Precision casting common problems and solutions: how to ensure high quality castings?
I. Introduction
Precision casting, as an important metal forming process, is widely used in numerous high-end fields such as aerospace, automobile manufacturing, and medical devices. It can produce castings with complex shapes, precise dimensions, and high surface quality, providing crucial component support for the development of modern industry. However, during the precision casting process, due to the involvement of multiple materials, complex process steps, and strict parameter control, various problems often arise. If these problems are not solved in a timely and effective manner, they will not only affect the quality and production efficiency of castings but also may lead to increased costs and delays in delivery time. This article will discuss in detail nine common problems in precision casting, including hammer jamming, injection plunger getting stuck in the gooseneck, abnormal material feeding, cracking of thin-walled die-cast parts, excessive tool wear caused by hard materials, black spots on the polished surface of aluminum die-cast parts, splashing of die-cast metal, anodizing patterns on die-cast parts, and sticking of die-cast mold materials. Practical solutions will be provided for each problem, aiming to help precision casting practitioners better cope with the challenges in the production process and improve the quality and production efficiency of castings. Meanwhile, we will also introduce the outstanding contributions of EATHU in the field of precision casting, demonstrating how it relies on advanced technology and rich experience to assist enterprises in solving these problems and promoting the development of the precision casting industry.
II. Hammer Jamming
(I) Problem Description
During the precision casting process, hammer jamming is one of the relatively common problems. When the hammer cannot move normally, it will cause the entire die-casting process to be interrupted, seriously affecting production efficiency. Hammer jamming usually manifests as the hammer suddenly stopping during its movement and being unable to continue the injection action, or it cannot operate normally when starting.
(II) Cause Analysis
High Temperature: Continuous production for a long time or improper setting of die-casting parameters may lead to excessively high temperatures of the hammer and sleeve. High temperature will reduce the hardness of metal materials and increase their ductility, making them prone to deformation. During the frequent reciprocating movement of the hammer, due to high temperature, thermal expansion occurs, which may reduce the clearance between the hammer and surrounding components, resulting in jamming. Moreover, high temperature may also cause changes in the microstructure of metal materials, reducing their strength and wear resistance, further increasing the risk of hammer jamming.
Impurity Adhesion: Poor quality of the alloy materials used, containing impurities, is another important cause of hammer jamming. During the die-casting process, impurities may enter the mold cavity along with the alloy liquid, and some impurities will adhere to the surface of the hammer. Over time, these impurities will gradually accumulate, changing the surface shape and roughness of the hammer and increasing the friction with other components, eventually leading to hammer jamming.
(III) Solutions
Temperature Control: During the production process, high-precision temperature measuring equipment such as thermocouple thermometers should be equipped to regularly measure the temperatures of key components such as the hammer and sleeve. Based on the measurement results, adjust the die-casting process parameters in a timely manner, such as reducing the die-casting speed and shortening the single die-casting time, to reduce heat generation. Optimize the design of the mold cooling system to ensure that the cooling channels are unobstructed and improve the cooling efficiency. The circulating water cooling method can be adopted, and the flow rate and temperature of the cooling water can be adjusted according to actual needs to enable the hammer and sleeve to work within an appropriate temperature range.
Material Selection: Select high-quality alloy materials with extremely low impurity content. When purchasing raw materials, strictly check and require suppliers to provide quality inspection reports of the materials to ensure that they meet the requirements of precision casting. Conduct sampling inspections on the incoming alloy materials and adopt advanced detection methods such as spectral analysis to detect their chemical compositions and impurity contents. If the impurity content exceeds the standard, promptly negotiate with the suppliers to replace the materials or take corresponding purification measures.
(IV) EATHU's Solutions and Advantages
EATHU has unique technologies and rich experience in solving the problem of hammer jamming. The company adopts an advanced temperature monitoring and control system, which can accurately monitor the temperatures of the hammer and sleeve in real time and automatically adjust the cooling parameters according to the preset temperature range to ensure that the temperature is always maintained at the optimal state, effectively preventing hammer jamming caused by high temperature. In terms of material selection, EATHU has established long-term cooperative relationships with high-quality raw material suppliers, strictly screens alloy materials to ensure their purity and quality. Meanwhile, EATHU has a professional material testing laboratory equipped with advanced spectrometers and other equipment to conduct comprehensive inspections on each batch of incoming materials to ensure that the materials meet high-standard requirements, reducing the risk of impurity adhesion from the source and providing reliable material guarantees for precision casting.
III. Injection Plunger Getting Stuck in the Gooseneck
(I) Problem Description
When the injection plunger gets stuck in the gooseneck, the die-casting machine cannot perform the injection operation normally, resulting in production stagnation. This situation usually occurs during or after the die-casting process, and the injection plunger cannot be smoothly withdrawn from the gooseneck, seriously affecting production efficiency and the normal service life of the equipment.
