Diamond Systems Tritan Guia de Resolução de Problemas descarregar pdf (Página 37)

Other fastening techniques

Bosses, snap ﬁts, and locating features that take advantage

of the ductility and toughness of these polymers should be

designed using proper part design guidelines.

Many Eastman

™

polymers have the required ductility to

perform well in swaging and staking operations. The material

can be softened using a heated horn or ultrasonic energy, and

in many cases, the material can be swaged “cold.”

Part IV Troubleshooting

Troubleshooting guide

The Troubleshooting Guide provides possible remedies for

problems that may occur. Read across the top to ﬁnd the

problem being experienced, then search down the page for the

highest priority remedy. If the number is followed by a plus sign,

increase the variable shown. (Example: “Fill speed +” means to

increase ﬁll speed.) If the number has a minus sign, decrease the

variable. If both a plus and minus are shown, it means that the

setting is probably not correct; the proper setting may be either

above or below the current one. If changing the ﬁrst variable

does not solve the problem, proceed to number 2, and so on.

See also “‘Reading’ parts as they are molded,” page 40.

One defect not listed in the table is a wavy surface. Waves are

of two basic types: (1) very ﬁne waves, almost like ﬁngerprints,

running along the ﬂow front perpendicular to the ﬂow direction

and (2) much larger, irregular waves. The ﬁrst type is ordinarily

caused by slow ﬁll speed or momentary changes in ﬁll speed.

The second type is usually caused by underpacking or by a mold

that is too hot.

For possible cause, corrective action, and photos, reference

Eastman publication PPD-407, Injection Molding Troubleshooting

Guide for Eastar

™

Copolyesters or visit our website at

http://www.eastman.com.

Descriptions of terms in troubleshooting guide

Short shots are simply shots that do not ﬁll the mold completely.

The plastic has not ﬂowed far enough to ﬁll the part, usually in

areas farthest from the gate.

Brittle parts break easily.

Voids or sinks indicate that not enough material was packed

into the part, resulting in an indentation of the surface (sink) or

a cavity inside the part (void). These occur most often in thick

walls and areas where ribs or bosses join the wall.

Bubbles of trapped air can show as lumps on the part surface

in opaque materials, or as gas bubbles in clear materials. In

clear materials, they typically appear with foamy tails pointing

toward the gate. The foamy tails differentiate them from voids.

Conversions of metric/U.S. customary values may

have been rounded off and therefore may not be

exact conversions.

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