Key takeaways
- Cardboard and foam shed fibers and dust, which can contaminate a part even after it leaves the washer clean.
- VDA 19.2, the guideline on technical cleanliness in the assembly environment, identifies packaging as a source of particles.
- Smooth, washable plastic trays reduce the risk of contamination, as long as they're cleaned and handled correctly.
- The switch works best when it starts at the points in the process where the part is already clean.
Cardboard is being pulled from the line because it sheds fibers and dust, and that cardboard contamination can make a part that left the washer clean fail particle analysis. VDA 19.2, the technical cleanliness guideline, identifies packaging as one of the sources of contamination in the assembly environment. That's why, once a customer starts requiring technical cleanliness, packaging becomes part of the specification. Below, we explain where the particles come from, what the guideline says in plain language, and how to make the switch without stopping the line.
Where the particles on a clean part come from
A machined or stamped part usually goes through industrial washing before assembly. It leaves the washer within the cleanliness spec, goes into a cardboard box with dividers, and moves on to storage or to the customer. When it reaches particle analysis, it fails. In many cases, the contamination didn't come from the process. It came from the box.
Cardboard is made of pressed cellulose fibers. Every time the box is folded, cut, stacked, or dragged, those fibers break loose, along with paper dust. Foam used as padding also sheds fragments through friction. Cardboard dividers touch the part directly, and the movement during transport carries particles onto the surface and into holes and threads.
The problem is more serious for parts with technical cleanliness requirements, such as components for hydraulic, fuel, brake, and transmission systems, and for sensitive components such as optical modules and sensors, where a single particle can compromise performance.
What a contamination failure costs
The cost of a particle failure rarely shows up in the packaging budget. It's spread across quality, production, and logistics. It includes rewashing or scrapping the parts, the lab analysis, the time spent investigating the cause, return freight, and, when the lot has already reached the customer, the formal complaint and the corrective action plan.
There's also the cost of not knowing. Until the source of the particles is identified, the washing process is usually the first suspect, and the team can spend weeks adjusting the washer before anyone looks at the box. That's why the first step is to measure where contamination enters the process, before you change anything.
What is VDA 19.2, and why does a technical cleanliness guideline cover packaging?
In one sentence, VDA 19.2 is the guideline from the German Association of the Automotive Industry (VDA) on technical cleanliness in the assembly environment. It complements VDA 19.1, which covers the method for inspecting component cleanliness, and looks at everything that can contaminate a part between washing and assembly, such as the environment, people, equipment, logistics, and packaging. It's a paid publication, sold by its publisher in the VDA QMC online store under its English title, Technical Cleanliness in Assembly (1st edition, 2010).
Packaging appears in the guideline because it stays in direct contact with the clean part longer than anything else. The guideline lists both cardboard and plastic as possible sources of particles. In broad terms, the guidance is to use low-shedding materials and keep packaging clean throughout its service life.
VDA 19.2 is a guideline, not a law. It typically becomes a requirement when a customer includes it in the technical specification or in its supplier quality manual. This is common in the automotive and auto parts industry, and it usually reaches suppliers of cleanliness-critical parts first.
Cardboard and plastic: what to watch for in each
With cardboard, the critical issue is fiber. Fibers come loose with handling, the box can't be washed to remove them, and shedding gets worse each time the box is reused. Cardboard also absorbs moisture and oil, which speeds up wear. It can stay at points in the process where the part hasn't been washed yet or is protected by another layer, but it tends to be phased out of areas where the part is already clean.
With plastic, the smooth surface typically releases far fewer particles and can be washed. Even so, a plastic tray isn't free of contamination. Burrs left by poorly finished trimming, deep scratches, dirty trays that go back into circulation without washing, and trays that rub against each other when stacked can generate or trap particles. That's why edge finish, ease of cleaning, and the washing plan are part of the specification.
Material choice also depends on the washing process. Detergents, temperatures, and drying methods vary from one plant to the next, and each plastic reacts differently. Our page on materials for thermoformed trays summarizes the characteristics of the main materials we use.
When to replace cardboard with washable trays, and how to do it without stopping the line
The switch usually makes sense when your customer requires technical cleanliness, when parts have already been rejected for particle contamination, or when the same cardboard box is reused many times in the process. In those cases, a smooth, washable plastic tray designed around the part reduces the risk of contamination and also prevents contact between metal parts.
To keep the line running, you can make the switch in stages. Start where the part is already clean, usually from the washer exit to assembly or shipping. The tray is sized to fit the container you already use, whether that's a KLT bin (small load carrier), a rack, or your customer's standard packaging. The prototype and pilot run are tested in your operation before volume production.
Because a washable tray circulates many times, it's usually a returnable tray, with wall thickness and material chosen for the expected number of cycles. Comparing its cost with cardboard means looking at the full cycle, which we cover in our article on expendable vs. returnable trays.
How to build technical cleanliness into the tray specification
Technical cleanliness becomes a design requirement for the tray, alongside the part, the volume, and the workflow. The clearer your customer's requirement, the more straightforward the specification. The information listed below helps our engineering team propose the appropriate tray.
- Your customer's cleanliness requirement, such as the specification document or the particle limit.
- Where in the process the part is washed, and how far downstream it needs to stay clean.
- How the trays will be washed, how often, and in what type of equipment.
- The standard box or rack you use today, and the expected use cycle.
- Whether parts have already been rejected for particle contamination, and at which stage it was detected.
With this information, our engineering team reviews your case and presents an initial tray proposal, with the material and finish recommended for your washing process. You can request a quote and note your technical cleanliness requirement on the form.
VDA 19.1 covers the inspection of technical cleanliness of components, and VDA 19.2 covers technical cleanliness in the assembly environment. The requirements that apply to your case are the ones in your customer's specification.
Frequently asked questions
Usually, no. Cardboard doesn't have to be removed from the entire plant. It can stay in areas where the part hasn't been washed yet or is protected by other packaging. What typically has to go are the boxes and dividers that touch the part once it's clean, from the washer to assembly or shipping.
Plastic trays can generate particles, though typically far fewer than cardboard. The most common sources are trim burrs, deep scratches, friction during stacking, and trays that go back into circulation without washing. Edge finish, the appropriate material, and a washing plan reduce that risk.
VDA 19.2 is a guideline, not a law. It becomes a requirement when your customer includes it in the technical specification or in its supplier requirements. That's why it's worth checking your customer's document before you define the packaging.
A washable tray helps, but on its own it isn't enough to meet VDA 19.2. The guideline looks at the entire assembly environment, including people, equipment, logistics, and storage. A washable tray reduces a major source of particles. The result also depends on how the tray is washed, stored, and handled.
