62265758 Advance Injection Mould Design

CORPORATE TRAINING AND PLANNING

ADVANCE INJECTION MOULD DESIGN

01


SPLIT MOULD

02


• It is required for components incorporates a recess or projection right angle to the line of draw, to relieve the undercut before the moulding is removed.

• A moulding which has a recess or projection is termed as undercut moulding.

• The undercut may be external, internal, local part of the component.

• Two or more parts of the cavity closed together in a chase bolster by using locking heels during injection.

SPLIT MOULD

03


Fig: 1.1 Fig: 1.2

04


VISIBLE LINE ON MOULDING

• Parting line: The line formed on the molding surface where the core and cavity closed together.

• Joint Line: The line formed on the molding surface where the splits (side cores) are closed together.

05


SLIDING SPLITS

• The splits are positioned in guides on a flat mould plate are actuated by mechanical or hydraulic system and those are held together by locking heels which project on the other mould half.

• The splits are possible to mount on either the moving or fixed mould plate.

06


Fig: 1.3 Fig: 1.4

07


GUIDING AND RETENTION OF SPLITS - SLIDING FIT

Fig: 1.5 Fig: 1.6

08


Fig: 1.7 Fig: 1.8

09


DESIGN CONSIDERATION OF SPLIT MOULD

• The side movement should ensure the split halves always come together in the same plane.

• In split mould all the parts should have enough strength to withstand the force applied to the splits by the operating system.

• It should allow smooth movements of splits.

10


• Amount of splits movement and delay period required.

• Ease with which the molding can be removed.

• Whether a short or long production run is required.

• Whether the available machines are programmed for ancillary cylinder control.

• Whether molding inserts are to be incorporated.

SPLIT DESIGN CONSTRAINTS

11


1. Finger cam actuation method

2. Dog-leg cam actuation method

3. Cam track actuation method

4. Hydraulic actuation method

5. Angled-lift splits

6. Spring actuation system

SPLIT MOULD ACTUATION METHODS

12


1.FINGER CAM ACTUATION

Fig: 1.9 Fig: 1.10

13


FINGER CAM ACTUATION MOULD FOR CAP COMPONENT


FINGER CAM MOULD FOR LEDHOLDER


FINGER CAM PIN

• Hardened, circular steel pins, termed finger cams are mounted at an angle in the fixed mould plate.

• Length and angle of the finger cam determine the distance traversed by each split across the face of the mould plate.

14


FINGER CAM PIN

M = splits movement = Angle of finger cam, 10-25L = working length of finger camC = clearance (0.75mm)

Fig: 1.11

15


CALCULATION

The finger cam movement can be computed by the Formula

M = (L sin ) – (C / cos )If the required movement is known, the following formula used to determine the finger cam length.

L = (M / sin ) + (2C / sin 2)Where, M = splits movements, = Angle of finger cam, 10-25L = working length of finger camC = clearance (0.75mm)Cam diameter is usually 13 mm.

16


2. DOG - LEG CAM ACTUATION

This actuation system is used where a more splits delay time is required compare to finger cam actuation method.

17


Fig: 1.12

DOG-LEG CAM

18


DOG-LEG CAM ACTUATED MOULD

Fig: 1.13 Fig: 1.1419


DOG LEG CAM ACTUATED SPLIT MOULD

M = movement of each split,La= angled length of cam,Ls = straight length of cam,

= Cam angle, C = clearance, D = delay,e = length of straight portion of the hole.

Fig: 1.15

20


CALCULATION

Formula for calculating the opening movement, the length of cam, and the delay period

M = La tan - CLa = (M + C)/ tan D = (Ls – e) + (C/tan )Where M = movement of each split,La= angled length of cam,Ls = straight length of cam,

= Cam angle, C = clearance,

D = delay,e = length of straight portion of the hole.

21


3. CAM TRACK ACTUATION

• This type of actuation system is used for components having under cut which requires more delay period

• Due to external fitment of cam track the mold actuation system becomes simpler and mold cost is reduced.

• The cam track is machined into a steel plate attached to the fixed mould half. • A boss fitted to both sides of the split runs in this cam track.

• The movement of the splits accurately controlled by specific cam track design .

22


CAM TRACK PLATE

Fig: 1.16 Fig: 1.17

23


SLIDING SPLIT MOLD (CAM TRACK PLATE

ACTUATED)

Fig: 1.1824


ASSEMBLY OF CAM TRACK ACTUATION MOLD IN CLOSED

POSITION

Fig: 1.19

25


CAM TRACK

M = movement of each split,La= angled length of cam track, = cam track angle,C = clearance,D = delay,R = radius of boss

Fig: 1.20

26


CALCULATION

M = La tan - CLa = (M + C) / tan D = Ls + C/ tan + r ( 1/tan - 1/sin )M = movement of each split,La= angled length of cam track, = cam track angle,C = clearance,D = delay,R = radius of boss

27


4. HYDRAULIC ACTUATION

The splits are actuated by hydraulic system. It is independently opening movement of the mould. The splits can be operated automatically at any specific time by the operating program of the machine

ADVANTAGES

• Cycle time less

• Large delay movements and large split movements can be achieved

28


DISADVANTAGES

• The mould is more bulky as compared with the other designs

• Mould setting more difficult and the hydraulic system has to be connected each time the mould is set up.

