Specifications of design and usage of mold core insert

Mold core insert is a generic term used in a mold to refer specifically to irregular mold parts that are embedded in the mold. It is a separate mold part that is used to form the glue position. Core insert is corresponding to the original body retention. When a mold is composed of a single piece of steel, it is the original body retention. When it is composed of multiple workpiece, in addition to the main body of steel embedded parts can be called core insert. From the appearance ,core Inserts can be square, round, or slice. Like all mold components, core inserts require a high degree of precision. In addition to core pins can order standard size, generally no finished core inserts, they should make according to the needs of the mold customized.

Types of core inserts: core pins, mold inserts, core pillar, rings…etc.

Material of core inserts: SKD61, SKH51, ASP23, SKD11…etc.

Hardness of core inserts: more than 50HRC

Tolerance: +/-0.01mm

In mold design, we often design core inserts structure by taking into account such factors as precision of parts, exhaust cooling, processing technology, mold strength, processing capacity, material saving, product change and so on.

The benefits of designing core Inserts include the following:

1. Simplify the processing process of complex concave dies.

The core part of some molds is more complicated. If the molding process is done in the whole mold cavity, the processing technology is more complicated and the processing equipment required is also larger. The core insert design is adopted to allow the more complex core part to be processed separately, which will undoubtedly simplify the complex mold processing technology.

  2.Save raw materials and reduce costs.

When purchasing raw materials, the thickness of raw materials for the back die is determined by the highest point of the die. If only a certain part has a high protruding shape, core Insert can replace this part, and the whole back die template can use a thinner raw material template, so that core insert can save raw materials and reduce costs.

3. Core Insert is convenient for mold exhaust

In some deep bone positions, it is not easy to process the EDM, and the deep bone position will lead to poor exhaust during the molding process. In this case, core insert is often required, and the gap at the splicing point of core insert is conducive to exhaust.

4. Ensure mold accuracy

Among all the processing methods, the accuracy of the grinder is relatively high. In order to ensure the accuracy of some parts, core inserts can be designed to facilitate the processing of the grinder.

5. Core Insert is easy to replace

Sometimes customers require that the label or logo of the same product can be changed at any time, so they need to do a core inset that is easy to change. The mold date isnerts often used on molds is one of these core inserts that can change the date every year.

 6, Easy for polishing and modifying.

There are some deep positions that don’t make it convenient, so make it as core insert. And some parts are easy to wear or require too high precision, so it is easier to replace and process this part as core insert. For some large molds with multiple cavities and different parting surfaces, the cavity is complicated, inconvenient to process and difficult to maintain, and a part of the cavity is easy to be damaged. In this case, core Insert can meet the above requirements.

7. Core Insert is good for heat dissipation.

Some die cores require good heat dissipation. If the whole mold uses beryllium copper, the manufacturing cost is very high. We only need to use beryllium copper to make the part of core Insert.

Application of core inserts:

1. Core Insert must be done when there is a parting surface (PL) stop on the product. Note that when the inner mold core is the integral core insert, blind set should be adopted as far as possible considering the strength and water transport design.
2. Many bone position designs require core insert, especially when the product structure is bone position array, core insert must be done when the bone depth is more than 3 times the glue thickness, and core insert must be done when the bone root thickness is less than 1.0mm.Core insert is required for bone positions perpendicular to the flow direction of the glue material in the cavity.
3. Where the product structure is complex and difficult to process, the core Insert structure should also be designed.
4. Core Insert must be done for perforation under 6.0mm; core insert must be done for irregular perforation.
5. When there is text and Logo or version number on the product, it must be designed as core Insert.
6. Core Insert design is required for both front and rear die cavities of gear products.
7. The partial structure of the mold can be replaced by parts so that the product style can be changed, which must be designed as core Insert.

Design method:

1. When the bone depth exceeds the glue depth 3-6 times, the design of unilateral slope is adopted.Pay attention to the side slope of the gate to reduce the shrinkage force when the product is pushed out.
2. When the depth of the bone is more than 6 times the thickness of the glue, the simple use of bilateral slope.The side of the slope close to the line cutting edge is made a straight position 0.5-1mm higher than the bottom of the bone position to avoid burring at the bottom of the bone position due to insufficient machining accuracy.
3. Where it is inconvenient to directly do core insert assembling structure (size less than 6mm or there will be thin steel on the edge) or cross bone position with too small size, a base support should be made at the bottom of core insert.
4. Do small core insert for blind set for such as mold date insert, Logo, etc. Note that the process hole must be removed at the bottom of the core Insert.
5. The core insert of Blind set must be from the surface of glue level, and a 15 degree chamfer must be made at the bottom to facilitate installation.
6. In order to protect the small core insert pierced by the front and rear dies, the core insert material of the rear dies is relatively soft steel.
7. For core insert with insertion parts, select steel materials with softer materials and hardness.
8. Fixed way of core insert
   • Design of die hanging platform

The most common way to fix core inserts is the die hanging platform design. The die hanging platform design should stay on the long side of core inserts as much as possible. Under special circumstances can be done in the short side, sometimes can be done on both sides, to increase strength.

The width of the hanging position is generally required to indent the shape of the unilateral 0.5-3mm.The thickness of the hanging platform depends on the situation, generally 1-4mm.When the core insert height is less than 50mm, the mount height is generally 4mm; when the core insert height is greater than 50mm, the mount height is 6mm.Note that if the thickness of the core Insert mount cannot be increased due to constraints, you can compensate by increasing the mount height.The first factor affecting the strength of the suspension is the height of the suspension.

The circular core insert die hanging platform design adopts the flat position of the mount pin when there is a requirement to prevent rotation

• Bottom lock screw fixed

For large core inserts, bottom lock screws are also a common way to secure them.The balance of lock screws should be paid attention to, and there should be extraction process holes for Blind set core insert.

• Slope position

For core inserts that cannot do hanging platform positioning, you can use oblique positioning (try not to use it).

Note that core Insert incline should be 3 degrees on one side.Less than 3 degrees, incline core insert easy to loose, too large slope is not conducive to fit.

If we are going to do core insert arrays in an internal die steel, the edge of the core insert should be designed with a single bevel to facilitate core insert assembly.

9. Exhaust of core insert

All core inserts need to be vented. The circular core insert is processed by draining the air thimble. Square core insert refer to the die design standard for exhaust.