(II) Cause Analysis
Equipment Temperature Change: During the die-casting process, the equipment generates a large amount of heat, causing the temperature to rise. After the die-casting is completed, the equipment starts to cool down. If the cooling speed is uneven, it may cause uneven thermal expansion and contraction of the components. Due to the different thermal expansion coefficients of the materials of the gooseneck and the injection plunger during the temperature change process, the clearance between them may change, resulting in the injection plunger getting stuck in the gooseneck.
Mechanical Failure: After long-term use, the surfaces of the gooseneck and the injection plunger may have mechanical damages such as wear and scratches. These damages will destroy the flatness and smoothness of the component surfaces, increasing the resistance to the movement of the injection plunger in the gooseneck and easily leading to the injection plunger getting stuck. The failure of the equipment's lubrication system may also be one of the reasons. If the lubrication is poor, the friction between the injection plunger and the gooseneck will increase, accelerating the wear of the components and also increasing the possibility of the injection plunger getting stuck.
(III) Solutions
Normal Temperature Treatment and Component Replacement: When the injection plunger gets stuck in the gooseneck, first wait for the equipment to cool down to normal temperature. In the normal temperature state, try to turn the hammer with tools. If it can be turned, carefully remove the hammer and check whether there are damages on its surface and inside the gooseneck. If the hammer cannot be turned, it is necessary to replace the sleeve so that the hammer can be taken out. When replacing the sleeve, ensure that the size and quality of the new sleeve meet the requirements.
Material Pot Replacement (Quick Solution): If you want to quickly solve the problem of the injection plunger getting stuck, replacing the material pot is an effective method. As an important component in the die-casting process, the internal structure and working state of the material pot directly affect the movement of the injection plunger. Replacing the material pot can eliminate possible internal blockages, wear and other problems, enabling the injection plunger to resume normal movement. After replacing the material pot, it is necessary to debug and test the new material pot to ensure that it cooperates well with other components of the equipment.
(IV) EATHU's Solutions and Advantages
EATHU has developed an intelligent temperature adjustment and early warning system for the problem of the injection plunger getting stuck in the gooseneck. This system can monitor the temperature changes of the equipment during and after the die-casting process in real time, predict the thermal expansion and contraction of components through precise algorithms, and adjust the cooling strategy of the equipment in advance to ensure that the clearance between the gooseneck and the injection plunger is always within a reasonable range, effectively avoiding the jamming phenomenon caused by temperature changes. In terms of mechanical failure prevention, EATHU adopts advanced surface treatment technologies and high-performance lubricating materials to conduct special treatments on the gooseneck and the injection plunger, improving their surface hardness and wear resistance and reducing the occurrence of wear and scratches. Meanwhile, EATHU's equipment maintenance team regularly inspects and maintains the equipment's lubrication system to ensure good lubrication, reduce friction, extend the service life of components, and provide stable and reliable equipment guarantees for production.
IV. Unable to Feed Material after Casting Dozens of Molds and Need to Wait for Several Minutes before Continuing
(I) Problem Description
During the die-casting production process, there is a situation where it is impossible to continue feeding material after casting dozens of molds, and it is necessary to wait for several minutes before being able to feed material normally again. This intermittent feeding failure not only affects production efficiency but also may lead to unstable quality of castings because there may be slight changes in die-casting parameters each time the material is fed again.
(II) Cause Analysis
Nozzle Blockage: The state of the top of the material feeding head can reflect whether there is a nozzle blockage problem. If the top of the material feeding head is all gray in cross-section, it usually indicates that the injection nozzle is blocked. The reasons for the blockage of the injection nozzle may be the accumulation of impurities in the alloy liquid at the injection nozzle or the too low temperature of the injection nozzle, resulting in poor fluidity of the alloy liquid and solidification and blockage inside the injection nozzle.
Improper Die-Casting Parameters: The unreasonable setting of the injection nozzle temperature may be one of the factors causing the problem. If the injection nozzle temperature is too low, the alloy liquid is prone to solidify when passing through the injection nozzle, causing blockage. Moreover, if the time for the alloy liquid to leave the nozzle is too long, the residence time of the alloy liquid in the injection nozzle will increase, increasing the risk of solidification. In addition, if the cooling water flow rate of the fixed mold is too large, the mold temperature will be too low, further affecting the fluidity of the alloy liquid and promoting the occurrence of nozzle blockage.
(III) Solutions
Temperature and Time Parameter Adjustment: Moderately increase the temperature of the injection nozzle to improve the fluidity of the alloy liquid in the injection nozzle and prevent it from solidifying and blocking. This can be achieved by adjusting the power or temperature setting value of the heating equipment. At the same time, reduce the time for the alloy liquid to leave the nozzle by 0.1 to 0.2 seconds to reduce the residence time of the alloy liquid in the injection nozzle. Appropriately reduce the flow rate of the cooling water of the fixed mold to increase the mold temperature and improve the filling conditions of the alloy liquid. However, be careful not to over-adjust to avoid affecting the cooling and forming quality of the castings. After adjusting the parameters, closely observe the feeding situation and further optimize it according to the actual effect.
