The two primary ways to code and mark products, parts, and packaging are Laser Marking and Inkjet Marking. Both methods can mark almost the same surfaces types but vary on price, maintenance coding quality, and running costs. So, how do you decide which is most suitable for your application? It is essential to consider and evaluate operational, financial, and environmental factors and determine their relevance and importance to your requirements.
Overview of Inkjet Coding & Marking Printers
Inkjet marking technology has been around for a long time. Inkjet printers operate by propelling ink droplets onto the substrate. The two main types of inkjet printing technology are:
- Continuous Inkjet (CIJ) which generates a continuous flow of ink droplets
- Drop on demand (DOD) produces a drop of ink is only as needed
There are three types of DOD printers: thermal, piezo, and valvejet.
Overview of Laser Marking Equipment
Laser technology is becoming the new standard for most marking applications. Although it represents a higher initial investment than its alternatives, it provides a better return on investment and other unique benefits.
The main difference between laser systems is the wavelength of the laser beam. Stimulating the atoms of different material atoms release an energy in the form of electromagnetic waves.
The light absorption properties of surfaces are different, and therefore, different laser types with different wavelengths must be used.
Coding & Marking Factors to Consider
By considering the following eight factors, you can decide which marking technology is the most suitable for your requirements:
1. Marking Permanence and Durability
Laser marking results in permanent and durable markings. So, for coded items that are to be used in harsh environments, laser marking is the optimal choice. Inkjet markings can easily fade or smudge when exposed to some chemicals, heat, or abrasion.
Items or packaging that will be re-used (for instance, any bottles) require non-permanent coding, and therefore inkjet printing would be most suitable. Lastly, coding and marking applications that are to be compliant with Unique Device Identification (UDI) or Item Unique Identification (IUID) requirements will require permanent markings and consequently need to be marked with laser.
2. Production Volume
Generally, the initial investment for laser marking equipment is higher than inkjet coders. Typically, laser technology is more precise, capable, and versatile than inkjet. Add to this the potential need for fume extraction equipment, and it easy to see why the initial investment for laser marking systems could be more than inkjet technology.
However, the low operational cost offsets the larger upfront investments of laser markers. Therefore as production volume increases, the total cost of owning laser marking equipment decreases. Whereas, for inkjet markers, increased production quantities mean elevated cost due to the rising consumables usage.
Quality & readability of product markings is the cornerstone of any coding and marking activity. Unreadable marks lead to traceability failures resulting in lost revenues and additional expenses.
The ISO 15416 standard establishes the method for measuring specific attributes of bar code symbols, and it defines the following quality parameters for evaluating and assessing symbol quality and readability. This technique can be applied partially or wholly to other symbologies.
- Symbol contrast – a measure of the difference between the light and dark areas
- Axial non-uniformity – measures the distance between a symbol center location to determines if it is the same in horizontal and vertical directions
- Modulation – is a measure of the uniformity or consistency of reflectance from light and dark of the symbol
- Grid non-uniformity – is the measure of deviation between the measured results and the theoretical/ideal grid
- Unused error correction – is the extent of unused error-correcting capacity in a symbol. 100% unused is the best-case scenario. Error Correction is a method of reconstructing lost data due to poor printing, damage, or erasure.
- Fixed pattern damage – a measure and classification of any damage of fixed pattern or quiet zones
- Print growth – a measure of how symbols may have expanded or compressed from target size
- Decode – determines whether the symbol can be decoded or not
For lasers, code readability has a positive correlation with laser energy (and not laser power) and marking time. That is to say, code readability is dependent on laser energy and marking time. Short marking time and low laser energy usually result in low contrast markings and diminished readability (depending on surface color).
Using low laser energy for a longer length of time results in higher contrast and better readability without any adverse effect on the marking surface. (Optimal laser marking of 2D data matrix codes on Cavendish bananas – Nasution I.S., Rath T. (2017)).
So, once the correct parameters are set-up for a laser marker, a comparison can be made to inkjet marking,
Comparing the two marking methods based on each of the points above shows that laser marking’s readability is superior to that of inkjet marking.
4. The shape of the Marking Surface
As long as the print surface is two-dimensional and stays within the throw distance of the printhead, an inkjet maker can print as expected. But, any deviation in the orientation, shape, or distance of the surface will result in unreadable or poor quality marks. Also, print area and print size are more restricted on inkjet coders. However, optional distance sensors make it possible for laser marking systems to automatically correct focal points and ensure that the marking position is always correct. And, the marking system can detect each part and mark it accordingly. The 3-axis control makes it possible to mark virtually any shape, including sloped, conical, round, and varying height.
Continuous Inkjet (CIJ) coders could require regular maintenance to ensure no residual build-up, which would affect ink flow. And these printers could sometimes need an on-site technician visit to restore their operation. Piezo inkjet printers require less maintenance than CIJs, and this usually includes cleaning blocked nozzles.
Alternatively, laser marking machines could perform for years before needing any attention.
6. Operating Environment
Excessive dust, humidity, and temperature impact the coding and marking quality of laser and inkjet marking.
When it comes to inkjet markers, temperature affects their ink viscosity. As temperatures drop, ink viscosity increases, which reduces ink flow and transferability. So, a cold production environment would require an inkjet coder equipped with an ink heater. Conversely, higher temperatures decrease viscosity and accelerate the evaporation of the solvents in ink, diminishing print quality.
High humidity & condensation are obstacles to achieving clear prints and optimal ink adhesion to the substrate. Finally, dust could cause nozzle blockage, dust build-up on the print head, and cause print distortions.
7. Cost of Ownership
Inkjet coders and markers are generally less expensive to purchase than laser markers. However, the cost of consumables (ink, make-up fluid, cleaners) for inkjet printers can quickly drive up ownership cost: a higher production volume requires more consumables and, therefore, increased operating costs. Alternatively, laser markers function without requiring consumables resulting in a lower cost of ownership, especially for high volume production applications.
8. Environmental Impact
The inks and solvents used by inkjet printers often contain harmful chemicals, affecting the operator and or the environment.
The Material Safety Data Sheets (MSDS) for inks and solvents list Globally Harmonized System (GHS) Classifications for possible hazards associated with the formulations’ ingredients. Some hazards cited are:
- eye irritation
- dizziness & drowsiness
- allergic skin reaction
Waste ink and make-up solvents are considered hazardous materials, so they need to be disposed of properly. Moreover, depleted ink & solvent containers and cartridges are waste products that usually end up in landfills.
Both laser and inkjet markers offer viable methods for printing barcodes, variable data, and traceability information onto products and packaging.
Inkjet markers offer non-contact printing technology that performs best on flat and some, even on curved surfaces. The broad range of available inks allows these printers to code a large variety of substrates. However, the cost of inks and other consumables significantly impacts the total cost of owning inkjet marking equipment.
Alternatively, laser markers offer durable, highly precise, readable marks but require greater initial investment with little or no ongoing operating costs. Selecting the most suitable marking solution for your operation requires you to consider and evaluate operational, financial, and environmental factors and determining which are the most important for you.