CN112154054A

CN112154054A - Method for producing molded article

Info

Publication number: CN112154054A
Application number: CN201980025209.4A
Authority: CN
Inventors: 大桥克英; 五十岚拓也; 三木崇裕
Original assignee: Hitachi Automotive Systems Ltd
Current assignee: Hitachi Astemo Ltd
Priority date: 2018-05-31
Filing date: 2019-04-08
Publication date: 2020-12-29
Anticipated expiration: 2039-04-08
Also published as: WO2019230196A1; CN112154054B; JP6937907B2; JPWO2019230196A1

Abstract

A method for manufacturing a molded article capable of reducing a clearance inside a thick portion without generating burrs includes a molding step of filling a mold with resin to form the molded article, the molded article having a thin portion with a thin wall thickness of the resin and a thick portion with a wall thickness thicker than the thin portion, the thick portion forming the thick portion being disposed closer to a mold gate to which the resin is filled than the thin portion forming the thin portion in the mold, the molding step including a 1 st step of filling the mold gate with the resin, a 2 nd step of making a flow velocity of the resin at the thin portion zero after the 1 st step, and a 3 rd step of filling the mold gate with the resin after the 2 nd step.

Description

Method for producing molded article

Technical Field

The present invention relates to a method for producing a molded article.

Background

In the molded product, it is preferable to make the thickness uniform in order to prevent defects such as flow failure and various molding defects caused by the flow fluctuation of the resin during molding. However, the thickness cannot be made uniform depending on the required specifications of the product, and a thick portion having a thick wall and a thin portion having a thin wall are often disposed locally. In particular, it is known that a thick portion having a large wall thickness has a problem that a void is formed inside the thick portion due to resin shrinkage during molding. In order to suppress the existence of the gap, it is also conceivable to increase the holding pressure at the time of resin filling, but it is known that a burr is generated due to an increase in pressure. Patent document 1 discloses a composite integrally molded article which is a molded component obtained by insert molding a member molded from a preform having one or more convex shapes, wherein the composite integrally molded article is insert molded so as to include a resin portion for fixing the preform member to a mold other than the convex shape.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2000-326359

Disclosure of Invention

Problems to be solved by the invention

In the invention described in patent document 1, the gap inside the thick portion cannot be reduced without generating burrs.

Means for solving the problems

A method of manufacturing a molded article according to claim 1 of the present invention is a method of manufacturing a molded article including a molding step of filling a mold with a resin to form a molded article, the molded article having a thin portion with a thin wall thickness of the resin and a thick portion with a wall thickness thicker than the thin portion, the mold having a thick portion forming the thick portion disposed closer to a mold gate filled with the resin than the thin portion forming the thin portion, the molding step including: a step 1 of filling the mold gate with a resin; a 2 nd step of making the flow velocity of the resin at the thin portion zero after the 1 st step; and a 3 rd step of filling the mold gate with a resin after the 2 nd step.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the gap inside the thick portion can be reduced without generating burrs.

Drawings

Fig. 1 is an external perspective view of a flow meter 100.

Fig. 2 is a top view of the flow meter 100.

Fig. 3 is a front view of the flow meter 100.

Fig. 4 is a bottom view of the flow meter 100.

Fig. 5 is a V-V sectional view in fig. 3.

Fig. 6 is a diagram showing a manufacturing apparatus 90.

Fig. 7 is a diagram showing the structure of the mold 1.

Fig. 8 is a diagram showing a state immediately after the start.

Fig. 9 is a diagram showing a state before time t 1.

Fig. 10 is a diagram showing a state from time t1 to time t 2.

Fig. 11 is a diagram showing a state from time t2 to time t 3.

Fig. 12 is a diagram showing a state from time t3 to time t 4.

Fig. 13 is a diagram showing a state after time t 4.

Fig. 14 is a diagram showing a state from time t10 to time t20 according to the 1 st conventional technique.

Fig. 15 is a diagram showing a state after time t20 in the 1 st conventional technique.

