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RT Technology produces 50,000 office-chair components annually using 1,224 metric tons of recycled plastic. |
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A MoldMax HH insert stands up well to glass-filled nylon used in office-chair bases. |
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IR imaging technology helped identify hot spots on tooling inserts and was an important step in ensuring MoldMax inserts would provide uniform cooling. |
RT Technology annually ships 50,000 chair bases from its molding house in Toronto. One key factor that helps get chairs out the door quickly is the copper beryllium (98.2% Cu, 1.8%Be) alloy they use in core and cavity inserts for molding chair bases. The high hardness MoldMax HH alloy from Brush Wellman Inc., Cleveland, resists wear and has strength similar to that of tool steels, including H-13 and 420 stainless steel. It also sports a thermal conductivity three to four times greater than steel's and comparable to aluminum's.
The company switched to MoldMax HH inserts from steel versions, letting them cut cycle times by 20%, from 122 to only 98 sec/cycle. This, in turn, let them reduce the number of molding machines they needed from 20 down to only 16.
"Using copper-beryllium alloy also dramatically improves our ability to cool the glass-reinforced nylon bases and our dimensional control of hub diameters," says Paul Karim, director of Plastic Technology for RT Technology. "And we use MoldMax wherever uniform heat dissipation is required."
During mold design, Brush Wellman helped thermally analyze cooling patterns in the chair base molds to pinpoint where better thermal management might increase molding efficiency and reduce scrapped parts.
RT Technology recycles about 1,225 metric tons of plastic for molding parts for its office chairs. "With MoldMax, we streamlined our processing and limited the amount of rejects, further helping the environment," says Karim. MoldMax also machines three times faster than competing tool alloys. Despite costing more than conventional tool steels, the cost differential was recovered within the first three months of production.
According to Brush, the alloy is typically specified for full-cavity and core inserts, blow-mold pinch offs, neck rings and handle inserts, cavity and core sub inserts, injection-mold components, and hotrunner-system injection nozzles and manifolds. The alloy is available in plate sizes ranging from 0.25 to 12-in. thick, and in rod diameters from 0.5 to 22 in.
MAKE CONTACT
Brush Wellman Inc., brushwellman.com
| COMPARISONS OF TOOLING-ALLOY PROPERTIES | |||||
| Alloy | Hardness, Rc |
Thermal conductivity, Btu/ft hr °F |
Charpy V-Notch impact strength, ft-lb |
Yield strength, kpsi |
Thermal expansion coefficient, 10 6 /in./in./°F |
| 420 stainless steel | 50 |
10 |
5 to 10 |
200 |
6.1 |
| H-13 tool steel | 45 to 50 |
15 |
8 to 14 |
200 |
7.1 |
| MoldMax HH | 40 |
60 |
4 |
155 |
9.7 |
| Alloy 22 | 35 |
23 |
2 |
55 |
9.0 |
| Alloy 940 | 16 |
120 |
35 |
65 |
9.7 |
| P-20 tool steel | 30 |
17 |
5 |
120 |
7.1 |
| Mold components currently made from H-13 and 420 SS are candidates for MoldMax HH alloy that can boost their corrosion resistance and thermal conductivity. | |||||