Appearance
A European textile machinery manufacturer was producing 2,400 godet rollers per year for synthetic fibre drawing lines. Each roller — 320 mm diameter × 2,800 mm length in nodular cast iron — required a central heating fluid bore (80 mm diameter × 2,800 mm length) and six peripheral heating channels (20 mm diameter × 2,800 mm length). The existing process used gun drilling from both ends for the small channels, with a 15 % reject rate due to channel intersection errors at the centre joint. By switching to a 4-spindle BTA drilling system with 80 mm and 20 mm BTA heads, the central bore and all six heating channels were drilled in a single setup in 45 minutes per roller. The reject rate fell to 0.3 %, and the elimination of separate gun drilling setups reduced total cycle time by 60 %. The €950,000 investment was recovered in 18 months through reduced cycle time and scrap elimination.
Textile Machinery Components Requiring Deep Hole Drilling
Textile machinery contains several component types that rely on deep hole drilling for their core manufacturing.
Godet rollers: Godet rollers are heated or unheated rollers used to draw, heat-treat, and transport synthetic fibres during spinning and drawing processes. Each roller contains a central bore for the shaft mounting and, in heated roller designs, multiple peripheral channels for heating fluid circulation. Roller lengths range from 500–5,000 mm with diameters of 80–500 mm.
Drying cylinders: Textile drying cylinders are large heated drums (1,000–3,000 mm diameter, 2,000–6,000 mm face length) that remove moisture from fabric after washing or dyeing. They contain internal bores for steam heating and condensate removal.
Spinneret plates: Spinnerets are precision components with hundreds to thousands of micro-drilled capillary holes through which molten polymer is extruded to form fibres. Capillary diameters range from 0.04–0.8 mm with length-to-diameter ratios of 1:1 to 20:1. The hole geometry directly determines fibre cross-section and quality.
Extruder barrels and screws: Melt spinning extruder barrels contain a precision honed bore (40–300 mm diameter, 500–4,000 mm length) in which the screw rotates. The barrel must be wear-resistant and is typically nitrided or bimetallic-lined.
Melt blowing dies: Melt blowing die tips contain arrays of micro-drilled capillaries (0.1–0.5 mm diameter) arranged in a single row across the die width. These are used to produce melt-blown nonwoven fabrics.
Take-up roller and winding shafts: High-speed take-up rollers and winding shafts require precision central bores for balance and for cooling fluid circulation. Bore diameters range from 20–100 mm in shafts up to 4,000 mm length.
Godet Roller Heating Channels
Heated godet rollers are among the most demanding deep hole drilling applications in textile machinery due to the combination of long length, multiple parallel bores, and the need for absolute straightness to maintain roller balance at high rotational speeds (up to 4,000 m/min surface speed).
Heated roller designs:
| Roller type | Roller diameter | Roller length | Central bore | Peripheral channels | Channel diameter |
|---|---|---|---|---|---|
| Small draw roller | 80–150 mm | 500–2,000 mm | 30–60 mm | 2–4 | 10–16 mm |
| Medium godet | 150–320 mm | 2,000–4,000 mm | 60–120 mm | 4–8 | 16–25 mm |
| Large drying cylinder | 500–3,000 mm | 3,000–6,000 mm | 100–300 mm | 8–16 | 20–40 mm |
Drilling sequence for heated godet rollers:
- Central bore is BTA drilled (for diameters above 40 mm) or gun drilled (for diameters below 40 mm)
- Peripheral heating channels are BTA or gun drilled parallel to the central bore
- Cross-holes are drilled at the roller ends to connect the peripheral channels to the central bore for fluid circulation
- End caps or plugs seal the channel ends, creating a closed circulation circuit
Straightness requirements:
For a godet roller rotating at high speed, bore straightness directly affects dynamic balance. The typical requirement is straightness within 0.03 mm per metre of roller length. For a 3,000 mm roller, total bore deviation must not exceed 0.09 mm.
Tip: For multi-channel godet roller drilling, drill the central bore first, then use it as a reference for the peripheral channel positions. Mount the roller between centres in a BTA drilling machine with a rotary table indexing fixture. After the central bore is completed, the rotary table indexes the roller to each peripheral channel position without re-chucking, maintaining concentricity of all bores to within 0.05 mm.