Fig. 16 is a view showing molding according to the 2 nd conventional technique.

Detailed Description

Embodiment (c)

Hereinafter, an embodiment of the method for producing a molded article of the present invention will be described with reference to fig. 1 to 16.

(flow meter)

Fig. 1 to 5 are diagrams showing a flowmeter 100 as a molded article manufactured by the method of the present invention. Fig. 1 is an external perspective view of a flow meter 100, fig. 2 is a plan view of the flow meter 100, fig. 3 is a front view of the flow meter 100, fig. 4 is a bottom view of the flow meter 100, and fig. 5 is a V-V sectional view in fig. 3.

As shown in fig. 1 to 4, the flowmeter 100 includes a resin portion 101 and a substrate 102. The resin portion 101 includes a connector 104, a housing gate 105, a mounting hole 106, a flange 107, and a flow path 109. A metal terminal 103 electrically connected to the outside of the flowmeter 100 is disposed inside the connector 104. Mounting holes 106 and flanges 107 are used to secure flowmeter 100. The frame gate 105 is a portion that becomes an inlet of the resin when the resin portion 101 is formed.

As shown in the cross-sectional view of fig. 5, the flowmeter 100 includes a thick portion 110 having a large resin thickness and a thin portion 120 having a smaller resin thickness than the thick portion 110. In the process of manufacturing the flowmeter 100, the resin reaches the flow path 109 from the frame gate 105 through the thick portion 110 and the thin portion 120. That is, thick portion 110 is closer to frame gate 105 than thin portion 120.

(manufacturing apparatus)

Fig. 6 is a diagram showing a manufacturing apparatus 90 for molding the flowmeter 100. The manufacturing apparatus 90 includes a mold 1, a molding machine 2, and a computer 900. The molding machine 2 includes a heating pipe 2a, a screw 2b, and a plunger 2 c. In the molding machine 2, the granular resin 101a is fed to the molding side, and the resin 101a becomes a molten resin 101b by the screw 2b inserted into the heating pipe 2a, and is accumulated in the screw tip end portion 2 bb. The accumulated molten resin 101b advances by the screw 2b by the forward movement 2cc of the plunger 2c of the molding machine, and the molten resin 101b enters the mold 1. The computer 900 includes a CPU, a ROM, and a RAM, and the CPU expands and executes a program stored in the ROM into the RAM to control the screw 2b and the plunger 2c of the molding machine 2 as described later.

The amount per unit time of the molten resin 101b flowing into the mold 1 is influenced by both the operations of the screw 2b and the plunger 2c, but in the present embodiment, both the operations are collectively referred to as "screw speed". The state where the molten resin 101b does not flow into the mold 1 is defined as a screw speed of zero. That is, the screw speed is a real number equal to or greater than zero, and the amount of the molten resin 101b flowing into the mold 1 per unit time increases as the screw speed increases.

Fig. 7 is a diagram showing the structure of the mold 1. The mold 1 includes an upper mold 1a, a lower mold 1b, a runner 1c into which the molten resin 101b of the molding machine 2 flows, a cavity 1e engraved to form a molded article, and a mold gate 1d which flows the molten resin 101b into the cavity 1 e. In fig. 7, the mold 1 is shown in a closed state, but when the mold 1 is opened, the substrate 102 as an insert member is mounted inside a thin-wall forming portion 120Z described later or mounted on the opposite side of the mold gate 1d from the thin-wall forming portion 120Z.

Hereinafter, a portion of the cavity 1e where the thick portion 110 is formed is referred to as a thick portion 110Z, a portion where the thin portion 120 is formed is referred to as a thin portion 120Z, a portion where the flow channel 109 is formed is referred to as a flow channel portion 109Z, and a portion where the frame gate 105 is formed is referred to as a gate portion 105Z. The gate forming portion 105Z is adjacent to the mold gate 1d, and is arranged from the left side in the figure according to the gate forming portion 105Z, the thick-wall forming portion 110Z, the thin-wall forming portion 120Z, and the flow path forming portion 109Z, as shown in fig. 7. The molten resin 101b flows in this order. The flow of the molten resin 101b in the chamber 1e is hereinafter referred to as a resin flow mf.

