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CNC Machining of Foam Model for Automobile Die Casting Parts

Essai Industries Co.,Ltd | Updated: Mar 29, 2018

Based on the foam model CNC machining required for solid casting, it has a uniform and accurate margin, and the overall appearance of the mold is good. This lays the foundation for the full-program process of the automotive mold, so the full-program process of foam is the future development. direction.

Due to the non-uniform foam balance used in the traditional hand-made automobile mold casting parts, which has a great impact on the efficiency of mold processing, and parts omission phenomenon occurs from time to time, thus affecting the overall quality of the mold and the production cycle, so the use of CNC processing The status quo has been improved to a great extent, laying a solid foundation for the full-programming processing of automotive molds.

3D foam processing flow

● Data preparation

Before the processing, it is necessary to carefully analyze the acquired digital models. The data loss caused by data conversion of different software should be confirmed and repaired. In general, the property of the foam model data should be an entity. Therefore, the data obtained must be converted into entity attributes by surface stitching before other productions.

●Coloring

Conscientiously analyze and study the drawing of the mold, extract the information of the processing surface and non-processed surface of the mold from the drawing, and return and classify the obtained information and make corresponding records. For the processing of the surface, such as profile, guide plate surface, insert mounting surface, etc., for coloring confirmation, the coloring process is shown in Figure 2.

● shrinkage

Since the shrinkage rate of foam and molten iron cooling is different, a certain amount of shrinkage ΔX is put on the foam model, and the shrinkage rate ΔX of the foam model is different depending on the material of the cast filler, for example, the material of the cast is For MoCr cast iron, the entire foam model needs to be scaled by (1+ΔX), ie, (1+11/1000=1.011).

● Doing

According to the above-mentioned color of the processing surface, such as the guide plate, the mounting surface of the insert, etc., the surface with relatively regular appearance is processed and retained, and the stepped straight holes that need to be processed and the sharp angle surface appearing at the processing position should be filled. Processing, processing shown in Figure 3.

The specific treatment for the remaining amount has the following aspects:

1, the guide plate, insert mounting surface, back surface, etc. need to do the processing of the remaining surface: these surfaces are made as an offset (such as 10-15mm) margin, and then they are closed, to be materialized deal with.

2, the mold profile, the contour of the margin does not have to use the face of margin to control, due to the offset of the surface and curve is very cumbersome, and can be used to control the CNC program, the mold profile in the program generally 10-12mm balance.

For the mold surface: Generally, if the profile is small and simple, flat, and the undulation is small, put 10mm. For the large profile and large undulations, it is necessary to consider putting more allowance, generally it can be set to 12mm.


3, for the steel cutting edge: generally based on the above profile should be put in the margin plus the amount of cutting into the edge (such as the cutting amount of 5mm, then the edge of the cutting edge profile: 10 + 5=15mm)

Stratification

Foam processing firstly stratifies the 3D model, and the layered processing is very important in the programming and processing of the entire CNC program. Whether or not its splitting position and method is fair is not only related to the efficiency of the entire mold programming, but also to the mold. The quality of the processing has a large degree of influence. Therefore, how to layer the 3D model and summarize the work for a long time, we should consider from the following aspects:

1, according to production conditions: such as numerical control equipment X / Y / Z stroke, cutting tool non-interference length, processing required foam blank size;

2. For each segmentation, consider the convenience of processing, separate as many geometries that need to be processed as possible, and generate as few segmentation layers as possible to ensure the accuracy of the model after each unit layer is bonded;

3. When dividing, it is necessary to produce as few as possible geometries that are difficult or impossible to machine, such as narrow grooves and negative angles.

4. Geometry that cannot be avoided or cannot be processed at one time can be removed. After the machining is completed, the removed geometry is processed separately by CNC, and then the sticking and assembling are performed. Figure 5 is an example of a 3D foam entity delamination.

