What happens if you manufacture something that someone else has a patent on. A company in China has a patent on the product that I also thought of and would like to make. To date the other company has not began producing the product.
Basically, (for most jurisdictions, including the US, Europe, China)
a (granted) patent gives you the right to exclude others from selling, making, offering, etc. the patented invention in the country where the patent is granted.
Neither the nationality of the applicant nor the question if they are using the invention make any difference.
=> If the Chinese company has a patent in any place that you intend to manufacture or sell your product at, you're infringing the patent and might be sued for damages and/or liable to pay royalties. In other words, if they have a US-patent and you intend to produce or sell there, you'll be infringing the patent.