Spinneret Capillary Micro Drilling
Spinneret capillaries are among the smallest holes produced in industrial manufacturing. They are not produced by conventional gun drilling (which is typically used for holes above 1 mm) but by micro-drilling, EDM, or laser drilling.
Capillary specifications by fibre type:
| Fibre type | Capillary diameter (mm) | L/D ratio | Number per spinneret | Spinneret material |
|---|---|---|---|---|
| Polyester POY | 0.20–0.40 | 2:1–5:1 | 24–192 | Stainless steel 316L |
| Nylon FDY | 0.25–0.50 | 3:1–8:1 | 12–96 | Stainless steel 316L |
| Polypropylene | 0.30–0.60 | 4:1–10:1 | 24–144 | Stainless steel or tool steel |
| Melt-blown | 0.10–0.30 | 10:1–20:1 | 500–3,000 per metre | Hastelloy or stainless |
| Spandex | 0.04–0.15 | 1:1–3:1 | 4–40 | Stainless steel 316L |
Micro-drilling methods for spinnerets:
- Mechanical micro-drilling: Used for capillaries above 0.15 mm diameter. Tungsten carbide micro-drills with diameters as small as 0.1 mm are used at spindle speeds of 10,000–40,000 rpm. Coolant is typically oil mist or compressed air.
- Electrical discharge machining (EDM): Used for the smallest capillaries (below 0.15 mm) and for shaped cross-sections (trilobal, delta, hollow). Brass or copper electrode wire with deionised water dielectric.
- Laser drilling: Used for high-speed drilling of large spinneret plates. Nd:YAG or fibre lasers at 10–50 W with percussion drilling. Suitable for capillaries above 0.2 mm.
Micro-drilling parameters for spinneret capillaries (316L stainless steel):
| Capillary diameter | Drill diameter (mm) | Spindle speed (RPM) | Feed (mm/min) | Peck depth (mm) |
|---|---|---|---|---|
| 0.15 mm | 0.15 | 20,000–40,000 | 1–3 | 0.02–0.05 |
| 0.25 mm | 0.25 | 15,000–30,000 | 3–8 | 0.05–0.10 |
| 0.40 mm | 0.40 | 10,000–20,000 | 5–15 | 0.10–0.20 |
| 0.60 mm | 0.60 | 8,000–15,000 | 8–25 | 0.15–0.30 |
Capillary quality requirements:
- Diameter tolerance: ±0.002 mm (for premium spinnerets)
- Surface finish Ra: < 0.4 µm inside capillary
- Burr condition: Zero burr at entry and exit
- Hole roundness: < 0.002 mm
- Position tolerance: ±0.01 mm
Warning: Spinneret capillaries are among the most difficult micro-holes to produce consistently. The primary defect is burr formation at the capillary exit (the face from which the polymer extrudes). This burr deflects the extrudate and causes filament breakage during spinning. To eliminate exit burrs, use a backing plate of the same material drilled first, then clamp it behind the spinneret during micro-drilling. The drill exits into the backing plate, not into air, suppressing burr formation entirely.
Drying Cylinder Manufacturing
Textile drying cylinders are large-diameter drums that use steam heating to dry fabric. They present unique deep hole drilling challenges due to their size and the need for uniform wall thickness.
Drying cylinder specifications:
- Drum diameter: 1,000–3,000 mm
- Face length: 2,000–6,000 mm
- Shell thickness: 10–30 mm
- Material: Nodular cast iron (EN-GJS-500-7) or carbon steel (P355GH)
- Working pressure: 3–8 bar (steam)
- Operating temperature: 140–180 °C
Manufacturing process:
The cylinder shell is cast or rolled and welded. Deep hole drilling is required for the end journals central bores (steam inlet and condensate outlet). These bores are typically 50–150 mm diameter, drilled through the journal shaft (500–1,500 mm length). BTA drilling is the standard method.
