Example：
Silica gel mould for automobile lamp housing
Vacuum casting technology is a new technology in the field of rapid prototyping and rapid tooling technology, which is usually used in the manufacture of soft mould. The following is the introduction of vacuum casting technology to manufacture the process of the lamp shell silicone mold.
1 test equipment
The equipment used includes MK-Mini vacuum casting machine, solar electronic balance, silent air compressor, stripping tools and supplies. Mold making materials using silica gel T2 and hardening agent (generally by the proportion of 10:1).
2 silicone molding process
(1) prototype surface treatment
General rapid prototyping forming method of making lights prototype, the laminated section often exist gap or uneven bench marks, usually need anti-seepage treatment, strengthening treatment to improve the prototype of moisture resistance, heat resistance and dimensional stability. At the same time, to clean the prototype surface to improve the smooth degree of the surface. Only the prototype surface is smooth enough to ensure that the smooth surface of the cavity of the silicone model is made, thereby ensuring that the product has a high surface quality and is easy to be removed from the silicone mold.
(2) measurement of silica gel and curing agent, mixing and pumping vacuum
First, according to the prototype (headlight shell) the size and shape of the estimated volume of prototype parts, then calculate the volume of the box type, both subtraction to obtain silica gel volume. According to the silica gel density calculation of silica gel weight and harden agent weight (both ratio is about 10:1), then mixed into the MK-Mini vacuum casting machine in vacuum, which is mainly to remove glue mixing when mixed with air and of the reaction products. Needed to pay attention to in this process is according to the estimate of the prototype size to weigh silica gel to moderate, box volume made too small, can reduce the silica dosage, mold making cost saving, but will the use effect of the influence of silica gel and is not conducive to the silicone rubber mould casting, so that the mold production defects; volume obtained is too large, is not only a waste of silica gel increased cost also increases the difficulty to remove the product from the silicone rubber mould.
(3) select the separation surface, tape and gate
Vacuum casting technology in principle, no matter how complicated the parts, including convex, concave parts, can be formed. The key problem is to correctly and accurately determine the location of the separation surface, because it directly affects the casting products can be successfully mold release and product quality is good or bad. Pouring mouth should locate the resin is equal to of arrival type box of each edge of the path length, like this is advantageous to the pouring, even may dispense with the riser.
The fixed part of the channel position of the pouring mouth is best to use a smooth round bar, which is usually used as a silica gel bar. For the selection of headlight shell bottom surface separation surface, and paste the adhesive tape in the separation surface, and then use the rod to make the gate. Gate position can only choose the end face position, can not choose the upper and lower surface, because this will affect the surface finish and optical properties of the car, thus affecting the quality of the.
(4) the silica gel casting and vacuum curing and drying
The exhaust over the silicone carefully from the side into the box, the silica gel along the side of the box wall into the box, until the prototype parts are not in the silicone. The box into the MK-Mini system, the vacuum again, the purpose is mainly to take off in the casting due to adsorption or by blocking the presence of bubbles in the rubber material. These bubbles have a great impact on the quality of the mold, and the removal of pores and other defects will not be completely generated on the surface of the mold. The time of the exhaust is about 50 minutes, and the silica gel is removed from the vacuum chamber to be dried in an oven to accelerate the hardening of the silica gel.
(5) mold release
After the silicone hardening, the mold can be opened. Before opening, the air is compressed through the pouring opening, so that the mold is separated from the prototype, so the next step is convenient for the next step.
The first wave pen line dividing line in the separation of surface painting, with a knife in a wavy line open mold. Because of the transparency of the silica gel, the cutting process can be clearly seen. Attention should be paid to the separation surface as far as possible, in order to prevent the incision from too far away from the section. In order to prevent the casting of the mold when the dislocation, cutting the mold, the incision should be cut into serrated. Then the prototype is removed by using the releasing tool, remove the residual adhesive tape and the silica gel on the silica gel, and then the silica gel mould of the lamp is made.
Use this mold can produce many color samples but the same shape of the car lamp shell products.
