About Injection Molds

The ideal injection molding system delivers molded parts of uniform density, and free from all runners, flash, and gate stubs. In Sarmold we design our molds very precisely to achieve highest possible efficiency.

A well-designed runner system delivers a number of benefits, such as:

  • • Achieving the optimal number of cavities
  • • Delivering melt to the cavities
  • • Balancing filling of multiple cavities
  • • Balancing filling of multi-gate cavities
  • • Minimizing waste
  • • Allowing for easy injection
  • • Providing efficient energy consumption
  • • Controlling the filling/packing/cycle time

Cold runner injection molding systems consist of two or three plates contained within the mold. The system injects the plastic into the mold through the sprue and feeds the runners, which lead to the parts in the mold cavity. The simplest type of cold runner system consists of two plate molds, which has a parting line that separates the two plates. This system has the runner and part attached. You can only gate the part of its perimeter. An ejection system separates both the runner and part from the mold.
Three-plate cold runner systems consist of three plates. There are two parting planes that allow the mold to separate into three sections upon ejection of the part. The runner connects to a separate plate and only the part requires ejection. Three plate molds allow for greater design flexibility and allow flexibility for gate installation based on the requirements of the application. Both types of plates require the runner to be recycled and reground (or disposed of) to reduce waste, which adds to the cycle time.

Here are a few of the benefits of cold runner injection molding systems, including:
• Inexpensive to produce and maintain
• Suitable for a wide variety of polymers
• Allows for quick and easy color changes
• Faster cycle time for a system that includes robotics
The main disadvantages of cold runner systems has to do with slower cycle times compared to hot runner systems and the waste from runners, especially runners that cannot be recycled and reground.


Often referred to as runnerless molding or hot-manifold systems, hot runner molds describe a set of temperature control heating-devices installed in the mold. The purpose of a hot runner injection system is to maintain a molten flow of plastics or rubber from the injection molding machine nozzle to the gate in a plastic injection mold — keeping the runner above the melting point of the plastic.
To achieve this, a hot runner system, in contrast to a cold runner system, is employed. The material in the hot runners is maintained in a molten state and is not ejected with the molded part. Hot runner systems are also referred to as hot-manifold systems, or runnerless molding.

Types of hot runner systems

There are two types of hot runner systems:

Insulated runners 

Insulated runner molds have oversized passages formed in the mold plate. The passages are of sufficient size that, under conditions of operation, the insulated effect of the plastic (frozen on the runner wall) combined with the heat applied with each shot maintains an open, molten flow path.

Heated runners

For heated runner systems, there are two designs: internally heated and externally heated. The first is characterized by internally heated, annulus flow passages, with the heat being furnished by a probe and torpedo located in the passages. This system takes advantage of the insulating effect of the plastic melt to reduce heat transfer (loss) to the rest of the mold. The second consists of a cartridge-heated manifold with interior flow passages. The manifold is designed with various insulating features to separate it from the rest of the mold, thus reducing heat transfer (loss).
Some advantages of a hot runner system include:
• Extremely fast cycle time
• Improvement of component consistency and quality
• Less waste generated without the cold runner
• Ideal system for fabrication of large parts
• Reduced injection pressure
• Operator has more process control and ability to fine-tune
Hot runner molding systems cost more for part fabrication and system maintenance. They are not suitable for thermal-sensitive materials like resins and polymers, and you must allow for downtime.

PPR Fittings Molds

Sarmold has Intimate experience in PPRC Pipe Fitting Molds. PPRC fittings are used for different purposes but commonly used for water supplying pipe systems and we can provide any type of design and size of a mold according to your choice

PVC Fittings Molds

We have different mold designs for PVC group fittings such as UPVC, CPVC

PE Fittings Molds

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