INDUSTRIAL CLEANING SYSTEMS
by Silberhorn

Industrial parts cleaning encompasses processes designed to remove particulate and film-like contaminants from components in a controlled manner. These include, for example, swarf, dust, abrasion residues, oils, greases, emulsions, salts and machining residues. What matters is not simply ‘visual cleanliness’, but the level of cleanliness required for the subsequent manufacturing, coating, assembly or testing process. The process, medium, mechanics, temperature, duration, rinsing and drying must therefore be coordinated as an integrated system to suit the component, the type of contamination and the specification.

Any remaining particles or films can adversely affect assembly, leak-tightness, coating, bonding, welding, functionality and service life. The level of cleanliness that can be achieved also depends on upstream processes such as machining, deburring, handling and interim storage. Cleaning should therefore be taken into account early on in process planning and linked to clear limit values, test methods and protective measures to be taken after cleaning.

Typical examples include particulate residues such as swarf, abrasion particles, dust and blasting media, as well as film-like contaminants such as oils, greases, coolants, emulsions, waxes, polishing compounds and salts. Corrosion products, scale or deburring residues may also be relevant. When selecting a process, the type, quantity, adhesion, polarity and accessibility of the contamination are just as important as the material and the permissible surface alteration.

In a chamber system, components are cleaned in batches – often in baskets or on carriers – within a sealed working chamber. Several steps, such as spraying, immersion, ultrasonic cleaning, rinsing and drying, can be combined within the same chamber or in connected modules. Chamber systems offer flexibility in terms of part variants and batch sizes and are also suitable for complex parts, provided that the part holding, movement and media delivery systems are appropriately designed.

Continuous-flow systems are particularly suitable for high output volumes, defined cycle times and direct integration with upstream or downstream processes. Components pass sequentially through fixed cleaning, rinsing and drying zones. The advantages include a continuous flow of material and high productivity; prerequisites are a relatively stable range of parts and a process layout that takes into account carry-over, accessibility and maintenance.

A sequential immersion system consists of several separate tanks for defined stages such as cleaning, rinsing, passivation, preservation and drying. An automated handling system transports baskets or product carriers from stage to stage. The concept is suitable for multi-stage fine and precision cleaning, can be configured on a modular basis and can integrate ultrasonic cleaning, filtration, water treatment, as well as cleanroom or automation solutions.

Individual-part cleaning is advantageous when specific functional areas need to be targeted, very short cycle times are required, or parts need to be clearly traceable. It can be integrated directly into a production line and reduces unnecessary media movement. Batch cleaning, on the other hand, often offers greater flexibility for variants and smaller batches. The decision depends on cycle time, the range of parts, accessibility, cleanliness requirements and the degree of automation.

The design and orientation determine whether cleaning jets and airflows reach all relevant areas, whether air can escape from cavities, and whether media can drain off completely. They also influence the risk of damage, carry-over, drying and cycle time. Product carriers should therefore be designed as part of the cleaning process and validated using original components under real-world loading conditions.

Automation can encompass loading and unloading, parts transport, recipe selection, identification, process monitoring and handover to downstream processes. Interfaces with robotics, conveyor systems, the control system and quality assurance should be defined at an early stage. It is advisable to achieve a level of automation that improves cycle times and reproducibility without unnecessarily complicating variant flexibility, maintenance access or fault rectification.

The test method depends on the specified contamination. Particulate cleanliness can be assessed by extraction followed by gravimetric or microscopic analysis. For film-like residues, surface or chemical-analytical methods may be used, depending on the task. The test surface, extraction method, limit values, sampling and environmental conditions must be clearly defined so that results are comparable and auditable.

A robust specification describes the component or relevant test areas, the type of critical contamination, permissible limit values, test and extraction methods, sample size, test frequency and how to deal with non-conformities. It should be derived from the component’s function and agreed upon by development, production, quality and the supplier. Unclear or excessive requirements often lead to unnecessary equipment and testing costs.

Tests using representative original components, real-world contamination and the intended load demonstrate whether the medium, mechanical components, process sequence and drying achieve the desired outcome. They help to determine the process window, cycle time, medium maintenance and test methodology, and reduce design risks. Results, test conditions and evaluation methods should be documented and subsequently incorporated into the specifications, quotation and acceptance criteria.

Following the cleaning process, an open environment, improper handling, contaminated workpiece carriers, packaging or prolonged interim storage can compromise the result once again. This can be remedied by clean zones, controlled air, defined glove and packaging concepts, cleaned load carriers, and short, protected transport routes. Where requirements are stringent, the post-cleaning chain – including cleanroom handover and logistics – must also be taken into account.

Key cost drivers include energy for heating, pumps, vacuum and drying; water and chemicals; media changes and waste disposal; labour; maintenance; spare parts; scrap; and plant availability. For this reason, the purchase price alone is not the decisive factor. A comparable cost-benefit analysis should take into account throughput, utilisation profile, bath service life, reprocessing, set-up costs and quality-related costs over the entire life cycle.

Key areas for improvement include pump and heating capacity tailored to requirements, heat recovery, well-insulated tanks, optimised cycle and standby times, effective media treatment, cascade flushing and reduced carry-over. Lower bath temperatures are not automatically more efficient if they result in drying requiring more energy. The overall process per clean component should therefore be assessed, rather than just a single consumer.

Adaptive cleaning adjusts process parameters according to the component, the level of contamination or the measured process condition, rather than treating every part with a fixed, standard programme. Sensors, data analysis and appropriate control strategies can regulate cleaning time, water, chemicals and energy in line with requirements. This requires reliable measurement parameters, validated decision-making rules and a secure fallback system for production operations.

Process data provides transparency regarding temperature, pressure, flow rate, chemical composition, cycle time, energy consumption and deviations. Digital models can simulate plant conditions, flow patterns or cleaning processes and assist with design, optimisation and predictive maintenance. However, the benefits can only be realised with clear target values, reliable sensor technology, a clean data structure and a link to quality assessment.