Basic Die Structure 1_rev

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Table of Contents 1. Designations and Roles of Injection Mold Component Parts 1.1 2-Plate Standard Mold 1.2 3-Plate Mold and Hoop Mold 1.3 Side Core Relations 2. Types and Characteristics of Gates 3. Structure and Mechanism of Injection Mold 3.1 Mold Opening Sequence of 3-Plate Mold 3.2 Runner ejection mechanism 3.3 Lifter Mechanism 3.4 Side Core Mechanism 4. Insert Molding 4.1 Outline of Insert Molding 4.2 Cavity Structure 4.3 Individual Part Insert 4.4 Hoop Insert MOLD STRUCTURE BASIC KNOWLEDGE

Transcript of Basic Die Structure 1_rev

Page 1: Basic Die Structure 1_rev

Table of Contents 

1. Designations and Roles of Injection Mold Component Parts1.1  2-Plate Standard Mold1.2  3-Plate Mold and Hoop Mold1.3  Side Core Relations2. Types and Characteristics of Gates3. Structure and Mechanism of Injection Mold3.1 Mold Opening Sequence of 3-Plate Mold3.2 Runner ejection mechanism3.3 Lifter Mechanism3.4 Side Core Mechanism4. Insert Molding4.1 Outline of Insert Molding4.2 Cavity Structure4.3 Individual Part Insert4.4 Hoop Insert

MOLD STRUCTUREBASIC KNOWLEDGE

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2-plate Since parts and their runners are formed on the same flat surface, simply opening the mold to the stationary platen and movable platen ejects parts. This system can be applied to almost all gates including side gates and tunnel gates.

3-plate This system is exclusive to pin gates. Since parts and runners are formed on the different flat surfaces, the mold needs to open its sections separately to eject them. It is called “3-plate” because the mold is divided into three sections when it is open.

There are several factors that determine the type of the mold structure to be used: shape of the molded part, the runner system, and the runner/molded part ejection method. There are various kinds of structures depending on the combination of basic structures such as the ejector system or undercut treatment system.

guide pin

return pin

stop pin

ejector pin

molded part

locate ringsprue bushsprue

runner

sprue return pinmovable side

stationary sideParting face(PL)

Fig. 2.19 2-plate mold

runner

Fig. 2.22 Enlarged figure of section A.

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set screwrunner lock pinstop bolt

Runner stripper plate pin point gate runner

molded part

tension link

Fig. 2.20 3-plate mold.

molded part

runner

Fig. 2.21 3-plate mold (when the mold is open).

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Basic parts:

Stationary mold

Mold that is mounted on the plasticizing unit of the molding machine. The nozzle touches it and melted resin is injected into it.

Movable mold

Mold that is mounted on the ejector side of the molding machine. It keeps molded parts for a moment and then ejects them with the ejector

Side core Refers to a method of undercut treatment. It is able to open and close perpendicular to the closing and opening directions of the molding machine.

Stripper An ejection method. It is usually a plate. It is used as a runner ejector in 3-plate mold.

Mold base A set of plates forming the outline of the mold. It is also called a “mold die set.”

stationary top plate (1)

guide pin (4)stationary plate (2)

movable plate (1)

spacer block (2)

backing plate (1)

movable bottom plate (1)

ejector plate

Fig. 2 25 Die set. Fig. 2.23 Side core mold.Fig. 2.24 Stripper plate mold

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Locate ring Ring for locating the nozzle of the molding machine and the sprue that is the resin pouring spout of the mold. 

 

Sprue bush Bush used as a pouring spout of the mold. With the pressure of the nozzle touch, it forms the sprue that leads resin from the molding machine to the runner of the mold.

 

Guide pins Pins used to guide the stationary mold and the movable mold. At the same time, they protect cavities and cores.  

 

2-plate standard mold

Designations and roles of injection mold parts

sprue bushlocate ring

stationary plate

stationary cavityejector pin (K.O pin)

return pinmovable plate

spacer blockejector plate 1 (K.O plate 1)ejector plate 2 (K.O plate 2)

movable bottom platereturn spring

guide pinmovable cavity

knock pin

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Ejector pins(K.O pin)

Pins used to eject cooled and formed parts from the cavities. 

