Spring-Wire Cleaning – Intense Cleaning using Inline Ultrasonic Systems

Spring wires exit the drawing process with persistent surface contaminants, including lubricating oils, drawing soaps (commonly calcium or sodium stearates), metallic abrasion debris, and oxides. Ultrasonically assisted inline cleaning utilizes acoustic cavitation to reliably remove such contaminants – even from confined geometries – thereby safeguarding downstream operations such as straightening, coiling, coating, and heat treatment.

The Critical Role of Surface Cleaning in Spring Materials

Residues originating from the drawing process – particularly powdery calcium- or sodium-stearate-based soaps and thin oil films – significantly affect surface adhesion, wettability, and particulate cleanliness. These surface contaminants can impair coating quality and promote localized stress concentrations.
Extensive literature demonstrates the pronounced influence of surface condition – specifically roughness, microdefects, and particulate contamination – on fatigue performance and corrosion resistance. For spring wires and formed springs, reproducibly clean and particle-reduced surfaces are therefore process-critical.
Depending on production line configuration, cleaning may be required either at the wire stage (prior to coiling) or at the component stage (after spring formation).
A common objection concerns tightly wound springs with narrow inter-coil gaps: how can concealed surfaces be accessed effectively? This is precisely where ultrasonic cleaning provides a decisive advantage.

Physical Mechanisms: Why Ultrasound Is Effective in Crevices and Inter-Coil Gaps

The cleaning effect is governed by acoustic cavitation. Periodic pressure oscillations in the liquid medium generate and collapse microbubbles. Asymmetric bubble collapse near solid–liquid interfaces produces high-velocity microjets and localized shear stresses. In parallel, acoustic streaming induces convective mass transport, promoting fluid exchange even within confined geometries.
The combined effects result in efficient detachment of oil films, stearate residues, particulates, and loosely adherent oxides – even in geometrically challenging regions such as the interstices of helical compression springs.
A stable and spatially uniform cavitation field is essential to achieve consistent cleaning performance and standardized surface quality.
The image left shows acoustic streaming at a Hielscher ultrasonic probe. The effects of cavitation are used for the intense cleaning.
Click here to learn more about inline wire cleaning using acoustic cavitation!

Inline Ultrasonic Cleaning in Wire Production: The USCM700 as Example

For the wire industry, continuous and space-efficient integration into existing production lines is essential. The USCM700 addresses these requirements:

• Modular Power Configuration
  Equipped with industrial-grade ultrasonic processors of 500 W, 1 kW, 1.5 kW, or 2 kW (UIP series). Amplitudes up to 20 µm at 20 kHz are available and adjustable to accommodate varying contamination loads.
• Contactless Cleaning
  A specially engineered ultrasonic sonotrode treats the continuously fed profile in a non-contact mechanical manner. Standard bore diameters accommodate wire diameters up to 20 mm; larger dimensions are available upon request.
• Filtration of Cleaning Media
  Optional belt-based nonwoven filtration systems replace rapidly clogging cartridge filters. Integrated air nozzles provide post-rinse drying.
• Low Chemical Consumption
  Cleaning is frequently achievable using water or mild aqueous detergents, improving occupational safety and simplifying wastewater treatment.
• 24/7 Operational Capability
  Designed for continuous industrial operation with minimal maintenance requirements and high mechanical robustness.

For higher throughput requirements, the modular USCM series enables line speeds up to approximately 200 m/min (application-dependent), supporting high-speed drawing and rewinding processes.

Process Architecture for Spring Wire and Finished Springs

Two robust integration strategies have been established:

1. Cleaning Prior to Coiling (Wire Stage)
   Removal of drawing soaps and oils immediately before critical downstream processes such as coiling, coating, or quench-and-temper treatment. The USCM700 is specifically designed for continuous wire processing.
2. Cleaning After Coiling (Component Stage)
   Finished springs are ultrasonically cleaned prior to cutting to length or final packaging. Ultrasonic energy effectively penetrates narrow inter-coil crevices, offering distinct advantages for tightly wound geometries.

Chemical Matrix

• Oil and Stearate Removal
  Aqueous alkaline systems containing surfactants represent the state of the art. For heavily contaminated surfaces, pre-cleaning stages reduce bath overloading and enhance ultrasonic efficiency.
• Oxide and Scale Removal
  For oxidic surface layers, acid-assisted ultrasonic cleaning (e.g., dilute phosphoric acid, optionally combined with dual-frequency excitation) can substantially increase material removal rates while maintaining controlled substrate integrity.

Typical Contaminants in Wire Manufacturing

• Powdered stearates are routinely used as dry drawing lubricants, with calcium and sodium stearates being predominant. Additional contaminants include residual oils, metallic particles, and temper scale.
• The effectiveness of ultrasonic cleaning for removing these contaminant classes – including stearate-based residues – has been extensively validated in industrial practice.

Ultrasonic Wire Cleaners: Verified Effects on Surface Properties

Hielscher inline wire cleaners are used for the reliable in-depth cleaning of endless materials such as medials wires, bonding wires and stamped metal strips.
Multiple investigations demonstrate that ultrasonic cleaning:

• Reduces residual particle density
• Improves surface wettability (lower contact angles)
• Enhances adhesion of subsequent coating systems
• Increases surface energy uniformity

On metallic substrates, ultrasonic inline cleaning has been shown to decrease residual particle counts and favorably modify surface energy. After processes such as laser texturing, ultrasonic treatment effectively removes micro- and nanoparticles and improves corrosion performance metrics.

For spring manufacturing, this translates into:

• More consistent coating and passivation processes
• Reduced risk of particle-induced coating defects
• Improved long-term corrosion and fatigue resistance

The DRS3000 is a highly efficient ultrasonic inline cleaning system designed for continuous endless profiles, delivering maximum surface cleanliness, improved process stability, and reliable integration into high-speed industrial production lines.

Economic and Environmental Advantages

Hielscher Ultrasonics’ portfolio of inline wire cleaner offers small to large cleaning systems – all designed to achieve intense cleaning. For instance, the cleaner USCM700 combines a minimal footprint, reduced chemical consumption, and continuous-duty capability. This configuration lowers operating costs and improves environmental, health, and safety (EHS) performance.
Substitution of solvent-based cleaning processes with aqueous ultrasonic systems represents an environmentally favorable approach, provided that required cleanliness levels are validated.

Reliable Cleaning of Spring Wire and Springs Using High-Performance Ultrasonics

Ultrasonic cleaning addresses a well-known limitation in spring and wire manufacturing: reliable decontamination within narrow inter-coil gaps and demanding continuous processes–achieved through scalable mechanical action rather than aggressive chemistry.
The USCM700 demonstrates how this principle can be implemented in a compact, modular, and line-compatible configuration. When process parameters–amplitude, residence time, hydrodynamics, and chemistry–are systematically matched to the specific contamination profile and validated using particle-based and wettability metrics, a stable and future-ready cleaning process is achieved for both spring wire and complex spring geometries.

Design, Manufacturing and Consulting – Quality Made in Germany

Hielscher ultrasonicators are well-known for their highest quality and design standards. Robustness and easy operation allow the smooth integration of our ultrasonicators into industrial facilities. Rough conditions and demanding environments are easily handled by Hielscher ultrasonicators.

Hielscher Ultrasonics is an ISO certified company and put special emphasis on high-performance ultrasonicators featuring state-of-the-art technology and user-friendliness. Of course, Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.