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Guidelines for Quality-assured Process Management in Parts Cleaning

Prepared by the Technical Cleaning Committee at FiT, these guidelines aim to provide orientation for sharing experience, troubleshooting and the development of new solutions. They lay the foundation for cooperation between suppliers in the industrial parts cleaning sector and operators of cleaning systems and machines within the part manufacturing process chain.

This set of guidelines contains principles and rationales for the design, control and optimisation of the cleaning processes. The aim is to apply a solution with optimised technology, economic efficiency and environmental viability that ensures the necessary component cleanliness. Included in this are the key aspects from the perspectives of chemistry, methodology, system technology and measurement, testing and control, as well as knowledge transfer and qualification.

Principles and guidelines

  1. Creating quality instead of testing for it requires quality control by means of:
    • continuous evaluation of component cleanliness and regular monitoring of the process parameters that influence quality,
    • registration and assessment of changes,
    • timely intervention in the cleaning process.
  2. Quality control is based on the interdependencies between the required component cleanliness and the process parameters that influence quality.
  3. Process control includes management of the cleaning process through targeted measures by the process technology and system operator, with support from measuring, testing and control technology.
  4. Quality-assured process control demands the initiation of measures within process engineering to coordinate cleaning with the necessary protection of parts.
  5. Within industrial parts cleaning, process management aims to assure adequate part cleanliness for the specific downstream process, while keeping resource consumption as low as possible.
  6. Knowledge-based process control for a specific cleaning task builds on underlying knowledge that goes beyond the scope of the task in question (“How does it work in general?”), as well as new knowledge that needs to be developed for the task at hand (“Detailed solution for the specific case?”).
  7. These guidelines apply to both aqueous cleaning and cleaning with solvents and therefore to other cleaning processes and equipment as well.
  1. The chemistry used for cleaning must be coordinated with the method to ensure dependable part cleanliness.
  2. Quality-assured process control requires an understanding of the cleaning chemistry and how it works in the process.
  3. The selection of the cleaning chemicals and determination of the process are based on knowledge of the requirements for component cleanliness, the type and extent of contamination and the components material, as well as on the downstream process step (heat treatment, for example).
    Determining the cleaning chemistry and method restricts the universal suitability of the cleaning process. Only similar components (geometry, material, contamination) can be cleaned to the same high quality level.
  4. Some cleaning chemicals will only show their ideal effects if their constituent parts are regularly monitored, metered purposefully and kept stable. The same applies to preservation media for temporary corrosion protection.
    When changes are made in the process chain (such as the use of new cooling lubricants in parts production), their effect on parts cleaning must be taken into account. It may be necessary to examine and reappraise the suitability of the cleaning process.
  5. Successful conservation of corrosion-sensitive component surfaces is only possible by assuring the required component cleanliness and being aware of the corrosion processes that may be necessary.
  6. Quality-assured process control is predicated on understanding of individual chemical properties and the effects of the selected preservation media, as well as their application, drying behaviour and removal.
  7. Economically and ecologically efficient use of chemicals must be built on qualified system operation.
  1. Suitable system technology is used to achieve dependable part cleanliness. For this purpose, the part spectrum, type and quantity of contamination must be within defined limits.
  2. Dependable part cleanliness requires the components to be designed in a manner that facilitates their cleaning, as well as the optimised design of cleaning racks and conveying equipment to enable cleaning.
  3. The system technology is designed after specification of the necessary cleaning method and selection of the suitable cleaning medium.
    The entire process chain with part manufacturing must be considered and optimised where necessary to ensure that the solution process is efficient and safe.
  4. Mechanical washing processes (spraying, flooding, ultrasound) are selected to suit the component geometry, handling (individual part, set components, bulk material) and the type of contamination.
    Ultrasonic parameters such as frequency, duration and power must be adjusted to match the contamination and part surfaces. The same applies to the process parameters for spray cleaning.
  5. The process parameters within the system technology must be checked or monitored automatically to achieve dependable part cleanliness.
  6. Dependable part cleanliness requires regular monitoring and preparation of the cleaning medium as well as regular maintenance of the cleaning system.
  7. Qualified operating and maintenance staff keep the system in good working order.
  1. Besides the flow of parts and materials in the cleaning process, an information flow must also be established and integrated into process control.
  2. Process control is based on knowledge of the mechanisms at work in the cleaning process and of possible interference mechanisms in the entire process chain, as well as of how they relate to part cleanliness.
  3. Applying suitable process measuring technology and checking the cleanliness of the parts by means of appropriate measuring devices to monitor parameters that influence quality in the cleaning process improve the overall process quality and hence enable dependable component cleanliness.
    Changes can be taken and process control measures initiated by measuring actual values and comparing them to set points and limit values.
  4. Contaminant residues must be recorded to check part cleanliness. A distinction must be made in this context between particulate matter and filmic contamination.
  5. Laboratory analysis is used to analyse errors as a means of identifying the causes of process disruption. Troubleshooting is carried out by deriving and implementing measures to optimise process control.
  1. Basic knowledge and experience must be pooled among suppliers and system operators in the design, optimisation and control of cleaning processes.
  2. The relevant suppliers must provide individual training to operators to enable quality-assured process control.
  3. In-house knowledge and experience must be processed and made accessible through cooperation between suppliers and users across competitive boundaries.
  4. Meaningful research must be carried out to close gaps in knowledge about quality-assured process control.
  5. Knowledge transfer and qualification must be used to strengthen competencies among decision-makers so as to create practical, quality-oriented and efficient solutions, even for special requirements.

The guideline was prepared by

  • Dr. Thomas Dreyer, Weber Ultrasonics AG
  • Michael Flämmich, VACOM Vakuum Komponenten & Messtechnik GmbH
  • Hartmut Herdin, fairXperts GmbH & Co. KG
  • Robert Huber, PERO AG
  • Roland Jung, Hermann Bantleon GmbH
  • Ulrike Kunz, SurTec Deutschland GmbH
  • Katja Mannschreck, Hochschule Heilbronn
  • Markus Mitschele, Höckh Metall-Reinigungsanlagen GmbH
  • Georg Render, Georg Render GmbH
  • Wolfgang Schmitt, DODUCO GmbH
  • Lothar Schulze, SITA Messtechnik GmbH
  • Rainer Straub, Ecoclean GmbH
  • Kerstin Zübert, Hermann Bantleon GmbH