是吸收率常量，调节吸收率常量K和调节层厚——粉末层会吸收能量束的一小部分，可以总体控制打印过程的能量吸收。

Another important characteristics of the powder is the aspect ratio of theparticles (i.e. ratio of the particle's maximum dimension to its minimumdimension). That is, particles with certain aspect ratios tend to warp duringshrinkage of the part. With particles having low aspect ratios, i.e. nearlyspherical, part shrinkage is more three dimensional, resulting in greater warp.When particles with high aspect ratios are used (e.g. flakes or rods) shrinkageprimarily is in a vertical direction reducing or eliminating warping of thepart. It is believed that high aspect ratio particles have greater freedom toaccommodate bonding and interparticle contact is preferentially oriented inhorizontal planes causing shrinkage to occur primarily in a vertical direction.

另一个重要的粉末特性是粉末颗粒的纵横比（比如：颗粒的最大尺寸与最小尺寸比例）。就是说，有纵横比的粉末会在部件收缩的时候弯曲，低纵横比的颗粒，比如，几乎是圆形的，部件收缩更加三维地，造成更大的弯曲。当颗粒有高纵横比(比如：片状或棒状)，收缩主要在垂直的方向，减少或消除部件的弯曲。高纵横比的颗粒有更高的自由度来调节结合，并且颗粒间优先在水平面方向接触，导致收缩主要发生在垂直方向。

Turning now to FIGS. 9 and 10, the dispensing mechanism 114 has been foundto provide a controlled level layer of powder in the target area 102 withoutdisturbing the part being produced. A metered amount of powder 106 is depositedat end 110 of the target area 102. The drum 116 is spaced away from end 110when the powder 106 is dispensed. In the system illustrated in FIG. 10, theplate 130 and bar 120 (and attached mechanisms) are raised vertically after thepowder is dispensed in the mound. Travel of the plate 130 towards the hopper104 brings the drum 116 into position adjacent the mound of powder lined upalong end 110. The drum 116 is lowered to contact the mound of powder andbrought horizontally across the target area 102 to spread the mound of powderin a smooth even layer. Of course, the precise location of plate 130 relativeto table 128 can be controlled, so that the spacing between drum 116 and targetarea 102 can be precisely controlled to yield the desired thickness to thelayer of powder. Preferably, the spacing between the drum 116 and target area102 is constant to give a parallel motion, but other spacing options are available.

图9和图10,分发器114提供一个在目标区域102的可控的粉末层而不会中断部件打印。分发起分发一定量的粉末106一直到目标区域102的一头110，当粉末106在分发的时候滚轮116被从110拿开。在图10中，当定量的粉末分发后，平台130和柱子120（固定在设备上）被纵向升起，平台130向漏斗104移动时，带动滚轮116到邻近110的位置。滚轮116降低接触到粉末，水平滚过目标区域102，把使粉末光滑平整。当然平台130的精确位置与平板128相关，可以被控制以便滚轮116和目标区域可以被精确地控制，达到需要的粉末层厚度。滚轮116和目标区域之间的空隙最好是常数，即滚轮是平行地在目标区域表面运动。

As the drum 116 is moved horizontally across the target area 102 from end110 to end 112, motor 118 is activated to counter-rotate the drum 116. As shownin FIG. 9, "counter-rotation" means the drum 116 is rotated in thedirection R counter to the direction of movement M of the drum 116 horizontallyacross the target area 102.

In more detail (FIG. 9), the drum 116 is counter-rotated at high speed tocontact the mound of powder 106 along the trailing edge 160. The mechanicalaction of the drum on the powder ejects the powder to the direction of movementM so that the ejected particles fall in the region of the leading edge of thepowder 162. As illustrated in FIG. 9, a smooth, level layer of powder is leftbehind the drum 116 (between drum 116 and end 110) as depicted at 164.

