Method of multiphase jet curing
The MJS (Multiphase Jet Solidification) method, a schematic diagram of which is shown in Fig. 13.4, is based on the layered formation of a part by distributing the liquid material over the surface.
Fig. 13.4. Schematic representation of the MJS method:
1 - the melting chamber; 2 - replacement injector system; 3 - the liquid layer; 4 - previous layer
The processed material in the form of a powder in the chamber 1 is heated to a temperature slightly above the melting point and is poured out through the nozzle 2 . The path and speed of the 2 nozzle with the camera 1 is set by the computer. The material 3 poured onto the surface of the workpiece solidifies within a few seconds. In the initial period, he gives warmth to the previous layer 4, heats up and melts it. In this way, the layers of the formed workpiece are permanently joined together.
The temperature control is coordinated so that the molten material covers the surface with a layer of the required thickness. This method has a similarity to the FDM method. The essential difference is in the state of the starting material (powder, not wire) and the feed system.
With the MJS method, parts are made of low-melting metal alloys, high-quality steel, titanium, ceramics due to the processing of powdered mixtures. When manufacturing parts made of low-melting materials, they can be used immediately. When processing powdery high-melting alloys and ceramic materials (with a melting point up to 1300 ° C), the resulting blanks must be further processed.
Technological processes of dimensional processing of forming of details by volume building
The methods just considered can only be referred to the methods of dimensional processing. The actual dimensional processing with the increase in the volume of parts began to appear quite recently and is used in engineering for the time being only for limited tasks, primarily for making foundry and molds. If traditional methods of dimensional processing have been developed and applied (and in many cases unfortunately still continue to be used) based on the use of only human labor and manual control, additive technological processes have become possible solely through computers and related software.
There are several reasons for creating and implementing new methods. The first is the desire to reduce the cycle from the formation of the need for new products to their appearance on the market (due to the shortening of the terms of design and preparation of production). The second is the need to reduce the nomenclature of equipment and accessories for the production of parts. With the use of additive methods, it is realized, and consequently material and financial costs are reduced. The third is the need to reduce the negative impacts on the environment. Emerging methods are more sparing towards the environment than traditional ones. Traditional methods of dimensional processing lead to the formation of waste: chips, spent coolant, worn-out tools that are subject to recycling. Practically no new waste methods are used. The non-fused metal powder can be reused. The fourth reason is the possibility of obtaining an acceptable level of accuracy. The received details have the tolerance up to 0,025 mm, therefore after fast working they are ready for operation.
By now, a whole group of methods have emerged that have their own characteristics and are competing with each other, but with similar goals. In the literature, such integrated technologies have been called accelerated prototyping (Rapid Prototyping). Their main goal is a significant acceleration of design work by creating material models (static prototypes) of future products.
The methods used have their own symbol, consisting of the initial letters of the words that make up the name of the methods of materialization (RP):
• DMD - Direct Metal Deposition - direct deposition of metal;
• LENS - Laser Engineering Net Shaping - formation using a laser engineering network;
• SFP - Solid Foil Polymerization - solid foil polymerization
• SL (SLA) - Stereolithography - a method of stereolithography;
• SLS (LS) - Selectiv Laser Sintering - selective laser sintering;
• SGC - Solid Ground Curing - the main thermal effect;
• BPM - Ballistic Particle Manufacturing - manufacturing using ballistics;
• DLF - Directed Light Fabrication - production by directional light;
• DSPC - Direct Shell Production Casting - direct block fabrication of the shell.
In total, these methods are already over 20 and their number will undoubtedly grow. Let's consider only those that are interesting from the point of view of obtaining finished engineering parts from structural materials (primarily, from metal alloys, ceramics and polymers). Methods that are designed to create models of projected products or burnable models for casting (see Chapter 7) will not be considered.
All methods have a similar logic for constructing a part and principles based on a direct transition from a 3D-CAD image directly to a part without the use of a tooling, tools, process media, etc. A three-dimensional solid body (part) is obtained in a generative way. At the design stage of the product, the image of the part is set analytically, by drawing, by CT scanners or photographs. On this basis, a mathematical three-dimensional model of construction is created; the package of programs allows it to be optimized by some criteria. Further, the model by layer-by-layer build-up materializes (metal, ceramics, polymer, etc.).
Thus, it is common for the methods considered to be a layered construction of a part (similar to building a house of bricks - row by row) from the starting material in the form of a powder (the powders are the same in structure as in the powder metallurgy method). Basically, for the time being, the equipment and software that forms flat layers have been used. Boles promising methods, which laid the construction of layers along a curved surface.
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