The device described in the manual is a Herzog Machine Shut-off Nozzle Type A(S), which is spring-operated and designed for use in injection molding applications. This nozzle is specifically intended for processing thermoplastics, with the important caveat that it is not applicable for PVC.
Function Description
The primary function of the Herzog Shut-off Nozzle Type A(S) is to control the flow of molten plastic during injection molding. Its core mechanism is a shut-off mechanism operated by one axial high-performance spring. This spring-loaded design ensures precise and reliable closure of the nozzle orifice, preventing material drool and stringing between injection cycles. By effectively shutting off the melt flow, it contributes to cleaner molding operations, improved part quality, and reduced material waste. The nozzle is delivered pre-assembled, though optional heater bands and temperature sensors are installed separately.
Important Technical Specifications
The manual highlights several critical technical specifications for the nozzle:
- Applications: Specifically for thermoplastics, excluding PVC.
- Shut-off Mechanism: Spring-operated, utilizing a single axial high-performance spring.
- Maximum Injection Rate / Temperature: The nozzle is rated for a maximum injection rate of 2000 bar at 350°C. This indicates its capability to handle high pressures and temperatures commonly encountered in thermoplastic injection molding.
- Noise Emissions: The noise emissions from the nozzle do not exceed 70 dB(A), suggesting a relatively quiet operation within industrial environments.
- Material Compatibility (Cleaning): Plastics such as LCP or PPS can be burned away when the nozzle is heated in an oven for two hours at 500°C, indicating specific material properties relevant for cleaning.
- Temperature Limits (Maintenance): Steel parts should never be heated above 500°C to prevent damage.
Usage Features
The Herzog Shut-off Nozzle Type A(S) offers several usage features designed to optimize its performance and ease of integration into injection molding processes:
- Pre-assembled Delivery: The nozzle is delivered pre-assembled, simplifying initial installation. Users only need to install optional heater bands and temperature sensors.
- Installation Flexibility: The installation process involves checking surfaces, greasing threads with high-temperature paste, and pre-installing the heater band and sensor. It requires standard tools like hexagonal wrenches, Allen keys, and ring spanners.
- Temperature Equalization: A crucial step during installation and operation is to await temperature equalization before tightening components, ensuring proper fit and preventing stress.
- Initial Operation Procedure:
- Bringing the nozzle up to operating temperature.
- Retightening screws, tip, and heater band with maximum torque after first installation or assembly.
- Ensuring the material is completely melted.
- Discharging heated material by extrusion at low speed (25-30 seconds) or injecting out at three to five times the normal rate to properly prime the system.
- Leakage Management: A melt film between the needle and guide prevents blocking and is continuously renewed, leading to eventual leakage. Users are advised to reduce nozzle temperature during machine downtimes to manage this.
- Safety Instructions: The manual emphasizes safety, including the need for suitable personnel for installation and servicing, wearing full face protection and heat-resistant gloves due to extreme temperatures, and avoiding dropping the nozzle or exerting unnecessary forces. It also warns against foreign bodies entering working parts, adjustments during operation, and heating steel parts above 500°C.
- Explosion Danger Warning: A critical warning is issued regarding the potential for some plastics to produce gases if left in a heated environment for too long, which could escape explosively through the nozzle orifice.
Maintenance Features
Maintenance of the Herzog Shut-off Nozzle Type A(S) is crucial for its longevity and performance, with several features and recommendations provided:
- Cleaning Procedures:
- Cleaning should be performed as much as possible in a heated state while the nozzle is still installed.
- For thorough cleaning, the nozzle should be completely disassembled, and individual parts cleaned.
- Specific plastics like LCP or PPS can be cleaned by burning them away in an oven at 500°C for two hours.
- A strict temperature limit is imposed: never heat steel parts above 500°C.
- Users are warned to avoid kinking heater band and sensor cables during maintenance.
- Recommended Cleaning Tools: The manual lists several helpful tools for cleaning:
- Sand fluidized bed
- Glass bead blasting
- Cleaning oven
- Gas burner
- Wire brush
- Steel wool
- Pre-Reassembly Check: Before reassembly, all parts must be checked for damage or wear to ensure proper function and prevent future issues.
- Professional Cleaning Service: Herzog Systems AG offers a professional cleaning service where the nozzle is disassembled, checked, and repaired if necessary, after customer approval. This provides an option for expert maintenance and repair.
- Assembly and Disassembly Instructions: Detailed steps are provided for disassembly, including clamping the hexagonal part in a vice, unscrewing the tip, removing shut-off parts using a punch, inserting the shut-off part reversed back into the body, reinserting the positioning pin, and using a ring spanner to unscrew the spring chamber. Torque specifications for various components (e.g., spring chamber, tip) are also provided, categorized by nozzle type (A0, A1.0/A1.1, A2).
Overall, the Herzog Machine Shut-off Nozzle Type A(S) is a specialized component designed for precise melt flow control in thermoplastic injection molding, emphasizing robust construction, specific operational parameters, and detailed maintenance guidelines to ensure safe and efficient operation.
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