29


HYDRAULIC ACTUATION OF SPLITS

Fig: 1.2130


ANGLED-LIFT SPLITS

• In this method the splits are mounted in a chase-bolster, which forms part of the moving half of the mould.

• The splits are moving outward with an angular motion which relieve the undercut portion of the molding and retraction of the split alignment is controlled by using spring actuation or cam track actuation

31


ANGLED LIFT SPLITS DIAGRAM

Fig: 1.22 Fig: 1.2332


TYPES OF ANGLED LIFT SYSTEMS

• Angled guide dowel actuating system

• Cam track actuating system

• Spring actuation.

33


ANGLED GUIDE DOWEL ACTUATING

SYSTEM

• The Guide dowels are fitted at an angle to the underside of each split which passes through holes machined at an angle in the chase-bolster.

• When the ejector system is actuated, the relative movement between the ejector plate and the chase-bolster causes the guide dowels to move forward at an angle corresponding to the splits which opens.

34


ANGLED GUIDE DOWEL ACTUATION

Fig: 1.24

35


= Guide dowel angle.

Fig: 1.25 36


The convenient angle for the guide dowel is 10 it may be increased if large opening movement is required. The actual opening movement of each split calculated by the following formula.

M = E tan E = effective ejector plate movement, = Guide dowel angle.

37


CAM TRACK ACTUATING SYSTEM

• In this method the opening movement of the splits are controlled by a cam track. When the splits are actuated, studs fitted to each end of the split slide along this cam track.

• Actuation of the splits is by means of pin ejector system. The splits are fitted into an open channel type chase-bolster, which have wear plates.

• Studs, screwed into the splits, protrude into the cam track machined in the cam track plate which is attached to the bolster.

38


CAM TRACK ACTUATION

Fig: 1.26

39


CALCULATION

The opening movement of each split calculating byM = E tan E = effective ejector plate movement, = Cam track angle, usually 15

40


SPRING ACTUATION• The opening movement of the split depends on the slot provided in the chase bolster and the spring effective expansion length.

• This ejection method is suitable for shallow undercut components.

•The ejector pin actuates the split, the spring exerts the a force to vertical direction, which maintains contact between the split and the angled wall of the chase-bolster and gives angled movement to the splits. Thus the splits get open.

41


SPRING ACTUATION METHOD

Fig: 1.27 42


SPRING ACTUATION SYSTEM• This actuation system is suitable for small straight and angled undercut components.• In this method the compression springs are used to force the splits apart and utilizes the angled faces of the chase bolster to close them. The opening of split movement should be limited so that they will allow to re-enter the chase bolster when the mould is closed. • The splits are mounted on the mould plate and retained by guide strips. Studs project from the base of the splits into a slot machined in the mould plate. The length of this slot therefore controls the opening movement of each split. • A compression spring is fitted between the studs in a link-shaped pocket situated in the lower mould plate. The splits are held closed by the chase bolster. 43


SPRING ACTUATION

Fig: 1.28

44


SEQUENCE OF OPERATION

• The chase bolster holds the splits during the injection phase.

• The compression springs exerts a force to split halves immediately when the mould starts to open.

• The stud reaching the end of the slot in the mould plate stops the split movement.

• Continued movement of the moving mould half operated the ejector system to release the molding .

45


CALCULATION

The formula for calculating the splits opening movement isM = ½ H tan Where M = movement of each split, ApproximatelyH = height of locking heel= angle of locking heelSuitable angle for the locking heel is 20 to 25.

46


SIDE CORES

• It is a local core mounted at an angle to the mould axis for forming a hole or recess inside the molding.

• This side core prevents the in-line removal of the molding hence, side core must be withdrawn prior to ejection .

47


TYPES OF SIDE CORE

Internal Side Core Assembly

• The dog-leg cam actuation method• The spring-loaded system

External Side Core Assembly

• Side cores on the parting surface

• Side cores below the parting surface

• Angled withdrawal Curved side core

48


INTERNAL SIDE CORE ASSEMBLY

• In this method the side core is T-shaped is mounted in guides, which are securely attached to the moving mould plate. • The retaining plate to the carriage secures the side core element.The actuation of the carriage is by means of a finger cam/dog leg cam method• The carriage is locked in the forward position by the locking heel

49


DOG-LEG CAM METHOD OF ACTUATION

Fig: 1.29 50


THE SPRING-LOADED SYSTEM

The spring-loaded system is an operating method confined to those moldings that have very shallow undercuts or projections.

51


Fig: 1.30 52


EXTERNAL SIDE CORE ASSEMBLY

In this design, the side core is fixed to an extremely mounted carriage which is actuated by hydraulic or pneumatic means.