(production method)

The following describes the molding process with reference to fig. 8 to 13. In each of fig. 8 to 13, the upper "(a)" shows a time-series change in screw speed, and the lower "(b)" shows a state of the molten resin 101b inside the mold 1. Fig. 8 shows a state immediately after the start, fig. 9 shows a state at time t1, fig. 10 shows a state at time t2, fig. 11 shows a state at time t3, fig. 12 shows a state at time t4, and fig. 13 shows a state after time t 4. The screw speeds V0 to V3 are higher as the numerical values are larger, and specifically, V3 is the highest speed. The control of the screw speed and the determination of the timing of changing the screw speed, which are described below, are executed by the computer 900. However, instead of the computer 900, the operator may determine the screw speed and the timing of changing the screw speed.

Further, the faster the screw speed, the faster the inflow speed of the molten resin 101b at the mold gate 1d, and in the case where the screw speed is zero, the inflow speed of the molten resin 101b at the mold gate 1d is zero. Therefore, the screw speed and the inflow speed of the molten resin 101b at the mold gate 1d can be said to be in a proportional relationship.

Fig. 8 is a diagram showing a state immediately after the start. As shown in fig. 8 (a), the molten resin 101b extruded from the molding machine 2 is initially pressed into the mold 1 at the screw speed v 3. At this time, the screw speed v3 needs to be set high to avoid rapid cooling of the molten resin 101b in the mold 1. Inside the mold 1, the molten resin 101b flows from the runner 1c as shown in fig. 8 (b), and flows into the cavity 1e through the mold gate 1 d. However, the resin flow mf remains in the thick-wall forming portion 110Z.

Fig. 9 is a diagram showing a state after the start and until time t 1. At time t1, about 90% of the cavity 1e is filled with the molten resin 101 b. The screw speed from t0 to t1 at which filling starts is constant at v 3. Here, in the cavity 1e, the molten resin 101b is not filled to 100%, so that the pressure inside the mold 1 is low, and deformation and damage of the substrate 102 and burrs on the mold clamping surface are not generated.

Fig. 10 is a diagram showing a state from time t1 to time t 2. At time t2, the chamber 1e is filled with the molten resin 101b by about 100%. This step is also referred to as a pressure holding step. In order to avoid a sudden pressure increase in the chamber 1e due to the filling of 100% of the molten resin 101b in the chamber 1e, the screw speed is set to v1 at a low speed. Further, since a rapid pressure rise does not occur, the substrate 102 can be kept in a state where deformation, breakage, or burrs on the mold clamping surface do not occur.

Fig. 11 is a diagram showing a state from time t2 to time t 3. From time t2 to time t3, the screw speed is set to v0, i.e., zero. When the screw speed becomes zero, the flow of the molten resin 101b in the chamber 1e is stopped, and the molten resin 101b in the chamber 1e starts to be cooled and solidified from the surface layer. Further, resin shrinkage occurs in the molten resin 101b as it solidifies by cooling. This action makes the thin-walled portion 120 of the flowmeter 100 thinner in volume than other portions, and therefore, it is cooled and solidified in a short time. The time required for cooling and solidification can be calculated depending on the shape and the material of the resin used, and the time from time t2 to time t3 is the same as the calculated time or a time with a slight margin added.

At time t2 to time t3, in thick portion 110, gap 200 as a void is formed in the center of the thick portion due to shrinkage of molten resin 101 b. At this time, since the thick portion 110 has a large volume, the entire thick portion 110 is not cooled and solidified due to heat accumulation of the molten resin, and only the surface layer is solidified. The runner 1c and the mold gate 1d are portions having a smaller volume than other portions, but are flow paths through which the molten resin 101b flows in the entire volume of the cavity 1e, and therefore the periphery of the portions of the runner 1c and the mold gate 1d is heated to a high temperature by latent heat of the molten resin 101b, and is in a state of a temperature higher than the mold temperature of the cavity 1 e. This high temperature state causes a delay in cooling of the molten resin 101b in the runner 1c and the mold gate 1d, and therefore does not reach solidification.