图9中，滚轮116高速反向旋转，沿着后边缘160接触到定量的粉末106。滚轮在粉末上的机械运动，弹出粉末到移动方向M，这样弹出的粉末颗粒落入电源162的前边缘的区域，在图9中，平滑的粉末层留在滚轮116的后面（在116和110之间）如164所描绘的。

FIG. 9 also illustrates schematically that the powder 106 can bedistributed over the target area without disturbing previously sintered powder166 or unsintered powder 168. That is, the drum 116 is moved across the targetarea 102 without transmitting shear stress to the previously built up layersand without disturbing the article as it is being produced. The absence of suchsheer stress permits a smooth layer of powder 106 to be distributed on the fragilesubstrate in the target area, which includes both the sintered particles 166and the unsintered particles 168.

The interface hardware operatively interconnects the computer 40 with thelaser 12 and galvanometers 47, 48. The output port of the computer 40 (seeFIGS. 1 and 3) is directly connected to the laser 12 to selectively modulatethe laser 12. When operated in the pulsed mode, the laser 12 is easilycontrolled by digital inputs to the pulsed gate input of the laser.Galvanometer 48 is driven by the function generator driver 50 to drive the beamin the fast scan axis 68 independent of any control signals from the computer40. However, a position feedback signal from the galvanometer 48 is fed to avoltage comparator 74 as shown in FIG. 3. The other input to the comparator isconnected to the digital-to-analog convertor 76 which is indicative of theleast significant six bits (bits 0-5) of the user port of thecomputer 40. As shown in FIG. 3, the output of the voltage comparator 74 isconnected to the flag line on the user port of the computer 40. When thevoltage comparator determines that the feedback signal from the galvanometer 48crosses the signal from the digital-to-analog convertor 76, the flag line goeslow causing a nonmaskable interrupt. As discussed below, the nonmaskableinterrupt causes the next byte of data to put out on the user port of acomputer 40.

硬件接口可操作地把计算机40和激光器12和检流计47、48互相连接，计算机40的输出口（图1和图3）直接连接到激光器12以便选择性地调节激光器12.当在脉冲模式操作，激光器12很容易地通过数字输入到激光器的脉冲栅极输入来控制。

检流计48由函数发生驱动器50驱动，用来驱动光束快速地扫描轴线68，独立于任何计算机40而来的控制信号。然而，一个从检流计48而来的位置反馈信号，提供给电压校验器74，如图3所示。其他输入到校验器的信号连接到数字-模拟转换器76指示重要的6bits(bits0-5)计算机40的用户端口。如图3所示，校验器74的电压输出链接到计算机40的用户端口标志线，当计算机电压检测到从检流计48而来的信号反馈，与从数字模拟转换器76而来的信号交叉，标志线变低造成不可屏蔽中断，如下面所讨论，不可屏蔽中断造成数据的下一个字节放入计算机40的用户端口上。

Finally, as shown in FIG. 3, the galvanometer 49 driving the aim of thelaser beam 64 in the slow scan axis 70, is controlled by a second digital toanalog convertor 78. The digital-to-analog convertor 78 is driven by a counter79 which increments with each sweep of the aim of the beam 64 in the fast scanaxis 68. The eight byte counter is designed to overflow after 256 scans in thefast scan axis 68 to start a new cycle or raster scan pattern 66.

最后，如图3，检流计49驱动激光束64的光头低速扫描轴线70，由第二个数字模拟转换器78控制。数字模拟转换器78由计数器79驱动，计数器在每次快速扫描轴68的光束头扫描一次就增加一个计数。8字节的计数器在256次扫描后会溢出，以便开始以个新的光栅扫描模式66。

Preferably, the control information (i.e. defined boundaries of thecross-sectional regions) data for each raster pattern 66 would be determined bya CAD system given the overall dimensions and configuration of the part to beproduced. Whether programmed or derived, the control information data for eachraster pattern 66 is stored in the computer memory as a series of eight bitwords. The data format represents a pattern of "on" and"off" regions of the laser 12, versus distance along the rasterpattern 66 traveled by the aim of the beam 64. The data is stored in a "toggle-point"format where the data represents the distance along each raster scan pattern 66where the laser is modulated (i.e. turned from on to off or from off to on).Although a "bit map" format might be used, the toggle point formathas been found more efficient for the production of high resolution parts.

每个光栅模型66的控制信息（比如：横截面的定义边界）数据由CAD系统决定，给定生产部件完整和尺寸和结构数据。无论是编程还是直接拿来的，每一个光栅模型66的控制数据保存在计算机内存，为一系列8bits字节。这些数据格式代表激光器12的“开”和“关”模式，相对于光束64的光方向沿着光栅模式66的距离，数据保存为“切换点”格式，代表每个光栅扫描模式66的距离，同时激光器可以被调校（比如，从开到关或从关到开）。虽然可能会用一个“比特图”格式，而切换点格式在生产更高精度部件时还是更有效。

For each eight bit word, the least significant six bits (bits 0-5)represent the location of the next toggle point--i.e. the next location formodulation of the laser 12. The next bit (bit 6) represents whether the laseris on or off immediately before the toggle point identified in the leastsignificant six bits. The most significant bit (MSB or bit 7) is used forlooping and for controlling the slow scan axis 70 of the aim of the beam 64.Because the Commodore 64 had limited memory, looping was required--it beingunderstood that a computer 40 with more memory would not require looping.

对每8比特字节，低6位bit（bits0-5）代表下一个切换点的位置——例如：下一个激光器12的调节位置，下一个bit（bit6）代表是否在切换点识别前激光器立即被开或关。最高位bit（MSB 或bit7）用来做循环和控制慢扫描轴70上的光束64的方向，因为64的内存有限，所以需要循环——应该明白如果计算机40有更多的内存则不需要循环。

FIG. 6 represents the flow chart for the data metering program. The datametering program is run whenever the flagline goes low causing a non-maskableinterrupt (see FIG. 3). The interrupt causes the microprocessor of the computer40 to retrieve a two byte interrupt vector which points to the location inmemory where program control is transferred at interrupt. As shown in FIG. 6,the data metering program first pushes the registers onto the stack and thenloads the next byte of data into the accumulator. The data word is also outputto the user port with the sixth bit used to modulate the laser 12 (FIG. 3).

图6表示计量数据程序的流程图，计量数据程序每当标志线变低就触发一个非屏蔽中断（见图3）。中断引发计算机40的微处理器收到2byte中断矢量，指向程序转移中断的内存位置。如图6.计量数据程序首先将寄存器入栈，并且调入下一个byte数据到累加器。数据字节也输出给用户端口，通过6bit来调节激光器12（图3）。

As shown in FIG. 6, the most significant bit (MSB or bit 7) of the dataword in the accumulator is examined. If the value of the most significant bitis one, that means the end of the loop has not been reached; therefore the datapointer is incremented, registers are restored from the stack, and the datametering program is exited, returning control to the microprocessor at thelocation of interrupt. If the most significant bit in the accumulator is zero,the data word is the last word in the loop. If the data word is the last wordin the loop, the next bit in memory is a loop counter and the following twobytes are a vector pointing to the top of the loop. As can be seen from FIG. 6,if the most significant bit equals zero (end of the loop) the loop counter(next bit) is decremented and analyzed. If the loop counter is still greaterthan zero, the data pointer assumes the value from the next two memory bytesafter the loop counter, registers are pulled from the stack and program controlreturns to the location of interrupt. On the other hand, if loop counter iszero, the data pointer is incremented by three and the loop counter is reset toten before exiting the program. It can be appreciated that the need for suchlooping is absolved if the memory size of the computer 40 is adequate.

如图6所示，累加器检测到数据字节最高位bit（MSB 或bit7），如果最高位是1，说明循环还没达到结尾，那么数据指针增加，寄存器从堆栈恢复。数据计量程序退出，返回控制到微处理器中断的位置。如果累加器中最高位是0（循环的结尾），循环计数器（下一个bit）被递减分析。如果循环计数仍然比0大，则数据指针假设是下两个内存字节的值，循环计数寄存器从堆栈取出，并且程序控制回到中断位置。另一方面，如果循环计数是0，数据指针递增3，循环计数器复位到10，如果计算机40的内存充足，则这个循环可以免除。

In FIGS. 4 and 5, an example part 52 is illustrated. As can be seen fromthe drawing, the example part 52 assumes an unusual shape in that it is notsymmetrical and would be difficult to fabricate using conventional machiningmethods. For reference purposes, the part 52 includes an outer base structure80 having an interior cavity 82 and a pillar 84 disposed within the cavity 82(see FIG. 4). FIG. 5 shows the part 52 within the confinement structure 28defining the target area 26 illustrated in FIG. 1. As shown in FIG. 5, some ofthe powder 22 is loose, while the remainder of the powder is selectivelysintered to comprise the structure of the part 52. FIG. 5 is shown in verticalsection with parts broken away and outlined in phantom to show the sinteredcohesive portions of the part 52.