53


Fig: 1.31 54


CURVED SIDE CORE

• The core is withdrawing from the mould along the arc of a circle.

• It is suitable for components requires smooth curved internal hole

• Example: telephone hand set and pipe fittings.

• In this type of component the side core can be mounted on the parting surface of the mould.

55

MOULDS FOR INTERNAL

UNDERCUT COMPNENTS

058

• An internal undercut is the internal protrusion or recessAn internal undercut is the internal protrusion or recess

formed in the molding by using matching core or cavity.formed in the molding by using matching core or cavity.

• It is prevents a moulding from being extracted from the It is prevents a moulding from being extracted from the

core in line of draw.core in line of draw.

INTERNAL UNDERCUTINTERNAL UNDERCUT

059


EXAMPLES OF INTERNAL EXAMPLES OF INTERNAL UNDERCUT COMPONENTSUNDERCUT COMPONENTS

Fig: 2.1 Fig: 2.2

060


FORM PINFORM PIN

A component, which has a local undercut portion, can A component, which has a local undercut portion, can be successfully moulded in the conventional mould be successfully moulded in the conventional mould by incorporating the undercut form on a pin. by incorporating the undercut form on a pin.

061


UNDERCUT COMPONENTSUNDERCUT COMPONENTS WHICH NEED WHICH NEED FORM PINS FORM PINS

ACTUATIONACTUATION

Fig: 2.3 062


TYPES OF FORM PIN TYPES OF FORM PIN EJECTIONEJECTION

Form Pin : Straight actionForm Pin : Straight action

Form pin : angled action Form pin : angled action

063


FORM PIN:STRAIGHT FORM PIN:STRAIGHT ACTIONACTION

This design is normally used for components, which incorporate an undercut on one internal wall only.

064


Fig: 2.4 Fig: 2.5

065


FORM PIN: ANGLED ACTIONFORM PIN: ANGLED ACTION

• The basic feature of this design is that the working face of the form pin is caused to move inwards relative to the core during ejection, thereby relieving the undercut.

• It can be used for components, which incorporate internal undercuts on one or more walls.

066


Fig: 2.6 67


CALCULATIONCALCULATION

The amount of withdrawal is calculated by the following relationship:

M = E tan θ

Where, M = the withdrawing movement E = ejection movement. θ = fitting angle of the form pin.

68


SPLIT CORE ACTUATIONSPLIT CORE ACTUATION

This split core may be moved forward either in a straight plane or an angled plane.

69


SPLIT CORES-STRAIGHTACTION

• This design is used for components, which incorporate an external undercut on one wall only.

• The moulding can be removed at right angles to the mould axis.

70


Fig: 2.7

71


SPLIT CORE ANGLED SPLIT CORE ANGLED ACTIONACTION

•In this design the split core is caused to move inwards during the ejection stroke, thereby withdrawing the restriction and allowing the moulding to be extracted in the line of draw.

•The advantages of this method is that the withdrawing action automatic and the moulding does not have to be removed at right angles to the mould’s axis.

•This design can therefore be used for components with undercuts on opposing faces in addition to being used for components with an undercut on one wall only.

72


Fig: 2.8 73


STRIPPING INTERNAL STRIPPING INTERNAL UNDERCUTUNDERCUT

Suitability:Suitability:

• The shape of the undercut,• The elasticity of the material, and • Whether the external form permits expansion during

ejection.

74


Fig: 2.975


CURVED SIDE CORE

Fig: 1.32 56


MOULDS FOR MOULDS FOR THREAD THREAD

COMPONENTSCOMPONENTS


MOULDS FOR MOULDS FOR

THREADED COMPONENTSTHREADED COMPONENTSThe threaded components are usually prepare for where the The threaded components are usually prepare for where the repeated disassembly or where the strength of assembly is repeated disassembly or where the strength of assembly is required. The threads can be formed in by three methods:required. The threads can be formed in by three methods:

Cored or drilled holes with either thread cutting or thread Cored or drilled holes with either thread cutting or thread forming using self-tapping type screws. forming using self-tapping type screws.

Molded with local inserts.Molded with local inserts. Molded thread formed by using unscrewing threaded Molded thread formed by using unscrewing threaded

inserts.inserts.


TYPES OF THREADSTYPES OF THREADS

External thread.External thread.

Internal thread. Internal thread.

According to thread shape subdivided into continues According to thread shape subdivided into continues and discontinuous thread.and discontinuous thread.


Fig: 3.1 Fig: 3.2


COMPONENTS COMPONENTS INCORPORATING THREADSINCORPORATING THREADS

Fig: 3.3 Fig: 3.4


MOULDS FOR INTERNAL MOULDS FOR INTERNAL

THREADED COMPONENTSTHREADED COMPONENTS The internal thread is an internal undercut in that the thread forms a restriction, which prevents the straight draw removal of the moulding from the core. The types of mould design for withdrawing the moulding, as follows:

• Stripping (jumping-off) thread design• Fixed threaded core design• Loose threaded core design• Collapsible core design • Unscrewing mould designs


STRIPPING (JUMPING) STRIPPING (JUMPING)

INTERNAL THREADSINTERNAL THREADS 1. The moulding must be free to expand during

ejection to permit the moulded undercut to ride over the restriction on the core.

