CN105436406A - Precision lost wax casting technology based on selective laser powder sintering 3D printing - Google Patents

Abstract

The invention discloses a precision lost wax casting technology based on selective laser powder sintering 3D printing. The precision lost wax casting technology comprises the following steps that S101, a target part is subjected to optimal design of a CAD casting technology; S102, selective laser powder sintering 3D printing forming is carried out; and S103, silica sol/water glass precision investment casting is carried out. A wax mold of the part can be fast manufactured without molds, the metal part is fast manufactured, fast manufacturing of complex parts can be achieved, and integration, automation and fastness in the precision casting technology process can be achieved; and the development period of new products are greatly shortened, development cost is reduced, and the precision lost wax casting technology is especially suitable for production of single small-batch complex castings and trial-manufacturing of new products.

Description

Precision wax casting process based on selective laser powder sintering 3D printing

technical field

The invention relates to a casting process, in particular to a precision wax pattern casting process based on selective laser powder sintering 3D printing.

Background technique

3D printing technology is based on the principle of layer-by-layer accumulation of discrete materials. According to the three-dimensional CAD model of the product, it is a digital manufacturing technology that quickly "prints" product prototypes or parts. It integrates computer software, materials, machinery, control, network information, etc. Systematic and comprehensive technology of subject knowledge. 3D printing changes "subtractive material" processing into "three-dimensional printing", turns three-dimensional entities into two-dimensional planes, reduces manufacturing complexity, and frees designers from the constraints of traditional craftsmanship and manufacturing resources, focusing on product form creativity and functional innovation. Under the concept of "design is production" and "design is product", the pursuit of "creation without limit"; in the design of parts and components, the optimal structural design can be adopted without considering processing problems, which solves the problems of traditional aerospace, ships, Difficulties in the manufacture of high-end complex and fine-structure parts for automobiles and other power equipment. At the same time, due to the simplification or omission of process preparation, testing and other links, the digital design, manufacturing and analysis of products are highly integrated, which greatly reduces the cost of product development and innovation and shortens the innovation and development cycle. 3D printing breaks through structural geometric constraints and can produce unconventional structural features that cannot be processed by traditional methods. It is especially suitable for complex structures, personalized manufacturing and rapid verification of innovative ideas. This process capability is helpful for realizing lightweight components and optimizing performance. extremely important. However, the traditional 3D printing-based precision casting process still has many shortcomings. For example, for different types of prototypes, it is necessary to add supports of different specifications, which increases the difficulty of printing and the prototypes are easy to deform, which affects casting efficiency and wastes materials. The conventional wax pouring system needs to manually set the wax stick on the resin prototype of the finished part, which is time-consuming and laborious, and is affected by the pouring system and manual process, it is difficult to ensure the quality and stability of the cast metal parts, which increases the complexity of the process .

Contents of the invention

The purpose of the present invention is to solve the problems mentioned in the background technology section above through a precision wax pattern casting process based on selective laser powder sintering 3D printing.

For reaching this purpose, the present invention adopts following technical scheme:

A precision wax casting process based on selective laser powder sintering 3D printing, comprising the following steps:

S101. Optimizing the design of the CAD casting process for the target part;

S102. Selective laser powder sintering 3D printing;

S103. Silica sol/water glass investment precision casting.

In particular, the step S101 specifically includes:

Establish the 3D model of the target part, pre-scale each part of the overall model of the target part according to a certain size ratio, and directly design the corresponding gating system on the 3D model of the target part, so that the 3D model of the target part and its pouring The system forms an overall model of the target part.

In particular, the step S102 specifically includes:

Convert the overall model of the target part into STL data format, and perform relevant pre-processing, which includes but not limited to the following processing parameter optimization process: part printing direction positioning, data simulation and processing estimation, heating layer identification and slicing processing;

Selective laser powder sintering 3D printing rapid prototyping system for laser sintering 3D printing of the model data that has completed the slicing process;

After the printing is completed, the prototype workpiece of the whole PS material of the target part with unsintered powder is obtained, and the powder cleaning process is carried out;

After the powder cleaning process is completed, the PS material prototype workpiece of the target part is treated with a certain wax temperature in a self-made wax infiltration mechanism, and then dried in a temperature-controllable oven for post-treatment.

