Strand pelletizers that cut cooled polymer strands into pellets · Die, water bath and feed rolls, cutting rotor against a bed knife, pellet length set by feed timing, tooth relief and strand curve, bed knife wear and replacement, cleaning access, and strand versus die-face cutting
A strand pelletizer (strand cutter) is the machine at the end of a compounding or recycling extruder line that cuts solidified polymer strands into short cylindrical pellets. Strands leave the die, cool in a water bath, are pulled in by feed rolls and are chopped by a rotating toothed cutter against a fixed bed knife. Ask three things first: which polymers, fillers and throughput it must handle, how pellet length and cut quality are controlled, and how easily the cutting chamber can be cleaned and the knives changed.
Strand pelletizers and strand cutters (wet or dry cut) for thermoplastic compounds and recycled plastics, including feed rolls, cutting rotors, bed knives and housings, with their interface to the die and water bath. Underwater and die-face pelletizers, extruders, water baths and dryers as separate machines are outside this page except where compared.
CNFX editorial research · Sources checked October 12, 2026 · 4 sources
US patent 5,020,404 (Testing apparatus for strand pelletizing operation, 1991) describes the operation: molten material is forced through a nozzle capped by a plate with small orifices, spaced so the sticky hot strands do not weld together; the strands descend through a water-filled trough where they solidify, are guided by grooved rollers out of the bath, and are captured between a feed roll and a pinch roll that continuously feed them into the cutter, where they are severed into pellets between the cutter teeth and the bed knife. The feed roll rotates in an adjustably timed relation to the cutter to regulate pellet length, and the melt pressure is balanced against the feed roll's demand to keep the pellet cross-section. [1]
It explains that a curve forms in each strand between the feed roll and the cutter, which matters for cutter design, and that each tooth has a relief land from its cutting edge to its heel whose width is critical: if the land is too narrow, cutting forces are carried by the flank instead of the relief angle and the edge breaks down early. [1]
US patent 4,960,020 (Strand cutter with bed knife that can be replaced during operation, 1990) notes that hot die-face cutting serves bulk plastics at high throughput, while engineering plastics, "which often tend to form filaments", cannot be granulated satisfactorily that way; strand cutters are preferred for somewhat lower throughputs and for filled and reinforced plastics, with strands extruded through multi-orifice dies into water and cut by a cutting rotor with multiple knives against a fixed bed knife. [2]
Editorial calculation: pellet length ≈ strand speed ÷ cuts per second; strands fed at 1 m/s (60 m/min) into a 20-tooth rotor at 1,000 rpm (about 333 cuts per second) give pellets about 3 mm long. Ask the supplier for the feed-to-rotor ratio range for your target length. [1]
Give the supplier the polymers and fillers (including glass fibre or mineral content), throughput, strand count and diameter, die hole layout, water bath length and temperature, wet or dry cutting, target pellet length and tolerance, rotor type and tooth count, knife materials, feed roll surfaces, line speed range, dust and fines handling, cleaning and changeover needs between grades, guarding and noise limits.
02
Plan bed knife wear, changes and cleaning
US 4,960,020 aims to replace the fixed bed knife without interrupting granulation, because progressive bed knife wear degrades cutting quality and pellet shape and knife changes cause downtime; it holds the bed knife without play in a guide at right angles to the strand direction and advances it slowly, or pushes a new knife in, during operation, at a feed rate low enough not to disturb the strands. [2]
US patent 5,313,864 (Plastic strand pelletizer, 1994) states that pellet suppliers take great effort to make pellets uniform and free of contaminants, but that poor access to the cutting chamber made cleaning difficult, so off-standard pellets from a start-up could lodge in the pelletizer and later contaminate good product. Its housing has a cover that pivots open and an end wall carrying the feed rolls that slides and pivots, both opened without tools, to reach the cutter, bed knife and feed rolls. [3]
Editorial note: ask the supplier how long a full clean and a rotor or bed knife change take, and whether they need tools.
03
Size a wet-cut strand pelletizer by working width and strand count
MAAG's brochure for its M-USG underwater strand pelletizing systems describes strands extruded through a die plate, carried by a water flow along a strand guide, captured automatically by the pelletizer's intake, cut, and flushed by water into an after-cooling line, with automatic strand feeding at start-up and after strand breaks, automatic pellet-length adjustment, a quick-change cutting head and rotor speed control as an option. For the horizontal M-USG H models its technical data list working widths of 300, 600, 900 and 1,200 mm; cutting-rotor drives of 11, 18.5, 30 and 37 kW; a 5.5 kW feed-roll drive; draw-in speeds of 80–350 m/min; 33–40, 66–80, 100–120 and 127–152 strands depending on product; strand guide lengths of 3,000–8,000 mm; water flows of 20, 35, 45 and 55 m³/h; and maximum throughputs of 5,500, 11,000, 16,000 and 20,000 kg/h depending on pellet weight and polymer. Vertical M-USG V models use shorter 800–1,500 mm guides and take up to 228 strands on the 1,200 mm width. [4]
Editorial calculation: 20,000 kg/h over 127–152 strands is about 130–160 kg/h per strand, and 5,500 kg/h over 33–40 strands about 140–170 kg/h, so the working width scales with strand count at roughly 17 kg/h per millimetre of width on the largest model. Give the supplier your polymer, target throughput, pellet size and strand count from the die so it can choose the width, rotor power and cooling-water flow. [4]
Die plate, water trough, feed and pinch rolls, toothed rotor, bed knife and opening housing
The rotor teeth and the bed knife are the wear-critical rows: US 5,020,404 links early edge breakdown to a relief land that is too narrow, and US 4,960,020 replaces the bed knife while the line runs. [1][2]
Throughput, rotor speed, tooth count, pellet length and drive power for a strand pelletizer
Rotor speed, tooth count and strand feed speed together fix pellet length, as the calculation above shows; throughput and drive power have published ranges only from MAAG's wet-cut systems. [1][4]
Field
What it means and published values
Ask the supplier for
Cutting Capacity (kg/h)
Throughput; e.g. 5,500–20,000 kg/h for wet-cut strand systems by width. [2][4]
3 companies list this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
Anyu Plastic Machinery (Taizhou) Co., Ltd.
Manufacturing site to be confirmed for the order
Its website has a product page for polymer pelletizing strand cutter.
Product scope checked 2026-10-12
Product page on own website · profile compiled by CNFX from public sources
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
How is pellet length set on a strand pelletizer?
By the timing of the feed roll relative to the cutter; the feed roll pushes strands into the toothed cutter against the bed knife (US 5,020,404). [1]
When is a strand cutter used instead of die-face cutting?
For somewhat lower throughputs, filled and reinforced plastics, and engineering plastics that form filaments (US 4,960,020). [2]
Why does cleaning access matter?
Off-standard pellets lodged in the cutting chamber can later contaminate good product (US 5,313,864). [3]
How much can a strand pelletizer produce per hour?
One maker's underwater strand pelletizing systems list 5,500 to 20,000 kg/h across 300 to 1,200 mm working widths, at strand speeds of 80–350 m/min. [4]
Sources and what still needs a direct check
Sources checked 2026-10-12. The three US patents (1990, 1991, 1994) describe strand pelletizing and their own improvements in their own terms; the MAAG brochure gives one maker's technical data for wet-cut strand systems.
