Diamond Systems Tritan Guia de Resolução de Problemas descarregar pdf (Página 17)

Edge gate

A gate land of 1.0–1.5 mm (0.040–0.060 in.) is suggested. A

generous radius at the edge of the gate will yield improved ﬂow

characteristics and reduce gate blushing. In general, the gate

thickness should be 0.5 to 0.80 times the part thickness. See

Figure 22.

Figure 22 Edge gate guidelines

Edge gating into a tab

Edge gating into a tab is an approach typically used on parts

that require a good, cosmetic ﬁnish. The idea is for any blush

or blemish to be conﬁned to the tab. One disadvantage is that

the tab must be removed in a secondary operation. To ensure a

high-quality ﬁnish on the part, the thickness of the tab should

be the same as the thickness of the part. See Figure 23.

Figure 23 Edge gating into a tab

Gating parts with maximum dimensions of

50 mm (2 in.) or less

• Gate diameter 0.9 to 1.3 mm (0.035 to 0.050 in.) for most

small parts

• Gate into thick areas

• Size gate according to part size

Countersinking the gate area slightly helps prevent gate vestige

or drooling from rising above the part. For example, gate vestige

is undesirable in medical parts. A typical gate recess is 0.5–0.8

mm (0.020–0.030 in.). Modify the opposite wall geometry to

maintain equal thickness, or high shear rates could develop at

the gate during ﬂow. See Figure 24.

Figure 24 Gating small parts

Runner

Part

Generous

radius

Gate land

1.0–1.5 mm

(0.040–

0.060 in.)

0.5T to

0.80T

1.3–1.5 mm (0.050–0.060 in.)

in gate land

• Reduces blemish problems on part

• Tab must be cut away

• Tab thickness = part thickness

Countersink the gate area

0.5–0.8 mm (0.020–0.030

in.) to allow for vestige.

Avoid forming a thin section

at the gate—high shear rates

may develop during flow.

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