In recent years, the production of automotive parts has shifted from manual, low-end manufacturing to automated production. Automotive parts forging involves high production intensity, fast cycles, large batches, and strict requirements for precision and product consistency. As a non-quenched and tempered steel forging, the temperature control during the entire production process of an engine connecting rod directly affects its hardness, microstructure, and mechanical strength. Therefore, achieving automated production is essential.
At QLM FORGING, we have provided many successful production solutions for connecting rod manufacturers. Today, we will share various technical designs for achieving automated production of engine connecting rods.
Process Route Design
Taking into account the factory space, equipment dimensions, and spacing, a fully automated connecting rod production line requires four gantry manipulators and four robots. The weight of the connecting rod forgings ranges from 1 to 5 kg, with the robot model designed to handle 35 kg. The layout of the production line is shown in Figure A.
Automation Process Design
- Material Cutting:
The primary material-cutting equipment includes bar shears and sawing machines. Bar shears have the advantage of no material waste but may cause deformation at the cut, affecting clamping in subsequent processes. Bar shears also have larger length control tolerances. Sawing machines have advantages and disadvantages opposite to bar shears. After a comprehensive analysis, we recommend using a CNC sawing machine for material cutting. - Material Feeding:
The cut billets enter an induction heating furnace. To replace manual labor, we designed an automatic lifting and feeding mechanism (Figure 2) to lift the billets sequentially into the furnace using a red moving plate. The heating equipment is an induction furnace, and heating temperature is a critical parameter. Therefore, we designed an infrared temperature monitoring device at the furnace outlet, connected to the PLC. Billets that are too hot or too cold will be automatically sorted and rejected.
3. Roll Forging:
After the billet reaches the required temperature, it moves to the automatic pusher, which detects the billet and pushes it to the automatic roll forging machine. Once the machine detects the billet, it starts the forging process. The design of the roll forging mold differs from manual production. In the automated line, the connecting rod blanks no longer require clamping heads, saving about 30g of steel per rod. However, this brings a challenge: manual clamping prevents billet rolling, but in automation, positioning must be precise with no rolling. After multiple tests and simulations with VERACAD software, we designed a flat, non-folding billet (Figure 3).
4. Flattening and Pre-Forging:
After roll forging, the billet is transferred to the flattening process by a combination of gantry manipulators and robots. Once flattened, the robot places the billet in the pre-forging die cavity. After forging, the robot transfers the connecting rod to the final forging step. Since robots require clamping space, the rod needs to be ejected to a certain height. Both pre-forging and final forging require ejection, so the mold must include an ejection device to meet automation requirements (Figure 4).
5. Trimming and Hot Straightening:
After pre-forging and final forging, the robot and gantry manipulator transfer the billet to the trimming process. After trimming, the robot transfers the connecting rod to the hot straightening process. The trimming tool is connected to the PLC, and any remaining trimmed material is ejected. The gantry manipulator transfers the trimmed material to the scrap bin.
6. Post-Processing:
Other processes such as heat treatment, flaw detection, and shot blasting require transferring carts and manual operation to transport the material to the equipment for further processing.
Equipment Arrangement and Cycle Time Analysis
After designing the production flow, the equipment was finalized. Next, we analyzed the cycle time for each step, arranging the operation time for each machine to ensure the bottleneck process has minimal delay compared to other processes. The cycle time for the entire process was recorded in Table 1. Based on Table 1, we conducted a cycle time analysis for each piece of equipment. Die forging was identified as the bottleneck process, with its cycle time calculated as:
Tpress = T7 + T8 + T9 + T10 + T11 + T12 + T13 = 16 seconds.
By integrating operations, the R1 robot transfers the billet to the flattening step while spraying graphite in the pre-forging die cavity. Similarly, when the R1 robot transfers the flattened billet to the pre-forging step, graphite is sprayed in the final forging die cavity. This integration saves 6 seconds, reducing the total cycle time to 10 seconds.
We designed a complete PLC control system and position monitoring system for the production line. If any action is incomplete or there is a position error, an alarm is triggered, allowing the automation control personnel to intervene and prevent accidents. Additionally, we designed an infrared safety system around the robots that automatically stops them if personnel approach, ensuring safety.
As the modern automotive industry develops, manufacturers demand greater product quality stability and consistency. In the past, forging environments were harsh, frontline workers were in short supply, and the production process required multiple operators, resulting in high labor intensity. Forging automation ensures product consistency and reduces labor intensity. By optimizing the mold design and using robots to clamp and transfer the hot billets during the connecting rod forging process, the production cycle time has been reduced from 13 seconds to 10 seconds, avoiding inconsistencies caused by human factors. This reduces labor and material costs, improves production efficiency, and guarantees higher product quality.
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