 

Return pins Pins used to reset the ejector plate. They are pushed by the stationary retainer platen to reset the ejector plate during mold closing. 

 

Return springs Spring to reset the ejector plate faster than mold closing after part ejection. 

 

Stationary retainer platen

Plate installed on the nozzle side of the molding machine. It holds the cavity to prevent cavity deflection or distortion caused by resin pressure. 

 

Movable retainer platen

Main plate installed on the ejector side of the molding machine. It holds the movable cavity. 

 

Ejector plate 1(K.O plate 1)Ejector plate 2(K.O plate 2)

Ejector plate 1 and ejector plate 2 cooperatively pinch and hold the ejector pins and return pins. These two plates work as an ejector of the molding machine. They eject molded parts with the help of the ejector pins.

 

Spacer block Block to support clamping force and assures the space for the ejector stroke with its thickness. 

 

Movable bottom plate

Plate installed on the movable platen with clamps or bolts. It holds the movable side of the mold.  

 

Stationary cavity Movable cavity

Most important parts to consist a mold, and their manufacturing costs account for 70 to 80% of the entire mold manufacturing cost. They are divided into the stationary side and the movable side by the parting face. The convex side is called “core” and the concave side is called “cavity” in principle, but both of them are called “cavity” for the sake of convenience because there is no definite distinction between the two. 

 

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Runner ejector KO plate

Plate to eject the pin gate runners in the 3-plate mold. There are two types: one type is activated by mold opening tension and the other is by the hydraulic cylinder of the molding machine.

Lifter Lifter lifts the hoop and its guide when feeding the hoop after a cycle of molding. When lifting the hoop, it needs synchronization with the ejector.

 

Hoop hold-down plate

Plate installed on top of the lifter to hold the hoop. It prevents the hoop from lifting up during insertion.

Lifter pin Pin to connect the lifter to the lifter plate. 

Lifter plate

Plate to fix the lifter pins. It is lifted by the ejector plate, keeps being lifted by the air cylinder while feeding the hoop, and resets after molding to insert the hoop. 

lifter lifter pin

stationary top plate

runner ejector plate (runner KO plate)

pin gate runner section

stationary plate

lifter

Lifter plate

Air Cylinder

3-plate mold and hoop mold

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boltstopper collar

press-fit section

mold opening spring

Runner ejector KO plate guide pin

Pin to guide the runner ejector plate. There are two types; one type is forced into the stationary bottom plate and the other is forced into the runner ejector plate, but both of them function the same. It is usually equipped with the stopper collar that limits the degree of opening. 

 

Runner KO pin Pin to eject the runners when the runner lock is ejected in force by the runner ejector plate. 

  

Runner lock pin Pin to fix the runner on the ejector plate and to cut the pin gate with its undercut.

 

Mold opening springMold opening bolt

Spring and bolt to make a gap between the stationary top/bottom plate and stationary plate for cutting the pin gates.

 

Tension link Link to connect the movable platen to the stationary plate and to connect the stationary plate to the runner ejector plate. It activates the runner ejector plate during mold opening. It also acts as a stopper for the stationary plate.

 

mold opening bolt

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runner KO pinrunner lock pin

mold opening spring

runner ejector plate guide pin

runner ejector plate

Stationary plate

3-plate moldOpening condition

runner

tension link

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Space between the stationary bottom plate and the stationary plate expands due to the force of the mold opening spring. The runner is lifted up with the runner ejector plate because it is fixed with the plate with the lock pin. Accordingly, the gates are cut off.

The runner ejection space and the part ejection space start to widen along with the mold opening. (The space that is easy to open opens first.)

When the part ejection space and the runner ejection space are maximum, the runner ejection plate is pulled by the tension link and the runner lock is forcibly ejected. At the same time, the runner KO pin activates to eject the runner.

