JPS59178229A - Molding method of hot runner of injection molding machine - Google Patents

Abstract

PURPOSE:To improve dimensional precision, molding stability by adding a drawing process of a nozzle tip from a plate and a reinserting process of the nozzle tip to the plate following the mold closing process and prior to the molding process. CONSTITUTION:Partial surface (a) is provided between the fixed plate 4 and the sprue plate 6 and two processes, process C (nozzle tip drawing) and process D (nozzle tip inserting) are inserted between a general molding cycle process B and a process C to obtain seven processes in total. The point portion of a nozzle tip 12 inserted into the fixed plate 4 comes in contact with the fixed plate 4 and heat is removed from the plate 4 to obtain a secure gate seal effect, in synchronization with opening motion of the partial surface (a) the point portion of the nozzle tip 12 is taken out of the fixed plate 4 and the point portion of the nozzle tip 12 is melted securely by the heat conduction of a preheating push 13.

Description

[Detailed description of the invention] This article relates to a hot runner molding method for a machine.

Conventionally, as an injection mold, only the molded product was released from the gate without cooling by setting part of the launch cycle as Rf.
The "-hot runner" method is often used for the purpose of reducing the amount of scrap by cooling and taking out the material, improving yield and shortening the cycle. For this reason, 114 of the hot runner mold
The part containing the runner must be kept at a high temperature, and the part containing the molded product must be kept at a low temperature.
It is necessary to pay careful attention to the upper level, and if a blockage occurs in the gate that cools the gate, and if the gate is kept at a relatively high temperature, the molded product will be difficult to cool down and the gate will be difficult to cool down.

Normally, the following problems occur when performing posotorunner molding using an injection molding machine.

(1) Bad gate balance.

(2) Drawling (nose/this) phenomenon occurs from the gate part.

(3) Due to insufficient melting at the gate, clogging occurs.

(4) The gate pitch cannot be made small.

(5) The leg on the temperature side is itchy.

(6) It is necessary to use a special temperature control device, which increases the cost.

(7) If the gateknoll type is a resin-solidified type, a high pressure (about ρθθ to 3θθkf/cm” in resin pressure) is required to destroy the seal film, and low-pressure injection molding is not recommended in Circular 1.菟.

Particularly, in low-pressure injection molding using a hot runner, the phenomenon of upper Re (31) occurs, which necessitates increasing the injection pressure, which poses a serious problem in low-pressure moldability.

The present invention aims to provide a hot runner molding method for thermoplastic resin that solves the above-mentioned problems. To,
This was invented to solve the above-mentioned items (2), (3), (5), (6), and (7).

The present invention will be explained below with reference to the accompanying drawings.

First, in FIG. 1 showing a cross section of a mold for carrying out the hot runner molding method according to the present invention, hot sprue,
It is attached to the sprue plate B and supports the manifold block 3 located below it. The manifold block 3 has a preheating block 3 and a nozzle chip/piece below it.
, 2, the nozzle tip 7.2 passes through the preheating block 3' and is screwed onto the manifold flock, 2. As shown in the enlarged detailed view of Fig. β, the nozzle tip /, 2 is slidably inserted in the vertical direction into the inner hole formed in the fixed plate gage, and its tip is connected to the fixed plate gage and the movable plate /θ. Consisting of TL, the product cavity/
'l (D upper surface K reaches. Nozzle tip/,,
As shown in Fig. β, the body of No. 2 has a preheating bushing/3Vc fixed to the preheating plate 3 and hanging from the plate.
More contact is surrounded. As shown by the arrow in FIG. 3, the tip of the nozzle depth 2 is configured to be insertable into and pulled out from the fixed plate.

Next, in the mold of an injection molding machine, a dividing surface, usually called a parting line, is formed between a fixed plate and a movable plate.
θ, and by dividing and separating the two, the molded product can be released.

The ejector plate, usually called the ejector plate, is
In the mold closing process that follows the molding process, after the split faces are separated, they are moved to one side and the molded product is ejected into the cavity/g via the connection 1 to the ejection rod 2. There is.

Furthermore, a fixed plate 1 and an elevating cylinder j are fixedly installed on the sprue plate B, and a piston that can slide within the cylinder is connected via a piston rod to a bracket 7 that is thinly attached to the fixed plate gage, and the hydraulic The sprue plate B and the fixed plate ge are opened and closed at the dividing surface a by reciprocating movement of a piston within the cylinder using fluid pressure such as pneumatic pressure or any other appropriate method.

Cartridge heater // is 1 as shown in figure 1 and hot sprue/, manifold block 3 and preheating block 3
are arranged to apply a predetermined amount of heat to appropriate positions of the parts to provide a heat source necessary to melt the resin contained in each part.

Next, the present invention will be explained in detail with respect to the mold having the above-mentioned configuration. First, in order to compare with the injection molding method according to the present invention, a general molding cycle of injection molding operation will be shown. The cycle is as shown in Figure 3, and the molding cycle starts (stops).
] It is formed by a 5-step process consisting of 22 people, mold closing process B, molding (injection, cooling) process C, mold opening process and ejection process E. In this figure, if the names of the construction ropes are representatively displayed in step A, then G is 1〃1 constant plate, /θ is movable plate, is protruding plate, 2 is protruding rod, and the dividing plane between fixed plate and movable plate is It is b. During the above steps, all the nozzle tips remain fixed to the fixed plate as shown in FIG.

FIG. S shows a molding cycle diagram according to the present invention.

The main point of the present invention that is different from the general molding cycle shown in FIG. 3 is that the apparatus used in the molding method according to the present invention is:
There is a dividing surface a between the fixed plate and sprue plate B.
In addition, two steps, 8C (nozzle tip extraction) and step D (nozzle depth insertion) shown in Figure 3, are inserted between steps B and C of the general molding cycle. That's what I did.

