basic die structure 1_rev
TRANSCRIPT
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
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.
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).
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
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
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.
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
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
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
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
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
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
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.
Gate positions and weld lines.
Gate Weld lineWeld line
1 gate 2 gates
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
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
Tab gate Disk gate Ring gate
disk gate face
Enlarged area
tab
sprue
Primary gate
Molded part
Over flowRing gate
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.
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.
“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
cartridge heater
hot runner block
spear
Spear system hot runner.
thermoelement
Mini runner.
Layout of mini runners.
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.
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
Round ejector pin Square ejector pin Ejector sleeve
ejector plate
bottom plate
Inclined pin
Stripper plate Ejector block
Types of ejectors.
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
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.
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
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
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
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.
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