Electronic calculator bottom case product is shown in Figure 1. Maximum dimensions of product are 124.84 mm * 66.20 mm * 5.40 mm; average thickness of plastic part is 1.50 mm, material of plastic part is ABS, shrinkage rate is 1.005, and weight of plastic part is 14.60 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 Electronic calculator bottom case product map
Electronic calculators are commonly used office supplies. This article introduces key points of electronic calculator bottom case mold design. Three plastic parts of surface shell, bottom shell and storage box cover can form a complete assembly. This calculator is from CASIO Corporation of Japan, which has characteristics of reasonable design and high quality. After assembly, face shell and bottom shell are required to have neat art lines and a smooth feel.
Whether it is engineering calculations, student learning, business finance and various other daily activities, calculators are essential office supplies. Mold structure of electronic calculator shell is not complicated. You can compare existing calculator at hand to analyze its mold structure. Through comparison of real objects, combined with explanation of this article. I believe that everyone will have a thorough understanding and mastery of electronic calculator shell molds. Therefore, mold of electronic calculator shell is also particularly suitable for students who are beginning to learn mold design.
Material of electronic calculator shell is generally ABS or HIPS, upper and lower shells are approximately rectangular flat shells. In addition to using buckles on the edges for assembly, self-tapping screws are also required for fastening.
According to structural characteristics of plastic part, mold design cavity is 2 cavities. Standard LKM mold base is DCI 3335 A60 B60 C90, and tie rod is 290 long. In order to ensure precision of mold, front and rear mold frames need to be directly processed by mold base factory. There are two processing methods for fine frame of mold. If it is a through frame, wire cutting or CNC processing can be used. Like blind frame of this set of molds, it must be processed by CNC machine tools to ensure accuracy of fine frame processing. Regarding accuracy of fine frame processing, depth of fine frame can be a negative tolerance, that is, depth can be several wires shallower. However, flatness of bottom surface is 0.02, and roughness is Ra1.6 or more. Verticality of side of fine frame is generally within 0.02. Horizontal dimension of mold opening frame needs to be increased by 0.02 to 0.03 on one side, as shown in Figure 3. In this way, size of processed mold base is just within required dimensional tolerance, which can make mold core easy to frame, improve accuracy of frame matching, and reduce time of frame matching.

 

Figure 2 Die parting surface diagram

 

Figure 3 Block Diagram of Rear Die Opening
Gate of plastic part is a point gate, which is located on the top surface of plastic part, and glue is injected at one point, as shown in Figure 1. Due to different structures, surface shell and bottom shell of electronic calculator shrink inconsistently. Due to influence of buttons, there are 47 small square holes and round holes on the front shell, and shrinkage rate is small. Usually, shrinkage rate is 1.004. Bottom shell is different, and shrinkage rate is usually 1.005. Therefore, due to different structure of plastic parts of surface shell and bottom shell, shrinkage rate is quite different, surface shell and bottom shell cannot be opened on same set of molds, otherwise, injection molding defects will be caused due to difference in plastic flow and filling speed.

 

Figure 4 Explosion diagram of mold
Mold is Japanese mold, steel is Japanese steel NAK80, and standard parts of mold are Japanese MISUMI brand. In this set of molds, design of mold inserts refers to design characteristics of Japanese molds.
Ejection of plastic parts adopts 2 lifters and ejector pins. Lifter adopts a slope of 5°, and lifter guide block is designed on the back of B board as guide for lifter. Thimble adopts Japanese Jialilai thimble. Thimble hole is cut with a slow-moving wire. After thimble is loaded into mold, thimble should be easily twisted from head of thimble, so that gap is correct.
Since mold is a small mold, front and rear mold cores are designed with straight-through water delivery, and nozzle push plate is also designed with a cooling circuit. For three-plate mold, to reduce molding cycle, we must pay attention to cooling of nozzle push plate.