10-minute quick overview: Cylinder head manufacturing processes, fixtures, and production line technologies

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Repost: The cylinder head is one of the key components of an engine. Although its dimensions are small, its structure is complex; it has thin walls with uneven thicknesses, and there are many areas that need to be processed. In particular, the presence of several planes and hole systems makes processing it very difficult. http://5b0988e595225.cdn.sohucs.com/images/20190122/ebc0d937a77e43a6821f1c710171ad1d.jpeg Analysis of engine head machining technology # |5 Y/ s- S+ p+ Q6 V Among the various machined surfaces on an engine head, the machining accuracy of flat surfaces is generally easier to ensure; however, it is more difficult to achieve the required high precision for the mounting holes, as well as the precise positioning between holes and between holes and flat surfaces. The technical requirements for cylinder head components can be summarized as follows: 1. Shape accuracy and surface roughness of the main planes. The main planes of the cylinder head serve as assembly references and are often used as positioning references during machining; therefore, they should have high degree of flatness and low surface roughness. Otherwise, this will directly affect the positioning accuracy during cylinder head machining, as well as the contact stiffness and relative positioning accuracy when the cylinder head is assembled with the engine block. The flatness of the main planes of a typical cylinder head is between 0.1 and 0.03 mm, while the surface roughness is in the range of Ra 2.5 to 0.63 μm. The perpendicularity of each main plane to the assembly reference plane is 0.1/300.2. As for the accuracy of holes, surface roughness, and the relative positioning of major holes and planes, the dimensional accuracy of holes in a typical cylinder head is IT6; the tolerances for roundness and cylindricity do not exceed half of the hole diameter tolerance, with the surface roughness ranging from Ra 0.63 to 0.32 μm. The precision for the remaining dimensions is IT7 to IT6, and the surface roughness is Ra2.5 to 0.63 μm. The tolerance for the spacing between holes is 0.12–0.05 mm, and the tolerance for parallelism should be smaller than that for spacing; it is generally set at 0.1–0.04 mm over the entire length. The perpendicularity tolerance between the main planes on the same axis, as well as between different main planes, is 0.1–0.04 mm. http://5b0988e595225.cdn.sohucs.com/images/20190122/8066bac75f4d46148f455d8985a32ed3.jpeg▲ Machining requirements and methods for various surfaces of the engine cylinder head; examples of specialized fixtures for use with cylinder heads. To ensure the quality of part machining, it is necessary to design specialized fixtures. The following are examples based on different machining scenarios: ① Precision requirement: ±0.01mm; Machine used: Horizontal machining center; Positioning via pin holes http://5b0988e595225.cdn.sohucs.com/images/20190122/a9b0b96644ff44eaa3462a3112403c8f.jpeg ② Precision requirement: ±0.01mm; Machine used: Horizontal machining center with pin hole positioning and two-station fixture http://5b0988e595225.cdn.sohucs.com/images/20190122/dafe477142874b8e9b0ab7c860f9ae43.jpg ③ Precision requirement: ±0.01mm; Machine used: Horizontal machining center with dual spindles, pin hole positioning, and two-station fixture http://5b0988e595225.cdn.sohucs.com/images/20190122/7f871b6846084519bbfff26ec3533393.jpg ④ Precision requirement: ±0.01mm; Machine used: Horizontal machining center with pin hole positioning; compatible with multiple products http://5b0988e595225.cdn.sohucs.com/images/20190122/5e276381f9ce4b67b75663a3901c9491.jpg ⑤ Product description and features: Precision requirement: ±0.01mm; Machine used: Horizontal machining center with dual spindles, pin hole positioning, and four-station fixture http://5b0988e595225.cdn.sohucs.com/images/20190122/1567d5fabac24c7a8c37d19932cc82e2.jpg Analysis and examples of technical applications in cylinder head manufacturing lines. Currently, in the machining of components such as engine cylinder heads, cylinder blocks, transmission cases, and clutch housings for automobile engines, flexible production lines equipped with high-speed machining centers have largely replaced conventional automated lines. High-speed machining centers have thus become the primary equipment used for machining these engine components. Companies need to consider the entire production line as a whole, with each processing stage needing to align with the future trend toward flexibility. Below is a brief introduction to four types of concurrent processing technologies that can be applied in different production environments. 1. Batch production with basically identical product shapes: Using the same fixtures is the most common approach in production environments. For parts that require machining with holes to allow for clearance, fixtures equipped with quick-change pin systems can be used; alternatively, pins and clamps can be replaced when changing the product model. The advantage of this type of production line is reduced equipment downtime, as well as lower replacement costs. http://5b0988e595225.cdn.sohucs.com/images/20190122/a21e063d86ba4d0f89542e586b7c38d4.jpg2. The product changeover cycle is relatively long: Quick-change fixtures have no special requirements regarding the product’s shape; they are designed specifically for a particular model. The downside is that these fixtures are heavy, making it difficult to replace them. Therefore, it is not economical to use them for products with a shorter changeover cycle. http://5b0988e595225.cdn.sohucs.com/images/20190122/9aa4740ee91448d2b5057ff440278b07.jpeg3. Mixed-product production on the same production line: The tray used in this system provides high flexibility, making it suitable for producing different products together; simply by changing the trays, it is possible to carry out mixed-product production, thus making effective use of the production line’s capacity. The downside is the high initial investment required. http://5b0988e595225.cdn.sohucs.com/images/20190122/6ce88b85f5de46c280dbcab3ccac97cd.jpg4. High frequency of model changes: Zero-point clamping is a solution widely used in German-made vehicles; it allows for high flexibility in the production line even when the engine model changes, as the same zero-point positioning holes can be used to ensure that the products are aligned on the machining equipment, without the need to replace tooling ； If it is not possible to design identical zero-point positioning holes, an adapter plate can also be used to achieve collinear production. http://5b0988e595225.cdn.sohucs.com/images/20190122/343c835ed26f4c73a90c38ed7cfc0b65.jpeg Production line example: Chery Jaguar Land Rover’s production line utilizes the latest pallet processing technology throughout the machining and assembly processes, enabling efficient and rapid switching between the production of various products. http://5b0988e595225.cdn.sohucs.com/images/20190122/eae050f7840f4649a42fca54d3f1c69a.jpg▲Trays are provided as part of the delivery. http://5b0988e595225.cdn.sohucs.com/images/20190122/1c2936ad96384682b24155185188f98e.jpg▲Automated production facilities. At present, there are not many manufacturing enterprises in China that truly possess the capability for flexible production. Taking cylinder head products as an example, as performance requirements increase, the demands on manufacturing processes also become more stringent; everything from the analysis of process details to the selection of processing equipment and even the design of production lines must ensure a high level of reliability and flexibility.