How can you tell the differences between revisions of the same board?
07 November, 2016
Over time most PCB designs need to change – a mistake is found, or a part becomes obsolete, etc. Typically once the changes are complete, a new set of manufacturing files (Gerbers, NC Drill files, BOM, Pick and Place, etc) are generated, and the updated design is stored as separate version within a version control system. Using a version control system makes it possible for design teams to go back later and compare differences between design versions.
What if there is no access to the version control system, and you only have the manufacturing files? How can you tell the differences between revisions of the same board?
This article will demonstrate how to quickly identify differences between two similar revisions of the same design, using only the manufacturing files.
- I will use FAB 3000 to compare the differences between PCB design revisions.
- In FAB 3000 terminology, a "Job" contains all manufacturing files (Gerbers, NC Drill files, BOM, Pick and Place, etc) for a specific design revision.
- To quickly load manufacturing files into a Job, use File > Import > Autoload.
- Two or more jobs must be created to perform comparison.
- For graphical comparison, a “Yellow” means that the design is the same between the two sets. Any "Red/Green" objects means that there are differences between the two sets.
- Use the layer display panel to turn on/off any layer that you wish to compare.
- Once a comparison is performed, the differences can be exported to either PDF, CSV, or TXT formats. They can also be exported into an Error Drawing to Gerber or any other format that FAB 3000 supports.
Import Manufacturing files, and Create a New Job.
Typically if you're starting FAB 3000 you'll have a blank screen with an empty job already created, so lets use that default job to import our first set of manufacturing files.
- Go to menu: File / Import / AutoLoad... Identify the folder where you have stored the manufacturing files and navigate to that folder. If you have your manufacturing files zipped or an ODB++ file, you can go to menu: File / Open Compressed File...
- Create a New Job (menu: File / New / Job...) and give any name you wish for your job. Repeat STEP#1 above for your second set of manufacturing files.
Perform Job Comparison
- Select Tools > Compare Jobs and Layers > Compare Jobs.
- Select jobs by choosing the job name and assigning a layer color.
- Choose a comparison method (Blend or XOR). Blend – Easier for viewing purposes. XOR – Best for singling out differences.
- Select Physical Comparison (Optional) to generate errors that can be used to pinpoint any differences between Jobs. If left unchecked, you will only be able to view the differences and not generate errors for them.
- Select OK. A Compare Jobs dialogue box will appear with the final error count
- Select OK. The Compare Jobs error browser will appear below the editor.
- Use the Compare Jobs error browser to compare and analyze each comparison error.
- Use the browser to differentiate and determine issues. You can also create a PDF, Text, or CSV error list. In addition, you can also use the browser to create error drawings for reference.
That's it, you now have the ability to tell the differences between revisions of the same board?
Tutorial movie demonstrating the above steps.
Note: To improve your experience, you can download the example files used for this tutorial by clicking here, and follow along with with example. Unzip and use the files located in the folder /compare
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