Structure and mechanism of injection mold

Opening sequence of 3-plate mold

gate cut

runner ejection spacerunner ejector

part ejection space

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Side core relations

Side core  

Angular pin Inclined pin to slide the side core during mold opening.  

 

Lock block Block to hold the side core during mold opening to prevent the side core from being opened by the resin pressure. 

 

Core to treat undercut such as side holes. It slides perpendicular to the mold opening direction due to the angle of the angular pin.

Undercut : The shape that is unable to release in the mold opening direction

lock blockside core angular pin

side mold

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Side Core Mechanism

At the time of mold opening, side core slides in the direction of the arrow due to the cam of the angular pin. Side core stops when the angular pin reaches the limit. The length of the angular pin can control sidestroke of the side core.

Stroke S = 5.5 angular pinlock block

Stroke S = 5.5 Stroke S = 20.3

side core

Mold OpeningStroke S = 5.5

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Product appearance Gates always mark products. Check if the marks do not destroy the product.

Resin flowability Set the gate in thick areas. When the product is long, set the gate at the end of the product.

After-treatment of gate Set the gate in the point where the product will not distort or chip

Measures to poor appearance of the gate

Set the gate where the gate is replaceable or the dent can be manufactured.

Measures to weld Avoid multiple gates as much as possible. One gate is much better than multiple gates.

Measures to distortionand warping

Note that some molding materials have fluid orientation.

Stress cracking There are residual stresses in the vicinity of the gate, so gates easily crack by external forces.

Gate balance For multiple-cavity molding, adopt simultaneous filling.

Mold intensity Resins must not hard hit slim pins.

How to decide a gate

(A) 1 side gate (B) 2 side gates (C) 3 side gates (D) Center sprue gate 3 pin-gates

Gate positions and transformations of disk shaped products.

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Gate positions and weld lines.

Gate Weld lineWeld line

1 gate 2 gates

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Direct gate Gate used for molding a single big article. There is a residual stress in the vicinity of the gate.

Side gate The most basic gate. It is easy to manufacture a mold, but the gate requires finishing.

Tunnel gate Gate that is cut by mold opening, but portion of the gate remain depending on the resin type. On top of that, it cannot be manufactured depending on the product shape.

Pin gate Gate that is cut by mold opening, but portion of the gate remain depending on the resin type. 3-plate mold is used.

Shaft-off gate Refers to an automatic cutting method for hardenable side gates, and requires a special structure. It cannot be used for elastic gates because it tends to cause thin burrs on molded parts.

Film/Fun gate Film gate and fun gate can reduce distortions and warping of molded parts caused by fluid orientation.

Disk/Link gate Disk gate and link gate are used for countermeasures against fluid orientation problems. However, they need to be pressed after molding.

Types of gate

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Direct gate Side gate Tunnel gate

depth of gaterunner

gate land

width of gate stationary platen side 2 ~ 3 mm

45° ~ 65°

movable platen side

ejector pin 15 °cone

Pin point gate system (4-point gate).

spruerunner

molded part

Film gate

gate runner gate

Fan gate

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Tab gate Disk gate Ring gate

disk gate face

Enlarged area

tab

sprue

Primary gate

Molded part

Over flowRing gate

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Realize simultaneous filling

Equidistant runners are good, but they increase material loss

Decrease material loss Minimize the pitch between parts as much as possible

Ease mold manufacturing Uniform the directions of parts to ease mold manufacturing

Ease mold repair Locate the side core on the outside to ease mold repair

Regarding hoop molding Consider the molded parts layout when designing the hoop

Points of molded parts layout

Round shaped runner Round shaped runner has the smallest fluid resistance but both upper and lower molds need to be manufactured.

U shaped runner It is cheap to manufacture U shaped runner because it requires processing only one side (upper or lower) of the mold.

Trapezoid runner When using bad fluid resins, trapezoid runner is used because it has an extended width.

Types of runner shapes

Trapezoid runner U shaped runner Round shaped runner

Runner shapes.