Materials for Textile Machinery Components
Roller materials:
| Material | Hardness (HB) | Application | Drillability |
|---|---|---|---|
| Nodular cast iron (EN-GJS-500-7) | 170–230 | Godet rollers | Excellent |
| Nodular cast iron (EN-GJS-600-3) | 200–250 | High-speed godet rollers | Good |
| S355J2 carbon steel | 150–190 | Drying cylinders | Excellent |
| P355GH pressure vessel steel | 160–200 | Steam-heated cylinders | Excellent |
| 42CrMo4 (AISI 4140) | 220–310 | High-tension roller shafts | Good |
| Hard chrome plated steel | 40–60 HRC | Take-up rollers (surface only) | N/A (drilled before plating) |
Spinneret materials:
| Material | Hardness (HB) | Characteristics | Drillability |
|---|---|---|---|
| 316L stainless steel | 150–200 | Corrosion-resistant, non-magnetic | Good (micro) |
| X5CrNiMo17-12-2 | 160–210 | Standard spinneret grade | Good |
| 17-4PH (H900) | 300–380 | High-wear applications | Moderate |
| Hastelloy C-276 | 200–250 | Corrosive polymer environments | Fair |
Extruder barrel materials:
| Material | Hardness | Application |
|---|---|---|
| Nitrided 38CrMoAl | 800–1,000 HV (case) | Standard extruder barrels |
| Bimetallic (Xaloy X-800) | 58–62 HRC | High-wear extrusion |
| 42CrMo4 nitrided | 650–850 HV | Textile extruder barrels |
BTA Drilling Parameters for Rollers
Nodular cast iron (EN-GJS-500-7, 170–230 HB):
| Bore diameter | Cutting speed (m/min) | Feed (mm/rev) | RPM | Coolant pressure (bar) | Coolant flow (L/min) |
|---|---|---|---|---|---|
| 30 mm | 80–120 | 0.12–0.20 | 850–1,270 | 20–35 | 100–200 |
| 50 mm | 70–110 | 0.14–0.24 | 450–700 | 18–30 | 200–350 |
| 80 mm | 60–100 | 0.16–0.26 | 240–400 | 15–25 | 350–550 |
| 120 mm | 55–90 | 0.18–0.28 | 145–240 | 12–20 | 500–750 |
| 200 mm | 45–75 | 0.20–0.30 | 70–120 | 8–15 | 700–1,000 |
Carbon steel (S355J2, P355GH, 150–200 HB):
| Bore diameter | Cutting speed (m/min) | Feed (mm/rev) | Coolant pressure (bar) |
|---|---|---|---|
| 30 mm | 60–100 | 0.10–0.18 | 25–40 |
| 50 mm | 55–85 | 0.12–0.20 | 20–35 |
| 80 mm | 50–80 | 0.14–0.22 | 15–28 |
| 120 mm | 45–70 | 0.16–0.24 | 12–22 |
Gun Drilling Parameters for Roller Channels
For peripheral heating channels and smaller bores in rollers:
Nodular cast iron:
| Bore diameter | Cutting speed (m/min) | Feed (mm/rev) | RPM | Coolant pressure (bar) |
|---|---|---|---|---|
| 10 mm | 60–100 | 0.04–0.08 | 1,900–3,200 | 30–60 |
| 16 mm | 55–90 | 0.05–0.10 | 1,100–1,800 | 25–50 |
| 20 mm | 50–85 | 0.06–0.12 | 800–1,350 | 25–45 |
| 25 mm | 45–80 | 0.06–0.12 | 570–1,020 | 20–40 |
Cast iron specific considerations:
Cast iron produces short, discontinuous chips that evacuate easily. This makes it one of the easiest materials for deep hole drilling. However, cast iron dust mixed with coolant forms an abrasive slurry that can cause rapid wear of seals and pump components in the coolant system. Use a magnetic separator followed by a paper filter with 20 µm rating.
