What's the difference between PPAP and APQP? Well in part, that depends on which PPAP and APQP we're talking about.
PPAP and APQP were originally created by the Automotive Industry Action Group (AIAG). There is an adaptation of PPAP and APQP for the Aerospace and Defense industries created by the Society for Automotive Engineers (SAE). This article is specific to the differences between PPAP and APQP defined by AIAG.
PPAP (Production Part Approval Process) is one component of APQP (Advanced Product Quality Planning).
Advanced Product Quality Planning (APQP) is a defined process used for introducing a new product in the market or incorporating changes in the product after its release. A Cross-Functional Team (CFT) composed of engineering, manufacturing, quality, procurement, and distribution professionals performs an APQP to ensure that products meet customer requirements.
PPAP is in the 4th phase of APQP.
If the PPAP results don't meet customer expectations, that usually means the APQP process isn't working properly. The test for both APQP and PPAP is a production trial run. If the finished trial product includes defective parts, the manufacturer has to go over the supply chain and find out where PPAP or APQP went wrong.