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HRunners

Sprueless mold — is a mold where the temperature of the injected plastic is maintained at a constant level throughout the whole cycle.

Sprueless molding system or “hot runner” is actually nothing more than injection nozzle extension, functioning as a distributor of molten material over every cavity. Single-cavity molds have a relatively simple and short cone-shaped distribution channel. The plastic material hardened in this channel is called a sprue. Multi-cavity distribution channel can have a very complex configuration since it supplies the melt into several cavities. The plastic material hardened in these channels is called a runner. In sprueless molding the sprues and the hot runners are made in different plates isolated from the cold cavities. Unlike traditional cold runner molds, they do not cool down and harden, and are not ejected together with the parts.

There are several advantages of hot runners over the traditional cold runner systems::

  • No need to cut the sprues
  • No problems with material impurities
  • Reduced labor costs
  • Potential for material saving
  • Decrease in mold maintenance costs and reduction of downtime losses
  • Low power consumption
  • Cooldown time reduction
  • Cycle time decrease
  • Improved profitability
  • Higher part quality
  • Part cost decrease
  • Better dimensional stability
  • Fewer markings on the part
  • Stable part weight
  • Lower mold pressure
  • Lower injection pressure
  • Greater feeder variety
  • Balanced melt flow

There are two manifold heating types: internal and external:

The Cool-One system features internal heating where the heater is located inside the distribution channel. This creates a loop flow in the isolated layer of hardened plastic, and the polymer is heated from the inside.

In the Hot-One system with external heating, on the contrary, the polymer is heated from the outside and has distribution channels without any limitations. Cool-One system is not universally applicable for any material type. When choosing this system one should take into account possible changes in color and material properties, bigger injection sprue, and possible material stagnation.

Hot-One system is better fit for heat-sensitive filaments, and it supports color reduction. It can also be used for casting multi-cavity parts in a wide range of sizes. This system is particularly good for shift-sensitive and unfilled materials.

Hot runner mold – is a mold where the polymer material is kept molten in the runners throughout the whole cycle.

Special electrical heaters are used for heating and temperature maintenance inside the mold. To control the temperature in the mold special temperature controllers are used.

The use of hot runners is justified for both single-cavity and multi-cavity molds.

When fabricating larger-size parts the use of hot runners will allow reducing both the injection boost time (which includes cavity fill time), and the part cooldown time. The central runner is usually quite big, and its injection boost time is approximately proportional to its cross-section squared.

When making a multi-cavity mold, application of hot runner system is justified not only by the above advantages, but also by sprueless production possibility, i.e. almost complete elimination of waste recycling processes. This is of particular importance when you have multi-cavity molds and small parts with the volume comparable to that of sprues obtained in the process.

One of the key factors for application of hot runners is the fact that the parts fabricated will have a higher quality, and some simply cannot be made using conventional cold runners.

Advantages of hot runner molds:

  • Complete or partial absence of casting sprues;
  • Material usage reduction through elimination of casting sprues;
  • Reduction of labor intensity on recycling of casting sprues;
  • Production time decrease through cycle time reduction;
  • Profitability improvement;
  • IMM injection pressure decrease;
  • Mold-clamping force decrease;
  • Melt flow balancing;
  • Product weight reduction;
  • Better product quality;
  • Reduction of residual stress in the product;
  • Smaller shrinkage cavities;
  • Higher product durability;
  • Product cost reduction.

Application of hot runner systems in the molds will indeed affect their price because of hot runner components themselves, and temperature control systems. Yet for production of large batches the advantages of hot runners outweigh the expenses.

Hot runners consist of a hot runner insert and a temperature control system.

The hot runner insert can consist of a single heated nozzle (for single-cavity molds) or have a complex structure of several nozzles and a manifold. Respectively, a single-, two- or multi-zone temperature controller will be used depending on the number of nozzles implied.

In their turn the hot runner nozzles are divided into internal (Cool-One) and external (Hot-One) heated ones. Application of certain nozzle type is conditioned by mold design, number of cavities, polymer material, etc.

The simplest hot runner system consists of a single hot sprue bushing or one multiple gate nozzle and a temperature controller.

A single hot sprue bushing is used in single-cavity molds and in so-called semi-hot runners.

Semi-hot runner system is used for multi-cavity molds with small-sized castings and runners. In this layout the hot sprue bushing ends with a cold runner manifold and feed gates. A single-zone temperature controller is used in this case.

This design is the easiest way to switch to hot runner molds.

Hot runners imply special temperature control instruments. The temperature required for the hot sprue bushings is achieved by electrical heating.

Essential series manifolds (2010) Download the catalogue Горячеканальные коллектора основной серии Essential (2010 г)
Heated Single Nozzles (2010) Download the catalogue Обогреваемые ГКС втулки Single Nozzles (2010 г)
Cool-One system Download the catalogue Горячеканальная система Cool-One
Polivalve system Download the catalogue
Горячеканальная система Polivalve
Bacchus system Download the catalogue Горячеканальная система DME Bacchus
Hot-One system Download the catalogue
Горячеканальная система от DME Hot-One
Heated sprue bushings and heaters Download the catalogue Обогреваемые литниковые втулки и нагреватели DME
Temperature regulators Download the catalogue Регуляторы температур DME
Integrity control modules Download the catalogue Модули управления ГКС Integrity

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