Polyester Filament Production: UDY, MOY, POY, DTY and FDY

Polyester filament production can follow several routes, and each route changes the yarn’s orientation, residual draw, elongation, package stability and downstream performance. A mill may spin directly from polymer melt or remelt dried PET chips. It may then use conventional, medium-speed or high-speed spinning, followed by separate drawing and texturing or an integrated spin-draw process.

For knitting and weaving buyers, the route name is useful but not enough. Polyester filament yarn from two suppliers may have the same dtex and still behave differently during texturing or dyeing. DTY can meet the count requirement yet show uneven stretch or barre in fabric. We therefore look at the production route together with filament count, luster, strength, elongation, shrinkage, finish oil, interlace and package build. The difference between continuous filament and staple-spun yarn is also important; our yarn classification guide explains that basic distinction.

How Polyester Filament Production Is Classified

Polyester filament routes are normally classified in three ways: by raw material, by spinning speed and by the number of processing stages. These classifications overlap. For example, a chip-spinning line may run at high speed to make POY, which then enters a two-step POY-DTY route.

Conventional, medium-speed and high-speed spinning

The traditional process windows in the source production system are:

• Conventional spinning: approximately 1,000–1,500 m/min
• Medium-speed spinning: approximately 1,800–2,500 m/min
• High-speed POY spinning: approximately 3,000–3,600 m/min

These figures describe established process routes rather than universal limits. Actual settings change with equipment design, polymer grade, spin-pack condition, filament count, quench system and target elongation.

Three-step, two-step and one-step routes

A three-step route separates spinning, drawing and texturing. A two-step route first makes an intermediate yarn such as MOY or POY, then draws or draw-textures it. A one-step route combines spinning and drawing on an integrated line to make FDY.

Process route	Spinning speed	Downstream operation	Stated yarn range	Main point
UDY-DY-TY	1,000–1,500 m/min	Separate drawing and false-twist texturing	33–167 dtex	Mature three-step route with good process control
MOY-DY	1,800–2,500 m/min	Low-speed draw twisting	33–167 dtex	Higher output than conventional spinning but below POY systems
MOY-DTY	1,800–2,500 m/min	High-speed draw texturing	55–88 dtex	Generally less efficient than POY-DTY
POY-DTY	3,000–3,600 m/min	High-speed draw texturing	50–167 dtex	Common two-step route for textured filament
Spin-draw FDY	Depends on line configuration	Drawing integrated with spinning	55–165 dtex in the stated process	Fully drawn yarn from a one-step line

Conventional Low-Speed Route: UDY-DY-TY

Conventional spinning, also called low-speed spinning, was one of the earliest industrial polyester filament yarn routes. It uses three stages:

1. Spinning and winding to produce undrawn yarn (UDY)
2. Draw twisting to produce drawn yarn (DY)
3. False-twist texturing to produce textured yarn (TY)

Spinning normally runs at 1,000–1,500 m/min. Draw twisting operates at about 600–1,100 m/min, while false-twist texturing runs at roughly 120–160 m/min. Before texturing, the remaining draw ratio is approximately 3.5–4.2. The route can produce filament from 33 to 167 dtex.

Its main advantage is separate control of each stage. The equipment and operating logic are mature, and technicians can adjust drawing and texturing without changing the spinning section. When spindle-to-spindle variation stays low, the route can produce both drawn and textured filament with stable quality and good dye uniformity.

Older mill records report a normal dyeing grade, called M grade, of up to 96%. In that classification, dye uptake of the tested textured yarn remained within half a grade of the standard yarn. The figure should be kept as historical process data, not treated as a universal purchasing requirement unless the supplier provides the grading method and test conditions.

The limitation is the long process. Three stages require more equipment, floor space, labor and package handling. Every transfer also creates another opportunity for damaged packages or mixed lots. These disadvantages became more important as high-speed spinning and draw-texturing equipment improved.

Medium-Speed Polyester Filament Production

Medium-speed spinning runs at about 1,800–2,500 m/min and produces medium-oriented yarn (MOY). MOY has more molecular orientation than UDY, so it needs less downstream drawing, but it is not ready for normal end use without further processing.

MOY-DY route

MOY-DY combines medium-speed spinning with low-speed draw twisting. Drawing speed is normally 800–1,200 m/min. The route can make 33–167 dtex drawn yarn, with 50 dtex and 75 dtex listed as common specifications.

Productivity is higher than the conventional UDY route but lower than high-speed POY production. The original process comparison also places its product quality below the conventional route. For sourcing, that general comparison is not enough to approve or reject a yarn. Strength, elongation, shrinkage and dyeing data should be checked against the intended fabric.

