News

October 30 2003

Technical Paper - UNITIZED AND INTEGRATED HOT RUNNER SYSTEMS COMPARED WITH “HOT HALVES” DESIGNS

October 30, 2003
Technical Paper - UNITIZED AND INTEGRATED HOT RUNNER SYSTEMS COMPARED WITH “HOT HALVES” DESIGNS

UNITIZED AND INTEGRATED HOT

RUNNER SYSTEMS COMPARED

WITH “HOT HALVES” DESIGNS

INCOE® Corporation, USA

Increased use of hot runner systems is being made for the production of injection molded parts, as it permits parts to be produced more rapidly with improved quality, making production more cost efficient overall. Present-day technologies such as insert molding, co-injection and multi-component would not be possible without hot runner systems. In the same way, large parts such as automobile bumpers can only be produced with hot runner systems due to the restrictions on the flow path/wall thickness ratio, and the presence of knit lines. Hot Runner technology is thus playing an increasingly important role in present day injection molding production. Although the hot runner system is incorporated within the injection mold, its tasks and functions are completely different from those of the mold itself. The system constitutes a self-contained unit with specific, highly precise requirements placed on its installation, connection and operation. For this reason, state-of-the-art hot runner systems are increasingly being supplied in ready-assembled form, as injection halves or “hot halves”. This prevents installation errors and simplifies connection of the system as well as reducing the amount of time required for installation in the mold. (Figure 1)

Image 1

Figure 1: Unitized Hot Runner System (also show Intergrated).

Nozzles are threaded into manifold and wiring is placed in covered

channels. The system becomes a self-contained “drop in” assembly. 

The design of Unitized Systems makes it possible to install pre-wired hydraulic connections directly on the system, independently of the mold to be used. The hydraulic mechanism driving the valve gate can also be mounted directly on the system, making the injection mold more flexible and enabling it to be used on machines without additional control valves. The electrical and hydraulic connections are configured to customer specifications. (Figure 2)

Image 2

Figure 2: Twelve-cavity Unitized System with electrical and

hydraulic connections, including control manifold and valves.

All the systems undergo electrical continuity, temperature, and pneumatic or hydraulic tests prior to delivery. The customer thus obtains a checked, ready-to-install system that can be easily assembled in the mold and brought directly into operation. When routine maintenance needs to be performed on the system or the mold, the Unitized System can be removed from the mold again by this same simple procedure. It can then be tested or repaired independently of the mold.

Conventional Hot Halves Designs

Hot halves were developed from hot runner systems, where the nozzles are not permanently attached to the manifold block but floats on the nozzle flanges. These systems require retainer plates to keep the system together.

Image 3

Figure 3: Structure of a hot half

Given an average temperature differential between the hot runner system and the mold is approximately 2000 C for most plastics and that the system is in contact to the mold plates, it is possible for increased temperature and energy losses to occur. Dead spots may also result at the transition between the manifold block and the nozzles. Hot halves typically need to be completely dismantled when the hot runner needs servicing. Since the nozzles are not connected to the manifold, the electrical and hydraulic connections need to be uncoupled, either entirely or in part, and clamped together again once repairs are completed. This involves a considerable amount of extra work compared with unitized systems, with a renewed risk of assembly and installation errors.

Integrated Hot Runners Systems

Reducing machine downtime for increased production.

The Unitized System offers considerable improvements in quality and addresses the cost of repair favorably. Since the Integrated system is based upon using the Unitized pre-wired design for installation in the mold, the chance for pinched or severed heater and thermocouple wires is eliminated during assembly.

Image 4

Figure 4: Integrated Hot Runner Valve Gate System. Valve

Gate connections and plumbing are also attached to the

manifold and become part of the selfcontained assembly.

All wiring from heater to junction box is encased within a conduit specially designed for that purpose. This is always a benefit whenever the mold/hot runner system is also disassembled. Also, since the Unitized manifold system is fully functional before being installed in the mold. Full testing of electrical and thermal functions are performed at the factory before shipment.