In particular, the step S103 specifically includes:

The overall PS material prototype workpiece of the target part is made of silica sol/sodium silicate slurry and sanding layer by layer;

After the shell making is completed, the overall PS material prototype workpiece of the target part is subjected to the shell dewaxing process. After the dewaxing process is completed, the overall PS material prototype workpiece of the target part and its shell are put into a high-temperature roasting furnace for high-temperature roasting;

Take out the shell of the target part after roasting from the high-temperature roasting furnace and pour molten metal into it. After it cools down, perform vibration shelling to remove the hard shell covering the outer surface of the casting;

The gating system is cut off, and then the post-processing of the casting is carried out, and the precision metal casting of the target part is finally obtained.

In particular, the post-processing in step S102 includes sequentially performing unsintered powder removal, wax penetration treatment, drying and surface cleaning.

In particular, in the step S102, the wax temperature should be set according to different thicknesses. When the thickness is uniform or the thickness of the prototype workpiece is less than 10mm, the wax temperature should be set at 65-70°C; when the thickness is between 10-30mm or the thickness is not For uniform prototype workpieces, the wax temperature should be set at 58-63°C; for prototype workpieces with a thickness greater than 30mm or uneven thickness, the wax temperature should be set at 58-60°C.

In particular, the wax infiltration treatment in the step S102 specifically includes: firstly setting the heating temperature to a predetermined value, then breaking the wax and putting it into the wax pool. If the workpiece is not softened by heat, the workpiece will be deformed and collapsed until the prototype has no bubbles, and the prototype will be lifted out of the wax pool at a constant speed.

In particular, drying in a temperature-controllable oven in the step S102 includes: drying the wax model prototype treated with wax penetration in an oven at 65° C. for 10 minutes, and then air cooling.

In particular, in the step S103, the silica sol/sodium silicate paste and sand shell manufacturing includes: every time the paste is applied, a layer of sand is correspondingly sprinkled, and after the previous layer of shell is dried and hardened, the next layer is prepared by paste and sand. layer shell, and except for sprinkling zircon sand as the surface sand after the first grouting, mullite is used for each subsequent sanding, and the silica sol/water glass grouting and sanding process is repeated for 4-6 times, and then Then carry out the silica sol/water glass paste treatment, and the mold shell is completed after it is dried and hardened.

In particular, the dewaxing process of the mold shell in the step S103 adopts water bath-roasting dewaxing, the water temperature is about 90-100°C, the time is 25-30 minutes, and the PS material in the mold shell is removed by roasting, the temperature is 250-280°C, The time is 30-50 minutes to completely disappear the prototype in the formwork; the temperature of the high-temperature roasting furnace for the formwork is 950-1000°C, and the temperature is kept for 2 hours until the formwork is completely sintered and solidified before pouring.

The precision wax pattern casting process based on selective laser powder sintering 3D printing proposed by the present invention can quickly produce the "wax pattern" of the part and quickly produce the metal part without using a mold. It can not only realize the rapid manufacture of complex parts, but also can Realize the integration, automation and speed of the precision casting process, greatly shorten the research and development cycle of new products, save research and development costs, and are especially suitable for the production of complex castings in small batches and the trial production of new products. Compared with the prior art, the advantages of the present invention are as follows: 1) Selective laser powder sintering 3D printing is used to quickly produce target parts, an integral PS prototype with a gating system and a complete wax mold, eliminating the need for wax for complex castings The labor costs and working hours required for mold assembly; 2) The precision size and surface quality of the parts are effectively improved, the accuracy of the wax mold can reach ±0.1, and the manufactured products have high surface gloss and good strength; 3) Traditional Precision wax casting must be molded, and the parts printed by selective laser powder sintering 3D are formed at one time, and no molds are needed in the entire manufacturing process, which not only saves mold manufacturing costs, but also shortens the part manufacturing cycle and improves product development efficiency; 4 ) does not require any supporting structure and can realize rapid precision casting of parts with arbitrary complex structures.

Description of drawings

Fig. 1 is a process flow chart of precision wax pattern casting based on selective laser powder sintering 3D printing provided by the embodiment of the present invention;

2 is a schematic diagram of an overall model of a target part provided by an embodiment of the present invention;

Fig. 3 is the overall cross-sectional view of the target part provided by the embodiment of the present invention;

Figure 4 is a schematic diagram of the overall model of the target part and the pouring system provided by the embodiment of the present invention;

Fig. 5 is a full cross-sectional view of the overall model of the target part and the pouring system provided by the embodiment of the present invention.

detailed description

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field of the invention. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Please refer to FIG. 1 , which is a flow chart of a precision wax pattern casting process based on selective laser powder sintering 3D printing provided by an embodiment of the present invention.

