阅读说明：本技术 一种汽车后尾门内板pp发泡注塑工艺 (PP foaming injection molding process for inner plate of rear door of automobile ) 是由 黄燃 宁鹏焕 孙裕谟 于 2019-08-29 设计创作，主要内容包括：本发明公开了一种汽车后尾门内板PP发泡注塑工艺,具体包括以下步骤,步骤一：合模操作,动模腔与静模腔在注塑机上合模；步骤二：注塑,注塑机向模具型腔内注射75％-85％模具型腔体积量的PP改性材料,其中,PP改性材料中添加了0.4％发泡剂；注塑压力分六个区,采用“低中高”递增模式,压力控制螺杆加料段在30-40bar,螺杆压缩段在50-60bar,螺杆计量段在70-80bar；注塑速度与注塑压力相对应,采用“高中低”递减模式,压力控制螺杆加料段在12-15mm/s,螺杆压缩段在8-10mm/s,螺杆计量段在5-6mm/s；步骤三：保压,保压压力值为10-15bar,保压时间为15-18s；步骤四：开模取件；解决经发泡后制品外观不均匀导致零件性能要求受损的工艺问题。(The invention discloses a PP foaming injection molding process for an inner plate of a rear door of an automobile, which specifically comprises the following steps: performing mold closing operation, namely closing the movable mold cavity and the static mold cavity on an injection molding machine; step two: injection molding, wherein the injection molding machine injects a PP modified material with 75-85% of the volume of the mold cavity into the mold cavity, wherein 0.4% of foaming agent is added into the PP modified material; the injection pressure is divided into six zones, a low-medium-high increasing mode is adopted, the pressure controls the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar and the screw metering section to be 70-80 bar; the injection molding speed corresponds to the injection molding pressure, a descending mode of high, medium and low is adopted, the pressure controls the screw feeding section to be 12-15mm/s, the screw compression section to be 8-10mm/s and the screw metering section to be 5-6 mm/s; step three: maintaining the pressure at 10-15bar for 15-18 s; step four: opening the mold and taking out the part; the process problem that the performance requirement of parts is damaged due to the uneven appearance of the foamed product is solved.)

1. The PP foaming injection molding process for the inner plate of the rear door of the automobile is characterized by comprising the following steps of: the method specifically comprises the following steps of,

the method comprises the following steps: performing mold closing operation, namely closing the movable mold cavity and the static mold cavity on an injection molding machine;

step two: injection molding, wherein the injection molding machine injects a PP modified material with 75-85% of the volume of the mold cavity into the mold cavity, wherein 0.4% of foaming agent is added into the PP modified material;

the injection pressure is divided into six zones, a low-medium-high increasing mode is adopted, the pressure controls the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar and the screw metering section to be 70-80 bar;

the injection molding speed corresponds to the injection molding pressure, a descending mode of high, medium and low is adopted, the pressure controls the screw feeding section to be 12-15mm/s, the screw compression section to be 8-10mm/s and the screw metering section to be 5-6 mm/s;

step three: maintaining the pressure at 10-15bar for 15-18 s;

step four: and opening the mold to take out the part.

2. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and in the second step, 79% of PP modified material of the volume of the mold cavity is injected into the mold cavity.

3. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and the injection molding temperature in the second step is controlled to be 1.2-1.3 times of the melting point of the PP modified material.

4. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and in the second step, the injection molding pressures of the six areas are respectively as follows: 35bar, 40bar, 55bar, 58bar, 68bar and 75 bar.

5. The PP foaming injection molding process of the automobile rear tail door inner plate is characterized in that: and in the second step, the injection molding temperatures corresponding to the injection molding pressures of the six zones are respectively as follows: 180 ℃, 190 ℃, 210 ℃, 220 ℃, 200 ℃ and 190 ℃.

6. The PP foaming injection molding process of the automobile rear tail door inner plate as claimed in claim 1, wherein the PP foaming injection molding process comprises the following steps: and in the third step, the pressure maintaining pressure value is 14bar, and the pressure maintaining time is 17 s.

Technical Field

The invention belongs to the technical field of polypropylene injection molding, and particularly relates to a PP foaming injection molding process for an inner plate of a rear door of an automobile.

Background

The polypropylene (PP) resin has the characteristics of rich raw material sources, light weight, superior cost performance, excellent heat resistance, chemical corrosion resistance, easy recovery and the like, and is one of the resins with wide world application and fast yield increase. At present, most researchers in the industry concentrate on the field of medium-high ratio foaming, and in reality, injection molding of large or thick-walled products using PP as a base material is always a difficult problem, because of the high crystallinity of PP, it is difficult to avoid various problems such as shrinkage and flow marks when manufacturing the large products.

The properties of foamed PP depend on the relative density and cell structure characteristics of the foamed material. Uniformity of cell distribution and reduction of cell size are key factors for enhancing the performance of the hair foam article with respect to cell structure.

The study of scholars finds that: under the same density condition, the smaller the cell size, the more uniform the distribution, and the higher the tensile property of the foam material; the weight reduction range of the material is increased, and the tensile property is reduced; the impact strength of the foamed product is greatly related to the relative density and the thickness of the skin layer.