FIG. 7 shows a horizontal cross-sectional region, takenalong line 7--7 of FIG. 4. FIG. 7 represents a discrete layer 86 associatedwith the cross-sectional region of the part being produced. As such, thesintered layer 86 of FIG. 7 is a product of a single raster pattern 66 asillustrated in FIG. 2.

For reference purposes, a sweep line through the sintered layer 86 hasbeen labeled "L." FIG. 8 illustrates the software and hardwareinterface operation during the sweep L. The top graph shows the position offeedback signal from the fast axis galvo 48 and the output signal of the firstdigital to analog convertor 76 (compare FIG. 3). The voltage comparator 74generates an output signal to the flag line of the computer 40 every time thefeedback signal and first D/A output signal cross.

In the top graph of FIG. 8, these points are labeled T to represent togglepoints. As can be seen from the bottom graph of FIG. 8, the flag line generatesa nonmaskable interrupt corresponding to each toggle point T. The sixth bit ofeach data word is analyzed and the current state of the laser 12 will reflectthe value. The penultimate graph of FIG. 8 shows the laser modulation signalfor the sweep line L of FIG. 7. The second graph of FIG. 8 shows that ahigh-going edge in the most significant bit will be encountered at the end ofeach sweep of the aim of the laser beam 64 in the fast scan axis 68. As shownin FIGS. 3 and 6, the counter 79 increments on a high going edge, and outputs asignal to the second digital-analog convertor 78 to drive the slow axisgalvanometer 49.

As can be seen from the example illustrated in the drawing, parts ofcomplex shape can be produced with relative ease. Those skilled in the art willappreciate that the part 52 illustrated in FIG. 4 would be difficult to produceusing conventional machining methods. In particular, machine tool access wouldmake the fabrication of cavity 82 and pillar 84 difficult, if not impossible,to produce if the part 52 were of a relatively small size.

In addition to avoiding the access problem, it will be appreciated thatthe production accuracy is not dependent upon machine tool wear and theaccuracy of mechanical components found in conventional machine tools. That is,the accuracy and tolerances of the parts produced by the method and apparatusof the present invention are primarily a function of the quality of theelectronics, the optics, and the implementing software. Of course, heattransfer and material considerations do affect the tolerances obtainable.

Those skilled in the art will appreciate that conventional machiningtechniques require considerable human intervention and judgment. For example, aconventional machining process, such as milling, would require creativity tomake such decisions as tool selection, part segmenting, sequence of cuts, etc.Such decisions would even be more important when producing a control tape for atape control milling machine. On the other hand, the apparatus of the presentinvention only requires the data relating to each cross-Sectional region of thepart being produced. While such data can be simply programmed into the computer40, preferably, the computer 40 includes a CAD/CAM system. That is, the CAD/CAMportion of the computer 40 is given the overall dimensions and configurationsof the desired part to be produced and the computer 40 determines theboundaries for each discrete cross-sectional region of the part. Thus, a vastinventory of part information can be stored and fed to the computer 40 on aselectable basis. The apparatus 10 produces a selected part without set-uptime, part specific tooling, or human intervention. Even the complex andexpensive dies associated with powder metallargy and conventional castingtechniques are avoided.

While large quantity production runs and certain part materialcharacteristics might be most advantageously made using conventionalfabrication techniques, the method and apparatus 10 of the present invention isuseful in many contexts. In particular, prototype models and casting patternsare easily and inexpensively produced. For example, casting patterns are easilymade for use in sand casting, lost wax casting, or other forming techniques.Further, where desired quantities are very small, such as with obsoletereplacement parts, production of such replacement parts using the apparatus 10of the present invention has many advantages. Finally, the use of the apparatus10 may be useful where size of production facilities is a major constraint, suchas on-ship or in outerspace.