3 production of products
To make the two halves of the silicone membrane with a cover and fix it with a pin. Vacuum first, and then placed in the vacuum casting machine, the pouring port alignment of the funnel mouth, the product materials into the cup Mini casting machine, the starter. The cast, after removed from the mold and drying, curing, and then remove the mold, so that products will be produced. Products can be selected according to the needs of different colors. From the experiment, we can know that the products produced by this rapid tooling technology are not inferior in quality, design, or surface precision, and can meet the requirements of rapid production.
Two, large automobile panel mold rapid system
The traditional method of large automobile die manufacture is first obtained by casting, and then processed by machining method to ensure the size of the mold. The shortcomings of the traditional mold processing methods are: long manufacturing cycle, high cost, reduce the cycle and cost of mold development and become an urgent problem to be solved.
Rapid tooling manufacturing (RT process) is a kind of new technology, the RT technique, one is through rapid prototyping manufacturing (RP) prototype are obtained, by baking free ceramic technology transition from prototype to ceramic, and precision casting casting dimension precision, surface finish good, after polishing treatment to obtain the manufacturing of mould.
RP/RT technology to produce large automobile panel die, the production steps are as follows:
(1) using Pro/E modeling software to make CAD model. MARC nonlinear finite element analysis software was used to analyze the size precision of the solidification process of the casting, and the CAD model was modified.
(2) the LOM Process manufacturing mold punch and die part of prototype, in Yin Hua company m-rpms - II type equipment, using LOM slicing solid manufacturing process, the YHCP-1004 coated paper, to complete the production of the prototype of the convex and concave die and the rest by sand mould manufacturing.
(3) prototype of convex and concave die part of the M-RPMS- II type multifunctional rapid prototyping machine production, contour scanning speed for 300mm / s, grid line speed is 500mm / s, carbon dioxide laser power 35W by YHCP-1004 coated paper, hot pressing temperature of 90 DEG C, total thickness of paper and adhesive layer is 0.1mm-1mm.
(4) using the technology of non baking ceramic conversion technology, the prototype of the mould is converted to the ceramic type, the solidification time is 8-10 minutes, and the surface roughness is Ra0.8-3.2.
(5) a combination of ceramic mold precision casting and lost foam casting technology to produce a convex and concave die (including the working part and other parts).
(6) a simple polishing of the mold casting, polishing, to obtain the required mold.
With the further integration of the global economy, the competition in manufacturing industry is becoming more and more fierce. How to shorten the production cycle and reduce the cost, has become the primary consideration of the manufacturing industry. To improve the development speed of the product and the degree of flexibility of production as a common goal.
At present, China's automobile, home appliances, electronics / communications, light industry and many other industries of the development of new products more and more can not be separated from the rapid tooling technology. For the development of the technology in China, our long-term goal is developed an original short process, high precision, fast molding new materials and new technology, to form China's independent intellectual property rights of rapid molding core technology. The priority is to increase the large and medium-sized, complex shape, durability, high precision metal mold rapid and low cost of manufacturing new processes and new materials development efforts.
Development trend of rapid tooling technology
The rapid tooling technology is produced and developed in the competition with the traditional machining technology. Although in recent years, the high speed milling technology obtained the rapid development, its up to more than 10 million RPM milling speed and good surface accuracy has been greatly improved in the competitiveness of mechanical processing of molding technology, coupled with the electric spark machining technology, resulting in mechanical processing of molding technology become rapid tooling technology powerful competitors. However, in the manufacture of surface with fine shape, the flow channel is complex, as well as the gradient of functional materials and different materials of the surface of the mold and other aspects, rapid tooling technology also has an unparalleled advantage of machining.
And the silica gel mould with lower cost, excellent durability, strong plasticity, corrosion resistance characteristics is more and more popular in making market favor, compared to the use in the mold resin, silicone mold more plasticity and fine degree, compared to steel mold costs are lower, it is more convenient to use. Although mechanical processing of molding technology still has enough competitiveness, but due to the impact of market is getting more and more rapid development of the Internet and information era products tend to personalized, diverse selection of case, silicone mold production will accelerate the model making new pattern.