Although a new metal component may appear simple in a drawing, the marking process can be quite different when the actual part is placed under a laser.
The surface finish could be different from that of earlier components, the geometry might affect the amount of area available for marking, the required serial number or code might be smaller than anticipated, and one particular surface could give less contrast than another.
That is why it is important to carry out laser marking sample testing before bringing a new metal component into production.
A test piece enables manufacturers to assess the marking process before producing the entire batch of components. Rather than finding a problem after hundreds or thousands of parts have been processed, the manufacturer can determine the appropriate parameters, positioning, mark size, and surface preparation during the trial phase. Utilizing test pieces is crucial for ensuring quality and consistency.
Recent advice regarding the testing of laser marking samples also stresses that marking parameters should be checked on the actual materials and surfaces before batch production, since different surfaces and products can lead to different results.
Why Is It Necessary to Test a New Metal Component?
One application is not automatically the same as another.
Two components made of the same material might still have different surface finishes, thicknesses, geometries, coatings, or marking requirements.
It is therefore possible that a previous laser setting will produce a different outcome when applied to a new component.
That is why the aim of the test is not simply to find out if the laser can mark the component. It should check whether the marking process is capable of producing the required result consistently.
What Counts as a Test Piece?
A test piece is a sample that is representative of the component and is used to assess the proposed marking process before production begins.
It may be a genuine production component, a scrap piece from the production process, or a representative sample that has the same material and surface condition.
The more closely the test sample resembles the final component, the more useful the result will be.
In the best-case scenario, testing should replicate the real material grade, surface finish, geometry, marking position, marking size, and production conditions.
What Needs to Be Checked When Testing?
The type of checks needed will vary according to the application.
With a simple logo, visual quality is the main consideration. When it comes to a serial number, character clarity and consistency are more important. In the case of a Data Matrix code, machine readability also needs to be checked.
Other factors may include the degree of marking, contrast, position, surface appearance, and the ability to repeat the result.
An effective test should not merely check that “the mark is visible.” It must also assess whether the mark satisfies the requirements of the actual product.
Why Does Material Matter?
Various metals react in different ways to laser energy.
Different metals such as stainless steel, aluminium, copper, brass, carbon steel, and others have their own physical and optical properties. Even when they belong to the same material group, the way the surface is treated and finished can affect the marking response.
A previous set of parameters should therefore not be automatically carried over to a new material.
The manufacturer should begin by determining the material and then design the marking process to achieve the desired result.
Why Should Surface Finish Be Included in the Test?
The surface finish may affect the look and contrast of a laser mark.
A surface that has been polished, brushed, machined, coated, or oxidized might result in different visual effects.
One reason a test piece with the wrong surface finish can lead to misleading results is that the marking developed during testing may not represent what happens on the actual production surface.
For instance, even if the base metal is the same, the final mark may not appear identical when a finished sample is used during development while the parts produced have a rough machined finish.
The test piece should therefore represent the real production surface.
Why Does Marking Position Matter?
You cannot completely validate a marking process unless you take into account the location where the mark will be placed.
It may be straightforward to mark a central flat area, but when the position is near an edge, a corner, a hole, a curved surface, or a step, different positioning considerations become necessary.
The test should therefore make use of the intended location as much as possible.
It not only checks the quality of the marking but also confirms that the design fits properly within the available surface.
Why Does Marking Size Need Testing?
A design that appears large and clear on a computer screen can be hard to mark when it is reduced to a very small physical size.
This applies especially to serial numbers, fine text, Data Matrix codes, and compact logos.
Instead, the manufacturer should determine the smallest acceptable size through testing rather than simply reducing the design until it fits.
The aim is to identify a size that remains legible and can be repeatedly produced under the production conditions.
Why Does Parameter Testing Matter?
Laser marking is influenced by a number of process parameters.
These may involve laser power, scanning speed, frequency, focus position, spot size, hatch spacing, the number of passes, and other settings. Research on laser processing parameters also shows how changes in marking conditions can affect the characteristics of the marked surface.
Altering one parameter can change the look or the depth of the mark.
The latest guidance on sample testing states that these variables can be adjusted during testing to establish an appropriate process window instead of depending on a fixed parameter table. This is particularly important in the case of a new part that involves a different material, surface, or marking requirement.
Why Should the First Mark Not Be Treated as the Final Mark?
It is useful to carry out a first test in order to find out the general response of the material, but it might not reflect the optimized production process.
For instance, the first setting might have good contrast but too much depth, while another one could give adequate depth but not enough visibility.
Testing provides an opportunity to compare various process conditions and find one that satisfies the product requirements.
The production setting used at the end should therefore be based on validated results rather than simply taking the first mark that looks successful.
How Does the Rock Laser Marking Machine Fit the Test-Piece Process?
The Rock Laser Marking Machine offered by Sparkle Laser is a pulsed fiber laser system that can be used for surface marking, engraving, texturing, scribing, surface annealing, and etching.
