Machine maintenance is performed properly at the right time (this include calibration, cleaning etc…). If machines are not calibrated properly and regularly then the change to get some slippage on quality is high over the time without they don’t understand why themselves.

Company has training process in place to be able to replace any worker at any time. Very few companies have this in place in a effective way.

Company has production and quality record (how many defects on each production, what kind of defects etc… to have a traceability and good control of what is going wrong, when and how)

Company has plastic tooling manufacturing in-house. It is much easier and remove a lot of headache to have everything in house because it allow incompatibility between stake holder.

Their employees and particularly their engineer and production manager are qualified, but the sales should be too. The easy test is to ask a lot of technical questions to those guys and to assess their knowledge. If they tell you : “we always do like this, and we don’t know why” then you should look elsewhere. I personally like manufacturers who know what they are doing and who are able to master their core business because the day when you have a problem they can identify and fix problems quickly. If they have to rely on X or Y to try to understand the problem then it can take ages to solve it. I regularly challenge manufacturers I visit with the WHY methodology to see how they react (particularly with the people you are going to be in touch with). The typical stereotype is the young chinese sales who has an english degree as background who is able to speak english, push a quote to you but when you ask some technical details she will tell you “wait I need to ask the engineer”, this mean those people don’t take the time to understand what they are doing, what they are selling and for me they are the worst sales ever… I used to work in the past with this kind of people for MP4 player, I ended producing the product on our own assembly line as I was so tired to know more technically that the people from factory.

The environment is clean and ideally dry. In south of China the humidity rate is very high. Quite often when you inject plastic you need to dry it and deshumididy it before injection so that if there is temperature variation over time your part will not crack. Some manufacturer don’t dry anything and just put the plastic material in their machine and inject straight away. Worst if their press have no hoper dryer it means they inject without drying at all. It simply means they don’t know anything what they are doing and they believe plastic injection is just melting some plastic by placing some granule into a machine and by pressing buttons

Capability to segregate bad plastic part. Like always, the manufacturing game is to avoid passing defects out.