For injection molding foaming PP, the foaming appearance is influenced by multiple factors such as temperature, shearing force, cavity pressure and the like.

With the increasing complexity of products, the tolerance requirements and the surface appearance quality requirements of parts are higher and higher, and the quality or cost requirements are difficult to achieve by adopting the traditional injection molding processing technology. Especially, the foaming material is controlled by constant air pressure, especially the sensitivity of the foaming agent to temperature is high, and if the temperature gradient is not properly controlled, excessive flatness of the foaming or insufficient foaming rate can be generated, the foaming efficiency is affected, and the expected weight reduction effect cannot be achieved.

Disclosure of Invention

The invention provides a PP foaming injection molding process for an inner plate of a rear door of an automobile, which solves the problems in the background technology.

In order to achieve the purpose, the invention adopts the technical scheme that: a PP foaming injection molding process for an inner plate of a rear door of an automobile specifically comprises the following steps,

the method comprises the following steps: performing mold closing operation, namely closing the movable mold cavity and the static mold cavity on an injection molding machine;

step two: injection molding, wherein the injection molding machine injects a PP modified material with 75-85% of the volume of the mold cavity into the mold cavity, wherein 0.4% of foaming agent is added into the PP modified material;

the injection pressure is divided into six zones, a low-medium-high increasing mode is adopted, the pressure controls the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar and the screw metering section to be 70-80 bar;

the injection molding speed corresponds to the injection molding pressure, a 'high, medium and low' decreasing mode is adopted, the pressure controls the screw feeding section to be 12-15mm/s, the screw compression section to be 8-10mm/s and the screw metering section to be 5-6 mm/s;

step three: maintaining the pressure at 10-15bar for 15-18 s;

step four: and opening the mold to take out the part.

Preferably, in the second step, 79% of the volume of the mold cavity of the PP modifying material is injected into the mold cavity.

Preferably, the injection molding temperature in the second step is controlled to be 1.2-1.3 times of the melting point of the PP modified material.

Preferably, the injection pressures of the six zones in the second step are respectively as follows: 35bar, 40bar, 55bar, 58bar, 68bar and 75 bar.

Preferably, the injection molding temperatures corresponding to the injection molding pressures of the six zones in the second step are respectively as follows: 180 ℃, 190 ℃, 210 ℃, 220 ℃, 200 ℃ and 190 ℃.

Preferably, the pressure value of the pressure maintaining in the third step is 14bar, and the pressure maintaining time is 17 s.

The beneficial effect of adopting above technical scheme is:

1. according to the PP foaming injection molding process for the inner plate of the rear tail door of the automobile, the actual foaming rate state is considered, the injection volume filling amount is controlled to be 75-85% of the volume of the mold cavity, the volume expansion rate after being pressed is 17-33%, and in the specific step II, a PP modified material with 79% of the volume of the mold cavity is injected into the mold cavity, so that the weight of the inner plate of the rear tail door of the automobile is reduced by 21%; 0.4% foaming agent is added into the PP modified material, so that the foaming efficiency is ensured.

Dividing the injection pressure into six zones, adopting a low-medium-high increasing mode, controlling the pressure to control the screw feeding section to be 30-40bar, the screw compression section to be 50-60bar, and the screw metering section to be 70-80bar, wherein the injection pressure of the six zones in the specific step II is respectively as follows: 35bar, 40bar, 55bar, 58bar, 68bar and 75bar, the injection speed corresponds to the injection pressure, a descending mode of high and medium, and the pressure control screw is provided with a feeding section of 12-15mm/s, a compression section of 8-10mm/s and a metering section of 5-6mm/s, so that the injection molding product with larger size, for example: the injection molding pressure and the injection molding temperature of different injection molding sections of the inner plate of the automobile back tail door are properly adjusted, so that the consistency of the viscosity of the PP modified material and the foaming uniformity are ensured, namely the uniformity of the foam cell distribution and the uniformity of the foam cell size are ensured.

2. The injection molding temperature in the second step is controlled to be 1.2-1.3 times of the melting point of the PP modified material, and the injection molding temperatures corresponding to the injection molding pressures of the six zones in the second step are respectively as follows: the temperature of 180 ℃, 190 ℃, 210 ℃, 220 ℃, 200 ℃ and 190 ℃ ensure the viscosity state of the PP modified material under the corresponding injection pressure, thereby ensuring the foaming saturation state.

3. And in the third step, the pressure maintaining value is 10-15bar, the pressure maintaining time is 15-18s, the pressure maintaining value is 14bar, the pressure maintaining time is 17s, a lower pressure maintaining value and a longer pressure maintaining time are adopted, the PP modified material is convenient to rapidly expand in volume in the die cavity, the foaming rate is increased, and the lightweight requirement is met.

Detailed Description

The following examples are included to provide further detailed description of the embodiments of the invention and to provide those skilled in the art with a more complete, concise and complete understanding of the principles and spirit of the invention, and to facilitate its practice.

The invention relates to a PP foaming injection molding process for an inner plate of a rear door of an automobile, which solves the process problem that the performance requirement of parts is damaged due to the uneven appearance of a foamed product.

The following specific working modes are illustrated by specific examples: