Why is the mold thimble easy to break

Update:24-06-2021
Summary:

The ejector pin is used to eject the product so that it […]

The ejector pin is used to eject the product so that it can be ejected from the mold cavity.

Principle of ejection: ejection originates from the injection molding machine, the ejector plate pushes the ejector rod, and the ejector rod pushes the product out.

However, (99)% of the ejector pins of the mold will break, so why is the ejector pin of the injection mold always easy to break? The most important thing is the arrangement of the ejector pins. If the design is not understood and the ejector pins are not considered when arranging, this problem will easily occur.

Principle of ejector arrangement

(1) The arrangement of the thimble should balance the top force as much as possible. Especially the parts with complex product structure require greater demolding force, and the number of thimble pins should be increased accordingly.

(2) The thimble should be set in the effective part, such as the bone position, the column position, the step, the metal insert, the part where the local glue position is thick and the shape is still more complicated. The thimble on both sides of the bone column should be arranged as correspondingly as possible. The distance between the thimble and the two sides of the bone column should generally be D=1.5mm, as shown in the figure. In addition, when arranging the thimble, it is necessary to ensure that the center line of the thimble on both sides of the column can pass through the center of the column.

(3) Avoid setting thimble on steps or slopes. The top surface of the thimble should be as flat as possible, and the thimble should be arranged in a structural part that has good stress on the plastic products. As shown in the figure.

(4) Flat thimble should be used in deep bone position (depth ≥20mm) or when it is difficult to arrange thimble. When flat thimble is required, inserts should be used at the flat thimble as much as possible, so that it is easy to process

(5) Avoid sharp steel and thin steel on the mold parts, especially when the top surface of the thimble contacts the front mold surface. Refer to the picture above.

(6) The arrangement of the thimble should consider the distance between the thimble and the waterway to avoid affecting the treatment of the waterway and water leakage.

(7) Considering that the ejector pin also has an exhaust function, the ejector pin should be placed in a location where a vacuum is easy to form, that is, trapped in order to exhaust when ejecting. For example, on a plane with a large cavity, although the clamping force of the bonding part is small, it is easy to form a vacuum, resulting in an increase in the demolding force.

(8) For those plastic products with appearance requirements, ejector pins cannot be set on the appearance surface, and other ejection methods should be adopted.

(9) For transparent plastic products, the thimble cannot be installed where light transmission is required.

The mold thimble is arranged, and then choose a high-quality thimble, the problem of mold thimble breakage can be greatly reduced

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