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2 parts in-series 4 parts in-series 4 parts in balance 4 parts in balance

8 parts in-series 8 parts in balance 8 parts in 3 rows

16 parts in 2 rows

16 parts in balance 16 parts in balance

Basic layouts of runners.

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“Hot runner” means “runner less molding.” This system can save resources by reducing material loss and can increase cycles by reducing cooling time.Types of runner less molding

Hot runner

Hot runner Refers to the runner that can keep melted resin right before the gate. It produces no loss material.

Mini runner When hot runner is inapplicable, mini runner could be used as a sub runner.

Sprue less Only spur works as a hot runner.

Warm runner

When the runner is hardenable, it is called warm runner.

Runner less molding. Sprue less molding.

molded product heat insulation board

cylinder

long nozzle type

molded product

long nozzlemold mold

bush type nozzle

cylinder

molded product

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cartridge heater

hot runner block

spear

Spear system hot runner.

thermoelement

Mini runner.

Layout of mini runners.

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After a cycle of molding, there remains half-cooled material at the tip of the nozzle. These half-cooled materials are stored in the cold slug well and ejected to prevent appearance failure during the next cycle of injection. Cold slug wells are usually located right under sprues or the ends of runners.

Cold slug well

Slug well combining sprue puller

Sprue slug well.

slug well

sub runner

sprue

Runner slug well.

Air vents are grooves that discharge air from cavities during injection. If air is not discharged, the air is insulated, compressed and overheated. Accordingly, short shot or discoloration will occur. Air vents shall be located on the front of gates or the ends of runners.

Air vent

PL face

gate 3 ~5mm

Depth0.01 ~ 0.05mm(gas)

Core air vent.

vent

Runner air vent.

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The point which has little influence of mold release

Ejectors should be located deep in the mold in principle.

Good mold release balance Ejectors should eject molded parts in good balance without causing distortion.

Thick areas Ejectors should be located at thick areas because they mark on thin areas.

Effect of gas vent Ejectors should be located at the point where resin is filled up and gases stack.

Good mold intensity Pin insertion should not decrease mold intensity.

How to design ejector

Ejector (Knockout, KO)

Round ejector pin Pin that is commonly used because of its ease of manufacture.

Square ejector pin Pin used for narrow areas that cannot accept round pins.

Ejector sleeve Sleeve to push thin cylindrical sections. (Set with a core pin)

Stripper plate Plate to push the circumference thin products such as cases. (One mold base activates.)

Ejector block A simple stripper type block. It pushes the circumference of a product.

Inclined pin Pin not only works as an ejector but also treats undercuts.

Types of ejector

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Round ejector pin Square ejector pin Ejector sleeve

ejector plate

bottom plate

Inclined pin

Stripper plate Ejector block

Types of ejectors.

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To shorten molding cycles

Lower the mold temperature to speed up hardening (plasticity).

To realize beautiful surface conditions

Keep the appropriate mold temperature for the resin to be used.

To prevent distortion or deformation

Uniform the temperatures of mold component parts.

To improve mechanical characteristics

When using crystalline resins, set the mold temperature high to heighten crystallinity.

To improve flowabitily For resins with bad flowability, set the mold temperature high

Purposes of mold temperature control:

Mold temperature control

Hot water or hot oil:Cold water:Electric heater:

Mold temperature controller is used. This is the most popular method.Cold water circulation unit (chiller) is used.Electric heater is applicable to hardenable resins and engineering plastics.

Mold temperature control methods

Cooling holes are usually located on the mold base. For thick or large-size products, cores should be cooled down to stabilize quality and improve productivity.

Core cooling

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V shaped path Refers to the method of manufacturing a reciprocating path in the core. It is used for relatively big cores.

Partition Partition is used when V shape path is inapplicable..

Heat pipe Pipe that makes use of heat transferability. It is used for big cores.

Logic seal The temperature controller made by Logic Device Co. (USA). Resistant to leaking since it absorbs cooling water at a lower pressure than atmospheric.

Methods of core cooling

V shape path Partition Heat pipe Logic seal

Methods of core cooling.