MOY-DTY route

MOY-DTY sends medium-oriented yarn to high-speed draw texturing. The remaining draw ratio is approximately 2.1–2.4, and draw-texturing speed is about 400–500 m/min. The stated product range is 55–88 dtex. For yarn above 110 dtex, two ends may be combined onto one package.

This route generally falls behind POY-DTY in productivity and overall product consistency. It remains useful for understanding how increasing orientation during spinning reduces the drawing required later.

High-Speed Routes: POY-DTY, POY-TY and POY-DY

High-speed spinning at around 3,000–3,600 m/min produces partially oriented yarn (POY). Faster take-up gives POY more orientation than MOY and leaves a lower residual draw for downstream processing.

POY-DTY

POY-DTY is the main two-step route for producing draw-textured polyester yarn. The POY first comes from high-speed spinning. Drawing and false-twist texturing then take place together on a draw-texturing machine.

Downstream speed commonly falls between 400 and 800 m/min, and the stated DTY range is 50–167 dtex. The shorter route improves production efficiency and reduces intermediate handling compared with UDY-DY-TY. It also lowers the investment and operating burden per unit of output when the line runs steadily.

POY can support storage and long-distance transport better than low-oriented undrawn yarn when it is packed and stored correctly. Still, finish oil, package condition, temperature, humidity and storage time can affect later texturing. DTY quality also depends on heater temperature, draw ratio, friction-disc condition, twist insertion, interlace and winding tension. Our production notes on polyester high-elastic DTY yarn provide more application context.

POY-TY

POY-TY uses high-speed spinning followed by low-speed rotor false-twist texturing. It can produce textured yarn around 111–167 dtex. However, the low texturing speed removes much of the productivity advantage created by high-speed POY spinning, so the route is generally unattractive from both technical and economic viewpoints.

POY-DY

POY-DY combines high-speed spinning with low-speed draw twisting. A typical draw ratio is 1.3–1.7, and the stated output range is 55–110 dtex. The resulting DY normally performs below drawn yarn made through the conventional UDY route. A supplier offering this construction should therefore provide measured performance rather than present it as a direct equivalent.

One-Step Spin-Draw Production for FDY

In a one-step polyester filament production line, spinning and drawing take place on the same integrated machine. The yarn leaves the line fully drawn and is called FDY.

One reported configuration spins at 900–1,500 m/min and draws at 3,200–4,000 m/min with a draw ratio near 3.5. It can produce approximately 55–165 dtex FDY. A second configuration spins at 2,600–3,500 m/min and draws at 5,100–5,500 m/min.

FDY does not need a separate drawing stage before many knitting or weaving applications. It is used where a smooth filament, controlled elongation and stable luster are required. However, FDY is not a complete specification by itself. Bright, semi-dull and full-dull grades look different, while round, trilobal and other cross-sections change luster, capillary behavior and fabric appearance.

HOY and HCY Production Routes

High-oriented yarn (HOY)

HOY uses one-step ultra-high-speed spinning. Winding speed in the stated process is about 5,500–6,000 m/min. The high take-up speed greatly increases jet stretch and molecular orientation. At the same time, the process can create larger crystallites and lower orientation in the amorphous regions.

The source records note good dyeing behavior but elongation of around 40%. Even when winding speed rises to 7,000–8,000 m/min, elongation may remain too high for general apparel use. For that reason, this version of the HOY route remained at an experimental or limited-production stage rather than replacing common FDY processes.

High-crystalline yarn (HCY)

HCY uses high-speed spinning with a hot-tube drawing stage. The heated tube is positioned after the filaments solidify and before gathering and finish-oil application. Hot air heats the filament above the glass-transition region but below its softening point. Winding tension then draws the heated yarn further.

The process can raise crystallization and orientation in one continuous route. Its control window is narrow, though. Temperature profile, residence time, tension and cooling must remain consistent across every spinning position.

Production Characteristics That Control Polyester Filament Quality

High production speed

Most established high-speed lines in the described production system run near 3,500 m/min. A higher speed improves output, but it also gives operators less time to respond. A brief disturbance can affect a large quantity of yarn before the line is corrected.

Larger packages

Wound filament packages increased from roughly 3–4 kg to about 15 kg in the referenced production development. Textured-yarn packages increased from around 1–2 kg to about 5 kg.

Larger packages reduce doffing and help downstream efficiency. They also require better control of package density, traverse, edge build and unwinding tension. An outer package inspection cannot show every problem. Tension may change as the yarn unwinds into deeper layers.

Stable raw-material quality

Polyester-chip quality has a direct effect on spinnability and final filament properties. Important indicators include intrinsic viscosity, softening behavior, diethylene glycol content, carboxyl end-group content, ash and agglomerated particles. Chip shape, black specks, molecular-weight distribution and moisture also matter.

