How to Accept an Industrial Cleaning Machine: Five Key Acceptance Criteria for Cycle Time, Cleanliness, Particle Size, Dryness and Temperature

Overview

Acceptance of an industrial cleaning machine is not simply a matter of determining whether a component “looks clean.” A proper acceptance process should use measurable and repeatable criteria to verify whether the equipment meets the agreed technical requirements.

For industrial cleaning systems supplied by Big Bird Industrial, formerly Harbin Shimada Big Bird Industrial, five parameters are commonly important during equipment acceptance:

• Cycle time
• Cleanliness
• Particle size
• Dryness
• Workpiece temperature

This article explains how these five indicators are defined, how they can be tested, and what should be clarified before acceptance to avoid disputes during equipment delivery.

1. Why Clearly Defined Acceptance Criteria Matter

Cleaning is one of the industrial processes that can be easily judged subjectively.

A component may appear clean during visual inspection while still containing measurable contamination inside oil passages, cavities, holes, or other critical areas.

If the acceptance process does not define measurable criteria, disagreements can arise after equipment delivery because the supplier and customer may be using different definitions of “clean.”

For this reason, industrial cleaning projects should establish quantitative acceptance requirements in the technical agreement before equipment manufacturing begins.

The agreed criteria should define not only the required values, but also the corresponding test methods, standards, measurement conditions, and acceptance procedures.

2. Five Core Acceptance Criteria

2.1 Cycle Time

Cycle time refers to the time required for the cleaning system to complete the specified processing of one workpiece, normally expressed in seconds per piece or minutes per piece.

One important point is to clearly define whether the cycle time includes loading and unloading.

For example:

• Commercial vehicle crankshaft cleaning: 180 seconds
• Commercial vehicle engine block cleaning: 300 seconds
• Marine crankshaft cleaning: 20 minutes, with loading and unloading excluded

These definitions should be clearly stated in the technical agreement.

A difference between a pure cleaning cycle and a complete production cycle can be significant, especially in automated production lines.

2.2 Cleanliness

Cleanliness refers to the total mass of residual contamination remaining on the workpiece after cleaning, normally expressed in milligrams (mg).

Typical cleanliness requirements may include:

• Passenger vehicle cylinder head oil passage: ≤16 mg
• Cylinder head water jacket: ≤10 mg
• Camshaft: <3 mg overall
• Passenger vehicle crankshaft: ≤8 mg
• New energy vehicle motor housing: ≤2 mg

These values should always be interpreted together with the specified extraction and measurement method.

A cleanliness value without a defined test method may not be sufficient for an objective acceptance decision.

2.3 Particle Size

Particle size refers to the maximum or specified size limit of residual particles after cleaning. It is commonly expressed in micrometers (μm) or millimeters (mm).

Typical requirements may include:

• Cylinder head body: ≤1.2 mm
• Cylinder head waterway: ≤2.4 mm
• Engine block: ≤800 μm
• Battery housing: ≤400 μm
• Camshaft: <300 μm

Particle-size requirements are different from total cleanliness requirements.

A workpiece can have a low total contamination mass while still containing an individual particle that exceeds the permitted maximum size.

Therefore, both indicators may need to be evaluated separately.

2.4 Dryness

Dryness describes the condition of the workpiece after cleaning and drying.

Typical acceptance requirements may include:

• No visible water marks
• No residual water on the shaft surface
• No visible water residue on surfaces or inside holes
• Completely dry
• No residual water inside internal cavities

Dryness is often evaluated visually.

Because visual inspection can be subjective, the acceptance agreement should specify the inspection conditions, such as lighting, viewing angle, inspection distance, and whether magnification is permitted.

2.5 Workpiece Temperature

Workpiece temperature refers to the temperature of the component after cleaning and cooling compared with the ambient temperature.

Examples of requirements include:

• Passenger vehicle cylinder head: less than 2°C difference from ambient temperature
• Passenger vehicle crankshaft: within approximately ±5°C of ambient temperature
• Passenger vehicle engine block: within approximately ±3°C of ambient temperature
• Commercial vehicle crankshaft: within approximately ±5°C of ambient temperature

Temperature requirements are designed to stabilize the condition of the component before subsequent processes.

This can be particularly important when the cleaned component proceeds directly to assembly, dimensional inspection, or other temperature-sensitive processes.

3. How Are Cleanliness and Particle Size Tested?

Cleanliness and particle-size measurements should be performed according to a defined extraction and analysis procedure.

A typical process includes:

1. Positioning the workpiece in the specified extraction equipment.
2. Removing residual contamination from surfaces and internal passages.
3. Using an agreed extraction method, such as pressure rinsing, ultrasonic extraction, or agitation.
4. Collecting the extraction fluid.
5. Filtering the extracted contamination.
6. Drying the filter membrane.
7. Measuring the contamination mass to determine the cleanliness result.
8. Analyzing the particles retained on the filter to determine particle-size distribution or maximum particle size.

