Selection of Injection Molding Machine

SUMIKASUPER LCP can be molded using both the standard inline type and plunger (preplasticating) type of injection molding machines.
However, for E5000 series, it requires a higher molding temperature (up to 420°C), and thus the injection molding machine with high temperature specifications (450°C) is required.

Screw and Cylinder

• Since glass fiber is filled for most grades of SUMIKASUPER LCP, it is recommended that the wear-resistant materials be used for screws and cylinders.
• A standard full flight type screw is good for SUMIKASUPER LCP. Sub-flight screws and high mixing screws are not recommended because metering time will be extended.
• A typical screw design suitable for SUMIKASUPER LCP is as follows.
  - L/D (screw length [L]/screw diameter [D]) : approx. 18 to 22
  - Compression ratio : around 2.0 to 2.2
  - Ratio of each zone:
  Feed zone : around 55%
  Compression zone : around 25%
  Metering zone : around 20%
• Screw heads for inline type injection molding machines are recommended to be equipped with backflow prevention mechanism.
• As the flow characteristics of SUMIKASUPER LCP are sensitive to temperature, it is necessary to use a PID controller to keep the cylinder temperature properly.
• Screws and cylinders require proper maintenance. Regularly monitor the check ring and the clearance between the cylinder and the screw to ensure that they meet the molding machine manufacturer's specifications.

Nozzle

• For the material of the nozzle, the same as those in "Screw and Cylinder" can be used.
• Open nozzles should always be used. Shut-off nozzles should not be used, as they have excessive dead space that can trap and retain resin.
• The nozzle heater must have a temperature controller (PID controller) that is independent of the cylinder.
• If their is a nozzle specifically designed for LCP, it is recommended to use it. It can be helpful in improving drooling and stringing problems.
• It is not recommended to use an extension nozzle. When using it, be sure to select one that enables uniform temperature distribution.

Injection Unit and Its Control System

• It is possible to use a general open-loop control type or closed-loop control type molding machine.
• Since the melt viscosity of SUMIKASUPER LCP depends greatly on the shear rate and it solidifies rapidly when cooled, it is recommended to use a high performance injection molding machine that enables high speed and high response when molding thin-walled products.

Injection Capacity

• It is recommended to select a molding machine whose shot size is about 1/3 to 3/4 of its maximum injection capacity. If the shot size is too small, the residence time of resin in the high temperature cylinder will be longer, and various molding defects are more likely to occur.
• When performing high cycle (short cycle time) molding, the shot size would need to be less than 1/2 of the maximum injection capacity to shorten the metering time.

Resin Temperature Control

Since the properties of SUMIKASUPER LCP molded products are highly dependent on the resin temperature during molding (cf. Figure 4-1-2), it is necessary to mold SUMIKASUPER LCP at an appropriate resin temperature. On the other hand, as the standard molding temperature for SUMIKASUPER LCP is extremely high (320 to 400°C), there may be a discrepancy between the setting temperature of the molding machine and the actual resin temperature. In this case, the potential of SUMIKASUPER LCP can not be fully utilized.
In order to prevent such problems, it is recommended that the resin temperature in the cylinder be monitored. The actual resin temperature can be measured, for example, by using an infrared radiation thermometer that can measure the temperature of a small area.

Figure 4-3-1 Measuring Method of Resin Temperature

High-Speed Injection Molding

As SUMIKASUPER LCP has a rapid solidification nature when cooled, it does not easily cause flashes during injection molding although its melt viscosity is very low.
However, when molding ultra-thin-walled products (< 0.2mm), there are cases where the resin solidifies in the thin-walled part and sufficient flow length cannot be obtained. As a countermeasure in such cases, the injection molding machines with high speed and excellent injection response characteristics, such as electric injection molding machines or hydraulic injection molding machines with accumulators, are effective.

Figure 4-3-2 Maximum Flow Length without Flash Generation

Hydraulic injection molding machine :	UH-1000 (Nissei Plastic Industrial Co., Ltd.)
Electric injection molding machine :	SE/SV series (Sumitomo Heavy Industries, Ltd.)
Electric injection molding machine :	FANUC ROBOSHOT -Si series (FANUC Corporation)
Electric injection molding machine :	LP/TR series (Sodick Co., Ltd.)

Figure 4-3-3 Comparison of Injection Response Characteristics

(As shown above, when compared to general-purpose molding machine, the high speed molding machine provides the high injection speed in the initial period and thereafter molding is performed at the specified injection speed.)

Flow Length Measurement Mold :	Use the one shown in Figure 4-3-5
Molding temperature :	360°C Grade : E6008 Injection speed 100mm/sec V-P switching pressure 60MPa
General-purpose molding machine :	PS-40E5 ASE (Nissei Plastic Industrial Co., Ltd.) Injection speed 90% Injection pressure 90MPa

Mold Design

When SUMIKASUPER LCP is molded by injection molding, its molecules can be easily oriented in the flow direction due to shear flow. As a result, a molded product with high strength and modulus can be obtained, but at the same time, it must also possess anisotropy.
It is important to pay close attention to how the flow pattern in the cavity will be when designing the mold.

Mold materials

• For prototyping and small lot molding, carbon steels such as S55C can be used, but quenching is recommended when sliding parts are present.
• Since glass fiber is filled for most standard grades of SUMIKASUPER LCP, for the molds that require high dimensional accuracy or for mass production, it is recommended to use steel materials with a hardness of HRC55 to 62, SKD11 or its equivalent materials (HPM31, PD613, RIGOR, etc.), or higher.
• Since almost no corrosive gas is generated by SUMIKASUPER LCP, it does not cause mold corrosion and general mold materials can be used. However, when using a material with a mold hardness of less than HRC55, be sure to carefully consider any potential problems in advance.