2. The outside form of the component to be formed in a cavity, which is fully contained in one half of the mould.

3. The internally threaded component may be stripped (Jumped) from the core using the stripper plate design providing a roll thread and the plastic material has sufficient elasticity during the ejection phase.

4. This method is recommended for polyethylene (PE), polypropylene (PP) material.


STRIPPING INTERNALLY STRIPPING INTERNALLY THREADED COMPONENTSTHREADED COMPONENTS

Fig: 3.5


FIXED THREADED CORE FIXED THREADED CORE

DESIGNDESIGN

• In this method, the thread form is incorporated on a non-rotating core fixed to the moving mould plate. An integer type cavity forms the external shape of the moulding. • In operation, when the mould is opened, the moulding remains on the core and is afterwards unscrewed by the operator by hand or using release devices.


FIXED THREADED CORE FIXED THREADED CORE DESIGNDESIGN

Fig: 3.6


ADVAMTAGES • Mould cost is cheaper than the unscrewing mould design because of its require ejector mechanism

• Maintenance cost is minimum as there are no moving parts within the mould.

DISADVANTAGES

• This design particularly used for multi-impression moulds where the individual moldings to be unscrewed manually. • Increases the moulding cycle time.


LOOSE THREADED LOOSE THREADED CORESCORES

• This method is suitable for a large component This method is suitable for a large component incorporates a local internally threaded hole or has incorporates a local internally threaded hole or has several internally threaded holes in close proximity to several internally threaded holes in close proximity to each other.each other.

• Prevents automatic unscrewing thereby considerably Prevents automatic unscrewing thereby considerably reducing the cost of the mould. reducing the cost of the mould.

• Where a number of holes are closely spaced, Where a number of holes are closely spaced, automatic unscrewing becomes impracticable. automatic unscrewing becomes impracticable. Because it require space for gear arrangement in Because it require space for gear arrangement in automatic unscrewing operation. automatic unscrewing operation.


LOOSE THREADED CORES

Fig: 3.7


COLLAPSIBLE CORECOLLAPSIBLE CORE

• This design is suitable for components having internal This design is suitable for components having internal thread and internal undercut.thread and internal undercut.

• The important advantage of this method over theThe important advantage of this method over the rotating threaded core designs is that it eliminates the rotating threaded core designs is that it eliminates the

need for complex unscrewing mechanism. need for complex unscrewing mechanism.


COLLAPSIBLE CORE

Fig: 3.8


EJECTOR PLATE ASSEMBLY OPERATED

USING COLLAPSIBLE CORE

Fig: 3.9


UNSCREWING UNSCREWING MOULDSMOULDS

High labour costs and other modern production High labour costs and other modern production requirements demand the maximum use of automatic requirements demand the maximum use of automatic operation. operation.

In an unscrewing type mould either the cores or the In an unscrewing type mould either the cores or the cavities are rotated to automatically unscrew the cavities are rotated to automatically unscrew the moldings from the mould.moldings from the mould.

To provide the required rotary motion an unscrewing To provide the required rotary motion an unscrewing unit is fitted behind the moving mould plate in place unit is fitted behind the moving mould plate in place of the conventional ejector unit of the conventional ejector unit


Manually powered fixed rotating core design


Manually powered fixed rotating core with gear transmission


POINTS CONSIDEREDPOINTS CONSIDERED

• In the axially fixed core design, the threaded core is merely In the axially fixed core design, the threaded core is merely rotated to remove the moulding.rotated to remove the moulding.

• In the extractor plate design, the extractor plate is actuated In the extractor plate design, the extractor plate is actuated at the same time as the threaded core is rotated to remove at the same time as the threaded core is rotated to remove the moulding.the moulding.

• In the withdrawing rotating core design, the threaded core is In the withdrawing rotating core design, the threaded core is rotated by sun & planet gear mechanism and withdraws rotated by sun & planet gear mechanism and withdraws the moulding from the core plate.the moulding from the core plate.


IMPRESSION LAYOUTSIMPRESSION LAYOUTS

1. The pitch circle diameter .

2. The In-line layout.


MACHINE POWEREDMACHINE POWEREDIN-LINE UNSCREW SYSTEMIN-LINE UNSCREW SYSTEM

Fig: 3.12


THE PITCH CIRCLE THE PITCH CIRCLE DIAMETER LAY-OUTDIAMETER LAY-OUT

Fig: 3.13



MULTIDAYLIGHT MOULD

01


MULTIDAYLIGHT MOULD

• It is a complex mould having more than one-daylight when the mould is opened. •It consists of three main parts:

• Fixed mould plate or feed plate,• Floating cavity plate or stripper plate,• Moving mould plate.

