We basically just looked on Alibaba for factories that could do all the metal work that we needed, sent them a quotation package, set up a tour, confirmed their

We basically just looked on Alibaba for factories that could do all the metal work that we needed, sent them a quotation package, set up a tour, confirmed their ISO:9001, negotiated terms, and were off to the races. If you have a CM where everything is received for final delivery it helps as they can do your IQC so your metal supplier accountability is baked in. At least thats what has worked for us.