Sprue

Runner

• Standard runners having either a circular, semicircular or trapezoidal cross-sectional shape can be utilized. However, it is recommended that runners having a circular or trapezoidal cross-sectional shape be used, as they are most efficient in terms of pressure loss and processability. As SUMIKASUPER LCP possesses excellent flowability, runner diameters can be decreased. Standard runner diameter is 2 to 5mmφ and guideline for runner diameters is 2/3 to 1/2 of that used for PPS and PBT (smallest: 1.5mmφ).
• When using multi-cavity molds, it is recommended that runners be correctly balanced so that individual cavities will be filled simultaneously with resin. Cold slug wells should also be installed at the ends of runners.

Gate

As the weld strength of SUMIKASUPER LCP is lower than that of other engineering plastics, it is necessary to limit the number of gates to only 1 to 2 places and give careful consideration to where to locate the gate, in order to avoid the formation of welds.

• Side gate
  The appropriate land length is 1mm or less, with a width of no more than 5mm. The land depth should be 70% of the wall thickness of the molded products, with a minimum depth of 0.2mm.
• Pinpoint gate
  The appropriate gate diameter range is from 0.3 to 1.5mm, with a land length of up to 1mm.
  If the gate diameter is increased, stringing and gate warpage may occur.
• Submarine (tunnel) gate
  The appropriate gate diameter is 0.3 to 1.0mm.
• Although the utilization of film gates and ring gates is possible, they are not commonly used in LCP molding.

Figure 4-3-7 Gate Diagram

Draft Angle

• The ideal draft angle is : 0.5° (1/90) to 1° (1/60) for thin-walled moldings; and 1° (1/60) to 2° (1/30) for thick-walled moldings.
• Using MR grades, moldings can be released from tool easier than general grades. The releasing force with MR grades is nearly the half of that with general grades. However, draft angle must be enlarged when moldings have greater depths.

Air Venting (Gas Drainage)

• As SUMIKASUPER LCP is often molded under high-speed injection molding conditions, the installation of mold air venting is recommended, in order that the air remaining in the mold can be discharged effectively.
• When welds occur in thin-walled products or at the ends of the flow, short shots defect tend to occur and weld strength will be insufficient.
  Therefore, it is recommended that air venting be installed to remedy this problem.
• SUMIKASUPER LCP has low melt viscosity and excellent flowability. However, as solidification occurs extremely rapidly, flash defect will not occur easily, even with the installation of air venting.
• The recommended depth for air vents ranges from 0.005 to 0.02mm.

Applying Hot Runner

During long-term continuous molding, resin can remain in dead spaces inside the molding machine, and the remaining resin may deteriorate or become colored. LCP can easily remain in such dead spaces since it has an extremely low melt viscosity. Therefore, when applying hot runners, it is necessary to pay sufficient attention to prevent black spots and cold slag caused by resin retention.

Points to be noted When Applying Hot Runners to SUMIKASUPER LCP

When selecting a hot runner for SUMIKASUPER LCP, please take note of the following points.

• The system must be capable of producing high levels of heating with a uniform temperature distribution.
  Heater integrated type is preferable. The manifold and nozzle temperatures should not be maintained too high.
  The areas coming into contact with the mold (gate areas) must be maintained at high temperatures.

  Table 4-3-1 Temperature Specifications of Hot Runner

  	Temperature specification of hot runner (MAX)
  E6000HF series	up to 370°C
  E6000 series	up to 380°C
  E4000 series	up to 400°C
  E5000 series	up to 420°C

• The hot runner design must be as free as possible from dead space within the flow channels.
  (To avoid the generation of black spots due to the long time retention of resin in the dead space.)
  External heating should be used, rather than internal heating, and the use of narrower flow channels will help to reduce the creation of dead space.
• The hot runner should be designed such that cold slag cannot easily contaminate into the hot resin.
  (To avoid the contamination of cold slags into the molded products.)
  When using open gates, it is recommended that the installation of sub-runners be considered (sprue-less molding).

Application of Hot Runners to SUMIKASUPER LCP

Table 4-3-2 Application of Hot Runners to SUMIKASUPER LCP

		Runner part		Gate seal			Application to SUMIKASUPER LCP		Remarks
		Internal heating	External heating	Open	Valve Gate	Thermal seal	Full hot runner (runner-less)	Sprueless molding
JU-OH INC. 614 System		-		-	-		-	G	φ4 Electromagnetic induction heating
DMK JAPAN Inc. Mini Runner		-			-	-	B	A-E	*1
SEIKI Corp. Spear System	Type B (conventional)		-	-	-		B	B
	EH Type	-		-	-		B	G	*2
Mold-Masters Corp Ltd. Master shot		-				-	B	A-G
FISA Corp. Plagate System		-		-	-		B	A

E = Excellent : Application examples to SUMIKASUPER LCP are available.
G = Good : Applicable to SUMIKASUPER LCP.
A = Average : There are no examples of application to SUMIKASUPER LCP.
B = Bad : Not applicable to SUMIKASUPER LCP

*1 :	When using multiple gates and extension nozzles for a sub-runner,it is better to control the temperature of each extension nozzle individually. It is also good to control the temperature of each nozzle individually for the molding of E5000 series which require high molding temperature.
*2 :	Internal heating system for chip part