Diamond Systems Tritan Guia de Resolução de Problemas descarregar pdf (Página 38)

Splay is an appearance defect in the surface of the part, usually

appearing as trapped gas bubbles being smeared across the

surface as the ﬂow front moves to ﬁll the part. Splay can

have several basic causes including moisture in the material

(inadequate drying); overheating and outgassing; long holdup

time either in the barrel or in a small dead spot; high ﬁll speed

causing high shear; part geometry causing high shear, usually at

the gate or along a high-shear ﬂow edge; trapped air because of

very low back pressure on the screw; or air trapped as a result

of part or runner geometry.

A second type of splay can come from unmelted or different-

viscosity material. The basic cause of this is large temperature

differences in the ﬂow path, such as a cold nozzle or manifold

or weak temperature control in a manifold. This appears very

much like gaseous splay but, on very close examination, can

sometimes be seen as unmelted particles.

Splay can also come from contamination by incompatible

materials either left in the machine or mixed with the pellets.

Notice in the Troubleshooting guide that the most probable

cures for splay at the gate are different from those for splay at

locations remote from the gate.

Sprue sticking in clear materials refers to the sprue sticking in

the mold, so it must be removed manually.

Part sticking refers to the entire part sticking in the mold—not

just the sprue.

Burning is the appearance of brown or black near vents, usually

in the last area of the part to ﬁll. It re sults from overheating of

gasses (air) as the part ﬁlls.

Flash is plastic that ﬂows into the parting line of the mold

beyond the edges of the part and freezes to form thin, sheet-like

protrusions from the part.

Brown streaks refer to streaks in the part that start at the gate

(or earlier, in the sprue) and ﬂow across the part.

Discoloration refers to any nonuniform coloration, whether

a general brown color such as that caused by overheating or

streaky discoloration resulting from contamination.

Black specks are tiny black particles that may be seen in the part.

Weld lines (or knit lines) are present and not a problem in many

cases. As used in the Troubleshooting Guide, the term refers to

weld lines that are excessively visible, or to incomplete welding.

Jetting or “snake ﬂow” appears in the part as a stream of

frozen plastic that is coiled or curled inside the part. It results

from the melt stream going through the gate and not impinging

on or spreading out across the mold surface but staying in a

small stream at least for part of the shot.

Warpage refers to the part not being as straight or ﬂat as the mold.

1 2 ... 33 34 35 36 37 38 39 40 41 42 43 44

Comentários a estes Manuais

Sem comentários

Diamond Systems Tritan Guia de Resolução de Problemas Página 38

Comentários a estes Manuais

Manuais e produtos relacionados com Quadros elétricos Diamond Systems Tritan