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Cold Runner Mold

Cold Runner Mold: Plastic Injection Molding, Simple Part Design, Limited Production Runs, Low Maintenance, Change Production Color, Low-Cost Mold

What is cold runner mold

A cold runner mold is a type of injection molding tool where the plastic material is cooled in a separate channel or “runner” before it reaches the individual cavities of the mold. The plastic resin is injected into the cold runner system, where it solidifies before being directed into the cavities to form the final parts. The term “cold” refers to the fact that the runner system is not heated, unlike a “hot runner” mold. Cold runner molds are often used for producing large numbers of small, simple parts and are relatively low-cost to produce.

SINCERE TECH (plasticmold.net) provides plastic injection mold solutions to industries of all types and sizes.

Our state-of-the-art mold building facilities include high-speed CNC Milling and mirror EDM Machining for many types of complex specialty injection molds, including insert molds, gas-assist injection molding, 2K mold, multiple cavities mold and unscrewing molds. We can build molds from small to big (25 ton) for both hot runner mold systems and cold runner mold systems.

Cold Runner Molds: Efficient and Economical

Each system has it’s advantages and disadvantages. Choosing the correct system depends on the requirements of the part to be produced. A few of the considerations include:Cold runner mold

  • Part complexity
  • Color requirements
  • Physical characteristics of the material
  • Type of material – virgin or “regrind”
  • Color changes during the production run

Cold runner systems are best used:

  • When the parts produced are of simple design,
  • For limited production runs, or
  • When a rapid change in production colour is needed

In a cold runner mold, the runner (excess material retained in the feed channels) is cooled and ejected with the part. Every cycle, apart, and a runner is produced.

There are two major types of cold runner molds:

  • A two-plate cold runner mold is the easiest and least expensive type of mold to produce. Two plate molds have a single parting plane, and the mold splits into two halves at the plane. Because the runner system must be in line with the parting plane, the part can only be gated on its perimeter.
  • A three-plate cold runner mold differs from a two plate in that it has two parting planes, and the mold splits into three sections every time the part is ejected. This feature provides greater flexibility of design, allowing gating to be placed in the most efficient locations. Since the mold has two parting planes, the runner system can be located on one, and the part on the other, for easier separation.

Cold Runner Mold Systems: The advantages & disadvantages

There are many significant advantages to using a cold runner mold system:

  • Simple, lower-cost mold design and construction
  • Considerably less expensive than a hot runner system
  • Moulds require less maintenance
  • Easier to set up and operate
  • Colour changes are easy – all plastic in the mould is ejected with each cycle

While it is a less expensive process that hot runner systems, there are a few disadvantages to cold runner systems that need to be considered, including:

  • Waste plastic generated
  • Runner material must be either disposed of or
    reground and reprocessed
  • Additional steps in the manufacturing process
  • Regrind will increase variations in the injection 
    molding process
  • Regrinding could decrease the plastic’s strength characteristics and mechanical properties

Is your project ready for molding parts yet? Welcome to send us your requirement for quotation, we will provide you with the best solution base on your part design?

hot runner with manifold

Hot Runner Molding

What is hot runner mold

A hot runner mold is a type of injection molding system that uses heated material feed channels, or “hot runners,” to maintain the temperature of the plastics as it flows through the injection mold. This allows for a more consistent and efficient molding process, as the plastic does not have to be reheated between shots so the cycle time will be reduced and will save the waste runner materials ( sometimes has no any runner with hot runner systems). Hot runner systems are commonly used in the production of large quantities of plastic parts, such as in the automotive and consumer goods industries, or used in the stack mold.

DONGGUAN SINCERE TECH CO.LTD(SINCERE TECH) provides plastic injection mould solutions to industries of all types and sizes. For almost 20 years DST has designed, built, and worked on almost every type of mold existing in the plastic industry.

