To select a good vendor, we need to consider the following:
Trustworthy - This is the most important, if the quality of the sample is different from when will be made, customers may face a lot of complaints from their customers and will damage the reputation of the company. This can be seen in the communication during project development
Engineering support - The vendor should have a strong engineering team that can predict and solve problems encountered during the whole manufacturing process.
Product quality - The vendor should be able to provide a stable product meeting the required quality standard. If this is done by sorting and by process control, the quality will definitely be unstable and should not be used.
Work instruction - If there is no work instruction in the line, workers most likely do what is convenient to them, they may skip test steps. A work instruction not only for the worker to follow the instruction but also for the supervisors to check if the workers follow the instruction.