Equipment
Submerged die-face underwater pelletizing system for high-output, dust-free spherical pellet production of TPU, TPE, hot melts, and engineering plastics.
Overview
Cuts extruded polymer melt strands directly at the die face submerged under circulating process water into uniform, spherical plastic pellets.
The Underwater Pelletizer (underwater hot-die face pelletizing system) delivers high-efficiency, spherical pellet production for difficult-to-cut thermoplastic polymers, including low-melting-point hot melts, highly elastic rubbers (TPE, TPU, TPV), high-melt-index polyolefins, masterbatches, and engineering plastics (PA, PET, PC). By cutting the extruded polymer melt strands directly at the die plate surface submerged beneath a circulating high-flow process water chamber, the system instantly quenches the cut molten droplets into perfectly uniform, dust-free spherical pellets without strand wrapping or airborne fumes.
Equipped with an electrically or liquid-heated precision die plate, hydraulic quick-clamping cutting chamber, servo/inverter-driven cutting shaft with micro-precision blade advancement, and an integrated tempered water loop (water tank, heat exchanger, and circulation pump), the underwater pelletizer operates continuously without operator intervention. Pellets are immediately swept into the slurry water pipeline and transferred directly to the centrifugal dewatering dryer, eliminating strand dropouts and labor-intensive line re-stringing.
Key features
Each picture names one part of the machine and what it does for the material and the batch.
High-precision alloy die plate equipped with vacuum-brazed tungsten carbide cutting surface and thermal insulation layers. Optimized flow distribution channels ensure uniform melt exit velocity across every die hole, preventing hole freeze-off and uneven pellet size.
Quick-clamping hydraulic cutting chamber mounted on linear guide rails. Closes tightly against the die plate with high clamping force, ensuring zero process water leakage under high circulation flow.
High-speed cutter rotor driven by a variable-speed servo or AC motor with dynamic balance. Features fine axial micrometer adjustment to maintain continuous, uniform contact with the die plate surface, eliminating tailing and fines.
Closed-loop tempered water system (TWS) comprising a stainless steel reservoir, high-flow centrifugal slurry pump, plate heat exchanger, and electric heating elements. Automatically maintains water temperature within ±1.0°C to prevent pellet agglomeration.
Centralized PLC control with intuitive touchscreen HMI. Coordinates water temperature, water flow rate, cutter RPM, melt pressure interlocks, and start-up bypass sequences for one-touch automatic operation.
Material and process
Read the conditions together: a machine is selected for the material and the output, not from its name alone.
Engineered for high-value compounding, recycling, and masterbatch lines producing top-tier spherical granules.
Particularly suited for materials that are sticky, soft, low-melt-strength, or prone to strand breakage in conventional water baths, including Thermoplastic Polyurethane (TPU), Thermoplastic Elastomers (TPE, TPV), Ethylene Vinyl Acetate (EVA), Hot Melt Adhesives (HMA), high-flow Polypropylene (PP), Polyamides (PA6, PA66), and masterbatches. Capable of producing standard pellets (2.0–3.2 mm) and micro-pellets (0.8–1.5 mm).
The underwater pelletizing system operates under submerged high-flow water quenching; key operating boundaries include:
Accepts continuous, pressurized, thoroughly plasticized and filtered polymer melt delivered directly from the upstream extruder or melt gear pump via a hydraulic screen changer.
Melt entering the pelletizer die plate must exhibit stable pressure (typically 40 to 180 bar) and uniform temperature distribution without unmelted polymer chunks or foreign particulate contaminants that could block die orifices.
Produces highly uniform, dust-free spherical or lenticular plastic pellets with consistent diameter (typically 2.0–3.2 mm) and smooth, sealed surfaces.
Pellets are instantly swept by process water through the slurry pipe into the centrifugal dewatering dryer and vibrating classifier, yielding dry, ready-to-pack pellets with surface moisture < 0.05%.
Throughput
Read a figure together with the basis below it: the same machine reaches different numbers on different materials.
Throughput ratings range from 100 kg/h up to 3,000+ kg/h depending on extruder melt delivery capacity, polymer melt flow index (MFI), die plate hole pattern count (ranging from 12 to 300+ holes), and cutter rotor blade quantity (2 to 16 blades).
Low-viscosity hot melts and high-MFI resins require high cutting speeds and smaller die hole diameters to prevent pellet agglomeration, whereas high-viscosity elastomeric resins (TPE/TPU) require precise water temperature control to prevent die hole freeze-off.
Scope of supply
The quotation states the scope for the confirmed configuration; the groups below describe how a supply is normally split.
Installation planning
These are the connections the machine and the line around it have to agree on before the layout is fixed.
Mechanical: Standard circular flanged connection (DN80 to DN200) bolted to the upstream screen changer or diverter valve; flexible slurry transfer pipe connecting cutting chamber outlet to the centrifugal dewatering dryer inlet.
Electrical & Automation: Three-phase industrial power supply to the electrical control cabinet; dry I/O contacts and industrial fieldbus (Profinet/Ethernet-IP) for interlock coordination with upstream extruder melt pump and downstream dewatering dryer.
The buyer provides a reinforced level floor foundation, chilled/process cooling water supply up to the tempered water system heat exchanger inlet, dry instrument air lines, and main electrical power drops terminated at the local control cabinet disconnect switch. Buyer also provides drainage trenches for process water dumping during cleaning and recipe changeovers.
Spare parts
The parts that wear in normal service, and the spares worth keeping on site. How often a part is replaced depends on the material and the duty the machine runs, so the basis is confirmed for each machine.
Inspect blade edge sharpness weekly; hone or replace when cutting edges show chipping, micro-grooving, or uneven wear causing pellet tailing.
Precision ground cutter knives mounted on the rotating cutter hub. Direct wear contact with the die face under high-speed water flow. Keep 3 to 5 full replacement sets in stock; specify blade angle and thickness when ordering.
Inspect resistance draw during monthly preventive maintenance; replace defective heaters immediately to prevent localized hole freeze-off.
High-density electric cartridge heaters embedded inside the die plate body to maintain uniform die orifice temperature.
Inspect for cuts, chemical aging, or water weeping; replace during scheduled quarterly maintenance.
High-temperature silicone sealing gaskets sealing the cutting chamber to the die plate body under water pressure.
Inspect for water weeping at the pump shaft seal; replace seal faces during scheduled maintenance or every 8,000 operating hours.
Heavy-duty mechanical seal for the high-flow slurry water pump circulating water and cut pellets to the dewatering dryer.
Replace seal assembly and check bearing play during bi-annual maintenance overhaul.
Dynamic sealing assembly isolating the cutter motor drive shaft from high-pressure process water in the cutting chamber.
Blades, screens and other normal consumables are outside the standard warranty. How a spare part is identified and ordered is set out under Warranty & Spare Parts.
Selection
Work through what you already know. The rest is settled in the conversation, not before the first message.
Select the optimal underwater pelletizing system configuration based on polymer rheology, pellet size, and throughput requirements:
Request a Quote A model name, a material or a drawing is enough to start.
Tell us the material, the process and what you need to achieve. Technical details can be completed later together with our sales team.
