Injection molding bleed amount measurement mold

Abstract

In the powder injection molding process, the high temperature and pressure during molding causes part of the binder to separate as liquid bleed, which then penetrates into gaps in the mold that have a degassing function and solidifies, thereby inhibiting the degassing function and causing molding defects such as "burns," "blisters," and "poor filling."To avoid this problem, we provide a mold for measuring the amount of bleed produced by injection molding, which directly measures the amount of bleed and uses it as an evaluation scale. [Solution] The mold for measuring the amount of bleed during injection molding has a porous adsorbent (e.g., a laminate of filter paper, a porous ceramic sintered body, etc.) built in, and the bleed that seeps out during injection molding is absorbed and impregnated into the adsorbent. Specifically, the adsorbent, whose weight has been measured in advance, is set in the mold, and after injection molding, the adsorbent is removed and its weight is measured again. This difference in weight before and after injection is quantified as the amount of bleed, enabling quantitative evaluation. The extremely thin "filter paper" that comes into direct contact with the molded body is separated from the adsorbent and excluded from measurement. Furthermore, if the amount of bleed is so small that measurement accuracy is insufficient, injection molding can be repeated multiple times to measure the accumulated amount of bleed, improving measurement accuracy.

Description

[Technical Field]

[0001] This invention relates to a measuring mold for measuring bleed that occurs during powder injection molding. [Background technology]

[0002] In powder injection molding, the high temperature and pressure generated by adiabatic compression of the final filling portion of the mold cavity causes some of the binder to separate as liquid bleed, seeping into gaps with gas venting functions such as the parting line, ejector pins, and slide cores, and solidifying. This inhibits the original gas venting function, causing molding defects such as "burns," "blisters," "welds," and "poor filling" in the molded product. Therefore, research and development into binder compositions that do not cause bleeding is required. Summary of the Invention [Problem to be solved by the invention]

[0003] In the research and development of binder compositions that do not cause bleeding, there has been a problem in that there is no means for directly measuring the amount of bleeding and using it as an evaluation scale.

[0004] In order to solve this problem, the present invention aims to provide a means to serve as an evaluation scale for directly measuring the amount of bleeding that occurs. [Means for solving the problem]

[0005] To solve the above problem, the following method was discovered. A porous adsorbent, the weight of which has been measured in advance, is placed inside a mold for measuring the amount of bleed during injection molding. After the adsorbent is impregnated with the bleed that has seeped out during injection molding, the adsorbent is removed from the mold and its weight is measured again. The difference in weight before and after injection is quantified as the amount of bleed, enabling quantitative evaluation.

[0006] A laminate of commercially available "filter paper" is used as a general-purpose adsorbent. In this case, an ultra-thin "filter paper" is placed on the surface that comes into direct contact with the molded body, and this ultra-thin "filter paper" that adheres to the molded body after molding is separated from the adsorbent to exclude it from measurement. Therefore, the object of bleeding amount measurement is the remaining "filter paper" laminate impregnated with the bleed, and its weight is measured before and after injection.

[0007] This ultra-thin "filter paper" should preferably be made of cellulose fibers containing 99% or more of alpha cellulose and be 180 μm thick. Furthermore, it is also possible to use porous materials such as porous ceramic sintered bodies, porous metal sintered bodies, and carbon fiber adsorbents as the adsorbent.

[0008] If the amount of bleeding is so small that it is no longer possible to obtain a sufficient amount as a measurement value, the injection molding is repeated several times and the accumulated amount of bleeding is measured to improve measurement accuracy. [Effects of the Invention]

[0009] By using this injection molding bleed measurement mold, the amount of bleed can be measured, which is an essential quantitative evaluation measure for research and development of binder compositions that do not cause bleed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a half cross-sectional view including a mold for measuring the amount of bleeding after injection molding, a molded body, an ultra-thin "filter paper," and an adsorbent. [Figure 2] Figure 2 shows a three-dimensional view of the compact removed from the mold, the ultra-thin "filter paper," and the adsorbent.

[0011] The adsorbent (3) with the "filter paper" laminated on it is inserted into the lower mold part (4)-3, and the ultra-thin "filter paper" (2) is placed on top of it. The middle mold part (4)-2 and the upper mold part (4)-1 are then overlapped and fastened together with the mold fastening bolts (5). At this time, the adsorbent is compressed, so the tightening torque of the bolts must be kept constant.

[0012] Immediately after heating the bleed amount measurement mold (4) with a heater table or the like, set it in the injection molding machine and injection mold the powder injection molding feedstock to be measured. The conditions for this can be the standard conditions of mold temperature, material temperature, injection speed, and holding pressure, or the worst conditions for each can be selected.

[0013] After the injection mold has cooled, the bolts (5) are removed, the mold (4) is disassembled, and the molded body (1) and the ultra-thin "filter paper" (2) are removed. The adsorbent (3) remaining in the lower part of the mold (4)-3 is removed by pushing it out with a pin or similar device through the gas escape hole on the bottom of the mold.

[0014] The weight of the removed adsorbent is measured accurately to the nearest 0.1 mg using an electronic balance, and the weight of the adsorbent after injection molding is then measured again using the electronic balance. If these weights are before W and after W, the amount of bleed is calculated using the following formula: Bleed amount (mg) = after W - before W [Explanation of symbols] ▲1▼Molded body ▲2▼Ultra-thin "filter paper" ▲3▼Adsorbent ▲4▼Mold ▲4▼-1 Upper part of mold, nozzle touch area ▲4▼-2 Center of mold, cavity ▲4▼-3 Lower part of the mold, adsorbent holding part ▲5▼Mold fastening bolt

Claims

[Claim 1] In research and development of binder compositions for powder injection molding feedstock, an injection molding bleed amount measurement mold is provided with a mechanism for incorporating a porous adsorbent whose weight has been measured in advance into the injection molding mold, and the adsorbent is impregnated with bleed that exudes during injection molding.The adsorbent is then removed from the mold and its weight is measured again, thereby quantifying the amount of bleed as the difference in weight before and after injection.The porous adsorbent is a laminate of commonly available, commercially available "filter paper," and an ultra-thin "filter paper" is used on the surface of the laminate that comes into contact with the molded body incorporated into the mold.After molding, the ultra-thin "filter paper" attached to the molded body is peeled off and the weight is measured.The injection molding bleed amount measurement mold is characterized in that the adsorbent is also made of a porous ceramic sintered body, a porous metal sintered body, or a carbon fiber adsorbent.

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