desain sistem saluran

Desain Sistem Saluran

High-performance Mold

A high-performance mold harus memilliki karakteristik

yang baik dalam hal ：

High-performance dalam sistem pengisian

High-performance sistem packing

High-performance sistem pendinginan

Contoh Mold Casting System

Konsep Desain Sistem Saluran

Gating system：flow channel to the cavity

Effect：smooth and orderly filling of plastic fluid, fully pass

injection pressure to the various part during filling and

solidification process, get density

Classification：

Common gating system：Cold runner

runnerless gating system：Hot runner, insulated runner

Gating System and their effects

Sprue Runner gate

runner system has a direct impact on the appearance, physical properties and of

dimensional accuracy and cycle time of molded product

Main

runner Branch

runner

Branch

runner

runner

Cavity

Prinsip Desain Sistem Saluran

1. guarantee the quality of parts

(to avoid the common problem of filling)

hesitation is easy to make overpacking on

some part of the workpiece, and underpacking

for other part

Minimize hesitation

From the thickest pouring provide better filling and packing effects

If there are underpacking, the thinner areas will solidify faster than thick

regions

Avoid gate on the region with sudden change of wall thickness, prevent

hysteresis or short shot

不推荐

未凝固处

缩坑

缩坑

浇口保压不足

gate

Un-cure

Sink mark

Sink mark

Under packing


Gate Placed on the Thickest part of Product



Meltline exists primarily affect the

appearance, making the poor surface of

product; poor Weld strength

Try to avoid meltline


Meltline

Melt Lines

• Melt from different directions, the front part of the molten resin is cooled in the

junction can not fully integrated. Under normal circumstances, affect the

appearance, impact on the coating, electroplating. Severe impact on the

product strength (especially fiber reinforced resin)


avoid overpacking

and underpacking

poor gating system design or improper operating conditions,

make the melt pressure in the cavity takes too long or too

high

overpacking will make the product density, to increase the

internal stress, or even flash

underpacking

overpacking


rib

sink


Minimize the flow disorderly

flow disorderly make poor workpiece strength and surface flow

Simple Complex


Consider Molecules orientation

If the product is long and

narrow shape, provides a

single direction from a

unilateral into the pouring

uniform plastic flow

Although the volume

shrinkage of products at the

different ends is different,

there is no warpage

Molecular distribution in a

different direction often leads

to warping

均匀分子(纤维)定向翘曲变形小

非均匀分子(纤维)定向翘曲变形大

均匀

均匀

均匀

均匀

浇口

浇口

不均匀

gate Uniform

Uniform

Uniform

Uniform

Runner

Uneven

Non-uniform molecular orientation

and warpage deformation and large

uniform molecular orientation and

warpage deformation and large

2. Minimize the cross-section and length of gating system

Reduce the amount of plastic and mold size

Minimize heat loss and pressure loss of the plastic melt

3. synchronize filling

For multi-cavity mold, make different cavity melt arrive at the same time, and

equal to the pressure at the entrance of each cavity


Filling in the Central

Gate placed in the central of the product are available for same flow

length

Long flow length will affect the required injection pressure

Central pouring makes all directions holding pressure evenly to avoid

uneven volume shrinkage

Symmetry of Gates

Symmetry gates can avoid product warpage

Asymmetric flow will lead to filling first in certain areas, even before solidification

may cause uneven product of the volume shrinkage, which will cause warpage

Sprue Design and Manufacture

Effect：Is a bridge connecting the injection machine nozzle and mold, the first

part for plastic melt filling in

Design points

Sectional shape, taper, length, spherical R, fillet r

shape and size of sprue

Nozzle

diameter

spheric radius

Sprue bushing through two plate should be a

ladder-like, or using gate sets

Sprue Design and Manufacture

Runner Design and Manufacture

Effect：Smooth conversion of flow and filling cavities as soon as possible

Runner section shape

Runner size design

Runner manufacturing points

Runner Road layout

Runner design points

cross-sectional shape of the flow channel will affect the volume of plastic

flow in the flow channel, and flow within the molten plastic


1. Runner section shape

Circular cross-section

Advantage：The shape of flow channel with high efficiency, up to 0.25D

Shortcoming：Increase production costs, flow channel interleaving will

affect flow efficiency



Rectangular cross section

The efficiency of flow channel is nearly

equal to Circular section, 27% area more

than that of Circular, increase injection

waste and demolding force



Trapezoidal cross section

39% more area than that of circular, and more waste, while with simple

making method



U shaped

Also known as the modified trapezoidal flow channel, combined with the round and

trapezoid advantages, 14% area more than that of circular



Hexagonal cross-section

An area of only 82% of the

circular flow channel, but

manufacturing is not easy, and

seldom used


2. Runner design points

Volume and wall thickness of the products, the Runner section thickness is greater

than the wall thickness of the products

The fluidity of the molding resin, the resin with glass fiber and less flowability, larger

flow channel cross-section needed

Change the direction of the flow channel around the corner, should be properly set

cold slug

make the plastic parts and flow channel in the geometric center of the clamping

force, in the center of projected area


2. Runner design points

Ensure quickly and evenly filling

Runner size as short as possible, easily as small as possible

To facilitate the processing and tool selection

Each branch runner is larger than the next branch

10 ~ 20% (D = d+d × 10 ~ 20%)


3. Runner size design

D>=Product most wall thickness+1.5mm B=1.25D



Flow channel diameter is too large: not only a waste of materials, and the cooling

time increased, the molding cycle also grows, resulting in waste costs.

Flow channel diameter is too small: the flow resistance of the material, could

easily lead to the filling or injection pressure must be increased in order to fill.

