Coring uniform wall thickness

when design a mold then we find nonuniform wall thickness, we can make little graduation translation using core, of course if there was not function parts,
ordinary parts like not cosmetic parts, touching with others parts, sliding and etc, should we change by making insert in core or cavity side. look at picture below
when a parts have no uniform thickness after injection process, sink marks and unfill product like void will occurs,




Different wall thicknesses in the same component cause differential shrinkage which, depending on component rigidity, can lead to serious warpage and dimensional accuracy problems To attain uniform wall thickness, thick-walled areas of the moulding should be cored like picture above,
the best core for graduation translation and easier material flow is by make radius in every corner, beside flow more easier there will easy when machining process used,and no need EDM process so it's should cost down the price of product.

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Wall Thickness Design - Maksimum

Dependent on the part design and size, typically, for injection molded parts, the wall thickness will be in the range 0.5 mm to 4 mm (0.02 - 0.16 inch).
For parts made from most thermoplastics, nominal wall thickness should not exceed 4.0 mm. Walls thicker than 4.0 mm it is will increase time required for cooling and will result in increased cycle times

Changing the wall thickness of a component has a significant effect on the following key properties:

1.component weight
2.achievable of cycle time because more time 3.for cooling and injection
4.tolerances of product
5.achievable flow lengths in the mould
6.production cycle time of the component
7.rigidity of the moulded part
8.quality of the component in terms of surface finish, warpage and voids.
9. will affect to determines mechanical properties

What the Disadvantage when Thickness not Uniform

In the design of plastics components, it is important to aim for uniform wall thickness. Different wall thicknesses in the same component cause differential shrinkage which, depending on component rigidity, can lead to serious warpage and dimensional accuracy problems

what we should do when design a mold that have different thickness, look at the following picture, we should make as possible uniform or make the transition of product is gradual



Generally, the maximum wall thickness used should not exceed 4 mm. Thicker walls increase material consumption, more need time for cycle time considerably, and cause high internal stresses, sink marks and voids, look at picture below

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Wall thickness in mold design

when design a product The basic wall of the part of the melt during injection, should be kept uniform, this important to prevent sink after injection.
even we use cooling after injection part well deform because shrinkage, at this time if wall thickness does not same part will warpage stress

they key is keep wall thickness part as uniform as posible

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SPRUE BUSH and LOCATING RING

when you choose sprue bush, make sure you was know the diameter ball nozzle of plastics injection (SR) is less than diameter ball (SR - at picture below indicate by R)

if diameter R of Sprue bush to little than nozzle SR diameter, that will not good match or touching, if injection machine working plastic flash will out between nozzle and sprue

LOCATING RING
some mold designer usually use Locating ring to prevent unmatching nozzle of injection machine, before choose inside diameter of locating ring, we must know the outer diameter of nozzle that will touch with locating ring, at the picture below written in purple

Red color indicating flow of plastic material, from this picture we can take a conclusion that the picture is 2plate type of mold, look at picture there is no runner plate, and the gate type is side gate




Z pin Ejector
is used to make the runner ( RED COLOR) still adhere in core side when mold open and take the product, then Z pin will push the runner together with other ejectors

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Runner System and Construction

picture below show a simple runner system in mold construction, begin from nozzle until gate, nozzle for mold usually located in plate 1, plate 1 is upper plate,
when you design a runner system, basically like picture below, you must know location of product, is important when we decide where gate to be placed, here is the basic rule :
1. Look at drawing and 3D CAD data from the product, make sure you was choose where is cavity side and where is core side, give attention for tolerance of product
2. Do not locate gate in the precision tolerance, if is must to make a little grove in the product when you choose pin point gate type, Picture below use pin point gate type.
3. make sure the flow will steady for all side

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