DIRECT METAL LASER SINTERING is rapid prototyping additive manufacturing technology. This technology was invented and patented by Pierre Ciraud in the 1970’s and EOS of Germany.
This method fabricates metal prototypes directly from Computer Aided Design (CAD) file. Powders of numerous compositions of metals or polymers can be used as a raw material. Based on our experience of working with Fused Deposition Modeling (FDM) further step is taken towards understanding and identifying some of the important physical parameters and constraints in DMLS.
Data from CAD file is prepared by slicing the 3D model and is fed to the system. High power laser then scans 2D layer, fusing the metal powder. The process is repeated until whole part is generated.
The Direct Metal Laser Sintering is an accustomed technology. It is rapid prototyping and additive manufacturing technology as parent technology. It enables user to produce a complex geometry part of almost any metal composition.
DMLS is considered as the new industrial revolution which will going to take over the existing manufacturing methods. But building machine using this technology is not an easy work.
Basically the most difficult thing to carry out will be,
Designing of Machine would be difficult and time consuming task.
Achieving desirable temperature inside the powder bed.
Finding wanders for supplies of various machine part would be difficult.
Also machine components like laser will be very expensive.
So some of the common obstacles includes:
- Cost overruns
- Designing of Machine
- High power requirement
- Fragile machine component
- High maintenance cost
- Scope and Objective of Project
DMLS Machine has got an abundant amount of scope. It can produce metal part of highly complex geometry in approximate no time compare to conventional process used for manufacturing.
Manufacturing accurate products without using any conventional machining process.
It can be used for manufacturing a unique product.
Time taken for manufacturing product is negligible.
Different metal composition parts can be produce easily.
Almost no or very less machining is needed to carry after the metal is produce.
It can be used widely for research work, in aerospace technology, in jewelry manufacturing industries and many more.
It can vividly use by Bio-Technology for research and development of complex part related to medical.
Complex design part production.
Prior Art Search/Literature Review
Material properties and fabrication parameters in selective laser sintering process
Authors: Ian Gibson and Dongping Dhi
Rapid Prototyping Journal 1997
This paper comprehensively analyses the relationship between powder properties, fabrication parameters and the mechanical properties of SLS parts. Experimental results and investigation show that the mechanical properties of SLS parts are influenced by powder properties and fabrication parameters. To satisfy the requirements of applications, post-processing methods to improve mechanical properties are also discussed.
When preparing to build RP parts in a Sinterstation, many fabrication parameters are needed in the software. To achieve optimum quality, these parameters are set differently according to powder properties and requirements of application. It is therefore important to understand the relationship between the fabrication parameters and powder properties.
- Part bed temperature (Tb): The temperature at which the powder in the part cylinder is controlled. Before the laser scanners move, powder in the part cylinder will be heated to part bed temperature. Tb is used for reducing laser power and distortion in the sintering process.
- Fill laser power (P): The power available from the laser beam at part bed surface. This parameter should be set to ensure that the powder at part bed surface will be heated close to Tm during scanning. The maximum laser power of Sinterstation 2000 is 50w.
- Scan size (SS): The distance that scanners move in one time step with the laser on. This parameter determines laser beam speed.
Beam speed (BS) = SS*17.22 (mm/sec)
- Scan spacing (SCSP): The distance between two neighboring parallel scan vectors. If scan spacing is too great, the cross-section may not be completely sintered. It is related to the laser beam size and energy density (defined later).
- Slice thickness (h): The depth that the part piston lowers for each layer, which determines powder thickness of each layer in the part cylinder. A stair-step effect is caused by slice thickness. The range of slice thickness in the Sinterstation 2000 is from 0.07mm to 0.5mm. The default setting is 0.1mm.
Direct selective laser sintering of metals
Authors: Mukesh Agarwala, David Bourell, Joseph Beaman, Harris Marcus and Joel Barlow
Rapid Prototyping Journal 1995
Sintering or bonding between particles during SLS occurs by raising the temperature of the powder above the softening or melting temperature by a laser beam heat source. Similar to other laser assisted material processing techniques, success of SLS depends strongly on adequate absorption or coupling of the laser energy.