Fig. 12 is a diagram showing a state from time t3 to time t 4. From time t3 to time t4, the screw speed is set to v2 which is faster than v1, and the molten resin 101b starts to be pushed into the mold 1 again from the molding machine 2. As described above, since the runner 1c and the mold gate 1d are not yet solidified, the molten resin 101b can be press-fitted into the thick-walled portion 110Z. In addition, the thin portion 120 is already cooled and solidified from time t2 to time t 3. Therefore, the molten resin 101b flowing from the mold gate 1d into the cavity 1e is blocked by the resin 101c of the solidified thin portion 120, and flows into the gap 200 existing in the thick portion 110Z. Thus, the gap 200 is reduced.

Since the screw speed from time t3 to time t4 is set to v2 which is faster than v1 in the previous step, the molten resin 101b easily flows into the gap 200. Further, the screw speed was set to v2 which was faster than v1, but since the molten resin 101b on the surface layer had already cooled and solidified, no burr was generated on the outer periphery of the chamber 1 e. In addition, similarly to the substrate 102 mounted in the vicinity of the thin portion 120, the thin portion 120 is cooled and solidified before time t3, and therefore the substrate 102 is not deformed or damaged.

Fig. 13 is a diagram showing a state after time t 4. After time t4, the screw speed is again set to v0, i.e., zero. After time t4, the entire molten resin 101b pushed into the mold 1 is cooled and solidified. However, the time of this step is not particularly limited, and the flow meter 100 may be cooled to such an extent that it can be taken out from the chamber 1e without being deformed or damaged.

(conventional method)

Two molding steps according to the conventional method will be described with reference to fig. 14 to 16. First, a 1 st conventional technique will be described with reference to fig. 14 to 15.

According to the 1 st conventional technique, as shown in fig. 14, filling is performed at a constant screw speed v30 from time t0 to time t10 when filling is started. Then, from time t10 to time t20, the screw speed was reduced, and 100% of the molten resin 101b was filled in the chamber 1e at v 10. After time t20, the screw speed is set to v0, i.e., zero as shown in fig. 15. Accordingly, the molten resin 101a starts to be cooled and solidified, and the thick portion 110 is formed with a gap 200 as a void due to the shrinkage of the resin. Then, it is directly cooled to form a molded article in which the gap 200 still remains.

In the 2 nd conventional technique, the pressure for filling the molten resin 101b is set high as a measure for the gap 200. Fig. 16 is a view showing a molded article formed by the 2 nd conventional method. As shown in fig. 16, in the 2 nd conventional technique, the rigidity of the mold 1 cannot withstand the pressure inside the mold 1, and burrs 101d are generated from the parting surfaces of the mold 1. In addition, the pressure inside the mold 1 becomes high, and the substrate 102 may be deformed and damaged.

The flowmeter 100 manufactured by the method of the embodiment can realize a method for molding a resin product without burrs and without deformation or damage of the substrate.

In addition, the flowmeter 100 manufactured by the method of the embodiment can greatly reduce the gap that becomes a void in a large area inside the resin.

According to the above embodiment, the following operational effects can be obtained.

(1) The method of manufacturing the flowmeter 100, which is a molded product in the present embodiment, includes a molding step of filling the mold 1 with the resin 101a to form the molded product. The flowmeter 100 includes a thin portion 120 made of a thin resin and a thick portion 110 made of a thicker resin than the thin portion 120. In the mold 1, the thick portion 110Z for forming the thick portion 110 is disposed closer to the mold gate 1d to which the resin 101a is filled than the thin portion 120Z for forming the thin portion 120. The molding step includes a 1 st step of filling the mold gate 1d with the resin 101a, for example, a step from time t0 to time t2, a 2 nd step of making the flow velocity of the resin in the thin-wall portion-forming portion 120Z zero after the 1 st step, for example, a step from time t2 to time t3, and a 3 rd step of filling the mold gate 1d with the resin 101a after the 2 nd step, for example, from time t3 to time t 4.

