【Abstract】Original process of upper and lower half shells is to put hundreds of cylindrical inserts into mold, put upper core and upper core sleeve into inner hole of upper end of mold, vibrate mold core with a hand hammer to make upper core and upper core sleeve flush with upper end surface of mold, and efficiency is particularly low. A uniform vibrating material device was researched and designed. After inserting multiple cylindrical inserts into mold, core components were compressed by pressing device. Vibration device automatically vibrated and knocked mold to make inserts in place, and innovation effect was remarkable.

Upper half shell and lower half shell (see Figure 1) are made of hundreds of cylindrical inserts and plastic injection, and multi-cylindrical inserts are required to be evenly distributed. Before injection, hundreds of cylindrical inserts should be loaded into upper and lower half shell molds, and upper core should be installed in inner hole of upper end of lower half shell mold. In addition to upper core, upper core sleeve should also be installed.

 

Figure 1 Shell
a——upper half shell b——lower half shell
Original process is to put a cylindrical insert into mold, put it into simple tooling of half-shell set, and manually tap vibration mold. Since material is a cylinder and has poor fluidity, it requires dozens or even hundreds of times of manual vibration and knocking of mold with a hand hammer. It has caused many adverse consequences. First, mold is re-disassembled and reloaded, fatigue of people will increase rapidly, and work efficiency will be significantly reduced; Second is that sometimes cylindrical inserts are unevenly distributed, and half-shell sleeves produced by injection molding will appear white areas, resulting in substandard products. Analyzing reason, simple tooling only blocks core assembly with a baffle from upper end. When upper core and upper core sleeve are vibrated with a hand hammer, vibration and percussion force is transmitted to cylindrical insert, flow force of cylindrical insert acts on mold, causing upper mold to move up and squeeze onto upper baffle, making it difficult to remove mold. This production method is very backward. I believes that this situation can be changed, and uniform vibration material device is designed to replace manual production method.

Through in-depth analysis of product drawings, technological processes, and fluidity of cylindrical insert materials, an improved technological solution was conceived.

In order to prevent injection mold core assembly from moving, taking into account convenience and time saving, a compression device with a cam structure and a positioning mechanism was conceived, curved movement trajectory of cam was used to realize fast and convenient compression of core assembly. Calculating reasonable size of each part of cam is key to designing pressing device. Upper core sleeve is 15mm higher than plane of upper die, which requires device not only to compress upper core and upper die at the same time, but also to make core assembly convenient and quick to install. into the compression device. After careful calculation, the designed upper half casing pressing device has a cam lift of 16mm, which is convenient for operation. Designed upper half shell pressing device, support, positioning pin and pillar are fixedly installed above bottom plate; handle and cam are connected with pressing arm through rotating shaft; pressing arm has 3 holes on left side, 3 holes are respectively installed with pressing rod, middle pressure rod and pressure rod respectively from left to right. There are two holes on the right side, which are respectively connected with through holes corresponding to support and cam through rotating shaft; Injection mold core sub-assembly is placed on bottom plate, positioned by support and positioning pin, handle is turned down, cam curve moves, pressure arm, pressure rod, and middle pressure rod transmit force to core assembly, thereby pressing core assembly, cams R3mm and R15mm turn to upper plane of strut, which locks injection mold core assembly.

After injection mold core assembly pressing device is designed, it is necessary to consider how to make cylindrical inserts in inner cavity of core assembly evenly and densely distributed. It is necessary to strike upper core sleeve to make it flush with upper end face of upper die, and to vibrate core assembly to make cylindrical inserts evenly distributed. After consulting relevant information, AH-60 pneumatic hammer is selected as vibration source to realize automatic vibration and percussion functions. Selected AH-60 pneumatic hammer has a vibration force of 8~15kgf and a vibration frequency of 3~30Hz. A bracket is added on the bottom plate to fix pneumatic hammer firmly, pneumatic hammer is started and stopped by a switch, core assembly is vibrated and knocked, which constitutes a vibration device. Vibrating device and pressing device are combined into a uniform vibrating material device. Above half-shell uniform vibration material device (see Figure 2) is taken as an example, pneumatic hammer is connected to compressed air source, adjust air pressure, put upper half-shell injection mold core component into pressing device. After core assembly is quickly pressed by cam mechanism, pneumatic hammer is turned on. Pneumatic hammer automatically strikes upper core sleeve through hammer head at a frequency of 15 times per second, upper core sleeve is vibrated in place within 3s, and handle is turned up to take out core assembly. During debugging process, there was a problem with hammer head at lower end of main shaft of pneumatic hammer. Original hammer head material was made of CrWMn alloy steel. During vibration and knocking process, upper core sleeve jumped violently, upper core sleeve could not be flush with upper mold. Analysis of reasons, CrWMn alloy steel material has high hardness, hardness of upper core sleeve is also very high, which causes upper core sleeve to jump. After analysis, hammer head is made of red copper with lower hardness, several narrow grooves are opened on lower end face to buffer vibration. After test, problem of upper core sleeve jumping has been effectively solved, and efficiency of vibration knocking has been improved.
Lower half shell is used to vibrate material uniformly. Except for different hammer heads, different pressing arms, and no intermediate pressure rods, rest of components are basically same, and will not be described in detail here.

 

Fig. 2 Vibration pressing device of upper half shell

Improved operation steps are as follows:
(1) Put the cylindrical insert material into inner cavity of injection mold core subassembly, cover upper core and upper core sleeve.
(2) Put core assembly into uniform vibration material device, turn handle downward, press core assembly, open pneumatic hammer, automatically vibrate and strike mold, so that upper core and upper core sleeve are flush with upper end surface of core assembly.
(3) Turn handle upwards, release pressing device, and take out core assembly.

According to above operation, there are following advantages:
(1) High production efficiency: According to statistics, number of new technology assemblies per hour is more than 150, before improvement is not more than 120 per hour, production efficiency is increased by 30%.
(2) Fatigue reduction: Uniform vibration material device is adopted to save manpower and reduce human fatigue.
(3) Production organization and quota management: Using new technology, number of operators in each shift is reduced from 4 to 2, which brings benefits to production organization and quota management.
(4) Safety management: After new device is adopted, mold is automatically vibrated and knocked, which eliminates hidden danger of unsafety.

Based on above, after production verification, production efficiency has increased by 30%, product qualification rate has been improved, production cost has been reduced, economic benefits have been improved, innovation has achieved remarkable results, this technology can be used as a technical reserve to be applied to other similar products.