In the molding cycle start (pause) step of Fig. 5A,
The fixed plate moves up and down/the piston of the cylinder j acts upward, and the dividing surface a is in a closed state.

At this point, the tip of the nozzle tip 7.2 is inserted into the fixed plate and reaches the surface of the cavity 7. In this state, heat is removed from the tip of the nozzle tip/2 by the large-capacity fixing plate/IK, and the J finger on the melting side solidifies, maintaining the gate seal state. this(
The weak containment and split surface are kept open with mold opening 11.

Next, in the mold closing process shown in FIG. J, B, the mold is closed while the dividing surface a remains closed. At this time, the fixed plate elevating cylinder j is not operated and the dividing surface a remains closed, so that the nozzle tip 7.2
The distal end of is inserted into the fixed plate.

Subsequently, in the nozzle tip drawing process shown by CK in Fig. 5, the fixed plate 1 and lifting cylinder j are operated downward to open the dividing surface a, and the sprue plate B moves upward or the fixed plate ge moves downward. hot sprue/, manifold block supported by sprue plate B, 2. The preheating block 3 and the nozzle tip/2 move relative to the fixed plate gage, and the tips of the nozzle chips/2 inserted into the fixed plate gage are pulled out.

The tip of the nozzle tip 7.2 in the sealed state transfers the thermal energy of the preheating block 3 heated by the cartridge heat to the preheating block 3.
The resin in the assimilated state, which is received through U/3 and is located at the interface, is dissolved. That is, the gate seal is released. After this gate seal release state has been achieved, the nozzle tip insertion step is next carried out.

That is, in the nozzle tip insertion process shown in Figure S, the design is the same as in the mold closing process, the dividing surfaces a and b are closed, and the tip of the nozzle tip/2 is inserted into the fixing plate y. .

Next, the molding (injection, cooling) process shown by E in FIG. 5 is in phase with the molding process CK of the general molding cycle shown in FIG. The molded product is injected into the cavity from the tip of the nozzle tip 7.2 with the gate seal released through the flow path /j shown in FIG. Mold opening process (No. J1) shown by F in Figure 5
9J (corresponding to the mold opening process DK). During the above-mentioned molding step E, the gate seal is released, and the tip of the +V- nozzle tip 2 gradually loses heat from the fixed plate in contact with it, changing to the gate seal state again.

In the mold opening step F, the dividing surface is opened by the mold opening operation of the injection molding machine, but the dividing surface a is maintained in a closed state.

Next, in the take-out step shown by G in Fig. 5, the ejector pin is raised by the upward movement of the ejector plate, and the molded product formed in the cavity is ejected from the cavity, thereby performing the work of removing the molded product. be exposed. At this time, the dividing surface is open and the dividing surface is in a closed state. This corresponds to process E in Figure 3.

With the above, the molding cycle is completed, and the process returns to the molding cycle start (pause) step again, and the above cycle is repeated.

As is clear from the above description, the molding method according to the present invention includes a predetermined process following the mold closing process and prior to the molding (injection, cooling) process in the general molding cycle, and following the nozzle tip drawing process and fl. It is constructed by adding a nozzle tip reinsertion step that is performed after a certain period of time has elapsed.

With the above configuration and operation, the method according to the present invention ensures that in the hot runner molding method, the tip of the nozzle tip 7.2 inserted into the fixed plate gage is removed from heat by contact with the fixed plate gage. A good gate sealing effect can be obtained, and in conjunction with the opening operation of the dividing surface a, the tip of the nozzle tip/-2 is pulled out from the fixed plate, cutting off direct contact, and the nozzle tip is sealed by heat conduction of the preheating plate/3. /2 has the effect of releasing the gate seal by reliably melting the tip of the gate, preventing the phenomenon of clogging at the gate. θ~/θθI
<needle m 2) is now possible. Furthermore, control of gate seal release can also be adjusted by the opening time of the dividing surface a, and there is no need for delicate temperature control at the gate portion, making handling extremely simple.

It is still relatively simple in structure, easy to shift to automation, and greatly contributes to reducing equipment costs.

Furthermore, the present invention is fully compatible with the hot runner molding method for low-viscosity resins with reliable gate sealing effect 1, and has remarkable effects in terms of stable molding, dimensional accuracy, gate balance, etc.

[Brief explanation of the drawing]

Fig. 1 is a structural sectional view of an embodiment of a mold for carrying out the hot runner molding method according to the present invention, Fig. 3 is an enlarged view of the Δ section in Fig. 1, Fig. 3 is a general molding cycle diagram, and Fig. 9 is a The state of the nozzle tip in a general molding cycle, FIG. 5 shows a molding cycle diagram according to the present invention. / Hot sprue! Manifold block 3 - Preheating block Fixed plate S Fixed plate elevating 7 cylinder O - Blue brake 7 Bracket and protruding plate 2... Protruding rod /θ Movable plate // Cartridge heater /. , 2 Nozzle tip 73 Preheating bush/G cavity/j Flow path No. 1 Fig. 1 B E [) ・C1
Figure 13 o E (God X) (God

Claims (1)

[Claims] Using an injection molding mold consisting of a fixed plate and a movable plate that are movable relative to each other, one of the plates has a nozzle tip installed in the plate so as to be movable relative to the plate. In a hot runner injection molding method that performs a molding cycle including closing, molding (injection, cooling), mold opening and ejection steps, following the mold closing step and preceding the molding (injection, cooling) step. A hot runner for an injection molding machine, comprising: a step of pulling out the nozzle tip from the plate; and a step of reinserting the nozzle tip into the plate after a predetermined period of time following the drawing step.
Molding method.