CAD technology of cylinder block mold of bfl513 di

2022-10-15
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Bfl513 diesel engine cylinder block mold CAD technology

the design of diesel engine cylinder block casting mold is carried out with pro/engineer. With the help of the visibility, detectability and analyzability of 3D solid composite modeling technology, the difficult problems in mold design are solved. Taking the design of 513 cylinder block as an example, this paper introduces the methods and skills of using CAD technology to model castings, allocate sand cores reasonably and design molds. The convenience brought by 3D CAD technology to the manufacturing industry is beyond the reach of traditional 2D design

with the progress of the times, the development of science and technology and the application of CAD technology. The mold industry has changed from traditional two-dimensional design to three-dimensional design. The application of CAD technology to three-dimensional mold design not only shortens the design cycle, but also improves the mold accuracy and makes the mold structure more reasonable. At the same time, the mold designed by CAD can reduce the times of mold modification, reduce the trial production cost and save the trial production time of new products in the future trial production of castings. Taking pro/engineer software as an example, we will compare the time spent in traditional two-dimensional design and three-dimensional design

Figure 1 uses two-dimensional software for mechanical design

Figure 2 uses pro/engineer three-dimensional software for mechanical design

Figure 1 and Figure 2 are the design and development process and time spent by a domestic 3C product manufacturing company. Obviously, using 3D software to design saves about half the time compared with traditional design

the casting of the cylinder block mold designed by the traditional two-dimensional design method is fat, the dimensional accuracy is low, the appearance of the processed product parts is not beautiful and the weight is large, and the mold is repeatedly modified during trial production, which affects the service life of the mold and virtually increases the development cost of new products. Other core boxes, especially hot core boxes, are designed by traditional design methods, which cannot be processed by ordinary machine tools. If they are processed by NC, manual code programming is required, which is time-consuming and laborious

to sum up, using 3D CAD technology to develop and design cylinder block mold is an advanced method. The following takes 513 cylinder block as an example to introduce the methods and skills of using CAD technology for Casting modeling, reasonable distribution of sand cores and mold design

I. establishment of casting model

analyze the two-dimensional product drawings of cylinder parts and find out their main frame. Using CAD technology, first establish the main frame model of parts, and then establish those functional small models on the main frame (main model). Finally, make Boolean operations between these main models and functional small models to obtain the three-dimensional solid geometric model of cylinder parts. Carry out casting process treatment on the geometric model: add machining allowance on the machining surface, make sharp edges and corners into rounded corners, set up the positioning and clamping process boss used for cold processing, and scale the entire geometric model (most of the simple uses that are easy to convert from metal to plastic have completed the specified shrinkage rate with long glass fiber composites according to the different casting environment, casting methods and casting materials), This design enlarges the geometric model by 1.008 times, as shown in Figure 3

Figure 3 bf8l513 cylinder block casting model designed with pro/engineer three-dimensional software

II. Mold and core design of casting model

traditional casting external mold design and core box mold design are familiar to everyone. Due to the abstraction of two-dimensional engineering drawings and the separation of core mold design and manufacture, it is difficult for the external mold and core box mold made by this old method to reflect the precise effect required by the two-dimensional engineering drawings of the cylinder block after assembly, which will then affect the overall performance of the product

using 3D solid composite modeling technology can solve the problems that are difficult to solve in traditional mold design. The first is the accuracy of the mold cavity. When separating the core of the casting model, the following steps should be taken:

(1) establish a solid cube that can completely contain the casting model in three-dimensional space

(2) take the cylinder block casting model as the tool entity, and perform Boolean subtraction with the target entity cube to obtain an initial core combination entity

(now the material of the chip is silicon 3) use the cutting function in the software to cut the part connected between the core and the appearance into two separate entities (without characteristic parameters), that is, the reverse mold of the sand core assembly and the mold is obtained

(4) according to the molding process of sand core, the combination of sand core is reasonably distributed into several small sand cores, and cores are made respectively. (see Figure 4)

Figure 4 computer three-dimensional simulated sand core assembly drawing

where 1 is the end core; 2 is the first cylinder core; 3 is the second cylinder core; 4 is the third cylinder core; 5 is the fourth cylinder core, which adopts manual resin sand core; 6 is the core of transmission box, which is made of hot core box. The assembly sequence is as follows: put the sand core on the core assembly mould in the order of label, and screw it up with screws

(5) establish a solid cube as described in (1), divide the cube into two parts with the parting surface of the upper and lower mold as the boundary, take the reverse mold of the outer mold of the mold obtained in (3) as the tool entity, and take its corresponding half cube entity as the target entity, and perform Boolean subtraction operation to obtain the initial prototype of the upper model and the lower model of the shape (see Figure 5)

