Five principles for mold parting surface design

Five principles for mold parting surface design
The parting surface determines the demolding, stitching, and mold life, and the five principles are prioritized: first ensure demolding, then control stitching, and finally consider processing convenience.
Principle 1: The parting surface is set at the maximum cross-section
The parting surface should be set at the maximum contour of the casting to ensure that the casting can be smoothly removed.
At the location of cross-sectional changes, there may be scratches during demolding, and even inability to demold.
The parting surface of the wheel hub mold is mostly located on the outer edge of the wheel rim, taking into account both demolding and appearance.
Principle 2: Avoid appearance and sealing surfaces
The parting surface will leave gaps. After polishing the seams, there are still traces, which appear as a hard injury to the outside.
The sealing surface is the same. Covering seams can damage flatness and affect airtightness.
When it is impossible to avoid, the parting surface should be set on the side with lower appearance requirements, and the polishing requirements should be marked on the drawing.
Principle 3: Reduce the number of parting surfaces
For every additional parting surface, there is an additional seam, a risk of misalignment, and a maintenance point.
What can be solved with two molds, don't use three. The positioning and locking structure of multiple molds is more complex.
When multiple pieces of complex components are required, the parting surface should be set in non critical areas and positioned with stoppers.
Principle 4: Ensure the feasibility of processing and research and development
The parting surface should be able to be machined by machine tools. The processing difficulty and cost of surface parting surfaces are high.
The flat parting surface is the easiest to ensure accuracy, and the fitting clearance can be controlled within 0.02-0.05mm.
In the design of the parting surface of the wheel hub mold, Xinfeng Mold prioritizes the use of a flat structure with a stopper, balancing accuracy and processability.
Principle 5: Consider exhaust and flash cleaning
The parting surface is also one of the exhaust channels. The gap is too large, the exhaust is good but the flash edge is thick; Too small, with poor exhaust but thin seams.
The gap is often set at 0.02-0.05mm. This range can balance exhaust and seam control.
The convenience of edge cleaning should also be considered. The parting surface is set at a flat surface, making it easier to remove flying edges.
Common errors
Error one is that the parting surface is set on the rounded corner. The demolding resistance at the rounded corners is high, and the seams are difficult to clean.
Error two is that the parting surface conflicts with the sprue. The gate spans the parting surface, which is prone to flash and erosion.
Error three is ignoring thermal expansion. The gap in the cold state is appropriate, but it may open in the hot state, and it needs to be rechecked according to the working temperature.
Research and assembly of parting surfaces
Use red lead to inspect contact spots, with an area of no less than 75%. Uneven spots indicate problems with flatness or rigidity.
After research and development, a mold closing test should be conducted to check the gap with a feeler gauge. A 0.05mm feeler gauge should not be inserted into critical areas of the parting surface.
Maintenance of parting surface
Check the status of the parting surface every 5000 molds. If there is indentation or corner collapse, it should be repaired and ground in time to avoid the expansion of the seam.
Practical tips
The depth of the parting surface is often taken as 5-10mm. If it is too shallow, the positioning will be unstable, and if it is too deep, it will be difficult to process and prone to aluminum accumulation.
The bolts on the parting surface should be tightened in diagonal order in a staggered manner. One tightening can cause uneven stress on the template.
The waterway near the parting surface should avoid bolt holes, as getting too close can cause cracks on the hole wall.
Frequently Asked Questions
Question: Where is the parting surface located?
Answer: At the maximum cross-section, it takes into account both demolding and appearance.
Question: What is the gap between the parting surfaces?
Answer: It is usually 0.02-0.05mm.
Question: Is it better to have more parting surfaces?
Answer: No, the more seams there are, the greater the risk of misalignment.
Q: Can it be placed on the sealing surface?
Answer: It should be avoided as covering the seams will damage the flatness.
Q: Can surface parting surfaces be used?
Answer: Yes, but the processing is difficult and the cost is high.
Q: Do we need to review the thermal gap?
Answer: Yes, suitable cold state does not mean suitable hot state.
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