Printer drain product is shown in Figure 1. Maximum dimensions of product are 226.59 mm * 44.58 mm * 67.80 mm; average thickness of plastic part is 1.00 mm, material of plastic part is ABS, shrinkage rate is 1.005, and weight of plastic part is 23.53 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 printer drainer

 

Figure 2 3D drawing of mold
Printer drainer product is drainer shell inside a famous Japanese brand printer. The overall shape of plastic part is a long irregular and complex shell. Wall thickness of plastic part is relatively thin, and closed shell has a large tightness on rear mold, so it is necessary to prevent ejection deformation. Due to large production batch of plastic parts, the first set of molds is ejected by push plate. Due to irregularity of edge of plastic part and long plastic part, force on push plate is uneven, resulting in partial wear of push plate, resulting in appearance of a front, and life of mold is not long.
There are five rear mold sliders and one front mold slider on the edge of plastic part, as shown in Figure 4 and Figure 5. Position of mold cavity is 2 cavities. When designing mold, it is necessary to pay attention to position and direction of the two plastic parts to ensure that each slider and shovel have enough positions. Front mold slider is driven by T-shaped slots, and five rear mold sliders are all driven by inclined guide posts. Wear-resistant plates are designed on the bottom and slope of slider, which is convenient for flying molds and adjustments. A yellow rubber spring is designed between nozzle plate and A plate to facilitate core pulling of front mold slider.

 

Figure 3 Die arrangement and parting surface diagram
This set of molds is second set of molds, which summarizes experience and shortcomings of the first set of molds, cancels ejection structure of push plate, and uses ejector pins for ejection. Second set of molds is a long-life mold, gate is a three-plate mold with point gates, mold base is FCI5050, and gates are three-point gates. Sprue sleeve is designed as a bushing, and nozzle plate is designed as a cooling circuit. Mold is designed with a taper positioning block on each side of parting surface, which is convenient for accurate mold clamping of front and rear molds.

 

 

Figure 4 Structural diagram of rear mold slider
Batch of plastic parts is very large. After continuous production of mold reaches life span, if product still has a huge market, then a new set of mold will often be reopened. Reopening design of mold is not simply to use original drawings to repeat manufacturing, but a process of improvement and technical sublimation. If re-opening mold is originally designed and manufactured by our factory, original mold needs to be improved. Improvement needs to start with mold design, investigate use of mold, improve mold design or improve mold manufacturing process.
If original mold is not designed and manufactured by our factory, then it is necessary to redesign mold according to sample. When necessary, it is necessary to do surveying and mapping of model of plastic part, which belongs to reverse engineering, then convert 3D drawing of plastic part through copying. Shape accuracy of copy is generally controlled within 0.05mm, and accuracy of bone position is within 0.1mm. Before copying number, it is necessary to carefully review model of plastic part, distinguish mistakes in original mold of plastic part during production process, and make improvements.
Traces formed by mold structure during molding process of plastic parts, such as traces of insert and ejector mechanism, traces of gate, carefully analyze these traces, and structural scheme of injection mold can be clarified. Adopting its design essence and discarding its dross can make us avoid detours, avoid mistakes, prompt us to successfully imitate or copy molds and plastic parts.
During molding process of injection parts, molding processing traces caused by mold structure, such as insert traces, will be produced. There are two cases of insert traces, one is insert determined according to mold design plan, and the other is traces of inserts caused by manufacturing errors or traces caused by mold maintenance. When making a mistake, cut insert on non-appearance surface of plastic part (often moving mold) to avoid welding. Welding will seriously degrade properties of steel, and foreign customers generally will not accept welding solution. Therefore, when new mold is re-opened, inserts caused by original manufacturing errors should be avoided, and must be carefully identified when analyzing model of plastic part.
Processing traces on plastic parts, such as air marks, shrinkage, poor exhaust, drape, etc., will be reflected on plastic parts. When analyzing model, it is necessary to observe carefully with a high-power magnifying glass, find out plastic parts and their molds according to traces Insufficient design and manufacturing, unreasonable equipment selection and molding processing arrangements, incorrect materials and processing parameters, through experience accumulation, continuously improve level of mold design.
Improving mold design ideas and improving mold design scheme is focus of reopening mold design. A favorable condition for re-opening mold design is that plastic parts have gone through a round of mold design and production, and gating system, cooling system, lateral parting and core-pulling system, demoulding system and injection cycle have accumulated first experience. hand information. All these provide conditions for improvement of mold design scheme.

 

Figure 5 Die structure diagram

 

Figure 6 Front mold slider diagram

 

Figure 7 mold structure analysis