Machine readable bar code laser engraving technology has been developed that produces a permanent mark on production parts and materials (metals, plastics, wood, ceramics, glass, etc). This technology simplifies and facilitates production line Traceability Data Collection Systems. INDUSTRIAL LASER SYSTEMS has formed strategic partnerships to provide industrial customers with complete Traceability Data Collection Systems.
Benefits of Data Collection
- Effective Scheduling, JIT / Lean Manufacturing
- Work in Progress (WIP) Part / Asset Tracking
- Real-time Inventory Control and Distribution
- Quality Control, Testing
- Shipping and Order Fulfillment
- Warranty Fulfillment, Accountability
- Audit Tracking of Critical and High-Value Components
Barcode Technologies, Symbology
– Code 39, Code 128
- 2-D Barcodes
– PDF 417
- Bumpy Barcodes
Markers – Things to Consider
- Material, Uneven surfaces
- Serialization vs. Fixed
– Tracking individual parts
- Reading environment
– Controlled environment
– Dust, poor lighting
– Reading from a distance
- Integration with other systems
Direct Part Laser Marking (DPM) applies light energy density to the surface of a part that causes the surface of the part to change in various ways (subject to the laser wave length, pulse parameters, and substrate being processed) in order to produce a permanent mark. The resulting quality of the mark depends upon the interaction of the laser with the material it is marking. A laser can produce both round and square modules; typically, the laser is used to produce a square module and continuous finder pattern for higher density (large data capacity) codes. The laser marking process offers high speed, consistency, and high precision. Laser marking is widely used in the semiconductor, electronics, aeronautics, military, automotive, and medical device industries.
Bar Code Selection
Industry standards groups frequently define the appropriate code for a given application. For example, the Automotive Industry Action Group (AIAG) has published guidelines for Data Matrixâ„¢ and QR Code; the Air Transport Association (ATA) as part of the Spec2000 bar code specification defines Data Matrix for DPMI; the U.S. Department of Defense (DoD) specifies Data Matrix for their Unique Identification (UID). When specified, it generally makes sense to follow the industry guidelines because it improves efficiencies throughout product manufacturing and the supply chain. However, if no guidelines are available within your industry, investigate the standards and guidelines set forth in other industries. This will allow you to define guidelines for your company on not only what code(s) to use but also recommendations on marking methods, data encoding and verification. When there is no specified standard, Data Matrix ECC200 is recommended. This ISO code standard is the most widely supported for DPMI applications involving metal, glass, ceramic, or plastic materials. Because this code is in the public domain, marking and reading equipment suppliers have invested significant R&D resources to improve the performance of Data Matrix ECC200 supporting equipment.
Data Matrix 2D Barcode – DPM (DIRECT PART MARKING)
Data Matrix is a two-dimensional matrix symbology consisting of black and white square modules arranged in either a square or rectangular pattern. The ECC 200 version of the symbol utilizes Reed-Solomon error correction to ensure data reliability. A Data Matrix symbol can store up to 2335 alphanumeric characters.
One of the most popular applications for Data Matrix are direct part laser marking including small items such as integrated circuits and printed circuit boards and larger parts for the automotive, aeronautical and military. These applications make use of the codeâ€™s ability to encode approximately fifty characters of data in a symbol 2 or 3mm square and the fact that the code can be read with only a 20 percent contrast ratio.
Data Matrix is designed to pack a lot of information in a very small space. Since the information is encoded by absolute dot position rather relative dot position, it is not as susceptible to printing defects as are traditional linear barcodes.
2D barcode CCD reader scanners with Data Matrix support are required for reading Data Matrix.
Data Matrix encodes information in a machine-readable binary code that is dynamically variable in size, format and density. The coding scheme has a high level of redundancy with the data “scattered” throughout the symbol. This allows the symbol to be read correctly even if part of it is missing. The binary code is formed as a matrix. Each binary code symbol has two adjacent sides printed as solid bars, while the remaining adjacent sides are printed as a series of equally spaced square dots. These patterns are used to determine the size, the orientation and the printing density of the symbol.
Two main subsets of Data Matrix symbols exist. First subset is the conventional coding for error correction that was used in the initial installations of Data Matrix systems. These versions are referenced from ECC-000 to ECC-140. The second subset is referenced as ECC-200 and uses Reed-Solomon error correction techniques. ECC-000 to 140 symbols all have an odd number of modules along each square side. ECC-200 symbols have an even number of modules on each side. Maximum data capacity of an ECC-200 symbol is 3116 numeric digits, or 2335 alphanumeric characters, in 144 symbol modules.
Direct Part Marking
Direct Part Marking (DPM) is a technology used to produce two different surface conditions directly on the surface of a part. These markings can be created by laser marking, molding, dot peening,
Concern: Traditional print quality measures are based on the assumption that there will be a measurable difference between dark and light elements of a symbol. Because DPM symbols frequently do not have sufficient contrast between elements intended to be dark and light, it is often necessary to provide specialized lighting in order to produce highlights or shadows in order to distinguish the various elements of the symbol. (See examples below.)
Table of Contents: Reading Data Matrix bar codes with missing information
- Demo Code
2-D barcodes like Data Matrix are being used extensively in several industries such as automotive, aerospace, consumer goods, electronics, semiconductor, and life sciences. Major benefits of 2D codes over 1D barcodes include:
- Small size – more information can be packed into a smaller area
- Does not require precise sizing of individual elements (cells), because all elements are the same size. This is a major improvement over 1D barcodes, where bar thickness is critical to decoding.
- Built in error correction allows all information to be recovered even when a portion of the code is missing.
DataMatrix codes have 3 basic areas of interest. The 2D code in Figure 1 below illustrates these regions.
Figure 1. A DataMatrix code has three areas of interest: the Locator, the alternating black and white Boundary Cells and the Core Data area.
Figure 2 shows sample images of the same data matrix code with missing information. By definition, the data matrix code can ecover up to 20% of missing information by using error correction built into the Solomon-Reed algorithm used to construct code.
Figure 2. Original barcode (a) and the same bar code with missing information (b – f) .
These images will be used in the attached demonstration code.
For most applications, the size of the 2D code to be read is known. Sometimes, for a variety of reasons the code gets damaged. As the structure of the Locator template and the matrix size information is pre-known, the 2D code can be reconstructed. The example presented here illustrates how this can be accomplished using LV and IMAQ Vision.
Figure 3 User interface (a) and Block Diagram (b) for a demo code illustrating use of the example VIs for Pre-processing of the Data Matrix codes
The inspection systems can be trained on the size of the barcode and the number of elements in it. When a damaged barcode comes into the system it is then read correctly. Figure 3(a) shows the damaged DataMatrix code is reconstructed with the missing information for the Locator and the alternating black and white cells. The resulting image is then passed through the DataMatrix reader VI and is read correctly.
Machine readable laser marked bar codes on various materials (parts)
Direct Part Machine Reader
Diffuse On Axis Light (DOAL)