Diamond Systems Tritan Guia de Resolução de Problemas descarregar pdf (Página 6)

Part I Mold design

Design for moldability

Moldability as well as product performance can be enhanced by

proper part design features. Good design for moldability includes:

• Providing reasonable ﬂow length

• Appropriate weld line location

• Moderate injection pressures

• Minimum clamp require ments

• Minimum scrap rate

• Easy part assembly

• Minimal or no secondary operations such as degating,

painting, and drilling

Good design helps minimize:

• Molded-in stress

• Flash

• Sink marks

• Surface blemishes

• Many other common molding defects that reduce quality

or productivity

The ability to ﬁll a mold with reasonable injection pressures is

greatly inﬂuenced by the wall thickness of the part. Spiral ﬂow

data are helpful in choosing appropriate wall thickness. Gate

location and wall thickness can be varied to achieve the best

balance of part weight, clamp tonnage requirements, and weld

line location.

Mold ﬁlling analysis

Computer-aided mold ﬁlling analysis is particularly useful in

designing molds for larger, asymmetric parts. Flow patterns

can be observed to determine whether any ﬂow imbalances

exist. Flow imbalances can be corrected by adjusting wall

thicknesses, placement of ﬂow leaders, and/or relocating the

gate. Imbalanced ﬁll can result in underpacked areas or stalled

melt ﬂow fronts that become cool and difﬁcult to restart, causing

molded-in stress and nonﬁll conditions.

Mold ﬁlling analyses are critically dependent on the viscosity/

temperature/shear rate relationship of the molten plastic. Mold

ﬁlling analysis accepts data for the parameters shown under

“Inputs” and is capable of supplying the information shown under

“Graphic outputs.”

Inputs Graphic outputs

Material ﬂow

characteristics

Heat transfer properties

Melt temperature

Mold temperature

Runner and gate size

and location

Part and mold design

Using mold ﬁlling analysis, if a factor in the input is changed,

effects on moldability can be seen quickly. For example, changing

gate location will show the differences in ﬁll patterns, weld

lines, pressures needed, and other characteristics of the

molding process.

Eastman’s analyses also make extensive use of its knowledge of:

• Thermal conductivity

• Speciﬁc heat

• Melt density

• Rheological characteristics of the materials involved

All of these values vary with temperature and must be known

accurately for the complete range of processing temperatures.

Flow and ﬁll patterns

Weld line locations

Pressure to ﬁll

Pressure patterns

Clamping force needs

Temperature patterns

Shear patterns

Filling

Temperatures

Shear thinning

Freezing and reheating

(temporary stoppage of ﬂow)

Eastman

™

polymers

Processing and mold design guidelines

1 2 3 4 5 6 7 8 9 10 11 ... 43 44

Comentários a estes Manuais

Sem comentários

Diamond Systems Tritan Guia de Resolução de Problemas Página 6

Comentários a estes Manuais

Manuais e produtos relacionados com Quadros elétricos Diamond Systems Tritan