Methods for direct part marking
The practice of Direct Part Marking (DPM) is used across the automotive and aerospace industries for machine-readable identification of an array parts. This process, also referred to as machine-readable identification, is prevalent in the automotive and aerospace industries for marking alphanumeric and 2D DataMatrix codes on individual parts and assemblies.
For additional information on encoding and code verification, see our whitepaper entitled, Implementation of Direct Part Marking Identification.
The new standard for parts coding
DPM standards have been adopted by a number of associations within the automotive and aerospace industries. Manufacturers can use machine-readable codes to track parts throughout the manufacturing process and supply chain. It is ideal for locating parts for service or recall and can assist in liability and warranty resolution.
In parts production, the use of machine-readable codes can help reduce the need for manual code entry, increasing code accuracy and speeding-up data exchange. Electronically generated codes that include both 1D and 2D bar codes offer simple data storage and usage for internal IT systems. For many years, the 1D bar code has been widely used for data delivery, but this format is being replaced with 2D formats. 2D codes are able to contain more information in less space and can be applied with a variety of direct marking methods.
The three main elements in DPM are encoding, marking, and verifying. Encoding is the rendering of a string of data into a pattern of dark and light cells that includes data, padding, and error correction bytes to then be used by the marking device. Marking is the imprinting of content directly on your part with the appropriate technology for the substrate. Verification is the act of confirming code accuracy and quality. This is most commonly performed immediately following product imprinting at the marking station.
Marking methods
Aside from selecting code formatting and content, it is important to consider the best method for marking the part. The benefits of DPM are typically greater than that of other options, such as label application. However, the physical characteristics and make-up of the part can pose challenges for manufacturers. For the automotive and aerospace industries, two of the most common coding methods are laser marking and continuous inkjet printing. When comparing these marking technologies, it is important to focus on the material to be marked, the flexibility of the process, cost factors, speed, throughput and opportunity for automation of the marking process. DPM can be used on a wide variety of materials, but each substrate has unique aspects to be considered, such as roughness of the substrate, the ability to withstand thermal stress, and fragility of the material being marked.
Marking/printing technology and substrate suitability
Aluminum | Copper | Titanium | Iron | Steel | Magnesium | Ceramic | Glass | Synthetics | ||
---|---|---|---|---|---|---|---|---|---|---|
Laser | CO2 laser | • | • | |||||||
Solid state laser (fiber & UV) | • | • | • | • | • | • | • | • | ||
Continuous ink jet | • | • | • | • | • | • | • | • | • |
Stay ahead with real-time updates on the latest news:
Compare laser and inkjet part marking solutions
Benefit | Laser | Continuous ink jet |
---|---|---|
Flexibility Print on difficult surfaces, distance between part and marking device | High | Average |
Investment/initial outlay | High | Average |
Ease of integration Ease of communicating with a Programmable Logic Controller in production cell and space needed for installation and maintenance | High | High |
Type of marking method Non-contact (part is not touched by marking apparatus) Contact (part is touched by marking apparatus) | Non-contact | Non-contact |
Abrasion resistance of mark | High | Low |
Mobility Ease of moving marking equipment to other locations on the production line | Low | High |
Thermal or chemical stress | Yes | No |
Laser part marking
Laser technology is a popular solution for delivering permanent codes on parts. Laser marking systems apply clear, high-quality codes in a wide range of production environments. Marks are applied using heat instead of ink, so lasers are often considered to be faster, cleaner, and require less maintenance than other coding systems. Laser part marking systems can generate high quality marks including linear and 2D codes, optical characters, and alphanumeric messages on a range of substrates. Variations in specified wavelength, marking head and chosen lens will result in different marking effects on a given substrate.
Laser part marking methods
Laser mark effects can vary depending on the condition of the part’s surface, the kind type of material, and the laser’s wavelength. One laser part marking method, color change, is the result of a chemical reaction between laser and product.
Other methods include engraving of the surface and ablation or color removal of the surface coating to reveal an alternate color underneath. In addition, wood and board-based materials maybe be marked with carbonization or controlled burning method, while the melting of plastic materials may achieve either a raised or concave effect.
Illustration | Description | Materials | Sample | |
---|---|---|---|---|
Ablation | Removal of the top layer of a substrate, normally painted, by vaporizing the paint. | Cardboard, plastic, glass metal | ||
Engraving | Deeper material removal that generates a depression in the material. | Plastic, metal | ||
Tempering | Substrate reacts to the laser beam of a certain wavelength by changing the structure formation. | Plastic | ||
Change in color/bleaching | Change in color where laser touches the surface of the substrate. | PVC, metal, plastic, foil, laser-reactive coatings | ||
Inner-engraving | Internal color removal without affecting the top layer laminate. | Glass, plexiglass | ||
Fracturing | Material reacts to the laser beam by generating micro breaks on the surface. | Glass |
Laser technologies for marking parts include gas lasers, such as CO2, and solid-state lasers including UV and fiber. CO2 lasers are especially suitable for marking synthetic substrates and glass. Solid-state lasers can mark almost any kind of material. Fiber lasers provide extra advantages of a small footprint and long service life.
