1 Rapid Prototyping Technology Overview
Rapid Prototyping technology is a high-tech manufacturing technology that was developed in the 1990s of the 20th century. It integrates computer-aided technology (CAD / CAM), laser technology, computer control technology, network technology and other advanced technologies. Using this technology, we can create prototypes quickly and accurately based on digital mold without the need to make molds. It is effective in shortening the development cycle of new products, reducing the costs and risks of product development, producing marketable products of great significance.
Rapid prototyping technology has a high degree of flexibility, highly integrated technology, design and manufacturing integration, speed, free-form production, the use of materials and other characteristics of extensive. At home and abroad is currently widely used in machinery, electronics, household appliances, aerospace, automobiles, motorcycles, toys, medicine, communications and other fields, creating a good social and economic benefits.
2 Rapid Prototyping of The Main Process
At present, the rapid prototyping process can be divided into six types according to the processing method and the material used: SLA, FDM, LOM, SLS, SGC, DSPC.
This article explores how to use the rapid prototyping technology to create a gear chamber sample. Using a method of selective laser sintering and rapid prototyping of foundry sands minus materials to explore the application of rapid prototyping in the foundry.
3 The Application of Rapid Prototyping Technology in Casting
As mentioned earlier, rapid prototyping can produce prototypes. In this case, the 3D model of gear room is first drawn based on CRE02.0 software, and the sand mold and sand core are designed according to the model. According to the shape and structure of the sand mold/sand core, different rapid prototyping methods are selected to obtain the desired sand mold/ sand core, sequentially passing through the core, the grinding box and the pouring process to finally obtain the gear casting casting blank, which does not need the wood mold and the mold, Streamline the development of foundry blanks, shorten the development cycle of foundry blanks, and are particularly suitable for the rapid manufacture of small quantities of complex castings, enabling digital manufacturing in the traditional foundry industry.
3.1 gear room modeling
Gear Room Casting Process
Gear room is one of the important components of the diesel engine, it’s structure is complex. Using CREO2.0 for modeling and design of casting process. According to the process of separation of 7 sand cores and 8 sand molds.
3.2 RAPIDLY MANUFACTURING THE sand MOLD AND sand core
According to the existing equipment, the development of processing plans: We use selective laser rapid prototyping equipment processing part of the sand core; Use subtractive manufacturing equipment to processing the rest of the sand mold, sand core.
3.3 rapid prototyping equipment
3.3.1 Selective Laser Sintering (SLS)
Technical requirements for the coated sand: particle size 50/100 H, particle size concentration ≥ 75%, room temperature tensile strength ≥ 5.0 MPa, temperature resistance ≥ 1.2 MPa, gas production ≤ 14 ml / g. The actual service towel may adjust the process parameters involved in the rapid prototyping process according to the properties of the coated sand, the size, and the structure of the sand mold/ sand core. Mainly laser power and sweep speed, preheat temperature, layering direction, layer thickness, scanning distance and scanning direction, post-processing temperature. To get the required sand mold/ sand core strength and surface accuracy.
Selective laser sintering rapid prototyping method:
The first step is to first create a three-dimensional model in the computer, the model is sliced through a slicing slice, the processed slicing information is stored as a recognizable format of the forming device and entered into a rapid prototyping device, a Forming Device The layer-by-layer laser sintering is identified and based on the layer information.
The second step, sintering. Set the appropriate parameters: Thickness of the powder plaster 0.3mm, the laser power of 40W, the scanning speed of 2000mm / s, the scanning graduation of 0.1mm, preheating temperature of 60 ℃, each paved a layer of sand, the laser produces high-temperature sintering of the sand surface once, coated sand in the role of thermal high-temperature reaction occurs curing. The former repeats the same action until the sand mold (core) is completely sintered.
The third step, post-processing. ① sand cleaning: the sintered sand mold/ sand core mold from the towel to remove the room, using a brush and special tools to clean spare parts on the unreacted sand, polished clean; ② precuring: spray evenly with alcohol burner sand core surface, allowing the sand core in advance for the pre-curing, firing time can not over-burn or local to prevent sand core deformation or cracking; ③ Curing baking: Since only sintered sand mold/sand core also unreacted resin and urotropin, sand mold/sand core hardness is not very satisfactory, so in the pre-curing must also bake. Bake the sand, hardened into the curing box, with a diameter of lmm ~ 2mm glass beads filled sand core, the temperature l80 ℃ ~ 200 ℃, time 4h ~ 16h; Bake hardening Sand core strength will greatly improve; ④ complete sand core machining; Selective laser sintering by rapid prototyping sand core.
Selective Laser Sintering Rapid Prototyping of The Resulting Sand Core
3.3.2 Reduced Material Manufacturing Rapid Prototyping
Technical requirements for foundry suspension sand: grain size 70/140 mesh size, sludge content ≤ 0.3%, grain size concentration ≥ 75%; Resin sand T artificial sand should meet the tensile strength ≥ 1.2 MPa, gas ≤ 14 ml / g.
Rapid prototyping process for material production:
Choosing the resin sand block according to the size of sand mold and sand core to avoid unnecessary waste. The CREO modeling of the sand, the core data is converted into equipment to identify the G-code-driven equipment for processing, the use of special tools in the dry conditions of sandstone processing, sand processing should be removed immediately to ensure the processing. The sand mold/sand core, obtained by rapid prototyping.
3.4 research box, pouring
Before grinding, we should check if the sand mold/sand core size and surface accuracy meet the requirements. Taking into account the larger size of the product, sand mold/sand core more, in addition to the normal use of the box outside the box production process. After repair sand mold/sand core, paint brush, box shape, group core, baking, the box and other processes to get the final mold.
Complete casting, cleaning to get the fast shape of the gear chamber castings.
Gear Room Castings
4 Conclusion
1) Additive Manufacturing: Selective Laser Sintering Rapid prototyping technology is suitable for the production of coated sand cores with a complex structure that is not sensitive to deformation. However, it is still necessary to design the support structure for the locations susceptible to deformation.
2) Reduced material production: The resin mold / core precision and surface quality can meet the production requirements. However, the amount of sand that is eaten and the process gap should be reasonably designed to ensure the strength of the sand mold.
3) The rapid casting technology, which combines the rapid prototyping technology of selective laser sintering and the manufacturing technology of the subtractive material, can realize the direct informal production of a single complex part and obtain accurate product samples. At the same time, a favorable reference for the tool design can also be provided.
