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Mold wants to use well: mold frame selection is very important!
- Nov 02, 2018 -

There are more and more applications of the die base in engineering. How to choose the right one is a problem. Today, we summarize several criteria for the selection of the die base. Let's take a look at them together.

Standard die holder and standard accessories are generally used in the die holder, which is conducive to shortening the manufacturing cycle and reducing the manufacturing cost. In actual production, it is often decided by the price, structure of the die and the complexity of the processing of the die base.

In case of special circumstances or customer's specified requirements, some shapes, sizes and materials of the die holder can be changed or the die holder can be completely redesigned. In this case, when ordering the die holder, detailed die holder drawings should be provided to the die holder supplier, and the differences between the ordered die holder and the standard die holder should be indicated.

Confirm mold base and insert size

The size of the die mainly depends on the size and structure of the plastic products. For the face of the die, the more compact the structure is, the better the strength is. According to the shape size of the product (plane projection area and height) and the structure of the product itself (such as lateral parting slider), the shape size of the insert can be determined. After the size of the insert is determined, the size of the die frame can be roughly determined.

Determination of square iron height

The height of square iron should ensure enough ejection travel, and then set aside a certain margin (5-10 mm) to ensure that the ejection pin fixed plate will not hit the moving template or the supporting plate.

Determination of integral structure of mould frame

After the basic selection of the frame, the overall structure of the frame should be checked to see whether the determined frame is suitable for the selected or customer-designated injection moulding machine, including the size, thickness, maximum opening stroke, ejection mode and ejection stroke of the frame.

Selection of insert materials

There are four main properties of die insert materials: hardness, wear resistance, strength and toughness, and corrosion resistance.

The choice of materials for mould inserts is mainly determined according to the volume of plastic products and plastics.

Products for general plastics such as ABS, PP, PC and other plastics, usually choose model P20 and other types of pre-hardened and tempered steel, if the product batch is large, should choose quenched and tempered steel such as model H13.

High gloss or transparent plastic products, such as PMMA, PS, AS and other plastics or plastics containing glass fibers, mainly choose type 420 and other types of corrosion-resistant stainless steel.

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In addition to the above criteria, there are several points to choose from.

1. For different types and specifications of injection machines, different structure of clamping mechanism has different closure distances. The thickness of mould base H and the closure distance L of injection machine have different closure distances.

2. When designing the dimension relationship between the distance between the opening stroke and the distance between the fixed and the moving die and the distance needed for pushing out the plastic parts, it must be calculated and determined that the opening stroke of the injection machine should be greater than the distance between the fixed and the moving die needed for removing the plastic parts, and the distance between the pushing out of the mould and the pushing out of the hydraulic cylinder of the injection machine should be less than the rated ejecting stroke of the injection machine.

3. Attention should be paid to the installation and installation of the selected mould holder on the injection machine: the shape size of the mould holder should not be affected by the distance between the pull rods of the injection machine; the size of the positioning aperture and the positioning ring should be well matched; whether the position of the ejection rod hole and the ejection stroke of the injection machine are appropriate; whether the nozzle aperture and spherical radius are in line with the gate sleeve aperture and concave spherical surface of the mould. The position and aperture of the mounting hole of the die holder are matched with the corresponding screw holes on the moving template and the fixed template of the injection machine.

4. To ensure the quality of plastic parts and the performance and reliability of moulds, it is necessary to accurately check and calculate the mechanical properties, especially their strength and stiffness, to determine the length, width and thickness of the moving and supporting plates. So as to correctly select the specifications of mold base.