GUIDE FOR SPRUE BUSHINGS WITH STRING ELIMINATOR
■ Overview
■ Points to note for use
1. Install a cold slag well on the sprue lock before using the bushing.
Plate thickness (reference value)
P
2. A metal sheet is press – fitted into the nozzle touch part of the injection molding machine, so when removing the sprue (resin) be sure to remove it from the parting face PL side.
3.0 0.56 3.5 0.66 4.0 0.88 4.5 1.08 5.0 1.28 5.5 1.28 6 or more 1.58
Plate thickness
Metal Sheet
3. If the temperature of the nozzle tip of the injection molding machine is too low, the end part of the sprue may solidify before all of the resin has been injected into the mold, so appropriately adjust the molding conditions. (The molding conditions set using the normal sprue bushing specifications some- times differ from the molding conditions when this product is used.)
SK105 (Old SK3 ) Hard Product
SR depth
4. When using glass fiber filled resin, the metal sheet may wear as a result of long–term use, causing undercutting and poor mold separation. If mold sepa- ration trouble occurs frequently, change over the bushing with a new one.
Plate length (minimum)
Slit
Plate length (minimum/reference value)
SR depth
0 (*)
5 3
2
2.5
2.5
3 5
2
2 *When SR0 is specified, SR depth will be 0. *Plate length = SR depth + plate length (minimum)
Plate length
Cross section
Sprue Bush
● Features
This sprue bushing has been processed to eliminate “stringing” which occurs when the end of the sprue is being removed from the bushing.
Undercut due to wear of metal plate in slit portion
A thin metal sheet is gently press–fitted into the flange of the bushing, and a slit (groove) is processed in the center of the end part of the sprue. As a result, cooling and solidification of the end part of the sprue is promoted, enabling "stringing" to be prevented.
−Normal sprue bushing−
−Sprue bushings with string eliminator−
Image diagram
Sprue tip
High
Cools quickly and hardens
High temperature
Thick
Thin
String
Low
Slit
String
● String eliminator position
Low
High
Shoulder type
Bolt type (2 holes)
Bolt type (4 holes)
Resin temperature at the end of sprue ( ℃ )
45 °
675
676
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