Commonly referenced industry standards include ISO 16232 and VDA 19.

However, different standards and test procedures can specify different extraction methods, filtration conditions, and particle-classification requirements.

Therefore, an acceptance agreement should define both:

Required value + Test method

rather than specifying only a numerical cleanliness or particle-size limit.

For example, stating “cleanliness ≤220 mg” without defining the extraction method may leave room for different interpretations during final acceptance.

4. Common Problems During Equipment Acceptance

Problem 1: Accepting the Machine Based Only on One First-Piece Test

A first-piece test confirms that the machine can achieve the required result under a specific condition. It does not necessarily demonstrate long-term process stability.

During continuous operation, factors such as:

• Cleaning-fluid contamination
• Filter loading
• Nozzle wear
• Changes in fluid condition
• Accumulated contamination

may affect cleaning performance.

For this reason, acceptance should include a continuous operation or stability test where appropriate.

Problem 2: No Defined Test Method for Cleanliness

A technical agreement may specify a cleanliness requirement but fail to define how the value should be measured.

This can create disputes because different extraction methods may produce different results.

The acceptance document should therefore specify the applicable standard and extraction method.

Problem 3: Unclear Cycle-Time Definition

“180 seconds per piece” can mean different things depending on the project.

Does it include:

• Loading?
• Unloading?
• Fixture positioning?
• Robot movement?
• Cleaning?
• Rinsing?
• Drying?

The start and end points of the cycle should be clearly defined before acceptance.

Problem 4: Subjective Dryness Inspection

Terms such as “dry,” “no water marks,” and “no residual water” can have different interpretations.

The acceptance procedure should define the observation conditions and the exact acceptance criterion.

For demanding applications, additional quantitative verification may also be considered where technically appropriate.

5. How to Prepare for a Proper Cleaning Machine Acceptance Test

A well-defined acceptance procedure should ideally be established before equipment manufacturing begins.

1. Define the Five Core Parameters

Specify the required values for:

• Cycle time
• Cleanliness
• Particle size
• Dryness
• Workpiece temperature

2. Define the Cycle-Time Measurement Method

Clearly state whether loading and unloading are included and define the measurement start and end points.

3. Define the Cleanliness and Particle-Size Test Procedure

Specify:

• Applicable standard
• Extraction method
• Filtration method
• Measurement conditions
• Acceptance limits

4. Include Continuous-Operation Testing

Where production stability is important, acceptance should not rely solely on a single first-piece test.

Continuous operation can help verify whether the system maintains performance as cleaning fluid, filters, and nozzles operate over time.

5. Prepare Complete Process-Validation Records

The equipment supplier should provide appropriate process-validation and acceptance-test documentation to demonstrate how the agreed requirements were verified.

FAQ

Q: How many parameters are normally checked when accepting an industrial cleaning machine?

Five core parameters are commonly considered:

Cycle time, cleanliness, particle size, dryness, and workpiece temperature.

Depending on the component and application, additional requirements may also be specified, such as surface condition, residual moisture, passage cleanliness, dimensional impact, or internal passage accessibility.

The final acceptance criteria should follow the project technical agreement.

Q: Is passing the first-piece inspection enough to accept the machine?

Not necessarily.

A first-piece test demonstrates that the machine can achieve the required result under the tested conditions. It does not necessarily prove that the process remains stable during extended operation.

For production equipment, a continuous-operation test can provide additional evidence of process stability.

Q: How can dryness be evaluated objectively?

Dryness is often evaluated visually, but the inspection conditions should be standardized.

The acceptance agreement can specify:

• Lighting conditions
• Viewing angle
• Inspection distance
• Whether magnification is allowed
• Whether a thin water film is acceptable
• Whether internal cavities and holes must also be inspected

Expressions such as “no water marks,” “no residual water on the shaft,” and “no water residue on surfaces or inside holes” should be clearly defined before acceptance.

Q: Why should workpiece temperature be included in the acceptance criteria?

A workpiece that remains significantly above or below ambient temperature after cleaning may affect subsequent assembly and dimensional measurement.

Temperature can also influence the evaporation behavior of residual moisture.

For this reason, some automotive cleaning projects specify a defined temperature range relative to ambient conditions, such as approximately ±2°C to ±5°C, depending on the component and downstream process.

Conclusion

Acceptance of an industrial cleaning machine should be based on measurable and repeatable technical criteria rather than visual judgment alone.

The five core indicators—cycle time, cleanliness, particle size, dryness, and workpiece temperature—provide a practical framework for evaluating whether an automated cleaning system meets its agreed production and quality requirements.

For complex automotive and industrial components, the acceptance procedure should also define the test methods, operating conditions, inspection frequency, and continuous-operation requirements.

Big Bird Industrial, formerly Harbin Shimada Big Bird Industrial, provides customized industrial cleaning systems and supports customers from process validation through equipment acceptance testing. Acceptance procedures can be developed around the customer's workpiece, cleanliness requirements, production takt, drying requirements, and technical specifications.