This highly practical troubleshooting guide solves injection molding problems systematically and quickly. The rigorous but user-friendly approach employs the authors' proven STOP methodology, considering molding process, mold, machine, and material (4M's) as possible sources of part defects. Importantly, the interaction between tooling, processing, and material is emphasized, allowing successful resolution of difficultproblems where by-the-books approaches fail. Starting from troubleshooting methodology and tools, there is a focused discussion of key areas impacting troubleshooting, in particular the 4M's, followed by an in-depth troubleshooting guide for various molding defects, structured logically by type of problem / solution. Insightful case studies throughout show the strengths of the STOP method to get real processes to run smoothly and reliably, producing quality parts with optimal cycle time and cost. Drawing on a wealth of hands-on experience, this book serves as an ideal reference to be consulted at the machine, or as a learning and training manual, suitable for both beginners and experienced molders. With valuable information on robust process windows, cycle time evaluations, scrap savings, and runners / gates with no existing standard in the industry, no other book provides the unique insights found here. The 2ndedition is updated with new discussion and case studies on topics including additive manufactured inserts, unmelts, buildup, burns, cycle time, gloss variation, and read-through.