Diamond Systems Tritan Guia de Resolução de Problemas descarregar pdf (Página 9)

Mold shrinkage and warpage

Key factors in minimizing warpage include:

• Uniform wall thickness

• Consistent mold temperatures

A uniform wall:

• Promotes even flow

• Minimizes shear heating

• Reduces molded-in stress

• Tends to minimize warpage

A uniform mold temperature helps to ensure even heat

transfer from both wall surfaces. This will leave the part in a

balanced condition, provided the wall thickness is uniform.

The important factor is control. The mold should be designed

for adequate control of the temperature in the range required

for the material being processed. This will not only decrease

the amount of residual stress but will also permit reduction

of cycle time.

Suggested cooling line spacing

Figure 4 shows the suggested layout of drilled cooling lines

for a large part.

Cooling lines should be spaced 2.5–3 diameters apart (on

center) and 1.5–2 diameters away from the surface of the

part.

Uniform placement of cooling lines, as shown, will help

ensure equal and adequate cooling of the part.

Figure 4 Cooling line spacing

Core cooling techniques

Methods of achieving proper core cooling include:

• Bafﬂes

• Bubblers

• Highly conductive alloys

• Circular cooling channels around cavity and core inserts

Any of these methods are suitable, provided the heat removal

capacity is sufﬁcient to maintain uniform temperatures down

the length of the core. Although proper core cooling potentially

adds to mold construction costs, it will pay off in reduced cycle

time and improved part quality once the mold goes into production.

Bafﬂes and bubblers are two of the most common methods

used to provide core cooling. A typical bafﬂe conﬁguration

is shown in Figure 5. With this conﬁguration, a thin blade is

inserted down the length of the bore. This divides the bore into

2 semicircular ﬂow channels. Water travels up the length of the

core on one side of the bafﬂe blade and then down and out the

opposite side of the blade.

Figure 5 Typical bafﬂe conﬁguration

3 D

1.5 D–2.0 D

Part

P/L

Polish core in

direction of draw

Hollow section

Water out

Water in

Core pin

Sleeve ejector

P/L

Baffle blade

Water in close

proximity to

the end of

the core pin

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