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Undercut refers to the section of a molded part that cannot be released from the mold by the regular mold opening direction. Undercut is designed when the undercut is a part of the part design or when the undercut is necessary to keep the part on the ejector side.

Undercut

Side core Core that slides perpendicular to the mold opening direction. Its types vary from a mere part of the mold to a main part of the mold.

Inclined pin Pin that slides perpendicular to the undercut while ejecting the molded part.

Undercut Undercut makes use of elasticity of resins. This method is not suitable for molded part shapes, so it is mainly used to hold molded parts on the ejector side.

Undercut treatment methods

Angular pin The most popular pin. Many purchased pins are available at reasonable prices.

Angular cum When the stroke of the side core is small, the mold can be compact.

Hydraulic cylinder This method is used when the stroke of the side core is large or when cycle up is targeted.

Side core operation methods

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Pay attention to the use of inclined pins because their sliding faces are easily abraded.

Applications of inclined pins

Angular pin Angular cum Hydraulic cylinder.

inclined pin

This face receives resin pressure. When ejecting molded parts, angular pin slides.

The position of the slide core after ejection.

Enlarged section of the inclined pin

Inclined pin

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Sprue lock Lock used to keep the sprue section on the ejector side.

Runner lock Lock used to keep the runner on the ejector side after gate cut.

Molded product Make the product uneven to keep it on the ejector side, if no problem.

Applications of undercut

Ring type Reverse-taper Z pin Ring BTaper

Sprue lock Runner lock of pin gate.

Enlarged undercut section

Product shape Countermeasures against mold release

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It is difficult to calculate the actual intensity of movable/stationary plates because they usually have a manufactured hole. Even so, you should investigate their intensity very carefully because wrong calculation might lead to mold damages or burrs on products.

Movable/Stationary plate design

Pocket carving Pocket carving is the most common and the best method for keeping plate intensity. However, it is difficult to realize high accuracy of the bottom face.

Penetrating hole Penetrating hole is good for plate accuracy but deteriorates plate intensity. To use this method, therefore, the outline should be big.

Grooving Grooving is good for plate accuracy but deteriorates plate intensity. To use this method, therefore, the plate needs to be hardened.

Plate manufacturing methods

Pocket carving. Penetrating hole. Grooving

Plate manufacturing method.

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Type of Steel Code Hardness HRC Applications

Carbon steel for mechanical structureChrombriden steelCarbon steelAlloy tool steelHigh speed steel/Bearing steel

S50C S55CSCM440 SCM435SK2 SK3 SK5 SK7SKS2 SKD11 SKD61SKH9 SKH51 SUJ2

16-3030-3754-6058-6258-63

mold basescavities, corespinscavities, corespins

Classification

HRC

JIS code

Steel makers

Hitachi Metals. Ltd.

Daido Steel Co,. Ltd. Aichi Steel

Nippon Koshuha Steel

Co,. Ltd.Kobe Steel, Ltd. Uddeholm

Pre-harden steel

13 SC family HIT81 PDS1 AUK1 KPM1 KTSM2AKTSM21

28 SMC family HIT82 PDS3 AUK11 KPM2 KTSM3AKTSM31

33 SCMSNCMSUS familySUS family

HPM2HPM17HPM38ASL3OF

PD55PD555PD742

KPM25KPS1

KTSM3MKTSM60

HOLDAXIMPAXPAMAX-S

35 SUS family PSL NAK101 U630

40 SKD61AISI P21AISI P21

FDACHPM1HPM50

DH2FNAK55NAK80

FDASKAPKAP2

KTSM40EFKTSM40E

Hardening/Temper steel

60 SKD11 HPM31 PD613 AUD11 KSP2 RIGOR

52 SUS family HPM38 PD555 KSP1 KTSM60 STAVAX

High temperature aging steel

53 Mal aging -steel YAG MASIC KMS18-20 KMS-CF19

43 Non-magnetic steel YHD50FM NAK301 KTSM-UMI

Steel for molds Steel for molds stipulated by JIS

Contrast chart of steel brands for molds