We are experienced in building custom plastic molds for a variety of hot runner mold systems, from hot runner manufacturers like:

  • Husky hot runner systems
  • Synventive hot runner systems
  • Kona hot runner systems
  • DME hot runner systems
  • Mold-Masters hot runner systems
  • INCOE hot runner systems
  • HOSCO hot runner systems

Our state-of-the-art mold building facilities include High precision CNC machines, automatic CMM measurement machine, and Two heads of EDM Machines to create many types of custom molds, including complex specialty injection molds, insert molds, unscrewing molds, overmolding, hot runner mold, cold runner mold, stack mold, gas-assisted injection molds, double injection molds (2k molding), etc. We can build molds for both cold runner systems and hot runner systems.

Hot Runner Molding: Efficient High Production

Each system offers advantages and disadvantages. Choosing the system to employ depends on the requirements of the part to be produced. A few of the considerations include:

Hot runner mold structure

Hot runner mold structure

  • Type of material to use – virgin or “regrind”
  • Colour changes during the production run
  • Single or multiple design production
  • Part complexity
  • Colour requirements
  • Physical characteristics of the material

The primary difference between the two systems is that the hot runner eliminates the excess material retained in the feed channels of a cold runner mold. This feature reduces the number of production steps required and saves in material and energy costs.

Furthermore, mostly hot runners use 100% virgin resins; no reprocessed or “re-grind” material is added. This is an important feature for specific applications where regrinding can cause the material to yellow, or detracts from the material properties, such as clarity in light pipe or lens production, where long-lasting transparency is a specific requirement.

Hot runner molding systems normally inject melted material directly into the individual mold cavity. Hot runner is almost always used for large volume production of thermoplastic injection molded parts, or multiple part production using multi-cavity molds and stack-molding technology.

Hot runner molds are two plate molds with a heated runner system inside one half of the mold. A hot runner system is divided into two parts:

  • The manifold has channels that convey the plastic on a single plane, parallel to the parting line, to a point above the cavity
  • The drops, situated perpendicular to the manifold, convey the plastic from the manifold to the part

Hot-Runner Systems: The advantages and disadvantages

Primary advantages of hot runner systems include:

  • Shorter, faster cycle times – most of them have no runners to cool
  • Smaller machines – reduced shot volume into runners
  • Automated processing – runners do not need to be separated from the parts
  • Gates at the best position for economical design
  • Elimination of runners means
  • Materials cost savings – no runner to regrind or reprocess
  • Least expensive cost/piece
  • Reduction of energy costs
  • No runners to remove or regrind
  • Reduces the possibility of contamination
  • Lower injection pressures
  • Lower clamping pressure
  • Consistent heat within the cavity
  • Shorter cooling time
  • Shot size reduced
  • Cleaner molding process
  • Eliminates nozzle freeze

There are, however, a few disadvantages to hot runner mold systems that need to be considered:

  • Hot runner molds are more complex and expensive to build than cold runner molds
  • Higher initial start-up costs than for cold runner systems
  • Complex initial setup prior to running the mold
  • Higher maintenance costs – more susceptible to:
    • Breakdowns
    • Leakage
    • Heating element failure
    • Wear caused by filled materials
  • Risk of thermal damage to sensitive materials
  • Elaborate temperature control required
  • The colors change is more complex than the cold runner, sometime you will spend lots of time and cost to clean up the hot runner systems, especially for transparency and white color parts.

Hot Runner Molds: Applications & Possibilities

Hot-runner systems are almost always used when large runs have to be manufactured in highly automated production. Additionally, technological advances enable us to build molds with gates positioned to yield the best quality molded parts.

Hot runner molds are sometimes connected to needle valve nozzles, which are activated with precise computer-controlled timing. This allows for a number of advanced processes, including:

  • In-Mold Decoration – lamination with a colored film coating
  • Multi-Cavity Molds – cavities with different geometries and/or volumes
    • Parts that belong together produced in one mold
    • Injection valve opening and closing can be adjusted to the conditions of each individual cavity
    • Injection pressure and holding pressure may be adjusted  independently of each other
  • Controlled Volume Balancing – a weld line can be shifted into a non-critical area of the molded part
  • Stack Molding – two or more mold bases in production simultaneously creating multiple parting lines

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