0102


TYPES OF MULTI DAY LIGHT TYPES OF MULTI DAY LIGHT MOULDSMOULDS

1. Double day light, stripper plate mould1. Double day light, stripper plate mould

2. Double day light, under feed mould2. Double day light, under feed mould

3. Triple day light, underfeed and stripper3. Triple day light, underfeed and stripper Plate mouldPlate mould..

0103


DOUBLE DAYLIGHT, DOUBLE DAYLIGHT, STRIPPER PLATE MOULDSTRIPPER PLATE MOULD

Suitability : The circular box-type moulding, which have thin wall section.

Stripper plate:

•The stripper plate is a rectangular plate, has aperture to sliding on the core for ejection.

•It is mounted between the cavity plate and the core plate.

•These types of ejection will not leave any depression on the molding.

0104


• The moulding and feed system are removed in the first day light between the stripper plate and the fixed mould plate from the cavity plate.

• Second daylight between the core plate and stripper plate for ejection.

0105


STRIPPER PLATE EJECTION

Fig: 4.1 Fig: 4.2 Fig: 4.3

0106


DOUBLE DAYLIGHT STRIPPER PLATE MOULD

Double Day Light With Underfeed Mould

Fig: 4.4 Fig: 4.5

Fig: 4.6 Fig: 4.7

0107


DOUBLE DAY LIGHT WITH DOUBLE DAY LIGHT WITH UNDER FEED MOULDUNDER FEED MOULD

• An Underfeed mould is one in which the feed system is arranged to feed into the underside of the component. • In this mould the extra plate is added behind the cavity plate to allow a runner system to be incorporated below the cavity or cavities. • It consists of three main parts 1. Feed plate.

2. Floating cavity plate. 3. Moving mould plate.

0108


USE OF UNDERFEED TYPE USE OF UNDERFEED TYPE OF MOULDOF MOULD

1. Multi-point feeding can be accomplished on single-impression moulds and on multi-impression mould.

2. Off-centre feeding can be achieved for both single and multi-impression moulds.

0109


TRIPLE DAY LIGHT WITH TRIPLE DAY LIGHT WITH UNDERFEED AND STRIPPER UNDERFEED AND STRIPPER

PLATE MOULDPLATE MOULD• A three-plate mold or triple daylight mould differs from a two plate in that it has two parting planes and the mold splits into three sections, every time the part is ejected. • Since the mold has two parting planes, the runner system can be located on one, and the part on the other. • Three plate molds are used because of their flexibility in gating location. • A part can be gated virtually anywhere along its surface.

110


TRIPLE-DATLIGHT, TRIPLE-DATLIGHT, UNDERFEED-STRIPPER UNDERFEED-STRIPPER

PLATE MOULDPLATE MOULD

Fig: 4.8 Fig: 4.9

111


A THREE PLATE MOULDA THREE PLATE MOULD ASSEMBLYASSEMBLY

Fig: 4.10112


THREE PLATE MOULDTHREE PLATE MOULD• This mould is mostly prepared for multi This mould is mostly prepared for multi

impression circular cap components.impression circular cap components.

• It is the combination of stripper plate It is the combination of stripper plate and under-feed system.and under-feed system.

113


STRIPPER PLATE STRIPPER PLATE MOVEMENTMOVEMENT

Fig: 4.12

Fig: 4.11

114


SECONDARY SPRUE BUSHSECONDARY SPRUE BUSH

Multi daylight moulds are having two sprue bushes.

• Primary sprue bush is mounted at fixed plate backside.

• Secondary sprue bush is mounted in the floating cavity plate.

115


SECONDARY SPRUE BUSHSECONDARY SPRUE BUSH

Fig: 4.13116


• It is the simplest form of feed system.

• It is not practicable for all types of components. The shape of the component affects the design of the floating cavity plate, which in turn determines the type of feed system can be adopted and it requires the extra operation for removal of runner from the moulding.

117


REVERSE TAPER REVERSE TAPER SECONDARY SPRUESECONDARY SPRUE

Fig: 4.14

REVERSE TAPER SPRUE

118


REVERSE TAPERREVERSE TAPERSECONDARY SPRUESECONDARY SPRUE

• Standard type of pin point gate is used.

• The main use of this sprue is to release the component with automatic de-gating in three-plate mould.

• Drawback of this method: the feed system is not free to fall when the mould is opened because the secondary sprues are retained within the floating cavity plate.

•The feed system is removed by hand if the basic underfeed mould design is used.

119


UNDERCUT RUNNER UNDERCUT RUNNER SYSTEM SECTION VIEWSYSTEM SECTION VIEW

Fig: 4.15

Fig: 4.16 120


Fig: 4.17121


DESIGN CONSIDERATION• The float period must be sufficient to permit the floating cavity plate to clear the reverse-tapered sprues before the puller pulls the sprue.• Considerable runner deflection is necessary to ensure that the secondary sprues are not pulled back into their holes when the puller is actuated.• To ensure that the puller is pushed back to its moulding position when the mould is closed, the diameter of the puller must exceed the width of the runner.