It also allows alphanumeric marking, together with serial numbers, part numbers, barcodes, 2D Data Matrix codes, logos, and complex graphics. The system features real-time red-beam positioning together with boundary and round previews, and Sparkle provides circumferential marking for round parts.
These capabilities are relevant when a manufacturer wishes to test different marking designs, positions, code formats, or different part geometries before deciding on a standard production marking process.
The test result will still vary according to the material and the way it is used. Pasted markdown
What Constitutes a Good Test Piece?
An item that is useful for testing should be a good representation of the component that will actually be assessed.
The key characteristics include:
- Same material grade
- Same surface finish
- Same thickness where relevant
- Same part geometry
- Same marking location
- Same marking size
- Same production requirements
This makes the test more representative and decreases the likelihood of arriving at parameters that work only on an idealized sample.
How Should the Test Result Be Evaluated?
The evaluation must be carried out according to the real product requirements.
If the marking is being used for decorative purposes, the look and evenness of the mark should be checked.
For identification text, its clarity and consistency should be checked.
For machine-readable codes, make sure that the code can be reliably read by the inspection or scanning system intended for it.
When it is important to judge depth, the depth should be measured using an appropriate inspection method rather than being judged on appearance alone.
What Is the Advantage of Testing Multiple Parts Rather Than Just One?
A single example can show that the process can be carried out. Having a number of representative samples provides more information about consistency.
Minor variations in the material surface, the way the components are positioned, or the state of manufacture can have an effect on the final outcome.
Testing a number of pieces therefore provides a better understanding of the process window and helps determine whether the selected parameters can tolerate the normal variation encountered in production.
It is particularly important when the end application involves high-volume production.
What Takes Place After the Test Has Been Approved?
When the marking process has produced the required result, the conditions must be recorded. Once the process is approved, it can become part of the wider workflow for laser marking in metal manufacturing, from component preparation through marking and inspection.
The production specification may contain the approved design, the position of the part, the location for marking, the relevant machine settings, the material requirements, and the inspection procedure.
At that point, operators should be able to carry out the approved process without having to perform repeated experiments on production parts.
As a result, sample testing becomes a practical stage of quality control instead of being merely a single demonstration.
A Practical Test-Piece Workflow
1. Review the New Component
State the material, finish, geometry, where the marking is to be placed, and the information to be marked.
2. Get a Sample That Represents the Production Part
Use the real production material and the actual condition of the surface.
3. Mark a Few Test Versions
Modify the relevant parameters and, if needed, adjust the size or position of the markings.
4. Inspect the Results
Assess the contrast, clarity, depth, appearance, and code readability as required.
5. Choose the Appropriate Process
Select the set of parameters that satisfies the real product requirement.
6. Validate Repeatability
Before approving the process for regular production, test some additional representative parts.
Why Can Testing Prevent Production Problems?
It is not advisable to discover that a serial number is too small, that a Data Matrix code cannot be read, or that the selected settings result in an unwanted surface effect during a production batch.
A test piece offers a controlled opportunity to identify these problems at an early stage.
It also enables manufacturers to determine if the marking position is suitable for operators, fixtures, inspection systems, and subsequent processes.
The time used for testing can therefore help ensure a smoother move into production.
Final Thoughts
Laser marking sample testing goes beyond being just a preliminary experiment. It is a method of finding out whether a new metal part, marking design, and laser process work together under realistic conditions.
The final result can be affected by the material grade, surface finish, geometry, size of the marking, position, focus, and process parameters. A setting that worked for an earlier component cannot simply be regarded as appropriate for a new part.
The most dependable method is to use sample test pieces, examine a number of appropriate process conditions, look at the resulting marks, and then check repeatability before giving approval for production.
For manufacturers, the aim of carrying out tests is simple: verify the marking process on the part before relying on it for production. Pasted markdown
FAQs
1. What is the importance of using test pieces when laser marking a new metal component?
This enables manufacturers to find out before batch production starts whether the chosen material, marking design, position, and laser settings can achieve the desired result.
2. Should the test piece have the same surface finish as the production part?
Yes. Different surface finishes can lead to different marking results, so carrying out representative testing is more reliable.
3. Which laser parameters should be tested?
Power, speed, frequency, focus, spot size, hatch spacing, and the number of passes may be tested by manufacturers according to the application.
4. How many test pieces should be marked?
There is no single figure that applies to all cases. The number should be adequate for assessing the process and confirming its repeatability under realistic production conditions.
5. Should Data Matrix codes be tested before they are put into production?
Yes. The Data Matrix code should be checked for both marking quality and reliable readability using the intended inspection or scanning method.
6. Can test pieces help reduce problems with production marking?
Yes. Testing can help detect problems relating to contrast, size, positioning, surface response, and process settings before the manufacturer carries out a larger production batch.
7. What part testing capabilities does the Rock Laser Marking Machine provide?
The Rock Laser Marking Machine from Sparkle Laser is capable of surface marking, engraving, texturing, serial numbers, part numbers, barcodes, Data Matrix codes, logos, boundary preview, round preview, and circumferential marking for round parts, making it appropriate for a range of marking tests on representative components. Pasted markdown
