Cleaning, rinsing, drying is not enough for every cleanliness requirement — and every additional stage costs cycle time, space and a media circuit of its own.
Designing multi-stage cleaning processes
1 · The challenge
Why three process steps become more
The basic process of a parts cleaning system reads cleaning, rinsing, drying — extended depending on the project by a second rinsing, a second drying, air blow-off or vacuum drying. What differs between the systems is not the sequence, but how the process medium gets to the component and how the component runs through the system.
A multi-stage chain arises when the result is not reached with three steps. It can then read, for example: cleaning, rinsing, air blow-off, rinsing, drying, vacuum drying, cooling tunnel. Each of these stages has a reason of its own, and each presupposes that the previous one has reached its result — a chain is not a list, but a sequence.
The effort for it does not stand in the quotation, but in the system: an additional stage is not a line in the quotation, but one more pipe. A line with two rinsing stages runs each of them with its own riser pipe and its own shut-off valve, plus the fresh water supply. Whoever adds a stage adds a media circuit.
How many stages are possible therefore also depends on the machine type. With a rotary indexing cleaning system, the number of stations is structurally fixed, the process sequence cannot be extended arbitrarily later, and the slowest station determines the cycle of all others. With the continuous cleaning system, the number of zones can be chosen more freely. That is not a judgment, but the reason why the sequence of stages is clarified before the machine type.
2 · Engineering considerations
What we base the system design on
- 01
Residual contamination requirement
How clean the component has to become is the first reason for an additional stage. A second rinsing keeps media apart — separate tanks prevent mixing — and the higher the requirement, the sooner one rinsing pass becomes a second. Which stages are necessary follows from the requirement and not from the machine type. - 02
Drying
How dry the component has to leave the system determines the effort at the end of the chain: recirculated air, infrared drying, air blow-off or vacuum drying, designed to suit the project. Ultrasonic cleaning and vacuum drying are options here, not methods — an option supplements a method, it does not replace it. - 03
Cycle time
Every stage costs time, and not every machine type distributes it the same way. With a rotary indexing cleaning system, the slowest station determines the cycle of all others; the division of the process steps is the decisive design point there. Adding a stage therefore does not automatically mean lengthening the cycle — it means dividing it anew. - 04
Water and process media
Several stages mean several media circuits. That includes separate tanks, filtration, cascade rinsing systems and water treatment — and the question of which water quality is needed at which point in the chain. It depends on component, cleanliness requirement and downstream process, not on the type of system. - 05
Production concept and material flow
Whether the stages are distributed over stations, over successive zones or over one chamber is decided by the production. With the rotary indexing cleaning system, the workpiece moves from station to station, with the continuous cleaning system through zones, with the spray-immersion cleaning system several methods run one after the other in the same chamber. - 06
Downstream process
What has to stand at the end of the chain is dictated by the step after it. Whether testing, adhesive bonding, coating or painting follows the cleaning changes the requirement fundamentally — and where a defined part temperature is required, the chain does not end with the drying, but with a cooling stage. What this requirement means in detail is a case of its own.
3 · The system concepts
Which system concepts come into question
Spray-immersion cleaning systems
APOLLOIf several methods are to run one after the other without reclamping or transferring, a spray-immersion cleaning system can make sense: the stages run in the same chamber in a fixed sequence, instead of being distributed over separate processes.
Rotary indexing cleaning systems
RTIf the chain can be broken down into fixed stations, a rotary indexing cleaning system comes into question — loading and unloading then run parallel to processing. Two points belong to the decision: the number of stations is structurally fixed, and the slowest station determines the cycle of all others.
Continuous cleaning systems
ZDIf many process steps are necessary and the cleaning is to be integrated into a production line, a continuous cleaning system can make sense: successive zones instead of one chamber, and the number of zones can be chosen more freely than the number of stations of a rotary indexing cleaning system.
Special-purpose systems
Combining several process steps in one system is the normal case with a special-purpose system. The same modular kit is available as in the standard machine types — spraying, immersion, flooding, basket cleaning, lance technology and drying, supplemented by ultrasonic cleaning, vacuum drying, filtration, cascade rinsing systems, vapor condenser and water treatment. Which building blocks come together arises from the task.
Drying
The last stages of a chain are mostly drying stages. Which of them are necessary — recirculated air, infrared drying, air blow-off or vacuum drying — is decided by the drying requirement; vacuum drying comes into question in particular where conventional drying would leave residual moisture in bores and blind holes.
Cooling tunnel
If the downstream process demands a defined part temperature, a cooling tunnel can be the last stage of the chain. We build and integrate it as a component of cleaning and process systems; it stands after the drying, not beside it.
The principle
Why a multi-stage chain does not dictate a machine type
That a process chain needs several stages says nothing about which machine type the system has. It says that the stages have to be accommodated somewhere and coordinated with each other — on stations, on zones or in one chamber. Which distribution fits arises from residual contamination requirement, drying, cycle time, media concept, material flow and the downstream process together. There is no rule “many stages, therefore system Y”. What you see here is the consideration, not its result.
4 · What else to consider
What else has to be clarified beyond the number of stages
- 01
The sequence is not a list
A chain such as cleaning, rinsing, air blow-off, rinsing, drying, vacuum drying, cooling tunnel cannot be rearranged and cannot be shortened without the result changing: each stage presupposes that the previous one has reached its result. That is why the sequence is fixed before the system is designed, and not afterwards. - 02
An additional stage is one more pipe
What stands as one line in the task stands in the system as a media circuit of its own: riser pipe, shut-off valve, supply, maintenance of the process medium. Adding a stage is therefore a design decision and not an addition in the quotation. - 03
A chain does not end at the system housing
In a realized project for aluminum cylinder heads, the sequence reached from picking up the raw part to the handover to an existing test station — seven steps in one sequence, including robot handling, spray-immersion method, rinsing stage, material flow and conveying, vacuum drying and cooling tunnel. The test station itself did not come from us; the task was the interface to it.
Questions and answers
Frequently asked questions about the multi-stage process chain
What does a multi-stage cleaning chain look like?
Why is cleaning, rinsing, drying not always enough?
Can all stages be accommodated in one system?
What does an additional process stage mean for the system?
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Technically responsible for this page: Günther Zippel — International Sales & Technical Consulting