Impurity Cleaning and Prevention: Regularly clean the impurities in the injection nozzle and the material barrel. Special cleaning tools such as cleaning needles can be used to remove the impurities accumulated in the injection nozzle. Meanwhile, strengthen the refining treatment of the alloy liquid to remove impurities and reduce the possibility of impurities entering the injection nozzle. During the production process, pay attention to keeping the production environment clean to prevent impurities from mixing into the alloy liquid.
(IV) EATHU's Solutions and Advantages
EATHU applies an advanced intelligent die-casting control system to solve the feeding problem. This system uses built-in sensors to monitor the temperature of the injection nozzle, the fluidity of the alloy liquid, and various parameters in the die-casting process in real time. It can automatically adjust parameters such as the temperature of the injection nozzle and the time for the alloy liquid to leave the nozzle according to the actual situation to ensure the stability and continuity of the die-casting process. In terms of impurity cleaning, EATHU has developed efficient alloy liquid refining equipment and processes, adopting multi-stage filtering and impurity removal technologies to effectively remove tiny impurities in the alloy liquid and reduce the risk of nozzle blockage from the source. In addition, EATHU's production environment management system strictly controls the cleanliness of the production workshop, adopts measures such as enclosed production areas and air purification equipment to prevent impurities from mixing into the alloy liquid, providing a good environmental guarantee for stable feeding.
V. Easy Cracking of Thin-Walled Die-Cast Parts
(I) Problem Description
When producing thin-walled die-cast parts, cracking is prone to occur, which seriously affects the quality and qualification rate of the products. Cracking may occur on the surface, inside or at the edge of the casting, manifested as obvious cracks. These cracks will reduce the strength and sealing performance of the casting, making it unable to meet the usage requirements.
(II) Cause Analysis
Material Problems: The use of unqualified materials or improper material compositions may lead to cracking of thin-walled parts. For example, if the proportion of alloy elements in the material is inappropriate, it may affect its mechanical properties, resulting in insufficient toughness and making it prone to cracking during the die-casting process. If the use of recycled materials is not properly controlled, it may also introduce impurities or change the performance of the material, increasing the risk of cracking.
Mold Problems: Poor mold design is one of the important reasons for the cracking of thin-walled parts. Unreasonable design of the mold cavity, such as uneven wall thickness and too small transition fillets, will cause stress concentration during the solidification process of the casting, thus triggering cracks. Poor surface quality of the mold, such as the existence of sand holes and pores, will also affect the forming quality of the casting and increase the possibility of cracking.
Improper Selection of Process Parameters: An excessively high proportion of waste materials will affect the quality of the alloy liquid, resulting in unstable performance and increasing the possibility of cracking. If the mold holding time is too long, the casting will be subjected to excessive shrinkage stress in the mold, making it easy to produce cracks. If the ejection delay is too long, the casting will be subjected to additional stress during the ejection process, which may also lead to cracking.
(III) Solutions
Material Control: Strictly follow the original material ratio for batching and avoid using too much recycled material. For key thin-walled part products, try to select high-quality virgin materials as much as possible to ensure the stability of the chemical composition and performance of the materials. When using recycled materials, conduct strict screening and treatment to control their impurity content and performance fluctuations.
Mold Optimization: Optimize the design of the mold to ensure that the wall thickness of the mold cavity is uniform and the transition fillets are reasonable. During the mold manufacturing process, strengthen quality control, adopt advanced processing technologies and detection methods to ensure good surface quality of the mold without sand holes, pores and other defects. Regularly maintain and repair the mold to timely repair the worn and damaged parts.
Process Parameter Adjustment: Try to control the proportion of waste materials not to exceed 30% and conduct classified management and pretreatment of waste materials to ensure their quality stability. Determine the mold holding time reasonably according to the wall thickness of the casting. Generally, the mold holding time for each millimeter of wall thickness is controlled at about 3 seconds. Optimize the ejection system and shorten the ejection delay, generally controlling it between 0.5 and 2 seconds to reduce the stress impact on the casting during the ejection process.
(IV) EATHU's Solutions and Advantages
EATHU has outstanding technical strength in the die-casting of thin-walled parts. In terms of material control, EATHU cooperates with professional material research institutions to deeply study the relationship between material composition and the performance of thin-walled parts and develops high-performance alloy materials specifically suitable for the die-casting of thin-walled parts. These materials have excellent toughness and fluidity and can effectively reduce the risk of cracking. In terms of mold design and manufacturing, EATHU has an experienced mold design team, which uses advanced mold design software for simulation analysis to optimize the mold structure, ensure the reasonable design of the mold cavity and the optimization of transition fillets. Meanwhile, EATHU adopts high-precision CNC processing equipment and advanced mold surface treatment technologies to ensure the quality of the mold. In terms of process parameter optimization, EATHU's intelligent die-casting process optimization system can automatically adjust parameters such as the proportion of waste materials, mold holding time and ejection delay according to the characteristics of different thin-walled part products to achieve precise control and improve the quality and qualification rate of thin-walled part products.