Bought a Cleaning Machine but It Doesn’t Clean Properly? How to Conduct Process Validation and Trial Cleaning

Overview

Cleaning performance cannot be guaranteed by equipment specifications alone. It must be demonstrated through process validation and trial cleaning using actual workpieces and representative contaminants.

This article explains why cleaning process validation matters, what to prepare before a trial, how to conduct testing, and why passing the first-piece inspection does not necessarily guarantee stable mass production.

For manufacturers evaluating industrial cleaning equipment, a structured validation process helps establish reliable process parameters, verify cleanliness requirements, and reduce the risk of costly modifications after equipment delivery.

1. Why Is Cleaning Process Validation Necessary?

Industrial cleaning is a process-dependent operation. Even with the same machine, workpiece, pressure, and temperature, cleaning results can vary significantly due to differences in contaminant conditions, workpiece orientation, loading arrangements, and cleaning time.

Equipment selection should therefore go beyond comparing technical specifications.

Higher pressure, higher temperature, or longer cleaning time may improve contaminant removal in some applications, but each adjustment also introduces costs and potential risks. Excessive pressure may affect sensitive surfaces, higher temperatures may be incompatible with certain materials or cleaning chemicals, and longer cycles may reduce production throughput.

The key questions are:

• What cleaning pressure is actually required?
• What temperature is suitable for the workpiece and cleaning chemistry?
• How long should each cleaning stage last?
• Which cleaning methods are necessary for the specific contaminants and internal geometries?
• Can the process consistently meet the required cleanliness level?

These questions should be answered through trials using representative workpieces before the final process and equipment configuration are confirmed.

The purpose of process validation is to identify and verify a workable cleaning process before the cost of making changes becomes unnecessarily high. Discovering insufficient cleaning performance after equipment manufacturing or installation can lead to expensive modifications, schedule delays, and additional acceptance testing.

2. What Should Be Prepared Before Trial Cleaning?

A meaningful trial requires four essential categories of information.

2.1 Actual Workpieces with Representative Contamination

Whenever possible, provide actual production workpieces with contaminants representative of normal manufacturing conditions.

These may include:

• Metal chips and machining debris
• Cutting oils, lubricants, and other oily residues
• Core sand and casting residues
• Burrs and other process-related contamination

Clean sample parts are generally unsuitable for validating contaminant removal because they do not reproduce the challenge that the cleaning process must overcome.

Contamination should reflect real production conditions as closely as practical, including its type, quantity, distribution, and adhesion characteristics.

2.2 Defined Cleanliness and Quality Requirements

Before testing, clarify the required acceptance criteria, including:

• Residual contamination mass or cleanliness limits
• Maximum permissible particle size
• Dryness requirements
• Workpiece temperature after cleaning, where applicable
• Applicable inspection methods and acceptance standards

Cleanliness and particle size are separate criteria. A workpiece may meet a total residual contamination limit while still containing an individual particle that exceeds the permitted size. Both requirements should therefore be evaluated independently when specified.

2.3 Target Cycle Time and Loading Method

The trial should reproduce the intended production arrangement as closely as possible.

Confirm whether the target applies to a single workpiece, a multi-part fixture, a pallet, or a basket containing several components. Loading quantity, part spacing, orientation, and fixture design can all influence cleaning coverage and cycle time.

A process that cleans one part successfully may not deliver the same result when multiple parts are loaded together.

2.4 Workpiece Material and Technical Constraints

Provide information about the workpiece material, heat-treatment condition, dimensional accuracy, surface finish, and any restrictions on temperature or mechanical impact.

These details help establish appropriate limits for cleaning pressure, temperature, chemical compatibility, and handling.

Incomplete preparation makes trial results less representative and reduces the reliability of subsequent process decisions.

3. The Complete Trial Cleaning and Validation Process

A structured validation process typically involves five steps.

Step 1: Identify the Contaminants

Determine which contaminants must be removed and where they are located.

For example, loose chips on an accessible surface may require a different approach from tightly adhered oil, core sand trapped in a cavity, or debris inside a narrow oil passage.

The workpiece geometry and contamination distribution should be assessed together. This determines whether the application requires broad-coverage cleaning, targeted high-pressure cleaning, internal-passage cleaning, or a combination of methods.

Step 2: Establish Initial Process Parameters

Based on the workpiece and contamination characteristics, define an initial combination of:

• Cleaning method and process sequence
• Cleaning pressure
• Cleaning temperature
• Cleaning time
• Cleaning-agent type and concentration
• Rinsing and drying conditions
• Filtration and liquid-management requirements

These are starting parameters for testing, not assumptions that the process is already validated.

Step 3: Conduct Trial Cleaning and Inspect the Results

Run the trial using the agreed loading arrangement and initial parameters.

After cleaning, inspect the workpiece using the specified methods. Depending on the application, this may include residual contamination extraction and measurement, particle-size analysis, visual inspection, dryness checks, and workpiece temperature measurement.

Record both the results and the operating conditions used during the trial. Without this information, it is difficult to determine why a particular test passed or failed.

Step 4: Adjust Parameters and Repeat the Trial

If the results do not meet the requirements, identify the likely cause before changing the process.

For example:

• Persistent chips may indicate insufficient coverage, unsuitable nozzle positioning, or inadequate cleaning time.
• Oil remaining in internal passages may require a different flow pattern, pressure, or process sequence.
• Excessive residual particles may indicate inadequate filtration, rinsing, or contaminant removal.
• Residual moisture may require changes to air-blowing, heating, vacuum drying, or workpiece orientation.

Change relevant parameters systematically and repeat the test. This makes it easier to identify which adjustments actually improve performance.

Step 5: Establish the Process Window

Validation should not stop at finding one combination of parameters that passes inspection.

