Selection and aging law of sealing strip for differential pressure casting mold of wheel hub | Operation and maintenance of sealing system for low-pressure casting tooling mold
The sealing strip of the differential pressure casting mold for the wheel hub has aged and failed prematurely, resulting in unstable pressure difference of 47% and loss of consistency in casting filling.
Fluororubber rubber strips can withstand mold temperatures above 235 ℃ for a long time, resulting in a 2.4-fold increase in aging rate and a weekly increase of 11% in elasticity loss rate.
The width of the sealing groove is more than 0.3mm larger than the cross-sectional width of the rubber strip. The rubber strip slides laterally, and the compression is uneven, resulting in insufficient local compression and air leakage.
The compression rate of the rubber strip is less than 18%, the sealing pre tightening force is insufficient, and the gap opens when the pressure rises; The compression rate is higher than 32%, and the rubber strip undergoes rapid permanent deformation.
Release agent and aluminum liquid smoke continue to erode the surface of the rubber strip, resulting in micro cracks on the surface of the rubber strip. The depth of the cracks is greater than 0.1mm, and the sealing performance deteriorates.
When the rubber strip is stored in a compressed state for more than 72 hours during shutdown, its rebound performance decreases by 29%, and it is prone to continuous air leakage when put into production again.
The requirement for sealing reliability of differential pressure casting molds for wheel hubs is significantly higher than that of gravity casting molds. Low pressure die-casting molds (LPDC) and counter pressure casting molds (CPC) also rely on sealing to maintain the pressure environment in the mold cavity. Motorcycle wheel hub casting molds, low-pressure wheel hub casting molds, structural component casting molds, aluminum alloy wheel hub molds, aluminum casting forming molds, low-pressure casting tooling molds, and seals are continuous consumables. Simultaneous stocking of molds during procurement can reduce downtime losses. Zhejiang Xinfeng Machinery has sorted out spare parts feedback from overseas customers, and many customers have mistakenly used ordinary nitrile rubber instead of fluororubber. The temperature resistance limit of nitrile rubber is only 120 ℃, and it hardens and cracks after dozens of casting cycles. The cross-sectional shape of the sealing strip is preferably square. Circular sealing strips have poor lateral stability and are prone to rolling and misalignment when repeatedly opened and closed. During each mold maintenance, visually inspect the rubber strip for any surface bulges, carbonization, or cracking. It is recommended to replace it directly and not continue with trial production. The environment temperature in the Middle East workshop is high, and the aging speed of the rubber strips is twice as fast as in Southeast Asia. Therefore, the stock quantity needs to be increased to twice that of the conventional level. The sealing line of the differential pressure mold works continuously and cannot rely on glue to replace special sealing strips. The sealing glue will carbonize and fall off when heated, and debris will enter the mold cavity to form inclusions in the casting. Many customers have provided feedback that the slight fluctuations in the pressure curve cannot be attributed to any specific cause. Most of them are caused by local micro cracks in the rubber strip, which are difficult to directly identify with the naked eye. Replacing the rubber strip can restore stability. Google search for 'differential pressure casting mold seal strip aging' is a niche high conversion long tail keyword with little competition.
FAQ
1. Question: What is the long-term upper limit of temperature resistance for fluororubber sealing strips?
Answer: The continuous mold temperature should not be higher than 235 ℃ for a long time to delay aging.
2. Question: What is the recommended compression range for sealing strips?
Answer: The compression rate is controlled at 18% -32%, balancing sealing and lifespan.
3. Question: What is the upper limit of temperature resistance for nitrile rubber?
Answer: Nitrile rubber has a long-term temperature resistance limit of about 120 ℃ and is not suitable for casting molds.
4. Question: What is the upper limit of the difference in width between the sealing groove and the rubber strip?
Answer: The width of the groove should not exceed 0.3mm beyond the cross-sectional width of the adhesive strip.
5. Question: What kind of defect is recommended to replace the rubber strip directly?
Answer: If the depth of surface microcracks exceeds 0.1mm, they should be replaced.
6. Question: How long will the rubber strip decay after being compressed and stored for a long time?
Answer: Continuous compression and placement for more than 72 hours significantly reduces the rebound performance.