122


RUNNER STRIPPER PLATE • The fixed secondary puller is fitted directly below each secondary sprue. • To release the feed system from this fixed secondary puller a runner stripper plate is introduced between the feed plate and the floating cavity plate.

123


UNDERFEED MOULD UNDERFEED MOULD SECTION VIEWSECTION VIEW

Fig: 4.18 124


UNDERFEED MOULD

Fig: 4.19 Fig: 4.20

Fig: 4.21 Fig: 4.22125


STACK MOULDSTACK MOULD

• When two injection moulds are operated in tendem in the When two injection moulds are operated in tendem in the same molding machine it is called stack mould.same molding machine it is called stack mould.

Used for molding shallow, small parts in large quantities Used for molding shallow, small parts in large quantities like tape cassettes. like tape cassettes.

The cavities are located in two planes corresponding to The cavities are located in two planes corresponding to two parting lines and are filled.two parting lines and are filled.

The clamping force required is 15% higher than a The clamping force required is 15% higher than a standard mould. standard mould.

126


• It is a simplest mould design, from a runner point of view is a single-cavity, single-face mold arranged in back to back configuration of same impression or different impressions.

• The machine nozzle injects plastic directly into the mould cavity. The single-face mould can also be extended to a multi-cavity layout.

• The machine nozzle injects the melt into a runner system that feeds each individual cavity.

• It is suitable of which has the thin-wall injection molding with hot runner designs.

127


STACK MOULD IN IMMSTACK MOULD IN IMM

Fig: 4.23128


Fig: 4.24

129


TYPES OF STACK MOULDTYPES OF STACK MOULD

1. FOUR-FACE (FOUR-LEVEL) STACK MOLDS

2. THREE-FACE (THREE-LEVEL) STACK MOLDS

130


1.FOUR-LEVEL STACK 1.FOUR-LEVEL STACK MOULDSMOULDS

• Four-level stack molds quadruple output over single-face molds, and are suited to very high production volumes of shallow parts.

• Quick Change molds switch from one product to another in less than an hour in both single-face and two face stack mold applications. •Two-cavity slack molds allow molding of large parts in a back-to-back configuration, thus doubling the machine capacity.

131


• The four-face stack mold is two stack molds placed back to back and it increases the mold shut height.

• It operates in the same molding machine as a conventional slack mold.

• Cycle limes identical to those of a conventional mold. • Shot-to-shot changeover time of less than one hour

required for both mechanically and air ejected parts in the stack mold.

• Machine shut height remains the same from one product to the next.

132


2.THREE-LEVEL STACK 2.THREE-LEVEL STACK MOULDSMOULDS

• Three-level stack molds permit molding of deep-draw or tall pans to maximize the productivity of machine shut height.

•It is the development of a proprietary melt transfer system to pass the plastic across the mold parting line. •The system avoids drooling on mold opening due to the self-decompression of the central hot-runner system.

133


• The three-level stack mold uses triple valueless melt transfer system (VMTS) crossover nozzles to provide equal pressure and flow characteristics to the plastic melt to each cavity.

• This stack mold configuration fills in when a two-level mold cannot produce enough pans and a four-level mold is too large for the machine. • Three-level stacks is used to mold both shallow draw (for example, packaging lids) and deep draw pans (such as tall containers). • They can be combined with quick-change systems to give added flexibility to high-production tooling. 134


HOT RUNNER MOULD

01


1. COLD RUNNER

2. HOT RUNNER

A runner is the channel in the mold that conveys the molten plastic material from the barrel of the injection-molding machine to the part.

TYPES OF INJECTION MOULDTYPES OF INJECTION MOULD

02


COLD RUNNER MOULDCOLD RUNNER MOULD

The runner is cooled and ejected with the part.The runner is cooled and ejected with the part. Every cycle, a part and a runner are produced. Every cycle, a part and a runner are produced. There are two major types of cold runner molds: Two There are two major types of cold runner molds: Two

plate and Three-plate mould.plate and Three-plate mould.

03


• Mold requires less maintenance.Mold requires less maintenance.• The mold design is very simple and muchThe mold design is very simple and much

cheaper than a hot runner system.cheaper than a hot runner system.• Less skill to set up and operate. Less skill to set up and operate. • Color changes are also very easy, since all of Color changes are also very easy, since all of

the plastic in the mold is ejected with each cycle. the plastic in the mold is ejected with each cycle.

ADVANTAGES OF COLD RUNNER MOULD

04


DISADVANTAGES OF COLD DISADVANTAGES OF COLD RUNNER MOULDRUNNER MOULD

• The waste plastic is generated.The waste plastic is generated.• The runners are either disposed of or reground and The runners are either disposed of or reground and

reprocessed with the original material. reprocessed with the original material. • This adds a step in the manufacturing process. This adds a step in the manufacturing process. • Regrinding increases variation in the injection Regrinding increases variation in the injection

molding process, and decreases the plastic's molding process, and decreases the plastic's mechanical properties. mechanical properties.

