What's the Difference between RS-274D and RS-274X File Form
2018-11-23 17:47Writer: qyadminReading:
Since today's laser photoplotters treat ASCII Gerber files more like a modern image file, why don't we switch to a current format like PostScript? The answer is a bit of a catch-22 - modern photoplotters use the Gerber file format because most computer-aided design/drafting software creates files in that format, and most computer-aided software creates files in the Gerber format because modern photoplotters use it.
Two file formats can make Gerber file types:
• RS-274D: The older of the two Gerber file format standards, RS-274D spreads information for a single layer across two separate Gerber files.
• RS-274X: The newer of the two file formats, RS-274X allows all the information for a single layer to be in one file.
What does this mean in practice? Compared to RS-274X files, RS-274D files are much more prone to errors because of the packaging of their aperture files. Aperture files for PCB manufacture come in a wide variety of types, but almost all of them are proprietary to their original software, meaning the computer-aided manufacturing (CAM) engineer in charge must type them by hand. Because Gerber files contain ASCII text humans cannot easily read, this is a lengthy and time-consuming process.
On the other hand, it's much more straightforward for engineers to employ the RS-274X file format. In RS-274X, the aperture files embed as part of the file data, so there's no need for manual input. Using an RS-274X allows a PCB designer to define essential blocks of code, such as macros, pad shape and line width, in a single file, whereas an RS-274D would require these blocks to be a separate file.
The genesis of RS-274X derives from demand of greater flexibility for Gerber format. With the advent of laser/raster photoplotters, PCB manufacturers and designers were able to make the Gerber format more flexible, so it could better suit the requirements of continued PCB design. To bring the file format in line with the advances in photoplotters, EIA launched the RS-274X file format in 1991.
The RS-274X file format allowed the designer to image any shape in one of three ways - as a full pad, a long track or on a plane or polygon. Since aperture definitions did not need a physical wheel on the photo-image, manufacturers could pull the CAD file when necessary. Aperture and macro definitions are now inclusions in the Gerber file as a standard output, whereas they were separate files before.
The introduction of RS-274X in 1991 made it the standard file format for the transfer of PCB layer data. However, the RS-274D file format is still in use by some PCB designers, especially when they must design or copy older styles of PCB. Accordingly, professional engineers from reliable PCB manufacturers are still able to do something to compensate for disadvantages of RS-274D. For example, when confronted with RS-274D formats, engineers from PCBCart usually input D-Code manually to obtain a complete content of design files.