(1). In the plastic mold, the product is separated from the mold, is also the most commonly used; 2). Cemented carbide thimble such as tungsten steel thimble, etc., can be used to pass a long and thin hole; The thimble is a head conical metal round bar fitted to a lathe or a grinder to support the workpiece and rotate the workpiece around it, but it is completely different from the pin of the plastic mold fitting; 4). Can also be used inside the mold, Thimble it can play a solid role, called the needle.
Thimble placement principle
(1) thimble arrangement should make the top force as much as possible balance. The structure of complex parts required stripping force is greater, the corresponding number of thimble should be increased.
(2) thimble should be set in the effective parts, such as bone, column, step, metal inserts, local thick plastic and other complex parts. Bone position, the column on both sides of the thimble should be symmetrical arrangement, thimble and bone position, the column spacing of the general take D = 1.5mm, as shown in Figure 5.5.8, in addition, should try to ensure that both sides of the column The center is connected through the center of the column.
(3) to avoid cross-step or set in the slope of the thimble, thimble top should be gentle, thimble should be placed in the plastic parts of the better structural parts.
(4) A flattened thimble should be used when the deep bone bit (depth ≥20mm) or difficult to arrange the dome needle. Need to use the flat thimble, the flat thimble as far as possible in the form of inserts in order to facilitate processing.
(5) Thimble to avoid sharp steel, thin steel, especially the top of the thimble can not touch the front face. As shown in Figure 5.5.11
(6) thimble arrangement should consider the thimble and the side of the waterway spacing, Thimble to avoid affecting the processing and leakage of the waterway.
(7) To consider the exhaust function of the thimble, in order to eject the exhaust, in the easy to form a vacuum should be arranged thimble. For example, the larger cavity of the cavity, although the plastic package less compact, but easy to form a vacuum, resulting in increased stripping force.
(8) the appearance of the requirements of the plastic pieces, thimble can not be arranged on the appearance of the surface, should be used other top method.
(9) For transparent plastic parts, thimble can not be arranged in the need to light the site.
Thimble selection principle
(1) the choice of larger diameter thimble. That is, Thimble in the case of a sufficient ejection position, should use a larger diameter, and size priority thimble.
(2) the choice of thimble specifications should be as little as possible. When using a thimble, adjust the size of the thimble so that the size of the smallest, Thimble and try to use the preferred size series.
(3) the choice of thimble should meet the requirements of the top strength. When the top ejector, the thimble to withstand greater pressure, in order to avoid the small thimble bending deformation, when the thimble diameter is less than 2.5mm, should be used with a thimble.