Direct Molding Method
1.SLS laser powder sintering
The general process is as follows: firstly layer a layer of powder on the substrate, and after pressing the roller, a layer is selectively sintered by a laser. A new layer of powder access paving device is then placed over it, and the next layer of sintering is carried out and repeated until the final part is obtained. At present, there are two commercial SLS processes: one is the Rapid and Tool technology of DTM Company of the United States; the other is the Direct and Tool process of EOS of Germany.
(1) Rapid, Tool process
The process uses laser sintering of the steel powder coated with the binder, the computer scans the scanning path of the laser beam, and the heated and melted binder bonds the metal powder together to form a part having a porosity of about 45%, and is dried. After that, it is placed in a high-temperature furnace for sintering and copper infiltration to form a surface-hardened part. At this time, the upper material of the part is 65% steel and 35% copper. After the post-treatment process such as grinding, the final mold is obtained.
(2) Direct, Tool process
The low-melting point metal is infiltrated into the base metal powder by the sintering process to increase the powder gap, and the dimensional expansion compensates for the sintering shrinkage, so that the final shrinkage rate is almost zero.
2. Photocuring method for making injection molding mold
This is a method of molding an epoxy resin-based photosensitive resin on SL and equipment. It over-scans the surface to be molded with a dense laser beam, ie the laser beam scanning spacing is small, even partially coincident, while the illumination is very uniform. The precision and surface finish of the rapid prototyping parts produced by this method are the best among all current RP methods, so it is commonly used to make the master mold used in the mold making.
The cavity or core of the injection mold is directly produced by this method, and a very good effect is also achieved. It can be used to inject a variety of thermoplastic plastics, even injectable abrasive plastics, with a lifespan of 200 pieces, and the price is moderate. The production time is usually about 2 weeks. It should be noted that the thermal conductivity of the epoxy resin is poor, and although the benefits of using a smaller pressure injection are brought into consideration, the injection cycle problem is also considered.
The 3DP technology developed by MIT has been developed to selectively spray a metal powder onto a metal powder using a nozzle to form a metal powder using a binder. This low-density (approximately 50%) molded part is subjected to binder removal and copper infiltration to obtain a module having a density of over 92%. Its forming thickness is 0.17 mm, so its dimensional accuracy is only ±0.1 mm. The advantage of this method is that the materials that can be manufactured are varied, and this diversity can be embodied in different modules or on the same module. Its size can also be relatively large, geometric shape is arbitrary, the process is simple, it is a relatively promising technology.
Different from the general LOM, it is used to laminate the thin metal sheets directly on the molding machine. According to the CAD model, the laser or water jet method is used to form the contour. Diffusion bonding is used to stack the cut sheets to form pseudo-metal solid parts. Since the thickness of the plate village is large, a step effect is generated, so finishing processing is required.