Parameters Material properties
- Laser scanners Surface tension
- Laser power Particle size distribution
- Mechanical layering of powder Particle shape
- Atmospheric control Absorptivity/reflectivity
- Air flow Thermal conductivity
- Heaters (bed temperature) Specific heat
- Laser type Melting temperature
Scan vector length
These issues, outlined in Table above, are universal to SLS processing and have been discussed in greater detail elsewhere. Most of these parameters have the same influence on SLS processed metal parts as they do on polymer parts. However, surface tension and viscosity have a somewhat more significant role in determining successful processing of metals by direct SLS.
During SLS, the entire thermal cycle occurs locally very quickly, so rapid sintering is necessary. The duration of the laser beam on any powder particle is short, typically between 0.5 and 25ms. Therefore, bonding or sintering must occur speedily, in the order of seconds. This is achieved by viscous flow or by melting.
Metals do not have a softening phenomenon but rather have a generally much higher melting temperature. Therefore, a melting-solidification approach is used for SLS processing of metals. Early attempts to process single phase metals with congruent melting points were unsuccessful, and an approach in which only partial melting is achieved was employed.
As the laser power increased or the laser scan speed decreased, the amount of energy absorbed by the powders under the laser beam increased, causing a larger degree of melting and increasing the sphere diameters.
For a given laser power, the density of the SLS bronze-nickel parts increased as the scan speed decreased. Also, the density was found to increase with increasing laser power, at a constant scan speed. Higher density is achieved with slower scan speed and higher laser power due to an increased amount of energy input to the powder surface.
Method for Manufacturing a Metallic or Ceramic component by Selective Laser Melting Additive Manufacturing
Authors: Pavlov Mikhail
Additive manufacturing has become a more and more attractive solution for the manufacturing of metallic or ceramic functional prototypes and components. For example, SLM and SEBM (selective electron beam melting) methods use powder material as base material. The powder is molten by laser or electron beam. According to a CAD model there is a powder layer deposition and the desired object is built on a platform. That means the component or article is generated directly from a powder bed by a layer wise manufacturing.
Conventional scanning strategies, as they are applied in all SLM machines nowadays, use centro-symmetrical laser spot configurations providing uniform irradiation conditions in all scanning directions. Melting of powder material is realized by (often at least partially overlapping) parallel laser passes, so-called tracks. During the additive manufacturing process, powder in the selected area where subjected to laser radiation is molten into the desired cross section of the part.
The present invention relates to the technology of high-temperature resistant components, especially hot gas path components for gas turbines. It refers to a method for manufacturing a metallic or ceramic component / three-dimensional article by selective laser melting (SLM) additive manufacturing technology.
It is an object of the present invention to disclose a method for entirely or partly manufacturing a metallic or ceramic component/three-dimensional article by SLM additive manufacturing methods with an improved production rate and without a need for implementing more powerful lasers. It is also an object of the invention to disclose such a method without a need for implementing a new hardware on the SLM machine.
Direct Selective Laser Sintering of Metals
Authors: Suman Das
A method of fabricating a fully dense, three-dimensional object by direct laser Sintering is disclosed. In a chamber with a partial pressure atmosphere, a beam of directed energy melts metallic powder in order to form a solid layer cross Section. Another layer of powder is deposited and melted, along with a portion of the previous layer. The energy beam typically is in the form of a laser, Scanning along a path resembling a parametric curve or another, arbitrary piecewise parametric curve.
In the preferred embodiment, the laser does not follow the traditional raster Scanning path. Rather, the laser employs a continuous vector (“CV”) mode of scanning, which allows each individual motion Segment to take place in an arbitrary direction, but treating Successive Segments as part of a continuous path. This invention is adaptable to produce almost any Single layer or multi-layer three-dimensional metal part.
Prior to this technology, conventional methods were used for manufacturing complex shapes. Considering complex geometrical shapes it has some limitations, which is addressed very well in this new technology.