Since the thin-walled portion 120 is cured by the process from time t2 to time t3, the surface layer is also cured at the same time, and therefore, burrs generated on the mating surfaces of the mold can be suppressed. Thereafter, the escape portion of the resin 101a pressed between the mold gate 1d and the thin portion 120 disappears, and the resin is sandwiched therebetween. Therefore, the resin 101a can be pushed into the gap 200 formed in the thick portion 110, and the gap 200 can be reduced. That is, according to the present technique, the gap inside the thick portion 110 can be reduced without generating burrs. Further, the present method can be formed by 1-time molding without using a preform member, and therefore, reduction in man-hours and significant cost reduction can be achieved compared to the method using a preform member.

(2) The screw speed v2 from the time t3 to the time t4 is faster than the screw speed v1 immediately before the time t2 is reached. Therefore, the gap 200 can be further reduced.

(3) The time length from time t2 to time t3 is calculated based on the shape of the thin-walled portion 120 and the material of the resin 101 a. Therefore, the time during which the thin-walled portion 120 is cooled and solidified can be appropriately calculated.

(4) The step before the screw speed becomes zero includes a step from time t0 to time t1 and a step from time t1 to time t 2. The inflow speed of the resin 101a at the mold gate 1d in the process from time t1 to time t2 is slower than the inflow speed of the resin 101a at the mold gate 1d in the process from time t0 to time t 1. Therefore, a rapid pressure rise in the chamber 1e can be avoided, and the substrate 102 can be kept in a state where deformation, damage, or burrs on the mold clamping surface do not occur.

(5) In each of the steps from time t0 to time t1, the steps from time t1 to time t2, and the steps from time t3 to time t4, the inflow speed of the resin 101a at the mold gate 1d is constant. The flow rate of the resin 101a into the mold gate 1d in the process from time t3 to time t4 is slower than the flow rate of the resin 101a into the mold gate 1d in the process from time t0 to time t1 and faster than the flow rate of the resin 101a into the mold gate 1d in the process from time t1 to time t 2. Therefore, the gap inside thick portion 110 can be reduced without generating burrs.

(6) The resin 101a filled in the mold 1 is pressure-fed by a screw 2a, and the rotation speed of the screw 2a is controlled by a computer 900. Therefore, the molded member with the reduced gap can be easily mass-produced.

(7) The flowmeter 100 includes a substrate 102 and a metal terminal 103 as inserts, and the substrate 102 and the metal terminal 103 are disposed on the opposite side of the mold gate 1d from the thin-wall forming portion 120Z. The insert is often damaged or deformed due to its low rigidity and failure to withstand resin pressure, and is required to be molded at as low a pressure as possible. According to the method of the present embodiment, the step of making the resin flow velocity zero is performed before the resin of the thin portion 120 is cured. Therefore, the insert member mounted in the vicinity of the thin portion 120 and the insert member mounted behind the thin portion 120 are not damaged or deformed by the inflow of the resin 101a from time t3 to time t 4.

(modification 1)

In the molding step in the above embodiment, the screw speed may be constant from time t0 to time t 2.

(modification 2)

The speed may be variable at each of time t0 to time t1, time t1 to time t2, and time t3 to time t 4. In other words, the speed may not necessarily be kept constant at each time.

(modification 3)

In the molding step in the above embodiment, the screw speed from time t1 to time t2 may be equal to or higher than the screw speed from time t3 to time t 4. In other words, in the above embodiment, v1< v2 is defined, but v 1. gtoreq.v 2 may be defined.

