The application and precautions of core shooting machines
The core shooting machine is the core equipment used in the modern foundry industry for rapid and large-scale production of sand cores. It obtains a sand core with precise dimensions and high strength by shooting the core sand at high speed into a heated core box and making it harden rapidly.
The following is a detailed analysis of the main applications of core shooting machines and crucial precautions.
I. Main Applications of Core Shooting Machines
The core shooting machine is mainly applicable to the core-making process (hot core box method) that uses coated sand (resin sand). The sand cores produced by it are used to form complex inner cavities, holes or fine external structures of castings.
1. Applicable process
Hot core box process: This is the most classic and primary application of core shooting machines. Use coated sand (quartz sand with a layer of phenolic or furan resin coated on the surface). The core box is heated to approximately 200-280° C. Under the effect of heat, the coated sand injected melts, cross-links and solidifies within tens of seconds, forming a high-strength sand core.
The core box process: The principle is similar, but the core box temperature is lower (about 150-180°C), and special furan resin is used. The curing speed is slightly slower, but the quality of the sand core and environmental friendliness are better.
Cold core box process: Although there is also a "shooting" action, it is usually completed by a dedicated cold core box shooting machine. It causes the resin to cure instantaneously by blowing in amine gas (triethylamine) after sandblasting. The equipment structure and environmental protection requirements are quite different from those of the hot core box core shooting machine.
2. Application industries and products of core shooting machines
Core shooting machines are particularly suitable for the production of sand cores in large quantities, with high precision and complex structures.
Automobile manufacturing industry
Engine: Cylinder block, cylinder head water jacket core, oil passage core, crankcase core. This is the most advanced application field of core shooting machines, with extremely high requirements for the dimensional accuracy and surface finish of the sand core.
Gearbox: The inner cavity sand core of the housing and valve body.
Braking system: Brake calipers, brake disc cores.
Plumbing hardware and pipe fittings
There is a huge demand for the inner cavity sand cores of various valves, pipe fittings and connecting parts.
Construction machinery and agricultural machinery
Sand cores for hydraulic components, pump bodies and casings.
Other foundry fields:
Any cast iron, cast steel or aluminum alloy castings that require complex inner cavities can be cored by a core shooting machine.
3. Core advantages
High efficiency: Short cycle time (usually 20 to 90 seconds), capable of fully automatic continuous production.
High precision and high surface quality: High injection pressure, dense sand core, precise dimensions, smooth surface, thus achieving fewer burrs in the inner cavity of the casting and accurate dimensions.
High degree of automation: It is easy to achieve the automated connection of subsequent processes such as core sampling, core assembly, dipping coating, and drying.
Low labor intensity and relatively improved environment: Compared with traditional manual core-making, it has a higher degree of mechanization and enclosure.
Ii. Precautions for the Use of Core Shooters
The operation of the core shooting machine involves high temperature, high pressure, moving parts and chemical gases. It is necessary to strictly follow the procedures to ensure personal safety, equipment stability and product quality.
(1) Safety Precautions:
High-temperature protection
The core box, heating plate and surrounding components are at extremely high temperatures (above 200°C). It is strictly forbidden for any part of the body or flammable substances to come into contact with them. The equipment must be equipped with complete heat insulation protective doors and covers.
Before opening the protective door for maintenance, cleaning or adjustment, it is necessary to confirm that the heating has been turned off and wait for a sufficient period of time for the mold to cool down.
The removed hot sand cores should be placed on dedicated cooling trays or conveyor belts to prevent scalding and fire.
High Voltage and Mechanical Safety
During sandblasting, the pressure in the gas storage tank and pipelines is very high (usually 0.4-0.7 MPa). It is strictly prohibited to disassemble the airway components or carry out maintenance under pressure.
The actions of the core shooting machine such as mold closing, mold opening and core ejection are driven by hydraulic or pneumatic power, which is extremely powerful. Make sure your hands stay away from the mold closing area when the equipment starts up. Strictly follow the operating procedures for the two-hand start button.
