Design sprue gate or direct gate is the simplest and oldest kind of gate. it connects directly end sprue to the molding. It has a circular cross-section, is slightly tapered, and merges with its largest cross-section in to the part.
The sprue gate always is at the thickest section of the product. It uses for boxes , cups like bathtub, plastics bucket,… product.
1. Advantages and disadvantages of sprue gate.
– The injection pressure will reduce due to direct cavity filling.
– Gate and runner design easily.
– Mold making is easy, low cost of design.
– Easy to design and maintenance.
– We have to cut gate after molding.
– Sample has sink mark near gate position.
– This gate is big so after gate cutting process, sample have mark at gate position.
2. How to design sprue gate – direct gate?
dv: nozzle exit diameter.
d: diameter of sprue orifices.
D=t + 1.5 mm
+ t: The thickest of product.
+ D: The diameter of the sprue gate depends on the location at the molded part.
It should not be thicker, though, because it then the melt solidifies too late and extends the cooling time unnecessarily
You can read more gate design at injection molding gate design dimension.