See Figure 1 for wall mount end cap products. Maximum dimensions of product are 151.20 mm * 56.30 mm * 24.50 mm; average thickness of plastic part is 2.50 mm, material of plastic part is PA6 + 30GF, shrinkage rate is 1.005, and weight of plastic part is 48.75 grams. Technical requirements for plastic parts are that there should be no defects such as peaking, underfilled injection molding, flow lines, pores, warping deformation, silver streaks, cold material, and jetting lines, and meet ROSH environmental protection requirements.

 

Figure 1 Product picture of wall mount end cover
Wall mount end caps are an integral part of Vogel brand kitchen appliances. Its appearance surface is an etched surface, and etched grade is Yick Sang YS9286. Position of etching on product drawing of plastic part needs to be specified. If necessary, size of etching area should be limited, and it should be indicated by a dotted line parallel to outer contour of plastic part. Bottom of plastic part is required to be flat, with a flatness of 0.3. Since material of plastic part is PA6 + 30GF, nylon plus fiber material, it is particularly easy to deform, and it is difficult to correct after deformation. Therefore, a reasonable gating system and cooling circuit must be designed.

 

Figure 2 Analysis of technical requirements
Main technical requirements of plastic parts are shown in Figure 2. This technical requirement comes from 2D drawings of product. Its general idea is as follows: unfilled dimensions of plastic parts must follow 3D drawings when designing mold; generally unfilled wall thickness is 2.5 mm; volume of plastic piece is 33.7cm3; unfilled tolerances must follow DIN 16901-Reihe 1; As for draft angle, take 1゜ for surface without injection and etching, take 2.5゜ for surface without injection and etching; R0.4 mm for edge without injection, except for parting surface; size and arrangement of ejector pin, parting surface and position of insert must be agreed by customer. Ejector pin must be 0.15mm lower than surface, batch front of parting surface is less than 0.2mm, etching pattern is in accordance with specifications required by customer, and final appearance surface reaches model signed by customer. Three small pictures in Figure 2 show basic principle of demoulding slope. This principle has universal adaptability, that is, reducing thickness to make demoulding slope. This principle is very important, must be mastered and applied flexibly.

 

Figure 3 Die structure diagram
This set of mold plastic parts has a simple structure and no complicated mold structure. 3D drawing of mold is shown in Figure 3. Customer is from Dutch. This article takes plastic part as an example to systematically introduce design points of Dutch mold. Netherlands is a European country. Holland molds comply with general requirements of European molds. The most basic is to adopt DIN series standards. Most of mold standard parts are HASCO brands. The most commonly used European injection molds are German HASCO standards, German STRACK standards, German EOC standard, British DMS standard, American DME European standard (metric standard), French ROUBARDIN standard and Austrian MEUSBURGER standard, the most famous of which is German HASCO standard.
For European injection molds, front and rear mold cores generally require heat treatment, commonly known as hard molds. Steels commonly used for front and rear mold cores are DIN 1.2343 and DIN 1.2344, both of which are standard hot work tool steels commonly used in Europe. Heat treatment hardness of DIN 1.2343 is HRC50-54, which is suitable for mold cores and sliders with corrosive requirements, and DIN 1.2343 ESU is used for high polishing requirements. Heat treatment hardness of DIN 1.2344 is HRC48-52, which is suitable for mold cores and sliders with high wear resistance requirements, especially plastics with relatively high glass fiber content, and its toughness is slightly lower than DIN 1.2343. DIN 1.1730, equivalent to China's No. 45 or No. 50 carbon steel, is suitable for manufacture of unstressed or unimportant parts. DIN 1.2312, this steel belongs to pre-hardened steel, generally not suitable for heat treatment, but it can be nitrided. It is often used to make A/B boards, support columns (support heads) and top sticks of mold bases. DIN 1.2767, suitable for making small inserts or other moving parts such as sliders and lifters. DIN 1.2842, used to make parts such as slider bead and wear plate, heat treatment HRC48-52, and nitrided, thickness of nitrided layer is 0.2-0.4mm.

 

Figure 4 Die parting surface diagram
Dutch mold has many structural features. Like general European mold, its ejection system does not put a return spring on return needle. Instead, ejection system with strong pull and strong ejection is adopted. This ejection method is reliable in return and injection molding cycle is short. Thimble plate bears less force and is not easy to deform, thimble is naturally smooth and not easy to break, which has characteristics of a long-life mold. Mold design specification book is shown in Figure 5.
In order to realize fully automatic production smoothly, it is necessary to ensure that products and nozzle materials can be ejected reliably, grasped by manipulator and then transferred to conveyor belt, or dropped by their own weight. Automatic separation of product and nozzle material in mold is very important. Sub-gate and Cowhorn gate are the most common gate forms. European and American customers like sub-gate. Gating system of this mold is designed in this way.

 

Figure 5 Mold Design Specification Book