The original high-speed chip-spinning route calls for moisture not above approximately 30–50 ppm. This is a tight control point because excess moisture can hydrolyze PET during melting. The final limit should follow the resin supplier’s data and the line’s validated process. Drying temperature, residence time, dew point and closed material transfer all affect the result.

Strict process control

The source operating practice limits melt-temperature fluctuation to about ±1°C and position-to-position quench-air speed difference to no more than 0.1 m/s. It also calls for daily cleaning of the spinneret face. These values are useful process references, but the validated limits depend on the equipment and yarn specification.

The underlying production logic does not change: stable melt, uniform quenching, clean capillaries and consistent finish pickup help reduce position-to-position variation. Water, compressed air, steam and electricity must also remain stable because a utility fluctuation can affect many positions at the same time.

Position-to-position consistency

Polyester filament spinning, drawing and texturing take place across multiple positions. A downstream process can correct some small differences, but it may also enlarge them. Uneven melt flow, quench air, finish pickup, winding tension or heater condition can later appear as broken ends, elongation differences, package-density variation or dye streaks.

From our factory view, keeping lots separate during sampling is one of the simplest useful controls. For incoming cones, our sample-room check may record the lot, dtex, filament count, luster and package condition before a machine trial. In a sock program using 150D functional polyester, an 18G trial can reveal loops, tension changes or barre risk that are not obvious on the cone. We then judge the knitted sample again after the intended wash and finishing route. Our 150D anti-slip polyester yarn is one end-use example where yarn, knit structure and finishing need to be evaluated together.

Inspection, packing and storage

Each raw-material lot should be checked against its physical specification. Wound packages need inspection for visible defects, incorrect build and damage. Dyeing performance should be sampled or fully checked according to the product and risk level.

Different specifications and production lots should not be mixed during packing. Storage areas need protection from direct sunlight, rain and excessive humidity. Cartons should not be stacked beyond their safe load, while loading and transport should avoid impact that can deform packages or damage tube edges.

What Buyers Should Confirm Before Bulk Production

A route description does not replace a technical specification. Before approving polyester filament yarn in POY, DTY or FDY form, we recommend confirming the following points:

• Yarn identity: POY, DTY, FDY or another clearly defined form
• Construction: dtex or denier, filament count, cross-section and luster
• Mechanical data: tenacity, breaking force and elongation
• Thermal behavior: boiling-water or dry-heat shrinkage under agreed conditions
• Texturing details: interlace level, stretch requirement and finish-oil condition
• Package details: net weight, tube size, package density and unwinding direction
• Dyeing performance: dye uptake, lot consistency and barre risk
• Machine trial: actual gauge, stitch or weave, speed, finishing route and wash test
• Documents: test reports, restricted-substance information and any required certificate scope

For tensile testing, ISO 2062:2009 covers single-end breaking force and elongation for yarns taken from packages. The purchase specification should state the agreed method, conditioning and acceptance limits. Where chemical safety certification is required, the supplier should also confirm whether the yarn falls within the valid scope of OEKO-TEX STANDARD 100 or another specified program.

Keep the first trial within one spinning and texturing lot. If the approved sample uses one lot but bulk knitting combines several, a shade or tension problem becomes much harder to trace. A trial cone and written specification should stay linked to the same lot reference.

Frequently Asked Questions

What is the most common production route for polyester DTY?

POY-DTY is the common two-step route. High-speed spinning first produces partially oriented yarn. A draw-texturing machine then draws and false-twist textures the POY in one downstream operation.

What is the main difference between POY and FDY?

POY is partially oriented and still requires drawing, usually during texturing. FDY is fully drawn on an integrated spin-draw line and can enter many knitting or weaving processes without a separate drawing stage. The two yarns have different elongation, shrinkage and end-use behavior.

Why must PET chips be dried before spinning?

PET absorbs moisture. During remelting, excess moisture can cause hydrolysis and reduce polymer molecular weight. That may weaken the filament and make spinning less stable. The stated high-speed route uses approximately 30–50 ppm as a moisture ceiling, subject to the chip supplier’s and spinning line’s validated requirements.

Does higher spinning speed always produce better yarn?

No. Higher speed can improve orientation and productivity, but it also narrows the operating window. Polymer quality, filtration, quenching, finish pickup and winding must remain stable. Buyers should judge measured yarn properties and fabric performance, not spinning speed alone.

Which data matter most when comparing DTY suppliers?

Start with dtex, filament count, cross-section, luster, interlace, tenacity, elongation, shrinkage, dyeing uniformity and package build. Then run the yarn on the intended machine and through the planned finishing route. Lot control and consistent test methods matter as much as the average test values.