Mold-Masters Hot Runner - Page 113

3. Calculate the heat expansion factor.
Fh = (Processing temperature - Mold temperature) °C x 0.000012.
4. Calculate the heat expansion of the valve pin.
HE = distance BC x heat expansion factor = BC x Fh.
5. Cut pin to calculated length “L”.
L = AC - 36.35 (1.43) - HE + CD [mm (in.)].
6. Grind the valve pin tip to t the cylindrical gate. Refer to the system gate
detail.
7. Assemble the hydraulic unit.
8. Heat the Hot Runner system to processing temperature.
9. Soak the pin in the Hot Runner system for 10 minutes to achieve the
maximum heat expansion of the pin at the processing temperature.
NOTE
Mold cooling should be running.
10. Measure the distance CD in the heated condition. Check that the head of
the pin is seated.
11. Calculate the dimension to be ground (L2). L2 = CD (measurement) - CD
(specied).
12. Grind the pin end to remove L2 (nish cut).
NOTE
When the gate vestige is critical, it is recommended to mold sample parts
and measure samples to adjust the nal pin length.
Steel quality in the gating area must have:
• Tapered gates - High grade of toughness (H13, 1.2344), hardness HRc
46-48
• Cylindrical gates - Minimum hardness HRc 54
• No nitration
• No chrome plating
The bottom of the nozzle well in the gate area must be free of stress caused
by:
• Rough EDM
• Rough machining
• Sharp corners (JIG grinding is recommended)
7100 Series - continued
10-7HYDRAULIC / PNEUMATIC ACTUATORS
Hot Runner User Manual
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