Design Gate sumary from hanser book

embed object below taken from ipaper, at the text book below will explain clearly how to design a good gate in plastic mold, to view more large click a little arrow at the top right, after click choose plus mark to see more large.

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Read this doc on Scribd: hanser design of gates

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How to design fan gate in thermoplastic injection mold

fan gate, is a gate spreading toward in to cavity, basically this gate is thin similarly with previous gate (film gate) and is used in same purpose with film gate. with the gate construction it permits rapid filling of large parts or fragile section mold area with large entry area. it is used to create uniform flow into wide parts.
Purpose
1. thereby keeping the cross sectional area constant.
2. This ensures a constant and more even plastic flow into the cavity into a wide area at a slow injection speed, minimizing backfilling and reducing imperfections and stresses in the part.
3. used for thick-sectioned moldings and enables slow injection without freeze-off.
4. favored for low stress moldings or where warpage and dimensional stability are main concerns.
5.The melt velocity will be constant.
6.The entire width is being used for the flow.
7. The pressure is the same across the entire width

Construction and Design



side View

The gate should taper in both width and thickness, to maintain a constant cross sectional area, although at picture below thickness is doesn't tapered.



Dimension
the land thickness can be vary thin relative to the part thickness because the gate is very wide.the maximum thickness should be no more than 80% of the part thickness. if the parts very thin like 0,8 mm, you can also use 0.7 mm fan gate thickness, but when rubber is used as material parts, use 100 % of the thickness parts is more easy to control flow and product quality. The gate width varies typically from 6 mm up to 25% of the cavity length.in large parts is often use fan gate as wide as the parts it self.

Simulation Picture
all picture below based on injection simulation process, using material PS ASAHIPS 693 : Asahi Chemical
other data are
==== Machine setup ====

Melt temperature = 503.15 K
Mold temperature = 323.15 K
Fill time = 0.08 s
Packing/Holding time = 4.24 s
Cooling time = 7.72 s
Packing/Holding pressure = 12627300.00 Pa

==== Machine specification ====

Required clamp force = 27647.70 N
Required shot size (GPS) = 0.01 kg

Simulation results

mold time filling in seconds


time to cool after injection
from below picture we can learn where is the best position to make cooling layout, after you make cooling layout, enter the cooling simulation process to your parts. if the distribution is same in all shape of part (unless runner and gate) your design is good to realize.


Pressure distribution



all picture is enabled to enlarge, click the picture to enlarge.

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Film Gate Design (flash gate)

Film gate also called flash gate is very thin compare to another gate, this thin gate like film which have parallel runner before the gate, this type of gate used for straight edges. picture below shown film gate with main parts.


in generally this gate used in thin and flat requirement, like flat mobile phone cap, ipod cap and others. but sometimes this gate is not likely going to have a flat flow front, the make flow material more stable and flat, make temperature molds more higher than usual, but cycle time will also higher.

here is film gate from top view


Dimension
recommended dimension is approximately 0.2 mm to 0.6 mm in thick, the land area (parallel runner) is also be kept small approximately 0.6 mm - 1 mm depend the large and weight of product.

Other Design
picture below shown other design of film gate, with more reliable and easy in process.

look the different model of film gate, and different design of parallel runner.
picture below shown simulation of plastic flow from those design

and the last picture shown time that needed to cooling the melt plastic in mold


from the picture above we can choose the right place to make cooling pipe, the red color marks mean need more time to cool the product.

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