How to choose the tonnage of low-pressure casting machine? Matching algorithm with wheel hub mold

How to choose the tonnage of low-pressure casting machine? Matching algorithm with wheel hub mold
Select the tonnage of the low press machine, first calculate the projected area of the mold, then multiply it by the unit locking force, and finally leave a 20% margin. The lower limit can be determined in three steps.
The projected area is the starting point for calculation
The projection area of the wheel hub mold is calculated based on the maximum outer diameter. The projected area of the mold for 18 inch wheels is approximately 0.20-0.25 square meters, while for 20 inch wheels it is approximately 0.25-0.30 square meters.
The area calculation is incorrect, and everything else is wrong. Some quotations only state the size of the wheel hub and not the outer diameter of the mold, so it is necessary to inquire about the actual size of the template.
The projected area also needs to include the occupation of the gate and exhaust area. The actual value is usually 10% -15% larger than the wheel area.
How to obtain the unit locking force
The filling pressure of low-pressure casting is low, and the unit locking force is often set at 30-50 tons/square meter. Thin walled large diameter parts are taken as high values, while thick walled small parts are taken as low values.
Calculated at 0.28 square meters and 40 tons per square meter, the required clamping force is about 11.2 tons, with an additional 20% margin. The lower limit of the machine is about 14 tons.
This result is only a theoretical value. The actual selection also depends on the size of the press plate and the spacing between the pull rods of the machine. If the mold cannot fit in, no matter how suitable the tonnage is.
The insulation furnace and mold should be counted together
After the tonnage of the machine is determined, the capacity of the insulation furnace should be matched according to the weight of each piece and the cycle time. A single piece weighs 15kg, with a cycle time of 10 minutes, resulting in an hourly aluminum consumption of approximately 90kg.
The furnace capacity is usually taken as the aluminum consumption for 2-3 hours. The capacity is too small, the liquid level fluctuates greatly, and the filling pressure is unstable.
For every 50mm decrease in liquid level, the static pressure head changes by approximately 1.3kPa. For a filling pressure of 0.02-0.08 MPa, this disturbance cannot be ignored.
Constraints on machine height and travel
The total height of the mold must fall between the maximum and minimum mold heights of the machine. Exceeding the range, the pressure plate cannot be tightly pressed or cannot be closed at all.
The mold opening stroke should be greater than the height of the mold plus the space for taking parts. The pick-up space is usually 150-250mm, and automated pick-up requires an additional thickness of the gripper.
Xinfeng Mold will first request four parameters of the customer's machine for the wheel hub mold project: tonnage, pressure plate size, pull rod spacing, and maximum and minimum mold height, before starting the design.
Common selection misconceptions
Misconception one is to choose a machine based on the size of the wheel hub. The outer diameter of molds with different wheel types may differ by 30-50mm for the same 18 inches.
The second misconception is to ignore the weight of the mold. The pressure plate of large tonnage machines has load-bearing limitations, and overloading can cause deformation of the pressure plate.
Misconception three is to only look at the parameters of the new machine. The measured tonnage of old machines is often lower than the nameplate value and needs to be converted by 80% -85%.
How to verify if the selection is appropriate
During the trial molding process, observe the flying edges on the parting surface. The even and thin edge indicates sufficient locking force; Local thick flying edges indicate issues with rigidity or parallelism.
Check if the ejection is smooth again. Insufficient top output is often an indirect manifestation of the mismatch between the tonnage of the machine and the mold.
Run 20 molds continuously and observe the mold temperature and size drift. Excessive drift may be caused by insufficient rigidity of the machine, resulting in elastic deformation.
Frequently Asked Questions
Q: What size machine is required for the 18 inch wheel hub mold?
Answer: The projection area is about 0.2-0.25 square meters, and the lower limit of the machine is about 12-15 tons.
Q: What is the unit locking force?
Answer: 30-50 tons/square meter is often taken, and the higher value is taken for thin-walled large items.
Q: How to determine the capacity of the insulation furnace?
Answer: Based on 2-3 hours of aluminum consumption, taking into account stable liquid level.
Q: Do we need to convert the tonnage of old machines?
Answer: Yes, it is more reliable to estimate based on 80% -85% of the nameplate.
Q: What should I do if I can't fit the mold in?
Answer: When changing the mold frame or machine, the pressure plate cannot be forcibly modified.
Q: Can flying edges reflect insufficient tonnage?
Answer: Yes, local thick flying edges are often related to locking force or rigidity.
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