(modification 4)

In the above embodiment, the flowmeter 100 is molded by molding, but other articles may be molded. That is, the above-described embodiment can be widely applied to a molded product injection-molded by a molding machine. In addition, the resin material can be similarly applied to various materials that can be injection molded. Further, an article having no insert may be molded.

The above embodiments and modifications may be combined. In the above, various embodiments and modifications have been described, but the present invention is not limited to these. Other schemes considered within the scope of the technical idea of the present invention are also included in the scope of the present invention.

According to the method for producing a molded article of the present invention, even in the case of an insert which is likely to be deformed or damaged by the filling pressure of the resin, a molded article in which at least a part of the outer periphery of the insert is integrally wrapped with the resin can be formed without deforming or damaging the insert, and an inexpensive and high-quality molded article can be provided.

Further, according to the method of manufacturing a molded article of the present invention, even in the case of an element in which the flow rate, temperature, and humidity of air are individually measured or an insert of a circuit board in which a plurality of the elements are combined and arranged, terminals to be electrically connected to the outside can be simultaneously inserted into a mold without damaging the elements and the substrate, and a molded article in which at least a part of the outer periphery of the substrate is integrally wrapped with a resin can be formed, and a molded article having a low cost and a high-quality sensing function can be provided.

Description of the symbols

1 … … mould

1d … … sprue

1e … … Chamber

2 … … shaping machine

100 … … flowmeter

101. 101a, 101b, 101 c. resin

102 … … base plate

110 … … thick wall part

120 … … thin wall part

200 · gap.

Claims

1. A method for producing a molded article, comprising a molding step of filling a mold with a resin to form a molded article, characterized in that,

the molded product has a thin portion with a thin wall thickness of resin and a thick portion with a wall thickness thicker than the thin portion,

in the mold, a thick-walled portion for forming the thick portion is disposed closer to a mold gate to which the resin is filled than a thin-walled portion for forming the thin portion,

the molding step includes:

a step 1 of filling the mold gate with a resin;

a 2 nd step of making the flow velocity of the resin at the thin portion zero after the 1 st step; and

and a 3 rd step of filling the mold gate with a resin after the 2 nd step.

2. The method of manufacturing a molded article according to claim 1,

the resin in the 3 rd step flows into the mold gate at a speed higher than that immediately before the end of the 1 st step.

3. The method of manufacturing a molded article according to claim 1,

the temporal length of the 2 nd step is calculated based on the shape of the thin portion and the material of the resin.

4. The method of manufacturing a molded article according to claim 1,

the 1 st process includes a 1 st half process and a 1 st half process performed subsequent to the 1 st half process,

the resin in the second half step 1 flows into the mold gate at a lower speed than the resin in the first half step 1.

5. The method of manufacturing a molded article according to claim 4,

in each of the first half step 1, the second half step 1, and the 3 rd step, an inflow speed of the resin at the mold gate is constant,

the resin in the 3 rd step flows into the mold gate at a speed slower than that in the 1 st half step and faster than that in the 1 st half step.

6. The method of manufacturing a molded article according to claim 1,

the resin filled in the mold is fed under pressure by a screw, and the rotation speed of the screw is controlled by a computer.

7. The method of manufacturing a molded article according to claim 1,

the molded article includes an insert disposed inside the thin-wall forming portion or on a side opposite to the mold gate from the thin-wall forming portion.

8. The method of manufacturing a molded article according to claim 1,

the molded article includes an insert which is easily deformed or broken by a filling pressure of a resin, and is formed by inserting the insert into a mold and integrally wrapping at least a part of an outer periphery of the insert with the resin.

9. The method of manufacturing a molded article according to claim 1,

the molded product includes an element for individually measuring a flow rate, a temperature, and a humidity of air, or an insert of a circuit board configured by combining a plurality of the elements, and also includes a sensing function in which a terminal for electrical connection to the outside is simultaneously inserted into a mold, and at least a part of the outer periphery of the circuit board is integrally wrapped with a resin.