1. Introduction to Integrated Die Casting Process
The melting process can be divided into two main approaches: in-house melting (typically using a melting furnace beside the casting machine) and direct molten aluminum supply. For sprue removal, two options are commonly used: plasma cutting and mechanical trimming. Deburring can be done manually, automatically, or through adaptive grinding. Dimensional control is achieved either through sampling inspection or online reshaping and measurement. Machining can be performed using cutting fluid or minimal quantity lubrication (MQL). Cleaning may or may not be included depending on the application. Assembly options include self-tapping screws, stud welding, riveting, blind rivet nuts, blind rivet studs, and more.
However, due to differences in production conditions across companies, process layouts and configurations vary. In practice, companies often face issues such as high energy consumption during low-production periods, frequent failures and low efficiency of plasma cutting with excessive surface spatter, dimensional instability affecting welding processes, inconsistent deburring results due to part variation, and overly complex assembly processes with too many standard parts. These issues lead to higher equipment failure rates, lower production efficiency, increased energy consumption, and unstable product quality compared to traditional vehicle manufacturing processes.
2. Application and Analysis of Integrated Die Casting Process
2.1 Melting Process Analysis
There are two main sources of molten aluminum for integrated die casting: in-house melting (usually using a furnace next to the casting machine) and direct molten aluminum supply.
In-house melting offers flexibility, allowing production to start on demand and enabling the use of different aluminum alloys for different casting cells. This is especially useful during new product trials and material development. However, during low production periods, maintaining furnace temperature results in significant energy waste. Additionally, remelting aluminum ingots increases energy consumption and metal loss, raising overall costs. Furnaces also require periodic maintenance, typically once a month, leading to production downtime and capacity loss.
Direct molten aluminum supply delivers molten aluminum as needed, reducing energy costs and metal loss. However, transporting molten aluminum is classified as hazardous, which can lead to delivery delays. Moreover, the supply distance is usually limited to within 100 km, requiring a nearby aluminum supply facility.
Based on a cost and quality comparison, direct molten aluminum supply is approximately 400 RMB cheaper per ton than in-house melting, as shown in Table.
When conditions allow, using direct molten aluminum supply not only reduces operational costs but also avoids production interruptions due to furnace maintenance. In terms of quality, centralized refining and slag removal in direct supply systems result in higher aluminum purity compared to intermittent refining in in-house systems.
2.2 Dimensional Control Analysis
Due to the large size of integrated die-cast rear floors, factors such as shrinkage and mold variations can lead to dimensional instability. These variations can cause issues in subsequent processes, such as poor adhesive application, excessive door closing force, and poor fit in the front fender area.
Currently, dimensional control methods include offline gauges, random inspections using blue light or LiDAR, and 100% online measurement of key points. As shown in Figure 2, a photoelectric inspection station uses precise positioning and sensors to measure multiple points simultaneously. This method offers high efficiency, strong data collection capabilities, and automatic pass/fail judgment.
However, measurement alone cannot solve the root cause of dimensional variation. Some companies have introduced reshaping processes, where a reshaping mold is used to correct all parts after casting, improving dimensional consistency. As shown in Figure 3, measurement data from the A-pillar area of a vehicle front floor after reshaping demonstrates improved stability. The reshaping mold can also be adjusted based on mold-specific conditions, and when combined with online measurement, it ensures better dimensional control.
2.3 Deburring Process Analysis
Burrs and flash on die-cast parts can cause serious issues such as damaged wiring harnesses or injuries during assembly. Therefore, removing excess burrs is a critical step in the die casting process.
Currently, manual deburring is widely used due to its low cost. However, it suffers from low efficiency, poor working conditions, and inconsistent quality. To address this, some companies have introduced automated deburring systems, such as robotic milling units shown in Figure 4. However, due to part-to-part dimensional variation, these systems may either overcut or fail to fully remove burrs.
To solve this, adaptive deburring is becoming a preferred solution. Before deburring, parts are measured and compared to a reference standard. Based on the deviation, one of several pre-programmed deburring paths is selected. This allows the system to adapt to each part's geometry, ensuring consistent deburring quality.
2.4 Cleaning Process Analysis
Different companies use different release agents, and machining processes may use either cutting fluid or minimal quantity lubrication (MQL). Depending on the coating adhesion requirements, some choose to include a cleaning step, while others do not.
Currently, companies like Tesla, Xiaomi, and Zeekr use MQL machining without cleaning, which significantly reduces both equipment investment and energy consumption.
2.5 Assembly Process Analysis
Various fastening methods are used in integrated die-cast floors, including stud welding, riveting, blind rivet nuts, blind rivet studs, thread inserts, and self-tapping screws. Most companies currently use manual riveting to ensure flexibility and efficiency.
Some have attempted automated riveting, but due to the tight tolerance (0.02–0.3 mm) between rivets and holes, and the mixing of different CNC parts, issues such as jamming during insertion or removal and short tool life have led to low equipment utilization.
Where possible, stud welding is preferred over riveting and clip installation, as it avoids the need for drilled holes and has a lower per-unit cost. Additionally, integral tapping can replace thread inserts, reducing machining time and part count. As shown in Table 2, tests on M6 and M8 integral threads verified that they meet the performance requirements of thread inserts, as shown in Figure 5.
When thread inserts are necessary, tailless inserts are preferred over tailed ones, as they reduce installation time and tool wear, thereby improving efficiency.
3. Conclusion
This paper analyzes various process routes in key stages of integrated die casting. Under current technological conditions:
- When feasible, direct molten aluminum supply significantly reduces costs and avoids downtime due to furnace maintenance.
- Using reshaping molds and 100% online dimensional measurement ensures dimensional stability.
- Adaptive deburring using measurement data improves both efficiency and quality.
- In assembly, stud welding is more efficient than riveting and clipping. Integral tapping can replace thread inserts for M6 and M8 threads. Tailless thread inserts are more efficient than tailed ones, and manual riveting remains a practical option under current conditions.
These strategies help improve production efficiency, reduce costs, and enhance product quality in integrated die casting applications.
