Industrial case study: Turnkey 600 kg/h TPU underwater pelletizing line for sports footwear and pneumatic tubing, reducing startup scrap from 8.5% to 0.4%.
The situation
A project is read from the conditions it began with — the profile, the background and the constraints are the customer's, and the result only means something beside them.
Achieve continuous, automated production of TPU micro-pellets (Ø1.2–1.8 mm) and standard pellets (Ø2.5–3.0 mm) with zero strand-break downtime, reduce startup and transition scrap below 1.0%, and ensure residual moisture ≤ 0.03% (300 ppm) directly after dewatering.
A specialized polymer elastomer compounding company in South China producing premium TPU compounds, supplying raw materials to global sports footwear brands and European pneumatic automation component makers.
With exponential growth in lightweight, high-rebound athletic footwear midsoles (E-TPU), sports brands demanded ultra-consistent spherical micro-pellets. Traditional strand granulation cannot maintain dimensional tolerances or prevent void formation on soft, tacky polymers, necessitating an automated underwater pelletizing solution.
The client operated an older water-bath strand extrusion line. When attempting to produce Shore 70A footwear TPU, soft strands repeatedly stretched and tangled, limiting line throughput to barely 300 kg/h, requiring three operators per line constantly restringing strands, and yielding irregular pellet lengths with unacceptable dust generation.
Extremely strict pellet size distribution requirements: for E-TPU foaming beads, 98.5%+ of pellets had to fall within Ø1.4–1.6 mm, with zero tolerance for twin agglomerates or internal void cavities.
Delivery
The scope below is what this project actually received; the configuration snapshot is the one agreed for this delivery, not a current product sheet.
Submerged underwater pelletizing was selected over water-ring and strand cutting because only full water submersion provides the immediate, high-velocity thermal quenching required to freeze tacky, low-modulus elastomeric droplets without surface smearing or blade wrapping.
Engineered an interchangeable dual-die-plate assembly with precision cartridge heating, allowing the customer to switch between standard Ø2.8 mm pneumatic hose pellets and Ø1.5 mm footwear micro-pellets in under 45 minutes.
Melts, compounds, and homogenizes TPU polymer with additives under precise low-shear temperature control.
Configured with multi-stage liquid stabilizer injection and high-vacuum degassing ports.
Decouples extruder surging and delivers laminar, pulsation-free melt pressure to the underwater die plate.
Integrated pressure transducer closed loop regulating extruder screw speed.
Submerged high-speed micro-pellet cutting with zero die freeze-off and micro-gap automatic knife positioning.
Supplied with both standard (Ø2.0 mm) and micro-hole (Ø1.0 mm) die plates.
Quenches molten droplets at ±0.5°C water stability and centrifugally expels surface water to ≤ 0.03%.
Includes plate heat exchanger, circulation pump, and fine bypass water filtration bag.
Scalps rare oversize doublets and dedusts micro-fines prior to automated packaging.
Equipped with quick-release latches and soft silicone food-grade gaskets.
Verification
A stage is written down only when there is evidence for it; a project that is running says so, and a project still in the factory does not claim more.
Factory Tested
Extruder mechanical alignment and dry runs conducted at 600 RPM; underwater pelletizer dynamic balancing checked up to 4,500 RPM with vibration amplitude < 1.2 mm/s; chiller cooling capacity and temperature stability verified at full thermal load.
Shipped
Dispatched in three 40-foot high-cube sea containers with export-grade moisture-barrier vacuum packaging and shock-absorbing timber framing.
Installed
The complete turnkey line was laid out over a 22 m x 5 m footprint. Mechanical alignment, piping, and electrical integration were completed in 7 working days by our factory service team.
Commissioned
Commissioning took place over four production days: testing Shore 75A polyester TPU micro-pelletizing (target Ø1.5 mm for foaming beads) and Shore 90A polyether TPU standard pellets (Ø2.8 mm for pneumatic tubing). Process water was locked at 14.5°C; continuous 8-hour acceptance run completed at 615 kg/h without a single blade stall or die freeze-off.
In Operation Verified
The line has run continuously on three shifts (24/7) for over 18 months, maintaining an average monthly output of 380 tons of high-grade TPU pellets with zero unplanned cutter downtime.
Results
Every result names its evidence. A number without the method and conditions behind it would not be a result worth quoting.
8.5 0.4
%
Startup and transition scrap dropped dramatically from 8.5% on the old strand line to just 0.4% on the turnkey underwater line, saving over 4.5 tons of expensive prime TPU resin per month.
Evidencia Customer Confirmation
0.18 0.021
%
Residual surface moisture after the centrifugal dehydrator was slashed from 0.18% (1,800 ppm) to 0.021% (210 ppm), allowing direct vacuum packaging without auxiliary desiccant hot-air drying.
Evidencia Factory Test Record
78.5 99.2
%
Pellet size uniformity ratio within target ±0.1 mm window surged from 78.5% to 99.2%, perfectly fulfilling supercritical CO2 footwear midsole foaming bead requirements.
Evidencia Customer Confirmation
Evidence
Only material the customer has cleared for publication is shown here.
Details
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