Industrial robot shell injection mold design
The maximum external dimensions of the industrial robot casing are ø307.20 mm x 299.36 mm, the average plastic part thickness of the plastic parts is 4.0 mm, the plastic parts are PC, the shrinkage rate is 1.006, and the plastic parts quality is 1333 grams. The technical requirements of plastic parts are not allowed. Pups, injection molding dissatisfaction, flow pattern, pores, warpage, silver, cold, spray, bubbles and other defects.
As can be seen from the above figure, the plastic part is a curved body. There are 6 small through holes at the top, and you need to design the front mold slider core pulling mechanism. The plastic mouth has 8 sets of screw posts along the circumference and is connected by the E-shaped bone. The screw column and the top of the bone position and the curved surface of the outer casing form an inverted buckle, and the mold core pulling mechanism needs to be designed. The difficulty in mold design is to design the inner slider mechanism and the ejection mechanism of the plastic part. Due to the large size of the plastic parts, there are many inner slides, and the mold cavity position is 1 out. 1. The mold belongs to a large mold, and the mold blank is a non-standard mold blank 90100, A=380 B=120 ST=150, for large molds. In other words, because the size of the mold is relatively large, the way of molding the mold is different. In this set of molds, the height of the plastic part is 299.36, and the height of the A-plate and the front mold core is 380. For the front mold core of such thickness, it cannot be blind-set with the open-cut frame like the small mold. Because the depth is too large, the edge of the fine frame is difficult to be vertical due to the limitation of the tool and the processing capability of the machine. On the other hand, the 6 sides of the mold are also difficult to grind to the vertical, which makes it very inconvenient to frame. In the actual mold design, the front mold adopts a through frame, which reduces the processing difficulty and improves the processing precision. The fine frame can be processed by wire cutting, and the remaining material in the center can be reused. In order to improve the precision of the front mold core, at the bottom of the through frame, a locking block 8 is designed on the two vertical frame edges to which the reference angle is opposite. The shape of the plastic part is a parabolic rotating body, and the small port portion sinks and forms a central through hole. In combination with the large size of the plastic parts, the ideal way to feed the plastic parts is to use the glue in the center of the plastic parts. The mold design adopts a large nozzle to enter the glue from the center of the plastic part to form a disc-shaped gate. After the injection molding, the design fixture is washed away from the nozzle material. The advantage of the disc gate is that it is beneficial for the filling of the plastic part, the stress is small, the size and geometric tolerance of the plastic part can be guaranteed, and here mainly refers to the roundness of the plastic part. Larger plastic parts, uniform and adequate temperature control system design is very necessary. Since the plastic part is a round plastic part, the cooling circuit of the front mold is a closed multi-layer water transfer circuit around the plastic part, so that the plastic part is cooled as much as possible. The rear mold is also designed with a sufficient cooling circuit. In particular, it is important to note that the front mold is most concentrated around the area of the sprue bushing, so a circular cooling circuit is designed on the periphery of the sprue bushing. See the mold design drawing for the front and rear mold cooling circuit diagram. Due to the large nozzle mold, the front mold slides of the six small through holes on the top of the plastic part are driven by the oil cylinder. In general, the sliders that use the core pull of the cylinder need to be designed with the shovel base to be locked during injection molding. The shovel base can be omitted only when the core is pulled or the pumping force is small. This is the case with this set of molds. The inner slide of the plastic part is demolded and ejected by the top of the push plate. When opening the mold, first complete the front mold slider core and then open the parting surface. 4 ejector pins 12 are attached to the bottom of the push plate with M16 threads. The injection molding machine ejector mechanism pushes the top rod 12 to push the push plate up. The pushing distance of the push plate is 180, which is limited by the limit screw 15. During the ejection process, under the action of the pull plate, the buckle locking plate and the B plate are separated from the bottom plate by a stroke of 90. The inner slider is pulled out of the buckle. Continue to eject, the B plate stroke is also limited by the screw limit, the B plate is separated from the push plate, the push plate continues to eject, and the plastic part is demolded.
The vertical wall on both sides of the large notch of the edge of the plastic part is close to 0o, and the draft of the rear mold slider needs to be designed because the draft is not sufficient. In this case, the use of the slider is the only correct mode of ejection, but it is often easy to ignore, resulting in poor mold release and affecting the appearance of the plastic part. Injection Mold