Image 5

Figure 5: The mold strap in the position shown will capture both

the core and cavity plates as the moving platen is retracted.

The Integrated Hot Runner System further provides the injection molder the added benefits of:

Routine maintenance can be performed without removing the hot runner system from the molding machine. While conventional injection halves also allow some maintenance to be performed when in the molding machine, it is limited to only the very front of the nozzle area due to the retainer plate. Servicing beyond this point requires the hot runner manifold system to be removed from the machine in order to expose the manifold system.

Simple hot runner system/mold interchangeability. Inserts can easily be interchanged without mold removal.

Valve gate operational plumbing can be serviced without disassembly.

Image 6

Figure 6: Remove the socket head screw used to fix the

cavity plate to the top plate.

Additionally all of the following operations
can now be performed without removing the
Integrated System from the injectionmolding
machine:

Gate tip exchange
End cap exchange
Nozzle heater exchange
Nozzle thermocouple exchange
Manifold thermocouple exchange
Complete Hot Runner inspection
(Figure 7)

Incorporating the Integrated design involves
preliminary review with the mold manufacturer to insure proper operation. The Unitized Hot Runner manifold is mounted directly to the top plate of the mold. (Figure 4)

 

Image 7

Figure 7: Integrated Hot Runner System is fully exposed inside the press.

Image 8

Figure 8: If necessary, only the top plate and the Integrated Hot Runner System need to be removed from the press.

Image 9

Figure 9: Once outside the press, the Integrated Hot Runner System is easily detached from the top plate.

Image 10

Figure 10: Once outside the press, the Integrated Hot Runner System can be completely refurbished. When complete, the Integrated Hot Runner System only needs to be re-installed for further production.

COMPARISON CHART – UNITIZED / INTEGRATED / HOT HALVES
Criteria Unitized System           
Integrated
System         
 
Hot Halves         
General
Assembly error, or errors in the electrical and hydraulic connections Not applicable Not applicable Not applicable for new units, possible with repairs
Leakage between nozzles and manifold Not applicable Not applicable Possible
Misalignment at nozzle/manifold transition Not applicable Not applicable Possible
Temperature drop in the
nozzle/manifold transition zone
Not applicable Not applicable Generally the case requires extra heat zone
System/mold insulation Excellent Excellent Average
Servicing

 

Replacement of cap and tip

Simple On machine On machine
Replacement of front nozzle heating and T/C Simple On machine Usually possible
Replacement of rear nozzle heating and T/C Simple On machine Dismantled
Replacement of manifold sensor Simple On machine Dismantled
Check for oil and plastic leakage Simple On machine Dismantled
Check for electrical errors Simple On machine Dismantled
Other
Cost Savings No retainer
plate
In machine service Plates from system suppliers generally more expensive
than from mold builders. Some in machine service
capabilities
Since the hot runner system remains firmly attached to the stationary plate during this work, the mold can be repositioned again immediately after the service work is complete and can be ready for production again in just a few minutes. Integrated Systems can thus save several hours or in large systems perhaps days during routine hot runner system maintenance.
Conclusion
Unitized Systems provide a considerable contribution to reducing the number of errorsa and achieving time savings for mold manufacturers during the manufacture and sampling of new molds. In addition, Integrated Systems permit additional savings for injection molders by reducing downtime during injection molding production.

About INCOE® Corporation
Since 1958, INCOE® has engineered productivity built hot runner systems starting with their original patented design of the first commercial hot runner nozzle. Today, a wide range of nozzles and manifolds, pre-wired unitized systems, complete hot halves and advanced control technologies provide optimized systems suitable for appliances, automotive, electronics, medical disposables, packaging and technical markets. A network of representatives in over 35 countries are supported by INCOE® facilities located in the United States, Germany, Brazil, China, Hong Kong and Singapore. Wherever your molding operation is, INCOE® can support your business with complete hot runner systems engineered for your application. That's
INCOE® Hot Runner Performance.


For more information:

INCOE® CORPORATION

1740 E. Maple Road
Troy, MI 48083
T (248) 616 0220
F (248) 616 0225
e-mail: info@incoe.com

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