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Author: Ian Rutherford

Bills of Material and Material Callouts

Material callouts

It can be incredibly helpful on a drawing to call out with a pointer where material should be used on the drawing.


  • Best practice is to callout items numbers on the physical layout, usually with a circled BOM item#.
  • This makes it much easier to identify which parts should be used together and where they should be used.
  • It’s also sometimes helpful to simply write part numbers directly next to items on a drawing.










Bills of Material

  • Best practice is to give a table with item numbers, those item numbers can be used for material callouts in the drawing.
  • Manufacturer part numbers for all components is ideal for all parts, except maybe where we stock generics like UL wire and heatshrink
  • We can certainly help with simplifying a BOM, but knowing exactly what materials we’re expected to use can be very helpful!


Drawing Cable Assemblies: Physical Layout

Creating a cable drawing that’s easy to understand and interpret can be pretty difficult, so here are a few pointers to help.




  • Right angles are easiest to interpret but not always necessary.
  • It should be clear where to measure dimensions from, like end of connector or back of connector (dimension lines are great!)
  • Dimensions should be measurable from places which can be measured on a completed assembly (wire cut lengths can be hard to inspect). We will 100% check these in final inspection.
  • Length tolerances should be wide enough to be easy to manufacture+/-5% is great. Use a -0 tolerance if nominal length is the shortest acceptable. (IPC has guidelines for this as well)









  • Labels and heatshrink should appear on the drawing with dimensions and tolerances (or specified as “about” or “TYP”)
  • Specifying the pinout of the connector, especially with colors, is very helpful. Best practice is 3rd angle projection of the connector face.