Quality Requirements
Roller bore quality:
| Parameter | Godet roller | Drying cylinder journal | Peripheral channel |
|---|---|---|---|
| Diameter tolerance | H8–H9 | H8 | ±0.1 mm |
| Straightness | < 0.03 mm/m | < 0.05 mm/m | < 0.05 mm/m |
| Surface finish Ra | < 1.6 µm | < 3.2 µm | < 3.2 µm |
| Bore-to-OD concentricity | < 0.05 mm | < 0.1 mm | N/A |
| Dynamic balance grade | G 2.5 (per ISO 1940) | G 6.3 | N/A |
Spinneret capillary quality:
| Parameter | Standard | Premium |
|---|---|---|
| Diameter tolerance | ±0.003 mm | ±0.002 mm |
| Length tolerance | ±0.02 mm | ±0.01 mm |
| Position tolerance | ±0.015 mm | ±0.01 mm |
| Surface finish inside capillary | Ra < 0.8 µm | Ra < 0.4 µm |
| Burr at entry/exit | None (10× magnification) | None (50× magnification) |
| Roundness | < 0.003 mm | < 0.002 mm |
Inspection methods for textile components:
- Air gauging: Bore diameter for roller bores
- Dynamic balancing: Godet roller balance verification after final machining
- Ultrasonic testing: Drying cylinder wall thickness verification
- Borescope inspection: Channel surface quality, cross-hole intersections
- Optical microscope: Spinneret capillary diameter, roundness, and burr inspection
- Flow testing: Capillary flow rate verification using test fluid at controlled pressure
- Hydrostatic testing: Drying cylinder at 1.5× maximum working pressure
Machine Configurations
Multi-spindle BTA machines for rollers:
For multi-channel godet roller production, multi-spindle BTA machines with workpiece rotation provide the highest productivity. A typical configuration includes:
- Headstock and tailstock for roller rotation
- Multiple BTA drilling units on a common bed
- Indexing fixture for peripheral channel positioning
- Automatic tool retraction and chip conveyor
- Coolant system rated for 150–300 bar for small channels, 10–40 bar for large bores
Micro-drilling machines for spinnerets:
Spinneret micro-drilling is performed on specialised micro-drilling centres:
- Spindle speeds: 10,000–60,000 rpm
- Positioning accuracy: ±0.001 mm
- Vision system for drill alignment and breakage detection
- Automatic tool changer with micro-drill cartridges
- Oil mist lubrication system
- Clean room enclosure (Class 10,000 or better)
Work-rotating BTA machines:
For long rollers (up to 6,000 mm), work-rotating BTA machines are preferred. The roller is held between centres or in a chuck and tailstock, rotating at 50–400 rpm while the BTA tool advances along a separate carriage. This configuration provides the best straightness for long bores.
Troubleshooting Textile Machinery Drilling
| Symptom | Likely cause | Correction |
|---|---|---|
| Godet roller out of balance after drilling | Bore eccentricity causing mass asymmetry | Maintain concentricity of central bore to OD within 0.05 mm; add balance correction after drilling |
| Spinneret capillary diameter oversize | Micro-drill wear producing undersized hole first, then oversize as drill wears | Implement tool wear monitoring; change micro-drills after predetermined hole count |
| Roller heating channel intersection error at centre | Gun drilling from both ends with misaligned entry points | Drill from one end only (BTA); or use through-coolant guide bush at centre joint |
| Peripheral channel breaks through to adjacent channel | Channel wall too thin relative to drilling tolerance | Increase minimum wall thickness to 2× expected bore deviation; verify bore position with ultrasonic wall gauge |
| Capillary exit burr on spinneret | Drill exits into air, material pushed ahead of drill edge | Use backing plate technique; reduce feed by 50 % for last 0.1 mm of drilling |
| Coolant leakage at godet roller end cap | Cross-hole connection between peripheral channel and central bore not deburred | Add deburring step for all cross-hole intersections; use 0.2 mm chamfer |
| Drying cylinder wall thickness variation | Bore off-centre relative to cylinder OD after machining | Sequence operations: bore journal first, then turn OD concentric to bore |
| Fibre breaks at spinneret | Capillary surface roughness causing polymer flow instability | Verify capillary Ra < 0.4 µm; check for residual burrs with 50× microscope |
| Uneven melt flow across spinneret face | Capillary diameter variation exceeding ±0.003 mm | 100 % air flow test each capillary; re-drill and ream out-of-tolerance holes |
| Chip packing in long roller BTA bore | Cast iron fines settling in coolant pool at bottom of bore | Increase coolant flow by 15 %; use horizontal orientation with chip trough at bottom |
Frequently Asked Questions
What deep hole drilling methods are used for textile godet rollers? BTA drilling is used for central bores and larger peripheral heating channels (30–200 mm). Gun drilling is used for smaller channels (10–25 mm). Multi-spindle BTA machines can drill all channels in a single setup.
