Diamond Systems Tritan Guia de Resolução de Problemas descarregar pdf (Página 24)

Nicklon

™

coating

This alloy is 10.5% phosphorous-dissolved nickel with 25% PTFE

suspended in solution. It is applied using electroless co-deposition.

As the coating wears down, new PTFE particles are continuously

introduced to the mold surface, maintaining lubricity over a

long period of time.

The coating is known to improve chemical resistance of the

steel surface. However, because of the slightly porous nature of

the co-deposition, in extremely harsh environments, the coating

can be chemically stripped. In this case, an electroless nickel

pretreatment of the steel should be considered.

The dynamic coefﬁcient of friction is 0.03 against itself. The

typical thickness is 0.008–0.013 mm (0.0003–0.0005 in.). The

hardness is 48 Rc as applied and can be heat-treated to 70 Rc.

As for wear resistance, it is equal to hard chrome after heat

treatment.

Nicklon

™

coating is provided by:

Micro Surface Corporation Bales Mold Service, Inc.

465 East Briscoe Drive 2824 Hitchcock Avenue

Morris, IL 60450 U.S.A. Downers Grove, IL 60515 U.S.A.

Tel: (1) 800-248-4221 or Tel: (1) 630-852-4665

(1) 815-942-4221 www.balesmold.com

www.microsurfacecorp.com

DLN (diamond-like nanocomposite) coating

DLNs are low coefﬁcient, e.g., ~0.07 (friction against dry steel),

very hard coatings that can be applied to various metal core

pins and cavity areas to improve mold release behavior and

increase wear resistance. This type of coating is approximately

1–4 µm thick and has a typical Rockwell C hardness of

~78. The coating assumes the surface ﬁnish of the substrate

on which it is coated.

Dylyn

™

/DLC coatings can be provided by:

Sulzer Metco Inc.

6000 North Bailey Avenue

Suite 9

Amherst, NY 14226

Tel: (1) 716-270-2228

www.sulzermetco.com

Part II Processing

Choosing the molding machine

Some of the parameters to consider in choosing a machine for

molding Eastman

™

polymers are:

• Machine capacity (weight of shot)

• Clamping force available

• Ability to proﬁle injection speed

A discussion of these and other factors follows.

Machine size

Selecting a machine with shot capacity about twice the

expected shot size usually allows a good operating window. It

is important to include adjustment for speciﬁc gravity of the

material when the part weight is determined. Operating at

approximately 10% of machine capacity causes long holdup

time of melt in the barrel and contributes to degradation;

approaching the 80%–90% end of the scale makes it more

difﬁcult to maintain consistent melt quality and shot-to-shot

uniformity. See the section on “Molding conditions—Barrel

and melt temperatures” (page 31) for suggestions on how to

compensate for using high or low percentages of shot capacity.

When operating near the low end of the scale (small shot in a

large machine), it is important to run as short a cycle as possible

to minimize holdup time.

Experience shows that excessive holdup time caused by an

oversized barrel is the second leading cause of degradation in

copolyesters (lack of drying is ﬁrst). Degradation can be quantiﬁed

by checking the Ih.V. (inherent viscosity) or by gel permeation

chromatography (GPC), which identiﬁes molecular weight. The

GPC test will measure molecular weight directly while the Ih.V.

test will measure solution viscosity, providing a relative indicator

of physical property retention.

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