A process window defines the range of operating conditions within which the required cleaning results can still be achieved.

Where practical, test how the results respond to reasonable variations in parameters such as cleaning time, temperature, pressure, or cleaning-agent concentration. The objective is to understand the sensitivity of the process and establish appropriate operating limits.

A process that only passes under one narrowly defined set of conditions may be difficult to maintain during mass production. A more robust process provides sufficient tolerance for normal operating variation while continuing to meet the agreed acceptance criteria.

4. Why Passing the First Piece Does Not Guarantee Stable Mass Production

Trial cleaning is often conducted with relatively clean cleaning fluid, new or well-maintained components, and closely controlled operating conditions. Actual production introduces additional variation over time.

Changes in Cleaning Fluid

Oil and particulate contamination can accumulate in the circulating cleaning fluid. As contamination increases, cleaning performance may deteriorate unless filtration, separation, and fluid replacement are properly managed.

Cleaning-Agent Concentration and pH Drift

Cleaning-agent concentration may change through consumption, replenishment, dilution, or carryover. Depending on the chemistry, pH may also drift and affect cleaning performance.

Filter Loading

As filter media accumulate contaminants, flow resistance may increase and filtration performance may change. Monitoring and maintenance requirements should be established for the selected filtration system.

Nozzle Wear

Wear can change nozzle geometry, flow rate, and spray characteristics. These changes may affect cleaning coverage and impact even when the machine's nominal pressure setting remains unchanged.

Fixture Wear and Positioning Changes

Long-term use may wear fixtures or locating elements, affecting workpiece orientation and the relationship between the workpiece and cleaning nozzles.

These factors explain why a successful first-piece inspection is only one part of validation.

Where production conditions permit, conduct continuous-running tests to assess performance over time. Define routine monitoring items, inspection frequency, maintenance requirements, and adjustment rules in the process documentation.

The aim is not simply to prove that the machine can clean a workpiece once. It is to establish that the process can repeatedly meet the required criteria under defined operating conditions.

5. What Documents Should Be Produced During Validation?

The validation process should result in practical documentation that can be used for equipment acceptance and ongoing production control.

5.1 Process Parameter Sheet

Record the agreed parameters for each process stage, including pressure, temperature, cleaning time, cleaning-agent concentration, filtration requirements, rinsing conditions, and drying settings where applicable.

5.2 Inspection and Test Report

Document the measured cleanliness, particle-size distribution or maximum particle size, dryness, and workpiece temperature as required by the technical specification. Include the inspection methods, test conditions, and acceptance criteria.

5.3 Process Window and Operating Limits

Specify the validated operating ranges, allowable parameter variation, and relevant precautions. Where testing has identified sensitive parameters, explain how changes may affect the results.

5.4 Routine Monitoring Checklist

Define which operating conditions require regular checks, such as cleaning-agent concentration, pH where relevant, fluid temperature, filtration condition, nozzle condition, and other application-specific variables.

Monitoring frequency should be based on the process, equipment design, production requirements, and validation results.

5.5 Equipment Acceptance Plan

Agree on the acceptance criteria, sampling method, inspection procedures, test conditions, and pass/fail rules for equipment acceptance and production verification.

Confirming these documents with the equipment supplier and customer helps establish a common basis for acceptance and future quality management.

Big Bird Industrial, formerly Harbin Shimada Big Bird Industrial Co., Ltd., supports cleaning process validation and equipment acceptance in accordance with the customer's technical agreement and application requirements. Trial plans and acceptance procedures should be tailored to the actual workpiece, contamination conditions, cleanliness targets, and production cycle.

Frequently Asked Questions (FAQ)

Q1: Can clean workpieces be used for trial cleaning?

They are generally not sufficient for validating contaminant removal. The purpose of a cleaning trial is to determine whether the process can remove representative production contaminants to the specified level. Testing only clean parts skips this critical variable and provides limited evidence of actual cleaning performance.

Use actual workpieces with representative contamination whenever practical.

Q2: If trial cleaning passes, will mass production automatically meet the requirements?

No. Production conditions can change as cleaning fluid accumulates contaminants, cleaning-agent concentration drifts, filters load up, and nozzles or fixtures wear.

Continuous-running tests, routine monitoring, and clearly defined maintenance and adjustment rules help determine whether the process remains stable beyond the initial trial.

Q3: Why is the process window important?

Mass production cannot maintain every parameter at one perfectly constant value. A process window identifies the range of conditions within which the required quality criteria can still be met.

A sufficiently robust window helps the process tolerate normal operating variation. A process that only passes at a single narrow setting may be more vulnerable to quality problems.

Q4: What information should be provided for cleaning process validation?

At minimum, prepare:

1. Actual workpieces with representative contamination.
2. Defined cleanliness, particle-size, dryness, and temperature requirements, together with the relevant inspection methods.
3. Target cycle time and loading arrangement.
4. Workpiece material, heat-treatment condition, and technical constraints.

The more accurately the trial represents production conditions, the more useful the validation results will be.

Conclusion

Selecting an industrial cleaning machine is only the beginning. Reliable cleaning performance depends on validating the process with representative workpieces, measurable acceptance criteria, systematic parameter adjustment, and appropriate production-stability checks.

Before finalizing an equipment solution, manufacturers should confirm not only whether the machine can achieve the required cleanliness, but also whether the process can maintain that result under defined production conditions.

For applications involving engine blocks, cylinder heads, crankshafts, transmission components, and other precision parts, Big Bird Industrial can work with customers to evaluate cleaning requirements and develop application-specific cleaning solutions. Trial cleaning and process validation help establish a more reliable basis for equipment selection, acceptance, and mass production.