Principal Manufacturing Engineer-Plastic Injection Molding

Principal Mfg Engineer

Job Description

Position Summary

The Principal Manufacturing Engineer – Plastics is the technical authority for plastic injection molding process development, optimization, and sustainment. This role leads the establishment of robust molding processes that deliver consistent quality, high throughput, and competitive cost performance across production operations.

This position focuses on process optimization, material performance in molding, molding parameters, and process control, while partnering closely with tooling, quality, automation, and operations teams. The Principal Manufacturing Engineer drives manufacturing excellence through data-driven decision making, advanced process control, and continuous improvement, while mentoring engineers and influencing site and business strategy.

Key Responsibilities

• Serve as the subject matter expert for plastic injection molding processes, including scientific molding principles, process window development, and process validation.
• Develop, optimize, and sustain molding processes to meet quality, delivery, and cost objectives across a range of polymers and part geometries.
• Help support and maintain standard molding methodologies, including start-up procedures, changeover standards, and process control plans.
• Lead mold qualification, process validation, and ongoing process capability improvements (Cp/Cpk).
• Analyze and optimize cycle time, cooling efficiency, clamp force utilization, part quality, and material usage.
• Lead advanced root cause analysis for molding-related defects (short shots, flash, sink, warp, burn, splay, etc.) and process instability.
• Apply DOE, SPC, and statistical analysis to define critical process parameters and ensure long-term process robustness.
• Partner with Quality to drive defect reduction, scrap elimination, and corrective/preventive actions.
• Provide hands-on technical support during process upsets, new product launches, and capacity expansions.
• Evaluate and select polymer materials in collaboration with Product Development and suppliers to optimize manufacturability and performance.
• Understand and manage the interaction between material properties, tooling design, and machine capability.
• Lead trials for new materials, colorants, regrind strategies, and process innovations.
• Research and implement advanced molding technologies (process monitoring, cavity pressure sensing, advanced cooling, automation).
• Support molding equipment selection and capital decisions through process requirements definition, technical evaluation, and throughput analysis.
• Lead data-driven continuous improvement efforts focused on molding efficiency, uptime, scrap reduction, labor optimization, and OEE through standardized processes and best practices.
• Support and maintain molding process documentation, manufacturing standards, and ERP/MRP data (routing, cycle time, labor) to ensure consistent and repeatable molding performance.
• Develop and share technical knowledge through documentation, repositories, and mentorship to build injection molding capability across the engineering team.
• Partner with Operations, Tooling, Quality, Maintenance, and Supply Chain to ensure stable and scalable molding operations.
• Provide clear technical direction and influence decision-making without direct authority.
• Communicate complex process concepts through clear documentation, data, and formal presentations.
  
  

Education & Experience Requirements

• Bachelor’s degree in Plastics Engineering, Mechanical Engineering, Manufacturing Engineering, or related discipline.
• 6 years of hands-on injection molding process engineering experience in a production environment.
• Demonstrated expertise in scientific molding, process validation, and process troubleshooting.
• Strong working knowledge of thermoplastics, molding machines, auxiliaries, and process monitoring tools.
• Familiarity with CAD and mold design concepts as they relate to process capability.
• Preferred experience supporting multi-cavity, high-volume, or tight-tolerance molding applications.
• Preferred exposure to automation, robotics, and in-mold or downstream process integration.
• Preferred knowledge with Lean Manufacturing, Six Sigma, or equivalent continuous improvement experience.
• Established ability to identify and communicate issues and offer proposed solutions
• Excellent attention to detail with good organizational skills are required
• Ability to function effectively in a fast-paced team environment
• Effectively collaborates across functions, drives continuous improvement, and communicates clearly with both technical and non-technical teams.
  
  

Milwaukee Tool is an equal opportunity employer.