Regularly inspect the hydraulic system, cylinders and pipelines to prevent oil leakage or pipe burst.
Electrical safety
The grounding of the core shooting machine must be reliable. Before repairing the electrical part, be sure to cut off the main power supply and lock it with a sign.
The heating system has a large power, and the circuits and components are prone to aging, so regular inspections are required.
Chemical and dust safety (especially cold core boxes) :
Hot core box: When the coated sand is heated, it will produce a small amount of smoke containing phenol and aldehyde. There must be a powerful dust collection and exhaust system above the equipment to lead the waste gas to the outside or to the treatment device.
Cold core box: The catalyst used (such as triethylamine) is toxic, flammable and explosive. The equipment must have excellent sealing performance and be equipped with an efficient exhaust gas scrubber (neutralization device). Gas leakage alarms need to be installed in the working area.
The core-making area should be well-ventilated and operators should wear appropriate protective masks.
(2) Precautions for the operation and process of the core shooting machine
Mold (core box) preparation and maintenance:
Preheating: New molds or those that have been out of use for a long time must be preheated slowly and thoroughly (usually for several hours) to prevent deformation or cracking caused by sudden temperature rise.
Cleaning and spraying of mold release agent: After each cycle, the residual sand on the parting surface of the core box and the nozzle should be cleaned with an air gun. Regularly and evenly spray mold release agents (such as silicone oil emulsion) to prevent mold sticking, but excessive application will affect the surface quality and size of the sand core.
Regular maintenance: Check whether the top rod, slider and guide column are worn or stuck, and lubricate them in time. Keep the exhaust plug unobstructed.
Optimization of sandblasting process parameters for core molding machine
Sandblasting pressure and time: Insufficient pressure can lead to loose sand cores and insufficient strength. Excessive pressure may damage the mold or cause "sand running" (sand ejecting from the parting surface). The optimal value needs to be found based on the shape and complexity of the sand core.
Curing time and temperature: Both temperature and time jointly determine the degree of curing. The time is too short, the sand core is "underbaked", and its strength is low. If the time is too long, the sand core will be overburned, its surface will turn black and become brittle, and the production efficiency will be reduced. The optimal process window needs to be determined through experiments.
Raw material control
The quality of coated sand: The particle size, resin content, fluidity and melting point of the sand must be stable and meet the requirements. Sand that has become damp and lumped must never be used.
Sand temperature: It is recommended to preheat the coated sand before use (such as to 25-40°C), which can significantly improve its fluidity and uniformity of curing.
(3) Maintenance and upkeep of core shooting molding machines
Daily inspection: Check the air source pressure, oil level, whether there are any abnormal noises from moving parts, whether the bolts are loose, and whether the safety devices are effective.
Regular maintenance
Seal replacement: The sealing rings of the sand injection valve and each cylinder are vulnerable parts and need to be replaced as planned to prevent air and oil leakage.
Cleaning and lubrication: Thoroughly clean the accumulated sand inside the equipment and apply lubricating grease to the moving parts such as guide rails, lead screws, and bearings as per regulations.
Electrical system inspection: Tighten the terminal blocks and check the status of relays, contactors and temperature control instruments.
Maintenance of the sand injection head: The sand injection nozzle is prone to wear and sand adhesion, so it needs to be cleaned, inspected and replaced regularly to ensure the smoothness of the sand injection channel.
Summary
Core shooting molding machines are powerful tools for enhancing the efficiency and quality of casting core production. However, behind their high efficiency lies strict operational requirements and potential risks.
Key application points: Specifically designed for the hot core box process of coated sand, it is suitable for the manufacturing of complex sand cores in large quantities and with high precision, especially in high-end fields such as automotive engines.
Key points to note: "Safety" must be given top priority. Strictly prevent high-temperature burns, mechanical pinches, high-pressure injuries and chemical hazards. Secondly, the quality and stability of the sand core are guaranteed through meticulous mold maintenance, optimization of process parameters and control of raw materials. Finally, implementing a strict preventive maintenance plan is the key to ensuring the long-term reliable operation of equipment and avoiding unplanned downtime.