In this embodiment, the precision wax pattern casting process based on selective laser powder sintering 3D printing specifically includes the following steps:

S101. Optimizing the design of the CAD casting process for the target part.

Establish the 3D model of the target part through 3D modeling software, pre-scale each part of the overall model of the target part according to a certain size ratio, and directly design the corresponding gating system on the 3D model of the target part, so that the target part The 3D model and its gating system form an overall model of the target part. In this embodiment, the 3D modeling software can use any one of CATIA, Pro/E, UG, CREO and SolidWorks.

S102. Selective laser powder sintering 3D printing.

Convert the overall model of the target part into STL data format, and import it into the pre-processing software for relevant pre-processing. The pre-processing includes but not limited to the following processing parameter optimization process: part printing direction positioning, data simulation and processing estimation, heating layer Identification and slice processing. Wherein, the pre-processing software adopts 3D model slicing software, and in this embodiment, self-developed HUST-3DP 3D model slicing software is used. HUST-3DP three-dimensional model slicing software is a special supporting software, the main function is two parts of equipment control and data processing, (1), with unique STL file fault-tolerant slicing technology, no need for additional error correction software and manual error correction ;(2) Self-adaptive slicing function: that is, in the part where the slicing section of the part does not change, the computer automatically sets a larger spacing to improve production efficiency; in the part where the slicing section of the part changes greatly, the computer automatically sets a smaller spacing to reduce the step effect , Improve the quality of the parts. (3) Prototype production dynamic simulation and independent development of heat source support technology. Heat source support with adjustable height and interval can be automatically generated according to the shape of the part. The use of heat source support can reduce the temperature of the key layer and make it easier to clean the part. It can prevent warping and deformation during the part manufacturing process and improve the quality of the part. . (4) Spot compensation algorithm with strong error correction function. During the part manufacturing process, in order to ensure the accuracy of the part, spot compensation must be performed. However, small parts or sharp corners of parts are prone to errors when performing spot compensation, resulting in wrong slicing of parts, resulting in processing failure. The spot compensation algorithm of this online slicing software can solve this problem. It should be noted that the positioning of the printing direction of the part does not require any support, no material is wasted, and the unsintered powder can be reused.

Import the model data that has been sliced into the selective laser powder sintering 3D printing rapid prototyping system for laser sintering 3D printing.

After the printing is completed, the prototype workpiece of the whole PS material of the target part with unsintered powder is obtained, and the powder cleaning process is performed to ensure the dimensional accuracy of the prefabricated workpiece.

After the powder cleaning process is completed, the PS material prototype workpiece of the target part is treated with a certain wax temperature in a self-made wax infiltration mechanism, and then dried in a temperature-controllable oven for post-treatment. Among them, post-processing includes unsintered powder removal, wax penetration treatment, drying and surface cleaning in sequence. The wax temperature should be set according to different thicknesses. For prototype workpieces with uniform thickness or thickness less than 10mm, the wax temperature should be set at 65-70°C; for prototype workpieces with thickness between 10-30mm or uneven thickness, the wax temperature should be set The wax temperature should be set at 58-63°C; when the thickness is greater than 30mm or the prototype workpiece with uneven thickness, the wax temperature should be set at 58-60°C, and it is preferably carried out under vacuum. The wax infiltration treatment specifically includes: firstly setting the heating temperature to a predetermined value, then breaking the wax and putting it into the wax pool. The workpiece is deformed and collapsed until no bubbles emerge from the prototype (generally takes 1 to 3 minutes), and the prototype is lifted out of the wax pool at a constant speed. The drying in a temperature-controllable oven includes: drying the wax-patterned prototype in an oven at 65° C. for 10 minutes, and then air-cooling.

S103. Silica sol/water glass investment precision casting.

Wax model tree; for the overall PS material prototype workpiece of the target part, the shell is made of silica sol/water glass paste and sand layer by layer. Silica sol/sodium silicate slurry and sanding shell making includes: every time the slurry is applied, a layer of sand is sprinkled correspondingly, and the previous layer of shell is dried and hardened, and the next layer of shell is made by slurrying and sanding again, and except for the first hanging Sprinkle zircon sand after the slurry as the surface sand, and use mullite sand for each subsequent sanding, repeat the process of silica sol/water glass slurrying and sanding for 4-6 times, and then perform silica sol/water glass sealing. Slurry treatment, after it dries and hardens, the mold shell is completed.

