Your digital camera is at least as important as your dictation recorder and will support your recordings with photos of specific details.
Shoot as may photos as possible even if you end up discarding some of them later. Most digital cameras have macro functions that allow you to take close-up photos. Consider this if you buy a new camera for your trip.
Your visit to the factory may have more than one goal. If you will be discussing a claim or quality issues from a previous purchase order, you need to bring photos of the parts in question or even bring the actual goods if that is practical.
Most digital cameras or cell phones also have a video recording function. That is even better then still photos if you want to record a working process.