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HOT RUNNER MOULDHOT RUNNER MOULD The hot runner mould contains a heated runner manifold The hot runner mould contains a heated runner manifold

block, insulated from the rest of the mould keeps the block, insulated from the rest of the mould keeps the runner permanently melt.runner permanently melt.

The hot runner mould replaces the conventional sprue The hot runner mould replaces the conventional sprue bushing with a hot sprue bushing or a heated nozzle.bushing with a hot sprue bushing or a heated nozzle.

The polymer material directed to the mould cavities The polymer material directed to the mould cavities without heat loss and pressure loss.without heat loss and pressure loss.

Large moulding like automotive dash board, bumpers, Large moulding like automotive dash board, bumpers, computer housing, multi colour moulding etc. are computer housing, multi colour moulding etc. are produced in this process.produced in this process.

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HOT RUNNER MOULDHOT RUNNER MOULD

• In a three-plate cold runner mold the runner system must be reground and the material is reused.• It is possible to eliminate the runner system entirely by keeping it fluid. •The material is kept plasticized by the hot runner manifold, which is heated with heating element (like electric cartridges). •The block is usually thermostatically controlled. •Heater bands, which are individually controlled, can be mounted round the nozzle. •The plastic is kept fluid and the injection pressure is transmitted through the hot runner manifold.

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Assembly of hot runner mould Fig: 5.1 08


Hot runner mould section view Fig: 5.2 09


TYPES OF HOT RUNNER TYPES OF HOT RUNNER

MOULDMOULD

A hot runner system is divided into two parts• The manifold • The drops .

• The manifold has channels that convey the plastic on a single plane, parallel to the parting line, to a point above the cavity.

• The drops, situated perpendicular to the manifold, convey the plastic from the manifold to the part.

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HOT RUNNER WITH HOT RUNNER WITH EXTERNALLY HEATED EXTERNALLY HEATED MANIFOLD AND DROPSMANIFOLD AND DROPS

Fig: 5.3 11


TYPES OF HOT RUNNER SYSTEMTYPES OF HOT RUNNER SYSTEM

• Internally drops and manifolds.

• Externally heated drops and manifolds.

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EXTERNALLY HEATED HOT EXTERNALLY HEATED HOT RUNNERRUNNER

• Externally heated hot runner channels have the lowest pressure drop of any runner system (because there is no heater obstructing flow and all the plastic is in molten state).

• They are better for colour changes none of the plastic in the runner system freezes.

• There are no places for material to hang up and degrade, so externally heated systems are good for thermally sensitive materials.

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INTERNALLY HEATED INTERNALLY HEATED RUNNER SYSTEMRUNNER SYSTEM

• Internally heated runner systems require higher molding pressures, and color changes are very difficult.

• There are many places for material to hang up and degrade, so thermally sensitive materials should not be used.

• Internally heated drops offer better gate tip control. It separate runner heat from the mold because an insulating frozen layer is formed against the steel wall on the inside of the flow channel.

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INTERNALLY HEATED CORE

ROD SECONDARY NOZZLE

Fig: 5.4 15


DESIGN CONSIDERATION FOR HOT RUNNER MOULD

• Insert plug close off manifold bores should be smooth.• Runner diameters should impart shear stress not more than 1 percent of the resin’s tensile strength.•The pressure drop from sprue bushing to tip should not be more than 25 percent of the maximum plastic fill pressure, with the resulting temperature increase remaining as close to the desired melt as possible.•A runner volume of 25 percent of the part volume, and a shear rate of about 1000 sec-1, are good •Sufficient heating elements should be incorporated so that the hot-runner unit heats quickly to the required moulding temperature from cold.

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. • Sufficient heat energy must be supplied to the hot-runner unit it replaces conduction, convection and radiation heat losses.• To ensure that the temperature of the melt in the flow-way is maintained without either hot or cold regions, careful location of the heating elements is essential.• Considerable production time may be lost if a heater fails. Thought must be given therefore to choice of heating element; its location and the facilities for. removing it.

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• The layout of the wiring system should be neat and easily traceable.

• Heating element wires, which are subject to, heat or abrasion attack should be protected.

• Use manufacturer’s recommended clearances when fitting heating elements of the cartridge type.

• Flat-type heating elements and induction heating elements should be completely enclosed within the unit for maximum efficiency.

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• The hot-runner unit must be insulated from the rest of the mould structure.

• For many materials, close control of the temperature of the melt is vital. Hence Careful consideration to be made for the location of thermocouples.

• To minimize degradation, color-changing and material-changing problems the melt flow-way must be as streamlined as possible, without sharp corners, ledges or other stagnation points which tend to hold back the polymer melt for extended periods.