The present invention solves many of the problems associated with known part production methods. By using the techniques described above, fully dense metal components can be formed by Direct SLS. These techniques are also useful for fabrication of integrally canned shapes for SLS/HIP processing. An integrally canned shape can be thought of as composed of four distinct regions: the bottom “end cap, the top “end-cap” the skin, and the interior powder core.
Laser sintered titanium alloy and direct metal fabrication method of making the same
Authors: Clifford C Bampton
In this method, a layer of titanium alloy powder is spread on the bed. There after a laser beam is scanned on the powder layer. This fuses the metal powder together. Iteratively, whole 3D component is made. Basically, main components are laser system, CAD software, titanium alloy etc. Laser is used to melt the powder and fuse it together and CAD software is used to generate desired shape component. Titanium alloy is used as raw product. In this process, initially command is sent to spread powder layer of certain thickness. Thereafter, command to laser is transmitted to scan the powder layer, which fuses the powder in solid form.
A method for Selective Sintering a powder, comprising the Steps of:
Spreading a layer of a powder blend on a platform.
A titanium base metal or an alloy and an alloying metal having a lower melting temperature than that of base metal.
Directing an energy beam onto selected areas of powder blend layer and thereby melting alloying metal.
And re-Solidifying alloying metal by withdrawing energy beam from powder blend layer, and thereby binding base metal or alloy with alloying metal.
In situ absorptivity measurements of metallic powders during laser powder-bed fusion additive manufacturing
The effective absorptivity of continuous wave 1070 nm laser light has been studied for bare and metal powder-coated discs of 316L stainless steel as well as for aluminum alloy 1100 and tungsten.
The experiments were carried out in a custom-built chamber with a suit of diagnostic tools with access to the melt pool as well as the ability to apply a controlled atmosphere and adjust the flow rate of the protective argon gas used.
At first, the laser absorption measurements with flat steel discs in the absence of metal powder are presented. The absorptivity dependence on power for a scanning speed of 500 mm s?1 is shown in figure below. The curve can be divided into three regimes. At low laser power, the absorptivity slightly increases with power from 0.29 to 0.31 (regime I). At an apparent critical power threshold, a sharp increase in absorptivity is observed to values over two times that at low power (regime II), and finally it saturates at about 0.78 (regime III).
Cross-sections of the tracks show a sharp increase in melt depth when the absorptivity rises from 0.3 to 0.78. The molten region in the cross-sections is the final frozen melt pool shape, but it does not reveal how such a deep region of melting occurred.
Grbl is a no-compromise, high performance, low cost alternative to parallel-port-based motion control for CNC milling. It will run on a vanilla Arduino (Duemillanove/Uno) as long as it sports an Atmega 328.
It accepts standards-compliant g-code and has been tested with the output of several CAM tools with no problems. Arcs, circles and helical motion are fully supported, as well as, all other primary g-code commands. Macro functions, variables, and most canned cycles are not supported, but we think GUIs can do a much better job at translating them into straight g-code anyhow.
Marlin is an open source firmware for the RepRap family of replicating rapid prototypes – popularly known as “3D printers.” It was derived from Sprinter and grbl, and became a standalone open source project on August 12, 2011 with its Github release. Marlin is licensed under the GPLv3 and is free for all applications.
Creo is a family or suite of Computer-aided design (CAD) apps supporting product design for discrete manufacturers and is developed by PTC. The suite consists of apps, each delivering a distinct set of capabilities for a user role within product development.
Creo runs on Microsoft Windows and provides apps for 3D CAD parametric feature solid modeling, 3D direct modeling, 2D orthographic views, Finite Element Analysis and simulation, schematic design, technical illustrations, and viewing and visualization.
SolidWorks is a solid modeling computer-aided design (CAD) and computer-aided engineering (CAE) computer program that runs on Microsoft Windows. SolidWorks is published by Dassault Systems.
Ultimaker Cura works by slicing the user’s model file into layers and generating a printer-specific g-code. Once finished, the g-code can be sent to the printer for the manufacturing the physical object.
Cite this essay
Development of Direct Metal Laser Sintering Machine. (2019, Dec 19). Retrieved from https://studymoose.com/development-of-direct-metal-laser-sintering-machine-essay