Evaluating laser marking systems
Laser systems offer a flexible method to mark parts even in manufacturing operations with a high level of automation. Lasers are a great choice for fast speeds and low maintenance. Lasers with large marking fields can mark multiple parts without requiring the reorientation of the laser or tray of components, optimizing power settings and improving efficiency.
Technologies like Videojet Smart Focus™ enable multi-level surface marking. With it, different sized parts can be marked in the same field with 2.5D technology, while the laser adjusts the focus distance to a predetermined distance during setup to simplify changeovers and eliminate manual focus adjustments.
Not all laser marking systems are equal, and expertise can go a long way in helping you specify the correct laser for your line. It is recommended that you work with a coding partner that offers a large selection of laser configurations and technologies. They can help to more easily identify and integrate an optimal solution for your needs, and not over-purchase more laser than you need for your application.
Advantages and disadvantages of laser marking
Laser marking delivers high quality marks on a wide range of substrates, allowing for a high level of flexibility and readability. Generally faster than continuous inkjet, lasers can help increase throughput and efficiency in high volume production environments. Also, since there are no consumables aside from fume extractor filters, operating and maintenance costs are relatively low. When using laser marking systems, the material being marked is exposed to thermal stress, which may compromise the integrity of the part. A beam shield and fume extractor must be installed to protect operators.
Continuous Inkjet (CIJ) printing
CIJ printing provides non-contact coding on a wide variety of products. With CIJ technology, a stream of ink drops is delivered to the print target via a printhead. The inkjet comes out of the printhead through a nozzle and an ultrasonic signal breaks the inkjet into tiny drops. These individual ink drops then separate from the stream and receive a charge that determines their vertical flight to form the characters printed on the product. CIJ printers deliver legible printing on nearly any surface, smooth or irregular, and can apply codes on the side, top, bottom or even the inside of a product. They are ideal for convex, concave, irregular parts, as well as very small or hard-to-reach surfaces where a non-contact printing method would work well.
CIJ is an ideal technology for printing DataMatrix codes as the distinctly formed drops used to create such codes provide excellent readability. Inkjet printheads can be positioned at a distance from the marking surface and still deliver clear, clean codes.
Initial investment for a CIJ printer is usually lower than a laser, and it can print on a wider variety of materials, depending on the ink selected. Inkjet printers also offer high marking speeds and can be specified with automated features that can help ensure the right code is marked onto the right product.
Evaluating CIJ printers
CIJ printers produce simple codes and are ideal for automotive and aerospace parts marking. They are cost-effective for low-to-high volume producers and are easily integrated into existing production equipment. Fast-drying CIJ inks can accommodate high-speed production lines. CIJ technology is also non-contact that will not damage or compromise the surface of the part.
Advantages and disadvantages of CIJ
Inkjet printing generally offers a low initial investment and can achieve excellent codes on a wide range of substrates. Fast printing speeds can also help to increase throughput.
Special CIJ ink formulations meet the application demands for contrast, adhesion, dry times, and resistance to transfer, light, heat, and solvents. Soft pigmented inks, like those used in the Videojet 1580 C printer, can produce codes with high visual contrast on both light and dark colored surfaces, such as rubber parts and windows.
Since CIJ inks are applied to the surface of a material, they are more susceptible to damage and can be more easily worn away by abrasion, unlike markings created with lasers which tend to be more durable. In addition, many inks can be removed with various solvents.
The bottom line
Direct part marking is essential to full cycle traceability throughout the manufacturing process and supply chain. A global leader in coding technology, Videojet understands lean manufacturing and the complex demands of direct part marking. Each production environment and product substrate is unique and requires special consideration with the selection of a coding technology. With the move to 2D coding, manufacturers are transitioning to laser or CIJ printing.
Unlike some coding providers in the automotive and aerospace industries, Videojet offers a wide range of technologies, including laser and CIJ, and the expertise to help choose the ideal solution. In fact, many top OEMs and part suppliers trust Videojet coding specialists and service engineers to help them identify, integrate, and maintain the right coding solutions for their production lines and cells. This expertise, combined with outstanding products can help you sustain your nearly non-stop production, even in challenging environments.