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APPLICATIONS OF HOT RUNNER MOULD

• It allows for the pin gating of mouldings on multi-impression types of mould• It allows for multi-point gating on single-impression and multi-impression mould• It allows for side or film gating of large mouldings.• It permits the semi-runnerless design to be adopted, where small groups of impressions are fed from secondary sprues.

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THE MANIFOLD BLOCKTHE MANIFOLD BLOCK

• Rectangular Manifold Block

• Circular manifold block

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Fig:5.5 Fig:5.6

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RECTANGULAR MANIFOLD BLOCK

Fig:5.7

Fig:5.8

Fig:5.8Fig:5.9 23


THE MELT-FLOW-THE MELT-FLOW-WAYWAY

Fig: 5.10 24


It is made from stainless steel for plugs in the flow path of It is made from stainless steel for plugs in the flow path of hot runner system to direct the plasticized materials.hot runner system to direct the plasticized materials.It has larger thermal expansion than the manifold It has larger thermal expansion than the manifold material. As the manifold is heated to operating material. As the manifold is heated to operating temperature, the stainless plugs will expand at a greater temperature, the stainless plugs will expand at a greater

rate making the possibility of leakage impossible.rate making the possibility of leakage impossible.

RUNNER PLUG

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TYPES OF NOZZLESTYPES OF NOZZLES

3. Antechamber nozzle

2. Barb nozzle

1. Extended nozzle

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•On the extended nozzle a resistance type band heater is provided which is controlled by means of thermocouple.

•To minimize the transfer of heat from the heated nozzle to the mould, a circumferential clearance of at least 7mm must be provided between the two parts.

•The main advantage of this nozzle is to minimize the length of the sprue gate as short as possible.

1.EXTENDED NOZZLE

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EXTENDED NOZZLEFig:5.1128


This type of nozzle is used to minimize the blemish on This type of nozzle is used to minimize the blemish on the component at the gate point.the component at the gate point.

The plastic material flows through to the nozzle, sprue The plastic material flows through to the nozzle, sprue and gate. After solidification, the sprue is pulled from the and gate. After solidification, the sprue is pulled from the sprue bush by the barb of the nozzle.sprue bush by the barb of the nozzle.

2.BARB NOZZLE

Fig:5.12 29


3.ANTECHAMBER NOZZLE3.ANTECHAMBER NOZZLE

It is termed as hot well design, a small mass of plastic It is termed as hot well design, a small mass of plastic material is retained in the antechamber which insulates material is retained in the antechamber which insulates the central core of plastic material.the central core of plastic material.

The plastic material remains fluid to allow it to pass The plastic material remains fluid to allow it to pass intermittently through the antechamber into the intermittently through the antechamber into the impression.impression.

This type of nozzle is used for moulding thin-walled This type of nozzle is used for moulding thin-walled components.components.

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INSERT

ANTECHAMBER

Fig:5.13 31


INSULATED RUNNER INSULATED RUNNER MOULDMOULD

In this type of mould the melt flows from standard or In this type of mould the melt flows from standard or extended nozzle into a large diameter runner via the extended nozzle into a large diameter runner via the reverse taper sprue and gate.reverse taper sprue and gate.

The outer layer of the melt solidifies against the cold The outer layer of the melt solidifies against the cold

runner wall which forms an insulating shell, while the runner wall which forms an insulating shell, while the centre core of the material retain in the molten state.centre core of the material retain in the molten state.

The outer layer of runner acts as an insulating media The outer layer of runner acts as an insulating media and avoids heat loss from the polymer melt to the mould.and avoids heat loss from the polymer melt to the mould.

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Fig:5.14 33


EXPANSION PROBLEMSEXPANSION PROBLEMS

•The hot-runner unit mould is that metals expand when heated.

• The manifold block increases in all three dimensions when the temperature is increased.

•The distance between the centers of the secondary nozzles increases with respect to the ‘fixed’ distance between the centers of the impressions machined in the cavity plate.

•When designing the hot-runner mould, allowance must be made for this expansion to ensure that the centerlines are in line during production

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EXPANSION PROBLEMS

Fig:5.15

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NOZZLE NOZZLE LENGTHLENGTH

200200 250250 300300

48 mm48 mm 68 mm68 mm

0.130.13 0.200.20

0.170.17 0.200.20

0.210.21 0.300.30

The equation for calculating expansion is as follows:e = L X X T

Where e = expansion (mm or in) L = length dimension (mm or in)

= Coefficient of thermal expansion (mm/mm C or in / inC)

T = increase in temperature ( C)

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DESIGN OF HOT RUNNER MOULD FOR CAP


HOT RUNNER MOULD FOR CAP SEAL


THREE PLATE HOT RUNNER MOULD FOR CAP


THREE PLATE HOT RUNNER MOULD FOR LEAD FRAME


UNSCREWING HOT RUNNER MOULD FOR CAP COMPONENT

Documents

62265758 Advance Injection Mould Design