August 19 Dalian Steel Market Price Quotes
The left side of the page is empty.
Scientific selection of appropriate processing methods and rational numerical control programming in mold manufacturing significantly enhance product quality, reduce the production cycle, and directly contribute to cost savings—such as minimizing tool consumption and maintaining machine tool accuracy. The automotive exterior mold plays a crucial role in determining the visual quality of the final vehicle. Ensuring high-quality outcomes through optimized programming and processing techniques remains a key challenge in the continuous evolution of mold manufacturing.
Automotive exterior molds include components such as the overall side wall, doors, front and rear fenders, hood, roof panel, trunk lid, and side wall molds. Among these, the overall side wall mold is particularly complex to program and process, making it one of the most representative examples in the industry. This paper focuses on the overall side wall mold to explore effective programming and machining strategies for automotive exterior molds.
**Overall Programming Ideas**
When performing roughing operations on large drawing molds, the primary goal is to remove the maximum amount of material in the shortest time, provided that cutting conditions allow. Choosing appropriate CNC programming parameters—such as machining methods, spindle speed, feed rate, step-over, cutting depth, and tool selection—is essential. Especially for roughing, selecting optimal parameters not only ensures efficiency but also reduces tool costs and improves productivity. Before programming, it's important to combine past experience from small-scale complex mold machining to implement partitioned roughing strategies, using multiple methods to optimize the process.
Semi-finishing does not focus on tool marks, so it can be programmed with any partition method as long as feasibility and efficiency are maintained. However, some areas may leave residual material, requiring additional programs to ensure precision during finishing. The choice of finishing methods and parameters directly affects the surface quality of the mold and the subsequent production cycle. It’s advisable to invest more time in early programming to guarantee surface quality and avoid costly rework by fitters due to programming errors.
**Analysis of Die Structure and Machining**
Figure 1 shows the physical structure of an integral side wall punch. Before starting the machining process, confirming the digital and physical coordinate system, material thickness, direction, and surrounding details is critical to prevent costly mistakes caused by simple errors.
If the programming software differs from the modeling software, data conversion issues may arise. For example, during the transfer between CATIA and DELCAM, problems like incorrect cuts, gaps, or unwanted scraps can occur. These issues may not affect general molds, but they have a significant impact on the surface quality of outer cover drawing dies. Therefore, thorough checks and targeted treatments are necessary before proceeding with the machining program.
**Roughing Procedure Preparation**
The overall side wall drawing die has a large surface area, making it more economical to use a rigid CNC machine with a large-diameter tool to ensure efficient machining. In China, due to limitations in casting blank manufacturing and uncertain unbalanced blanks, it's challenging to select appropriate profiling tools for roughing. Using D50mm or D40mm ball-end tools for different roughing areas remains a practical and cost-effective solution in actual production.
**1. Contour Roughing Program**
The contour roughing process can affect tool life, especially when moving from top to bottom. A test program should be used before roughing to ensure proper surface preparation. It’s important to either rough or finish the outline first.
**2. Local Processing and Contour Roughing**
The punch has steep areas around the surface, often processed using contour roughing. However, some flat regions require local processing. If local processing isn't done, the cutting amount may increase abruptly, leading to accidental programming errors. Local parallelism and three-dimensional offset before contouring are essential.
Contour programming results in many tool paths (as shown in Figure 5), but using fast sweeps between passes can minimize lost time. Each layer can be processed at the same height, reducing tool and machine wear, and improving safety and stability.
**3. Three-Dimensional Offset Roughing**
Steep areas are typically processed using three-dimensional offset (see Figure 6). The disadvantage is that each layer may not be at the same height, but the number of lifts is reduced significantly.
Careful checking is required to ensure the three-dimensional offset tool path covers all necessary movements. If not, the reference line or boundary must be adjusted, and the program recalculated to avoid tool collisions.
**4. Parallel Roughing**
After completing the steep areas, the flat top surface can be processed using the parallel roughing method (see Figure 7). The flat area can be divided into three layers for root clearing and line cutting based on retention levels.
Using D50mm ball-end tools for roughing and D30mm for semi-finishing, it's necessary to use a D40 tool to clear the roots after roughing. The root clearing method involves selecting single or multiple passes depending on the depth of the depression.
**Semi-Finishing Program Preparation**
Clearing the roots before semi-finishing (see Figure 8) is essential. Limited by tool length, the program must avoid collisions while ensuring proper cutting angles. Steps include preparing multiple root clearances with D30 ball-end tools, single root clearance, and multi-pen root processing with D20 ball-end tools, followed by semi-finishing with D30 ball-end tools.
**Finishing Program Preparation**
The finishing process includes root clearing with D16 and D10 ball-end tools, semi-finishing with D30, and finally the finishing program (see Figure 10).
The edges of finishing tools are prone to wear, and the steep faces may have a larger margin. To prevent rapid wear, a margin adjustment program should be added. Two solutions exist: using three-dimensional offset milling from top to bottom or cutting and compensating with a complementary cutter. If overcutting occurs due to tool extension or mismatched speed/feeds, the second method is preferred.
Key considerations when using three-dimensional offset for compensation include:
- Prefer milling over other methods.
- Check for collisions and measure tool length.
- Avoid using this method if the tool protrusion exceeds certain limits (e.g., D20 > 110mm, D30 > 145mm).
- Only use this method after semi-finishing.
Overcutting may result from excessive tool extension, improper speed/feeds, or worn blades. Additionally, the finishing process of the convex die is critical for surface quality, and matching empirical parameters like tolerance, step, speed, and feed cannot be overlooked.
**Partition Processing**
To improve efficiency, protect machine tools, save tool costs, and ensure safe cutting during roughing and semi-finishing, it’s better to apply different procedures in different areas. Partitioning allows full use of milling programming techniques.
For the above molds, crush milling is not typical but works well for most pressing rings and flat concave molds. As shown in Figure 11, a three-dimensional spiral roughing approach is applied to the concave model, with 80% of the area processed via crest milling. The part is divided into four roughing zones: outer profile smooth surfaces (areas 1 and 2), middle flat area (area 3), and facade area (area 4). Area 4 can be machined at the same height, but it’s best to use 3D offset from top to bottom.
Sometimes, a single-layer tool path is added at the beginning to avoid excessive cutting in the first pass.
**In Summary**
The automotive exterior mold directly impacts the appearance quality of the final product. Scientifically selecting processing methods and performing rational numerical control programming significantly improves mold quality, shortens the production cycle, and reduces manufacturing costs such as tool consumption and machine tool maintenance. For roughing, combining previous experience with various methods is essential. Semi-finishing should consider feasibility and efficiency, with supplementary programs for large residuals. Finishing requires careful root clearing and blade replacement, with attention to empirical parameters like tolerance, step, speed, and feed.
Servo Press Machine,Electric Cylinder Actuators,Servo Telescopic Linear Actuator,Electric Linear Actuator Cylinder
Suzhou Johnson Automation Technology Co., Ltd. , https://www.cn-johnson.com