Many sources recommend visiting suppliers as often as practical. The main reasons appear to be relationship building and the opportunity to discuss cost/scrap/quality and other production details that can be problematic.
We would also suggest carefully looking at the production floor itself. Some questions should be on a list of what to look for:
1) Do the operating instructions you see make sense and describe what is to be done?
2) What is measured at each work station? Is the documentation available to you to check? If gauges are needed, is calibration involved and up to date?
3) If the item’s manufacture involves multiple steps or cells, how does each successive one know they are receiving a properly made item?
4) Do you see evidence of work being set aside in order to permit some other work to be done? You may be interested in why this happens.
5) Are inventories and in-process items stored in such a way as to be easily identifiable?
6) Are employees seemingly in their work places and busy?
7) Is the production area orderly? If this were your company would it look like this?
When people answer these questions you’ll get an immediate indication of the attention paid to the things the supplier believes are important. Do these standards conform to yours?