Sprue bush cooling design and construction

some times sprue bush need cooling to cut the cycle time of injection process, when diameter of sprue is large cooling in sprue bush is important. some fabrication of mold part have their own sprue bush that containing cooling pipe. like picture below


from those picture some standard part mold company have their own methods to make inner cooling at the sprue bush, we can by cutting in some part that weld together again, or by other method.

the other way to make cooling in sprue is like picture below


by those type of sprue we change the entrance and exit flow by using stopper buffle, for example like picture below


or you can make the flow straight, the other cooling method in sprue is like picture below, by using this type is easy to attach the O ring, becouse in and out flow from below side that contact with moldbase. becouse when assembling of ring to moldbase is more easy by attach the O ring in Moldbase then put the sprue bush than attach the O ring in sprue bush and assembling it together in moldbase.

Read More

Locating Ring Design and Construction in Injection Mold

Locating ring is simple part but, very important when mold base attach to injection machine, ok here the construction of locating ring after assembled in mold base.



















then after attach in injection mold, the position of locating ring is like below


Basic Rule Design
1. when design locating ring, first rule is look at your injection machine catalog or hand book, and find the dimension of locating ring. like picture below

from picture above we know that locating ring diameter is 200 mm and diameter of nozzle is 52 mm, so your locating ring outer diameter must same with those injection machine locating ring hole.

2. don't worry about the tolerance, at the injection machine tolerance always about minus 0.01-0.1 mm, then the locating ring tolerance if we buy in standard mold part company is about minus 0.01-0.05.

3D Modeling various Locating Ring
below is some picture of locating ring that was i sketch using Google sketchUp, now i provide two type of locating ring. to choose right locating ring in mould is depend on injection machine nozzle, locating hole diameter, nozzle length in other factor.


Second type





















Third type
this type have large chamfer from top to bottom in inner hole, those chamfer provide shape so nozzle can touch the sprue more precise and easier.


and below is sample picture of locating ring base on Mold Part Industries

Read More

Sprue Bush Design in Injection Mold

The molten plastic injected from the injector nozzle will go through a sprue (sprue bush), a runner, and a gate and fill up in the cavity.
As the temperature of molten plastic is lowered while going through the sprue and runner, the viscosity will rise; therefore, the viscosity is lowered by shear heat generated when going through the gate to fill the cavity.
so learn Sprue bush design is important, becouse sprue bush is part that contact first time with melted plastic, bad design of sprue bush can make plastic product broken, especially sprue broken and runner broken.
picture below shown mold basic construction with sprue.



























below is 3D model of sprue bush with 2 bolts
































this type is commonly use in small mold size, until 350 ton injection machine is still used.

the other construction is 4 bolts, this sprue bush type commonly use in large mold type and mass production, more than 200 ton






























and below is sprue bush with ring attachment, this type use when top plate thickness is width, but some designer prefer use large chamfer in top plate so with first model sprue bush is still can be attach


































Sprue Bush Design Rule
1. Ball radius of sprue must larger than ball radius nozzle, so don't forget to check diameter of nozzle of injection machine, or you can look at injection machine catalog. for example when ball radius of nozzle of injection machine is 10 mm use ball radius sprue bush 11 until 13 mm.
2. Hole diameter inner must be larger than hole diameter nozzle, diameter nozzle is variating base on machine injection type and manufacture, is about 2 mm until 5 mm. use 0.5 mm more larger than hole diameter of nozzle.
3. check your plate thickness, make sure that length of sprue bush fit with the plate thickness.

Read More