Figure 5 upper and lower models

III. formation of upper and lower templates and mold simulation detection

the upper and lower models generated by Boolean operation are typeset according to the specification and connection mode of modeling equipment, and the tooling connection part is made. According to the requirements of the molding process, install exhaust columns of different quantities and sizes at the appropriate parts of the mold (see Figure 6), and add core forming blocks (see Figure 7) and sand core exhaust columns at the matching parts with the combined sand core, so as to obtain the mold models used in production (see Figure 6 and Figure 7)

upper template in Figure 6

lower template in Figure 7

from the above introduction, it can be seen that the molding mold and sand core mold are obtained from the same casting model, and the corresponding accuracy of its internal cavity and external shape is very high (which can be accurate to more than 0.001mm), thus realizing the accurate parameter conversion of the external surface and internal cavity of the casting in the automatic end face positioning of the mold sample, as well as the reasonable distribution of the sand core in the internal cavity

Boolean subtraction is also used to calculate the upper and lower templates to form the upper and lower cavities (see Fig. 8 and Fig. 9)

figure 8 upper cavity

Figure 9 lower cavity

use the assembly module in pro/engineer to transfer and assemble the assembled integral sand core into the corresponding core base, so as to form a complete simulation mold (see Figure 10). If you want to know the wall thickness of all parts in the mold, you can call the sectioning function in pro/engineer to perform sectioning at the position you want to see. At this time, if the size and shape of a part are inconsistent with the drawing, the design can be tested and modified; Moreover, the casting process parameters, which are considered unreasonable through the inspection of cutting size, can be corrected. However, the traditional design relies on pouring castings for anatomical inspection of castings and using plasticine for wall thickness inspection when closing the box, which will lead to long production cycle, high trial production cost, poor dimensional accuracy, poor surface quality and other disadvantages

Figure 10 computer three-dimensional mold fitting simulation diagram

IV. sand core mold design and selection of mold parameters (taking the transmission box core as an example)

also use the three-dimensional modeling technology of pro/engineer to establish a square solid to completely cover the transmission box core. Taking the square entity as the cutting object and the transmission box core entity as the cutting reference, the Boolean subtraction operation is carried out to obtain a hollow entity, and the inner cavity shape is exactly the same as the external shape of the transmission box core. According to the parting surface of the sand core, divide the solid into upper and lower half molds, and set the draft angle according to the mold starting direction to obtain the upper and lower core boxes (see Fig. 11 and FIG. 12)

Figure 11 upper core box

Figure 12 lower core box

1. Selection of core box exhaust process parameters

the quality of sand core largely depends on whether the core box exhaust is reasonable. Because when shooting sand, compressed air and sand core enter the core box together. If the gas in the core box cannot be discharged in time, the sand core cannot be fully compacted and the surface quality is poor. The exhaust is mainly through three channels: exhaust slot exhaust, gap exhaust and exhaust plug exhaust. The exhaust slot is generally set on the box surface, with a depth of 0.4 ~ 0.6mm, and the outlet end can be expanded to 1mm, with a width of 10 ~ 20mm. Clearance exhaust is to exhaust by using the gap between the core box, the top core rod and the movable block. In order to make the top core rod and movable block slide flexibly under high temperature and facilitate exhaust, the fitting gap between the core box and the top core rod is generally 0.2 ~ 0.3mm, and the fitting gap between the sliding (movable) block and the core box is 0.1 ~ 0.15mm on one side. Exhaust plug exhaust is to set the exhaust plug at the deep recess of the core box. For example, the positioning core head and water outlet hole of the water jacket sand core are equipped with exhaust plugs, and the specifications of the exhaust plugs vary from 6mm to 12mm

2. selection of process parameters of the top core rod and reset rod of the core box

in order to ensure that the top core rod and reset rod have sufficient strength and stiffness, D-top ≥ 10mm, d-complex ≥ 18mm, and the material is T10 (HRC)

3. Selection of core box material and heat treatment requirements

ht250, stress relief treatment, heating to 500 ~ 550 ℃, holding for 4 ~ 8 hours, and cooling to room temperature with the furnace

4. Jointly promote the rapid development of the new material industry. When the core box sand hole mold inclination is

D ≥ 3 °, the sand core can be ejected smoothly

5. determination of the power parameters of the electric heating tube

the power of the electric heating tube is selected according to the quality and productivity of each core box molding sand core. The empirical formula used is:

n=g · q/c

where: n is the power kw of the heating tube of the hot core box; G is the total mass of cores produced per hour, kg/h; Q is the empirical data of heat required for heating and hardening per kilogram of core, which can be taken as 251040j/kg; C is the thermal work equivalent constant (Joule heat per kilowatt hour is j/kw · h)

taking the transmission case core as an example, using the analysis and measurement module in pro/engineer, we can easily know that the total mass of the sand core is 25.65kg (the volume is 13.5dm3, and the density of the sand core is 1.9kg/DM3). According to the production arrangement, if 15 sand cores need to be produced per hour, then g=15 × 25.65=384.75(Kg/h),N=G·Q/C=26.843(KW)。 Based on this, 18 double headed electric heating tubes with a power of 1.5KW were selected

v. conclusion

(1) using CAD technology to develop molds improves the accuracy of castings and shortens the research and development cycle

(2) the data model (casting model) produced in the process of mold CAD development is not only the parameter entity used by the mold, but also the parameter entity used for NC machining. This fundamentally ensures the consistency of the corresponding mold and core and the consistency of design and manufacturing, so as to integrate cad/cam

(3) the application of pro/engineer 3D software has greatly promoted the development of mold CAD technology. (end)

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