How are spinneret capillary holes manufactured? Spinneret capillaries (0.04–0.60 mm diameter) are produced by mechanical micro-drilling (above 0.15 mm), EDM (below 0.15 mm or shaped holes), or laser drilling (high-speed production). The method depends on capillary diameter, material, and hole count.
What materials are used for textile godet rollers? Nodular cast iron (EN-GJS-500-7) is the most common material for godet rollers due to its good thermal conductivity, machinability, and vibration damping. Carbon steel (S355J2) is used for drying cylinders.
What straightness tolerance is required for godet roller heating channels? Straightness within 0.03 mm per metre of roller length is standard. For a 3,000 mm roller, total deviation must not exceed 0.09 mm. This is critical for dynamic balance at high rotational speeds.
How many capillaries are in a typical spinneret? A polyester fibre spinneret contains 24–192 capillaries. A melt-blown die can have 500–3,000 capillaries per metre of die width. Capillary diameters range from 0.04–0.60 mm depending on the fibre type.
What coolant is used for BTA drilling nodular cast iron rollers? Oil-based coolant with EP additives at 15–40 bar pressure is standard. A magnetic separator plus paper filter (20 µm) is essential to remove abrasive cast iron fines from the coolant.
What causes the most rejects in godet roller deep hole drilling? Channel intersection error at the roller centre (when drilling from both ends) and bore eccentricity relative to the roller OD are the most common reject causes. Single-ended BTA drilling and in-process concentricity measurement resolve these issues.
Can standard gun drilling machines be used for textile roller drilling? Yes, for rollers up to 2,000 mm length. Longer rollers (2,000–6,000 mm) require machines with extended bed length and workpiece rotation capability. Multi-channel rollers benefit from multi-spindle or indexing machines.
What quality inspections are required for spinneret capillaries? Optical microscope measurement of diameter and roundness (sampling or 100 %), air flow testing (mass flow at calibrated pressure for each capillary), and metallurgical sectioning (for first article qualification).
How does textile machinery drilling differ from hydraulic cylinder drilling? Textile roller bores require higher straightness for dynamic balance at high rotational speeds (up to 4,000 m/min surface speed). The materials (nodular cast iron, high-chromium steel) are different from the C45 and alloy steels of hydraulic cylinders. Spinneret micro-drilling requires entirely different technology (micro-drilling, EDM, laser) at tolerances an order of magnitude tighter than conventional deep hole drilling.
Summary
| Aspect | Godet roller central bore | Peripheral heating channel | Spinneret capillary |
|---|---|---|---|
| Typical bore diameter | 30–300 mm | 10–40 mm | 0.04–0.60 mm |
| Typical length | 500–6,000 mm | 500–6,000 mm | 0.2–2.0 mm (plate thickness) |
| Drilling method | BTA | BTA or gun drill | Micro-drill / EDM / laser |
| Typical material | Nodular cast iron, P355GH | Nodular cast iron | 316L SS, 17-4PH |
| Cutting speed | 45–120 m/min | 45–100 m/min | N/A (micro) |
| Feed | 0.10–0.30 mm/rev | 0.04–0.12 mm/rev | 1–25 mm/min (micro) |
| Coolant pressure | 8–40 bar | 20–60 bar | Oil mist / compressed air |
| Straightness requirement | < 0.03 mm/m | < 0.05 mm/m | N/A |
| Diameter tolerance | H8–H9 | ±0.1 mm | ±0.002 mm |
| Surface finish Ra | < 1.6 µm | < 3.2 µm | < 0.4 µm |
Textile machinery deep hole drilling spans an exceptionally wide range of scales — from 300 mm central bores in nodular cast iron godet rollers to 0.04 mm capillaries in stainless steel spinneret plates. The large-scale end uses BTA and gun drilling methods similar to hydraulic cylinder and roller manufacturing, while the micro-scale end uses entirely different technologies (micro-drilling, EDM, laser) with tolerances measured in micrometres rather than hundredths of a millimetre. As the textile industry continues to demand higher productivity (faster roller speeds, more capillaries per spinneret) and finer fibre deniers, both ends of the textile machinery deep hole drilling spectrum will require continued process development — larger and more precise BTA systems for rollers, and faster, more accurate micro-drilling systems for spinnerets.