With the progression of science and technology, the market competition is becoming more and more fierce, and the product renewal cycle is getting shorter and shorter, therefore, shortening the development cycle of new products and reducing the development cost are the urgent problems faced by every manufacturer, and the requirement of rapid mold manufacturing comes into being.
Rapid mold making technology includes the traditional rapid mold making technology, such as low melting point alloy mold, electroforming mold, etc., and Rapid Prototyping (RP) for rapid tooling.
Principles and characteristics of rapid prototyping technology
There are many specific process methods of rapid prototyping technology, but the basic principle is the same, that is, the material addition method is the basic method to rapidly transform a 3D CAD model into a 3D solid prototype composed of specific substances. Firstly, a 3D CAD model is obtained in the CAD modeling system, or the shape and size of the entity are measured by measuring instruments and transformed into a CAD model, then the model data is processed and discretized in a plane layering along a certain direction, and then the embryo is processed by a special CAM system for layering forming and stacking into a prototype.
Rapid prototyping technology opens up the way to rapidly manufacture various parts without any tool and provides a new manufacturing means for parts or models that cannot or are difficult to manufacture by conventional methods. It has shown good application prospects in the fields of aerospace, automotive design, light industrial product design, human organ manufacturing, architectural design, mold design, and manufacturing.
In summary, rapid forming technology has the following application characteristics.
1, because rapid forming technology uses the mechanism of transforming three-dimensional shapes into two-dimensional planar layered manufacturing, it is insensitive to the complexity of the geometric structure of the workpiece, thus it can manufacture complex parts, fully reflect the design details, and directly manufacture composite parts.
2, rapid manufacture of molds
①Can manufacture metal molds from die castings with the help of electroforming, arc spraying, and other technologies.
②The rapid manufacturing prototype as a vanishing mold also can be used for batch manufacturing of vanishing molds for precision casting by prototype turning and manufacturing master molds.
③Fast manufacturing of high precision complex master molds for further casting of metal parts.
④Make graphite electrode by prototype, and then process the mold cavity from graphite electrode.
⑤ Direct machining of ceramic cavities for precision casting.
3, application in new product development, through the prototype physical model, the designer can quickly assess the feasibility of a design and fully express its conception.
①Shape design. Although CAD modeling systems can view the design model of a product from all directions, they are in no way as intuitive and visible as the prototypes obtained from RP, especially for complex shapes. Manufacturers can use conceptual prototypes as a promotional tool to sell their products, i.e., they can use RP prototypes to quickly allow users to compare and evaluate the new products they develop and determine the optimal appearance.
②Checking design quality. Taking mold manufacturing as an example, the traditional method is to open the mold on a CNC machine according to the geometric shape, which is too risky for expensive and complex molds, and any carelessness in the design may cause irreparable damage. Using RPM technology, the parts to be die-cast can be accurately manufactured before the mold is opened, and various subtle problems and errors in the design can be seen at a glance on the model, greatly reducing the risk of blind mold opening. the model made by RP can also be used as a CNC copy milling machine against the mold.
③ Functional inspection. Using prototypes to quickly perform functional tests of different designs to optimize product design. For example, the design of a fan, etc., can obtain the best fan blade surface and the lowest noise structure.
4, rapid forming process room is highly automated, long time continuous, simple operation can do day and night unattended, once the machine is turned on, can automatically complete the whole workpiece processing.
5, the manufacturing process of rapid forming technology does not require the input of tooling, and its cost is only related to the operating cost of the forming machine, material cost, and operator's salary, and has nothing to do with the batch of products, which is suitable for the manufacturing of the single piece, small-batch, and special and new trial products.
6, reverse engineering in rapid modeling has a wide range of applications. Laser 3D scanners, automatic tomography scanners, and many other measuring devices can quickly measure the internal and external contours of objects with high precision and convert them into CAD model data for RP processing.
RP-based Rapid Tooling Technology
In the field of rapid prototyping technology, the most rapidly developing and obvious growth of production value is Rapid Tooling, RT technology. By applying Rapid Prototyping technology to make Rapid Tooling RP+RT, we can greatly improve the success rate of product development, effectively shorten the development time and reduce the cost by conducting new product trials and small batch production before the final production mold.
RP+RT technology provides a new concept and method of manufacturing molds directly from mold CAD models, which integrates the conceptual design and machining process of molds within one CAD/CAM system, creating good conditions for the application of parallel engineering. RT technology adopts RP multi-loop, rapid information feedback design, and manufacturing method, combined with various computer simulation and analysis means, forming a set of A new mold design and manufacturing system.
The manufacturing of rapid tooling using rapid prototyping technology can be divided into two categories: direct rapid tooling manufacturing and indirect rapid tooling manufacturing.
1, Direct Rapid Tooling Manufacturing
Direct rapid tooling manufacturing refers to the direct fabrication of a mold using different types of rapid prototyping techniques, followed by some necessary post-treatment and machining to obtain the required mechanical properties, dimensional accuracy, and surface roughness of the mold. Currently, the rapid prototyping processes that can directly manufacture metal molds include selective laser sintering SLS, shape deposition manufacturing SDM, and 3D Welding.
Direct rapid mold manufacturing links are simple and can more fully exploit the advantages of rapid forming technology, especially in close combination with computer technology, to quickly complete mold manufacturing. For those injection molds that require complex shapes and internal runner cooling, the use of direct rapid mold manufacturing has advantages that cannot be replaced by other methods.
Production injection molds can be produced in 5-10 days using the SLS direct rapid mold manufacturing process.
2, Indirect Rapid Tooling Manufacturing
Using rapid prototyping master mold and pouring soft materials such as wax, silicone rubber, epoxy resin, or polyurethane, it can constitute a soft mold. The mold life of the injection mold made with this synthetic material can be up to 50-5000 pieces.
A hard mold can be made by combining a rapid prototyping master mold or a soft mold with traditional processes such as investment casting, ceramic precision casting, electroforming, or cold spraying, which can produce plastic or metal parts in bulk. Hard molds usually have better machinability and can be partially machined for better accuracy and can be embedded with inserts, cooling parts, and sprue, etc.
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