LPDC top out system design, layout of top rod, top plate, and top pipe, to prevent top whitening, top concavity, and top cracking
The ejector system is responsible for smoothly pushing high-temperature castings out of the mold cavity. The layout, diameter, spacing, and distribution of ejector force of the ejector pins are unreasonable. Under the plastic state of high-temperature castings, it is prone to occurrence of top concave, top white, top piercing, and rib top cracking. Many defects only appear after cooling.
1、 Quantitative standards for specifications, spacing, and output distribution of top rods
The diameter of a conventional dome rod is between 6 and 12mm; Thin walled shells prioritize dense small-diameter top rods to disperse pressure; Thick walled and flange pressure bearing surfaces are equipped with top plates.
Top pole spacing: 60-100mm; the large-area plane is reduced to 50-70mm to ensure uniform top force and no overload of single point pressure.
The end face of the top rod is 0-0.02mm higher than the cavity surface; if it is lower than the cavity surface, the casting will produce protrusions; Above the cavity surface, the corresponding position of the casting is concave.
Top rod fit clearance: 0.01-0.015mm on one side at room temperature; if the clearance is too small, it may expand and lock up at high temperatures; The gap is too large, and aluminum liquid enters the top rod hole, causing jamming and pulling.
The layout of Xinfeng Machinery's top out follows the principle of prioritizing the placement of hot joints, thick flanges, and rib roots for top out, avoiding thin-walled isolated ribs and thin ribs to prevent top cracking.
2、 Key points for supporting ejector plate, guide, return, and cooling
The top out plate is equipped with independent guide columns to prevent the top out plate from tilting, and the top rod from being worn or broken on one side.
The return spring is selected as a high-temperature resistant rectangular spring, and the compression amount of the spring is controlled within 50% of the rated compression amount to avoid rapid fatigue fracture.
The position of the top rod hole should avoid the cooling water circuit to prevent water leakage; Priority is given to assisting cooling in the cavity near the top rod, reducing the casting temperature and minimizing plastic deformation.
The deep tube core prioritizes the top of the tube for even force distribution, avoiding deformation of the thin-walled tube top due to single point protrusion.
3、 Overseas customers highlight differences in system control
The number of Southeast Asian mold top rods is relatively small, relying on thicker top rods, allowing for slight whitening, and later polishing and repair.
The layout drawing of the North American automotive parts ejector is solidified, and the position, diameter, and ejector force of the ejector pin are simulated and verified. Concave and white ejector pins are appearance defects and cannot be polished or covered up.
European customers extensively use top plates and annular ejector to reduce single point pressure, prioritize ensuring stable casting shape, and reduce deformation risks.
Large and heavy castings in the Middle East have a high ejection load, and hydraulic synchronous ejection is used. Multiple sets of ejection cylinders are synchronously controlled to prevent uneven force from tearing the castings.
4、 Top out failure defect chain
Sparse layout of top rod, excessive pressure at a single point → plastic deformation of high-temperature castings → concave and white top;
The clearance between the top rod is too large → the aluminum liquid drills into the top rod hole → the top rod is stuck, pulled, or broken;
The top out plate has no guidance, and the top out is skewed → the top rod is subjected to unilateral force, and the root of the rib is cracked;
The height of the top rod end face is incorrect → the surface of the casting is convex or concave.
5、 Long tail traffic layout ideas
Low pressure casting ejector system, ejector pin layout, ejector pin, aimed at mold designers and fitters.
Keywords: LPDC ejection system design, ejection pin layout, low pressure casting mold;
Category of questions: ejector pin clearance for hot aluminum casting die;
Comparison class: ejector pin vs ejector sleeve for deep core LPDC.
Suitable for special pages on mold structure and tooling design.
6、 Common misconceptions in the industry
Misconception 1: The thicker the top rod, the better. The thicker the top rod, the higher the single point pressure, which is more likely to cause concave and cracking. Therefore, priority should be given to dense layout.
Misconception 2: Tighten the gap between the top rod to prevent aluminum leakage, lock up due to high temperature expansion, and stop the machine when the top is stuck.
Misconception 3: Randomly arrange the ejection position, and do not concentrate on the ejection of thin ribs and thin walls, which can easily cause tearing.
FAQ
Q: What is the regular spacing between top poles?
A：60–100mm， Large area flat 50-70mm.
Q: Is there a single-sided gap between the top pole at room temperature?
A：0.01–0.015mm。
Q: What is the standard height of the top rod end face?
A: Align with the cavity surface, 0-0.02mm.
Q: What is recommended for deep tube core ejection?
A: Top out of the pipe, with even force distribution.
Q: Control the compression amount of the ejector spring?
A: Within 50% of the rated compression capacity, extend the service life.
Q: North American parts export control?
A: Layout simulation verification, top white and top concave are not allowed to be polished or covered.
Q: Why does the top pole hole avoid waterways?
A: Prevent water leakage and affect mold temperature control.
Q: What are the consequences of pushing out the deviation?
A: The top rod is subjected to unilateral force, causing the rib to crack and the top rod to break.