After the shell making is completed, the overall PS material prototype workpiece of the target part is subjected to the shell dewaxing process. After the dewaxing process is completed, the overall PS material prototype workpiece of the target part and its shell are put into a high-temperature roasting furnace for high-temperature roasting. Wherein, the process of dewaxing the mold shell adopts water bath-roasting dewaxing, the water temperature is 90-100°C, the time is 25-30 minutes, the PS material in the mold shell is removed by roasting, the temperature is 250-280°C, the time is 30-50 The prototype in the formwork disappears completely in minutes; the temperature of the high-temperature baking furnace for the formwork is 950-1000°C, and the temperature is kept for 2 hours until the formwork is completely sintered and solidified before pouring.

The shell of the target part after roasting is taken out from the high-temperature roasting furnace and poured with molten metal. After it cools down, the shell is shaken to remove the hard shell covering the outer surface of the casting.

The gating system is cut off, and then the post-processing of the casting is carried out, and the precision metal casting of the target part is finally obtained.

The present invention will be further described below with specific examples. As shown in Figures 2 to 5, the precision wax casting process based on selective laser powder sintering 3D printing in this embodiment includes the following steps:

Use any 3D modeling software such as CATIA, Pro/E, UG, CREO and SolidWorks to carry out CAD optimization design for the precision casting process of the target part model.

Establish a three-dimensional model of the target part. FIG. 2 is a schematic diagram of the overall model of the target part provided by the embodiment of the present invention. 201 in FIG. 2 is the three-dimensional model of the target part, and FIG. The corresponding gating system is directly designed on the 3D model of the target part. According to the structural characteristics of different parts, the corresponding pre-shrinkage treatment is performed on a certain size ratio of parts with different wall thicknesses to ensure the accuracy of the parts during the rapid casting process. The three-dimensional model of the target part and the pouring system constitute a complete target part model. Fig. 4 is a schematic diagram of the overall model of the target part + pouring system provided by the embodiment of the present invention. 401 in Fig. 4 is the pouring system, and Fig. 5 is provided by the embodiment of the present invention The overall model of the target part + full sectional view of the gating system.

Convert the complete target part model completed above into STL data format, and use the self-developed HUST-3DP 3D model slicing software for pre-processing. According to the structural characteristics of the target part, select the best part printing direction to print layer by layer.

The prototypes that have been printed in this example are cleaned of unsintered powder in turn, and the wax infiltration process is performed in a self-made wax infiltration mechanism with a wax temperature of 65-70°C, and the infiltrated wax model prototype is placed in an oven at 65°C Dry for about 10 minutes and then air-cool, and finally perform surface cleaning treatment to ensure surface accuracy.

The overall prototype wax model of the target part is made of silica sol/sodium silicate layer by layer, and a layer of sand is sprinkled for each layer of slurry. After the previous layer of shell is dried and hardened, it is again coated and sanded. One layer of shell, and besides sprinkling zircon sand as the surface sand after the first grouting, mullite is used for each subsequent sanding, so repeat the process of silica sol/water glass grouting and sanding for 4-6 times, Then carry out the silica sol/water glass paste treatment, and the mold shell is completed after it is dried and hardened.

The finished formwork is dewaxed by water bath-roasting, soaked in a bath with a water temperature of 100°C for 10 minutes, and then baked in a furnace at a temperature of 250-280°C for 30-50 minutes to ensure that the PS material of the prototype is fully burned. 950 ~ 1000 ℃ high-temperature baking furnace heat preservation for 2 hours until the mold shell is completely sintered and solidified before pouring.

The technical solution of the present invention is to combine the selective laser powder sintering 3D printing technology with the traditional silica sol/water glass investment casting process, and make a complete wax mold at one time, eliminating the need for wax mold assembly of complex castings. The required labor costs and required working hours; no molds are needed in the whole manufacturing process, which not only saves the mold manufacturing cost, but also shortens the part manufacturing cycle and improves the product development efficiency; effectively improves the precision size and surface quality of the parts, and the wax mold The precision can reach ±0.1, and the manufactured products have high surface gloss and good strength; rapid precision casting of parts with any complex structure can be realized without any supporting structure. The invention can quickly manufacture the "wax model" of the part and the metal part without using a mold, not only can realize the rapid manufacture of complex parts, but also can realize the integration, automation and speed of the precision casting process, greatly shortening the The research and development cycle of new products saves research and development costs, and is especially suitable for the production of single and small batches of complex castings and the trial production of new products.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the present invention The scope is determined by the scope of the appended claims.

Claims (10)

1., based on the accurate lost wax casting technique that the powder sintered 3D of selective laser prints, it is characterized in that, comprise the steps:

S101, target part is carried out to the optimal design of CAD casting technique;

The powder sintered 3D printing shaping of S102, selective laser;

S103, the close casting of Ludox/sodium silicate precision investment.

2. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 1, it is characterized in that, described step S101 specifically comprises:

Set up the threedimensional model of target part, by certain dimension scale, pre-convergent-divergent process is carried out to each position of target part block mold and on the threedimensional model of this target part the direct corresponding running gate system of design, make the threedimensional model of target part and running gate system thereof form a target part block mold.

3. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 1, it is characterized in that, described step S102 specifically comprises:

Convert target part block mold to STL data format, carry out relevant pre-treatment, this pre-treatment includes but not limited to following machining parameters optimization technique successively: part Print direction location, digital simulation and processing is estimated, heat layer identification and slicing treatment;

The model data completing slicing treatment is carried out selective laser powder sintered 3D printing rapid prototyping system and carry out laser sintered 3D printing shaping;

Obtain the target part overall PS material original workpiece with non-sintered powder after having printed, carry out powder process clearly;

Target part after clear powder process being completed overall PS material original workpiece carries out oozing Lasaxing Oilfield in the certain wax temperature of self-control Shen La mechanism, then carries out dry post processing with the baking oven of controllable temperature.

4. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 1, it is characterized in that, described step S103 specifically comprises:

Successively Ludox/waterglass hanging stucco shell is carried out to the overall PS material original workpiece of target part;

After completing shell processed, the overall PS material original workpiece of target part is carried out formwork dewaxing operation, after dewaxing treatment to be done, the overall PS material original workpiece of target part and shell entirety thereof are put in high-temperature roasting furnace and carry out high-temperature roasting;

Taking out completing the target part shell after roasting from high-temperature roasting furnace and casting molten metal liquid, after its cooling, carrying out vibrations shelling, remove the hard shell being coated on cast outer surface;

Running gate system is excised, then carries out foundry goods post processing, final obtained target part precision metallic foundry goods.

5. according to claim 3 based on the powder sintered 3D of selective laser print accurate lost wax casting technique, it is characterized in that, in described step S102 post processing comprise carry out successively non-sintered powder remove, ooze Lasaxing Oilfield, drying and surface cleaning.

6. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 5, it is characterized in that, in described step S102, wax temperature should be arranged by different-thickness, when thickness evenly or thickness be less than the original workpiece of 10mm, wax temperature should be set in 65 ~ 70 DEG C; When thickness is between 10 ~ 30mm or original workpiece in uneven thickness, wax temperature should be set in 58 ~ 63 DEG C; When thickness is greater than 30mm or original workpiece in uneven thickness, wax temperature should be set in 58 ~ 60 DEG C.

7. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 6, it is characterized in that, ooze Lasaxing Oilfield in described step S102 specifically to comprise: first heating-up temperature is set to predetermined value, then wax pond is put into after wax being smashed, oozing Lasaxing Oilfield process answers uniform descent to all immersing wax pond, ensure that prototype does not occur workpiece deformation by thermal softening, caves in, until prototype bubble-free is emerged, at the uniform velocity prototype is proposed wax pond.

8. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 7, it is characterized in that, carry out drying with the baking oven of controllable temperature in described step S102 to comprise: the wax-pattern prototype of oozing Lasaxing Oilfield is placed in the baking oven of 65 DEG C after dry 10 minutes, then Air flow.

9. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 4, it is characterized in that, Ludox in described step S103/waterglass hanging stucco shell comprises: often hang primary pulp hanging and spread one deck sand accordingly, etc. next stratotype shell of hanging stucco system again after last stratotype shell drying sclerosis, and all use Mo Laisha except spreading zircon sand after hanging first as each stucco follow-up except surface layer sand, repeatedly carry out 4-6 Ludox/waterglass hanging and stucco process, and then carry out Ludox/waterglass seal mortar treatent, after its dry sclerosis, shell completes.

10. the accurate lost wax casting technique printed based on the powder sintered 3D of selective laser according to claim 9, it is characterized in that, in described step S03, the technique of formwork dewaxing adopts water-bath-roasting dewaxing, water temperature is at about 90 ~ 100 DEG C, 25 ~ 30 minutes time, the PS material in formwork is removed in roasting, temperature 250 ~ 280 DEG C, and the time is within 30 ~ 50 minutes, make prototype in formwork disappear completely; The temperature of formwork high-temperature roasting furnace is 950 ~ 1000 DEG C, and insulation 2 is little pours into a mould after the fully sintered solidification of formwork.