Runner diameter should be suitable for the weight of the product or the projected

area

Diameter of the

flow channel(mm) Product weight(g)

4 95

6 375

8 More than 375

10

12 Large-scale

Diameter of the

flow channel(mm) Projected area(cm2)

4 Less than 10

6 200

8 500

10 1200

12 Large-scale



The length of the flow channel can be calculated by the following empirical

formula:

D =

D——Runner diameter mm W - product weight g L - stream channel length

(mm)


4. Runner Road layout

principle of flow channel array

same distance for molten plastic from sprue to different gate

The cavity center of pressure coincide with the center of injection

molding machine

The layout of the flow channel

Natural balance Artificial balance

Unbalanced Natural balance Artificial balance


Flow Balance

Naturally balanced runner system

The same distance from nozzle and to different cavity, filling all cavities in the

same time under the same pressure

Artificially balanced runner system

Resizing flow channel to complete filling of all cavities in the same time under

the same pressure

filling order for different cavity is extremely complex, not only with the

section size and length of the Runner, and the plastic melt temperature,

pressure, viscosity, mold temperature and viscosity on pressure drop

and temperaturelowering the degree of sensitivity. Gate size of the

balance of each cavity can be fixed after the test mold or mold flow

analysis

Artificially Balanced Runner System

4. Runner

Road

layout balance of Runner arrangement

unbalance of Runner arrangement


Design and Manufacture of Gate

1. role of gate

gate：Gate: a bridge connected Runner and cavity, is the weakest and

most critical part in the system


•Adjust flow speed •Adjust feed time •Prevent back flow

Gate dimension often determined by experience, take low value first, then revised by trying. generally, the gate area size is about 3-9% of that of runner, with short length about 1-1.5mm, often using rectangle or round section

restrict gate(side gate, point gate, fan gate)

• Melt through the narrow gate, raising speed and temperature growth, good for

filling

• narrow gate first coagulation and closed cavity after Injection and packing,

which reducing the deformation and rupture of plastic parts

• Narrow gate facilitate the separation flow condensate from plastic part

• demolding convenient

Non restrict gate(sprue gate)


1.role of gate

the suitability of Gate location, number, shape, size has a direct impact on

product appearance, dimensional accuracy, physical properties and molding

efficiency

too large Gate: excess residual

stress around gate, resulting in

deformation or rupture, and the

gate removal difficult

too small Gate : easily lead to the

filling (short shots), sink marks,

weld defects in appearance, and

shrinkage increases too small gate

too big Gate

Dimension

reduced

swell


2. type and characteristics of gate

Direct gate(sprue gate)

Direct gate is widely used in single-cavity mold

Disadvantages: difficult removal of gate, leave

marks on surface of molding


side gate

typical size : thickness of 0.4 to 6.4mm,

width from 1.6 to 12.7mm.

Generally opened in the parting surface,

suitable for multi-cavity mold, convenient

gate removal; but the pressure loss, shell-

shaped venting inconvenience, easy to

produce the weld.



overlap gate

typical gate size: thickness 0.4 to 6.4mm,

width from 1.6 to 12.7mm.

Overlapping gate and side gate is similar,

there is overlap between gate and the

finished wall or finished surfaces



fan gate

Typical gate size: thickness 0.25-1.6mm, width of 6.4 to 25% of the length

of the cavity sidewall.



disk gate or dish gate

Disc gate is often used for forming the inside of the

opening of the cylinder or round products

This type of gate for concentric, demanding strict

dimension, and not allow Weld line

Typical gate thickness : 0.25 to 1.27mm



ring gate

melt flow freely along the center part of ring

gate, and then melt down to filling the mold

Typical gate thickness: 0.25 to 1.6mm.



spoke gate

Spoke gate, also known as 4-point gate or cross gate.

Mostly for tubular plastic products, and gate removing

easy and material saving

Disadvantages: may produce weld line , not possible to

create perfect roundness

Typical gate thickness: 0.8 to 4.8mm, width from 1.6 to

6.4mm.



film gate

Similar to ring gate, with straight edge of the plastic parts

Applies to flat and large area, warping reducing

Typical thickness: 0.25 to 0.63mm, with short length, approximately 0.63mm



tab gate

Normally used in tablet-shaped and thin moldings,

in order to reduce the shear stress

Gate around high shear stress is limited to

the secondary tabs, tabs will be removed

Convex tablets gate is widely applied to

the PC, SAN, and ABS resin molding

Tabs on the minimum width of 6.4mm,

the minimum thickness for 75% of the

cavity depth.



pin point gate

Suitable for multi-cavity, three boards

and two open mold, the mold point

gate off automatically.

Small Gate with high pressure loss,

which need higher injection pressure



Banana gate

Gate in core side, cut off during

ejection, L>L1+L2, and L1

could not too short



Gate design principles

A good gate can make fast, uniform and better single-directional flow, and

suitable gate solidification time

⑴To prevent the gate at the jet

phenomenon in the filling process,

the traces of the corrugated.

To prevent the approach: increase

the gate size or impact-type gate.

Non-

impact

gate

impact

gate

Core



⑵Symmetric gate can prevent warping

⑶gate location good for melt flow and feeding

Not recommended Recommend

Set up multiple gates to reduce the deformation



Gate location good for venting

Gate location good for venting, which

prevent short shot, burnt, or high

pressure in the gate


Gate Location Options

Gate Location Options

Location of

the gate

Reasonable

location of the

gate

Gate location example

TUGAS (Work in Pairs)

Part diatas akan dibuat sand casting dari aluminum casting alloy.

Buat desain sistem saluran dengan mempertimbangkan shrinkage

dan machining. Dapat menggunakan software yang anda miliki.

Desain dibuat dengan 2 jenis pola, yaitu :

A. Pola 1 bagian

B. Pola 2 bagian (atas dan bawah)

desain sistem saluran

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