● CNC side treatment

Due to the delamination of cutting, many loose surfaces may be produced, which will cause some inconvenience to processing. According to the processing characteristics of the foam CNC, a program is generally made for each side, but considering the cutting efficiency, CNC can be made One side of the surface as much as possible to deal with, that is, the same height of the surface or not much difference in processing surface for a one-time processing (step hole, convex table, relief holes).

● Delete negative angle

After segmentation and one-sided processing of the model, the physical properties of the segmented unit are analyzed. For example, the minimum slot width, the depth, the minimum arc radius, and the presence or absence of a negative angle exist when the negative angle exists in the specified area. Then separate the negative angle from the specified area; if the negative angle exceeds the specified area, consider removing it and let the manual repair.

●Design of CNC program

Before NC data, set the main negative coordinates of the divided model, record the machining direction and processing reference, collect the geometric shape of the model, and determine the required foam blank specifications, as shown in Figure 6.

●Tool track

Foam material is different from steel and other metal materials, the material is very loose, and foam mold base is mostly 25-40mm ribs structure, compared to the same thickness of the steel material mold, low strength, in the process, due to difficult to withstand tool cutting The resulting extrusion force can easily cause some thin-walled foam damage, so this requires that in addition to cutting tool edges to be sharp, high speed, feed can not be too fast, the method and skill of doing the tool rail is also related to processing Out of the bubble model quality is good or bad. In general, the following can be considered in the following aspects:

1. Programming of the profile. If the profile is relatively flat and undulating, consider the use of a Zig-Zig parallel toolpath or a three-dimensional offset toolpath. If the profile is complex and the undulations are large, steep and flat areas are guaranteed. The amount of stay is the same, and it can be considered to create a three-dimensional offset toolpath. The two machining methods are shown in Figure 7.

2, for the preparation of the cavity type surface of the program, we must consider the processing of the cavity bottom surface, but also consider the processing quality of the cavity wall, generally consider the processing efficiency and wall quality, can be made into a three-dimensional offset Tool path


3, the preparation of contour, ridge-like procedures do not have to make a three-dimensional bias tool path, because this type of only the requirements of the wall, the other headroom is to be removed, so this path can be used to drive the edge of the road, made a map The tool path shown in 9:

4, in the process of the preparation of the program, in order to die in place, do not make corners and other places left blank residue, some local processing methods.

5, if the hole exists in the surface, you need to do the program processing, then give priority to the hole closed for profile processing procedures, and then consider the hole processing.

6, local processing: In the process of programming, in order to facilitate, some places need to do flexible processing, which requires some places need to be made into a partial tool path, such as step surface, inclined surface, relieve holes, contours, etc.

● Edit tool path

The editing tool path is mainly due to the constraints of certain geometric conditions, and the resulting tool path is disorderly and irregular, which may have a certain impact on the quality of machining. This requires the tool track to be modified and rejected. To ensure that the knife road fair and smooth.

● Confirmation of machining program and generation of CNC program

After completing the preparation of the processing program, the following items must be confirmed as it is the last link to control the quality of the product:

1, processing range, determine the remaining area.

2, the confirmation of the processing allowance, such as 10mm of profile remaining enough.

3, the tool non-interference length and tool size confirmation. According to different equipment control systems, post-processing is performed in the specified file path, and toolpath files are converted into G codes for preparation.

According to the preceding processing information, in order to facilitate the processing, the necessary information shall be provided to the on-site CNC machining staff. In the CNC instruction book, the program name, tool type, tool geometry parameters, processing capacity, and cutting parameter range are generally included. Finished model inspection files, etc.

Conclusion

With the increasing level of modern mechanization, automation, and intelligence, high-tech has become more and more widely used in our production. The era of CNC revolution has come, and the foam model based on solid casting has a uniform headroom for CNC machining. Accuracy, the overall appearance of the mold has a good effect, and lays the foundation for the fully programmed processing of automotive molds. Therefore, full-process foam processing will be the direction of future development. Of course, there are many technical issues in this field that require us to further Exploration and research.