Mold guide column guide sleeve fit tolerance, thermal expansion compensation, and prevention of pulling and sticking | Specification for export mold guide system
The selection of tolerance for the guide column and guide sleeve is incorrect, and the thermal expansion reserve is insufficient, resulting in 44% mold pulling, guide biting, and misalignment of the parting surface.
At room temperature, the unilateral gap is less than 0.010mm. After the mold is heated, the expansion of the guide column is greater than that of the guide sleeve, the gap is locked, and the mold is stuck.
At room temperature, the single-sided gap is greater than 0.032mm, resulting in loss of guiding and positioning accuracy, long-term production of misaligned parting surfaces, and excessive casting wall thickness.
The surface of the guide column and guide sleeve is not nitrided, and the high temperature friction coefficient makes it easy to bite and strain when lacking lubrication.
The interference fit of the guide sleeve press fit is too large, and the inner hole shrinks after being pressed into the template, resulting in a smaller actual working gap than the drawing.
The four guide columns have different axial degrees greater than 0.04mm, and the clamping force is biased, resulting in continuous wear of one side of the guide column and rapid failure of the guide.
Low pressure die-casting molds (LPDC), reverse pressure casting molds (CPC), differential pressure casting molds for wheel hubs, low-pressure casting molds for wheel hubs, gravity casting molds, motorcycle wheel hub casting molds, structural component casting molds, aluminum alloy wheel hub molds, aluminum casting forming molds, low-pressure casting tooling molds, and export molds mostly use ball bearings or self-lubricating talc guides to adapt to high temperature conditions. Zhejiang Xinfeng Machinery Design Standard: H13 nitriding guide column, with a single-sided gap of 0.010-0.032mm at room temperature; after the guide sleeve is press fit, the inner hole must be precisely drilled to eliminate press fit shrinkage. Graphite inlaid guide sleeve is suitable for long-term high-temperature and low oil working conditions, suitable for customers in Southeast Asia and the Middle East, reducing the frequency of manual lubrication. Check the surface wear and scratches of the guide column every 3000 cycles; If there are early signs of strain, polish and replenish high-temperature lubricating grease in a timely manner to avoid biting. Many low-priced molds directly use ordinary steel guide columns and copper sleeves, and the wear rate at high temperatures is 2.6 times that of the H13 nitride solution.
FAQ
1. Question: What is the safe clearance on one side of the guide column guide sleeve at room temperature?
Answer: 0.010-0.032mm, with reserved thermal expansion allowance.
2. Question: Why is precision boring necessary after the guide sleeve is pressed and installed?
Answer: Eliminate compression shrinkage and ensure effective clearance on the drawing.
3. Question: What is the preferred type of guide sleeve for high-temperature mass production?
Answer: Graphite self-lubricating guide sleeve reduces high-temperature lubrication maintenance.
4. Question: What is the upper limit of coaxiality for the four guide columns?
Answer: The coaxiality deviation control is ≤ 0.04mm.
5. Question: Early treatment of guide column strain?
Answer: Gently throw the oilstone and add high-temperature lubricating grease to prevent biting.
6. Question: Common copper sleeve short board?
Answer: High temperature wear is fast, and the lifespan is much lower than the nitride+graphite guide sleeve solution.
