From: "William Chops Westfield" > > What I'm wondering is if that sort of thing happens before it becomes the > responsibility of someone besides the design engineer. A suitably large > company has a whole "manufacturing engineering" team that worries about > such things. I sorta assumed that before that level, I'd be working with > a distributer that would "kit" the parts for me (and do a lot of the work > of translating schematic symbols to actual 'real' parts), and shipping > them off to a contract manufacturer with "R1" type designations or > something. Isn't that the way it works? What level of business > wants/requires schematics laid out with exact part designations? > --- short reply --- It's not really a question of the amount of business. Most schematic software allows you to add text (such as internal part numbers) that can be hidden on the actual schematic, but is picked up by other software to automate tasks further down the chain. ---long reply----:) It must be the design engineer's responsibility to generate the parts list as only the designer knows exactly what is needed. This is generally done indirectly and automated as far as possible. For example, at a previous employer, all of the systems were linked together. As the designer, I would create a schematic on a Sun Workstation using Mentor graphics schematic capture. The schematic software was linked to a database that held all the parts that the company used, so in effect, I couldn't add a new part with unknown vendors to a schematic. If a new part was needed, I would generate a new parts request that got every one involved, from purchasing, production, safety, layout, etc. to verify that the new part was acceptable. Once approved, it could be added. When the schematic was complete, it would be sent to the layout people. They would layout the board (after several go-arounds with me for placement and general routing instructions). Once complete, the software would magically create a BOM with reference designators, parts quantities, etc. This would get sent to purchasing to "load requirements" into the purchasing system based on projected demand and production ramp-up. Unless the company is really small, purchasing is automated with the vendos/distributors. This used to be called EDA purchasing, now I think its under the heading B2B. The net effect is that the parts are automatically ordered based on lead times for each part and humans really only need to be involved if there is a problem (such as parts shortages). This used to be called JIT (or JTL if you liked to complain). As far as production goes, the layout people send the files to production. Production runs another software application that generates XY coordinates and rotations for each part. They don't use the reference designators at all. Most boards are too tightly packed to fit them on the silkscreen. Similar files are sent to test engineering to build test heads for electrical test. Even the production techs fixing the ocassional error don't normally use the ref des. They run on xy coordinates that feed back into a database. Automating and using good processes goes a long way to avoiding errors. Then, when an error does occur, it happens on all units of that build. Much easier to correct than an occasional "hand stuffed" board error. In effect, all the above processes are driven from the designers schematic. Ken -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist