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TECHAPPLICATION i IonNitriding Injection Molds · Goodyear has injection molded its products since...
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TECHAPPLICATION i * IonNitriding Injection Molds Published by the EPRl Center for Materials Fabrication c The Chdlenge: Qalnlng a Longer Mold Ufe A high-visibility product demands a flawless appear- ance. Goodyear Tire and Rubber Company expects just that for its fiberglass products, such as outboard motor covers, basketball backboards, and front ends of auto- mobiles and trucks. Since 1983, all its injection-molded prod- MAS have been made from molds with ion-nitrided surfaces, and Goodyear can count on them having a smooth product qmawKx. Goodyear has injection molded its products since 1981 but found that the mold surface would quickly become eroded o( scarred, producing parts with a poor appearance. Hard- ening the mold’s surface is the best way to re- I duce M a r and keep the molds at work longer. Goodyear decided its surface-hardening method would need several characteristics: Reliablycreateasmooth,uniformsurface L m Give the greatest surface hardness to each mold, especially in grooves and recessed areas d Be repairable Be cost effective. The Old Way Fiberglass products are injection molded at Goodyear because that method produces betterquality parts morequicklythanother I Vol. 1, No. 13, 1987 methods. But fiberglass is.abrasive and quickly erodes steel molds, creating washed-out channels. As a mdd erodes, it presents manufacturing problems: the quality of the part removed from a deteriorating mold is often unacceptable and requires sanding or other finishing to bring it up to standard. Sanding increases the porosity on the part, which can lead to paint pops and other surface im- perfections unless additional finishing steps are performed. And all these additional finishing steps require more manpower. crease hardness but gives a mold life of 20,000-40,000 shots. But chromiumplating had its own set of problems: Eroded molds had to be sent out for stripping, welding to repair the pits and channels, and rechroming-a &week process. A second mold, and sometimes a third, was needed for use when the first was in repair-an expense of $200,000-$300,000 for each mold. D Extreme care must be taken in mold repair or the repaired mold would erode more quickly than a new mold. Goodyear looked at other methods to increase mold life: Goodyear chromium plated the molds, which does not in- b Dies hardened to higher levels could not be used because D The high temperatures required by heat treating cause they were brittle. mold warpage or cracking. Other surfacehardening methods could not be applied: induction, laser, and electron beam hardening are not effective for complex mold shapes; gas carburizing and car- bonitriding may distort the mold metal at the high tempera- tures they require;ion implantation and chemical and physical vapor deposition would not provide a hardened layer with sufficient thickness. the best methodto harden the molds. Ion nitriding produces a smooth, uniform surface. It increases the surface hardness so that an injection mdd now produces 5 times as many parts before it shows any signs of erosion. Recessed areas not able to be chromium plated can be hardened, allowing more complex designs to be molded. Four to six weeks are
Transcript of TECHAPPLICATION i IonNitriding Injection Molds · Goodyear has injection molded its products since...
TECHAPPLICATION
i * IonNitriding Injection Molds Published by the EPRl Center for Materials Fabrication c The Chdlenge: Qalnlng a Longer Mold Ufe
A high-visibility product demands a flawless appear- ance. Goodyear Tire and Rubber Company expects just that for its fiberglass products, such as outboard
motor covers, basketball backboards, and front ends of auto- mobiles and trucks. Since 1983, all its injection-molded prod- MAS have been made from molds with ion-nitrided surfaces, and Goodyear can count on them having a smooth product qmawKx.
Goodyear has injection molded its products since 1981 but found that the mold surface would quickly become eroded o( scarred, producing parts with a poor appearance. Hard- ening the mold’s surface is the best way to re- I duce M a r and keep the molds at work longer. Goodyear decided its surface-hardening method would need several characteristics:
Reliably create a smooth, uniform surface L m Give the greatest surface hardness to
each mold, especially in grooves and recessed areas
d Be repairable Be cost effective.
The Old Way Fiberglass products are injection molded
at Goodyear because that method produces better quality parts more quickly than other I
Vol. 1, No. 13, 1987
methods. But fiberglass is.abrasive and quickly erodes steel molds, creating washed-out channels. As a mdd erodes, it presents manufacturing problems: the quality of the part removed from a deteriorating mold is often unacceptable and requires sanding or other finishing to bring it up to standard. Sanding increases the porosity on the part, which can lead to paint pops and other surface im- perfections unless additional finishing steps are performed. And all these additional finishing steps require more manpower.
crease hardness but gives a mold life of 20,000-40,000 shots. But chromium plating had its own set of problems:
Eroded molds had to be sent out for stripping, welding to repair the pits and channels, and rechroming-a &week process. A second mold, and sometimes a third, was needed for use when the first was in repair-an expense of $200,000-$300,000 for each mold.
D Extreme care must be taken in mold repair or the repaired mold would erode more quickly than a new mold. Goodyear looked at other methods to increase mold life:
Goodyear chromium plated the molds, which does not in-
b
Dies hardened to higher levels could not be used because
D The high temperatures required by heat treating cause they were brittle.
mold warpage or cracking. Other surfacehardening methods could not be applied:
induction, laser, and electron beam hardening are not effective for complex mold shapes; gas carburizing and car- bonitriding may distort the mold metal at the high tempera- tures they require; ion implantation and chemical and physical vapor deposition would not provide a hardened layer with sufficient thickness.
the best method to harden the molds. Ion nitriding produces a smooth, uniform surface. It increases the surface hardness so that an injection mdd now produces 5 times as many parts before it shows any signs of erosion. Recessed areas not able to be chromium plated can be hardened, allowing more complex designs to be molded. Four to six weeks are
lcJrebicity for chromium plating the same mold 5 times bo @ an equivalent number of shots wauld cost about $tlO including the necessary stripping. -
Greatly reduced mdd maintenance and the decrease in mjactkm due to surface imperfections lead to modest sav- i in mer usa 8. The elimination of product nmorking
inenergyusegeanddg" industrialc&npethmms
lhmdw4 m. I o n nitriding providee fdewe similar to chromium plating, so little or no rrJscrse
agmb are; required. ~ ~ ~ l n v e n t o r y s p a c e i s s a v e d b y b o t h t h e
nrCrllmdadmmOldsandthereductionafpartsware haudtoccrvwcwtomerdemandwhenthemddwas
Irr(l?(ma Mulk Ion nitriding the mdds r e s u b in &ingnworlsd.
rvrclr mfmxm which Cast longer, require less maintenance, wrj paduoe - quality products.
What Dld It All Cost? ~~coa~ionnitridingwasabouttwiceasexpen-
thrchmnimpleting.Thepeybad<pemodwaslessthgn oyw~lmauwdthE)"mddlita
Jackson, Ohio
as out- board motor covers, basketball backbaards, engine c w r s and front ends of automobiles aaxf trucks.
which are recognized as world leaders in a u d i with ~ Compdny philosophy: To manufacture praducts
~ lower cost than any world competitol
Ken Seals Gil Kiefer Steve Dillinger Plant Manaaer DweloDment Section Head
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