The Ombu Library, in the Medical Device Regulations aisle, has an article, Documenting Changes Using the 510(k) Guidance, that explains the changes in a medical device and when they trigger the threshold for a new 510(k).
A manufacturer can change a device using either a design change or a production/process change. Evaluate each change to determine if it triggers a new 510(k). If it does not, review all changes since the most recently cleared 510(k) to determine if the cumulative changes trigger a new 510(k).