If you are coming to China to manufacture, it’s is essential to have your ducks in a row and anticipate common problems. It’s probably not enough to have a handmade prototype. You need a completely designed PCB, a complete BOM, complete CAD drawings of all the parts and how they will be assembled. Knowledge of manufacturing processes and which will be most appropriate for your parts. You need to have the datasheets for all your components, know what materials you will be using, and how you will be assembling your parts into a finished product. You need people in your home country who you can contact with questions or to accomplish tasks for you or make revisions.
Even though you have all that lined up, you’ll still throw a huge chunk of it out the window when you arrive. When you realize that pricing schemes are completely different for components in the U.S. from China, what you thought was the cheapest part on Mouser or Digi-Key ends up being your most expensive component. Parts that aren’t even listed in the U.S. are now a cheap and frequently used component that simplifies your design. Your enclosure will turn out to have been designed wrong somehow. It’s almost impossible to get it completely right the first time. It will require slides* or manual processes that are inaccurate, or too much plastic or your mold will cool incorrectly in a particular part and lead to a weak part in that area.
Why so much knowledge beforehand? Because you have SO many learning curves it will be impossible if you haven’t gotten over some of them before coming, and you can’t just rely on the internet to teach you what you don’t know because it doesn’t work much of the time. You’re not just dealing with manufacturing when you come to China. You’re dealing with the hassles of living in China. And you’re not working 8 hour days. You still have a life in the U.S. that you need to maintain, which means working longer hours so that you can interact with people during the mornings and evenings when you both can be up. The daily commutes, the restaurant frustrations, doing laundry and paying rent. Everything you do is a learning experience, even if you’ve done it many times before in your home (See the post on the ordeal of getting sheets). All those learning experiences and frustrations add up. Having your life up in the air as well as work is extremely draining. Having to learn to use PCB layout software and solid modeling software at the same time is a hassle you don’t want to add.
If you’re throwing out so much, why bother preparing it in the first place? You can’t even start communicating with factories without a clear idea of what you want, and it is FAR easier to make changes to what you already have than to start from scratch using tools you don’t know. Think of it in terms of what work is necessary and what work needs to be done IN CHINA. Your time in China is limited and expensive and valuable. You need to do the things in China that you couldn’t have done at home, otherwise why did you bother coming? Revisions to something are easy. Designing a thing from scratch is way harder when you don’t have the contacts or the ability to communicate.
Also, when you arrive, you will find things to work so completely differently than you expect. You don’t always have to try to understand it. Choose your battles of learning. I don’t know how many times a day my experiences lead me to say “This is China” and move on. You can’t swim upstream all the time and some things just don’t matter.
* A slide is an extra part of an injection mold that is used to prevent part lock. Part lock is when you have designed your part so that it doesn’t slide straight out of the mold. For example, a hole in the side of the part means your part can’t just pop straight out because the part of the mold that makes the hole is holding the plastic in. So you have a slide, which is another part of the mold. The two halves of the mold come together, then the slide comes in, then the part is molded, then the slide comes out, then the halves separate. Slides add a lot to the cost and complexity of a mold.