The factory tour looked impressive. The quality certificates were current. Six months later, parts are late, dimensions drift, and communication requires constant follow-up. Due diligence failed somewhere. The evaluation process looked at the right things but didn’t dig deep enough, or it missed factors that matter more than clean floors and framed certificates.
Effective supplier evaluation goes beyond surface impressions to assess actual capability, system effectiveness, and organizational health. The goal isn’t finding a perfect supplier; it’s finding a capable supplier whose strengths match your requirements and whose weaknesses you can manage.
Capability Assessment
Capability means the ability to produce your parts consistently. Claims of capability are easy; proof requires verification.
Machine range should match your requirements with appropriate margin. If your part requires a 300-ton machine, a molder with machines ranging from 250 to 500 tons provides flexibility for your part and others. A molder whose only 300-ton machine would be dedicated to your part has less flexibility when problems arise.
Tonnage adequacy requires calculation, not just matching. Verify that the molder’s available tonnage actually fits your part’s projected area and material. Ask how they calculated machine selection; their answer reveals process sophistication.
Materials experience matters beyond basic capability. Running your resin occasionally is different from running it regularly. Ask what percentage of their production uses your material or material family. Ask about specific experience with any challenging aspects of your material (moisture sensitivity, shear sensitivity, specific processing temperatures).
Tolerance capability should be demonstrated, not claimed. Ask for capability studies on similar parts. Ask what tolerances they routinely hold and what requires special effort. A molder who casually claims ±0.001 inch capability for everything doesn’t understand their own process.
Questions that reveal real capability:
What was your most challenging recent project and how did you solve it?
What jobs have you turned down and why?
What improvements have you made to your process in the past year?
How do you determine optimal process parameters for a new job?
Generic answers suggest generic capability. Specific, thoughtful answers indicate depth.
Quality System Evaluation
Certifications establish baseline capability but don’t guarantee results. Actual quality system effectiveness requires deeper assessment.
Certifications as baseline: ISO 9001 is essentially table stakes for serious manufacturing. Industry-specific certifications (IATF 16949 for automotive, ISO 13485 for medical) indicate relevant experience and system sophistication. But certification only proves the system existed at audit time; it doesn’t guarantee current execution.
Process control assessment examines how variation is prevented and detected. Ask to see control charts. Ask how process parameters are established and maintained. Ask what happens when parameters drift. Robust answers indicate mature process control; vague answers indicate inspection-based quality.
Inspection capability should match your requirements. Do they have the measurement equipment to check your critical dimensions? Is equipment calibrated and traceable? Can they provide the documentation you need? A molder without a CMM can’t verify complex geometries regardless of their inspection commitment.
Corrective action systems reveal how problems get fixed and stay fixed. Ask to see recent corrective actions. Were root causes identified or just symptoms addressed? Were actions effective, or did problems recur? Effective corrective action systems distinguish good molders from those who repeatedly fight the same issues.
First-article inspection process indicates setup quality. How do they verify that production meets requirements before running volume? What documentation do they provide? How long does approval take? Thorough first-article processes prevent production problems; cursory processes allow problems to reach volume production.
Financial Stability
Supplier financial health isn’t awkward to assess; it’s essential for supply continuity.
Why financial health matters: A supplier under financial stress may reduce maintenance, lose key employees, stretch payment terms with material suppliers (affecting material availability), or fail entirely. Any of these scenarios disrupts your supply chain.
Indicators to assess: Payment history with your organization if applicable. D&B ratings or equivalent. Public financial statements if available. Facility condition (well-maintained suggests financial capability; deferred maintenance suggests cash constraints). Employee tenure (stable workforce suggests sustainable operations).
How to obtain information: Request financial statements or banker references. Check credit reports. Ask references about payment practices. Observe physical condition of equipment and facilities. These aren’t perfect indicators, but patterns across multiple sources reveal financial health.
Financial stress indicators: Sudden changes in payment terms. Requests for advance payment on tooling. Key employee departures. Delayed responses to quotations or quality issues. Visible deferred maintenance.
Communication and Responsiveness
Communication capability determines whether problems get solved efficiently or drag on destructively.
Time zone considerations affect response speed. A 12-hour time zone difference means questions asked in the morning get answered overnight, at best. Complex issues requiring back-and-forth take days instead of hours. Consider whether your products tolerate this communication latency.
Language capability affects communication accuracy. Technical discussions through translators lose nuance. Specifications interpreted through language barriers may be misunderstood. If your products have complex requirements, direct technical communication matters.
Documentation standards vary significantly. Some molders produce professional documentation automatically; others struggle to provide basic records. If your quality system or customers require extensive documentation, verify that the molder can provide it.
Testing communication during evaluation: Note how quickly quotations are returned. Observe response time to questions during evaluation. Judge clarity and completeness of information provided. Test whether the sales contact or engineering contact who seems capable will actually support production. Communication performance during courtship predicts communication performance during production.
References and Track Record
References provide outside perspective on what the molder is actually like to work with.
What to ask references:
How long have you worked with this molder?
What do they do well? What could they improve?
How do they handle problems when they arise?
Have you experienced quality or delivery issues? How were they resolved?
Would you give them more business? Would you give them less?
How to interpret responses: Vague praise suggests the reference relationship is shallow or the reference is scripted. Specific examples, including constructive criticism, suggest genuine experience. References who describe problems and how they were resolved indicate realistic relationships.
Industry-specific experience relevance depends on your requirements. Medical device experience matters if you’re making medical devices. Automotive experience matters if you need IATF 16949 capability. But a molder with excellent general capability may serve non-specialized applications better than one with narrow industry focus.
Track record investigation extends beyond provided references. Search for the company online. Check industry directories. Ask your network. Past quality problems, delivery failures, or legal issues may not appear in the reference list but may appear elsewhere.
Site Visits and Audits
Physical observation reveals what documentation and conversation cannot.
Beyond the tour: The standard tour shows the best machines and cleanest areas. Request to see areas relevant to your production: the specific machine or machine type, material storage, inspection area, shipping. Ask to observe production of a similar part if possible.
Process control evidence: Look for documented work instructions at machines. Check whether operators actually follow them. Look for SPC charts and whether they’re current. Ask operators what they do when a parameter drifts out of range. Answers reveal whether process control is real or performed for auditors.
Housekeeping as capability indicator: Disorganized facilities suggest disorganized processes. Material stored improperly suggests material handling problems. Dirty machines suggest deferred maintenance. Housekeeping isn’t just aesthetics; it correlates with operational discipline.
Employee engagement: Do employees seem engaged or just present? How do supervisors interact with operators? What’s the tenure of key technical staff? Engaged, experienced employees produce better results than disengaged or constantly turning over staff.
Qualification Process
Building confidence before committing volume reduces risk.
Sample submission should demonstrate capability on your actual part before volume commitment. Production samples, not hand-finished samples, show real capability. Multiple samples reveal variation.
PPAP or equivalent formalizes qualification evidence: dimensional data, process capability studies, material certifications, control plans. For automotive, PPAP is required. For other industries, similar documentation demonstrates readiness.
Ongoing monitoring continues after qualification. Initial capability doesn’t guarantee sustained capability. Establish monitoring metrics, reporting requirements, and escalation triggers before production begins.
Supplier selection is risk management. Thorough evaluation reduces the probability and impact of supplier-related failures. The investment in evaluation pays back in avoided problems, stronger relationships, and better outcomes over the supplier lifecycle.
Sources
- Automotive Industry Action Group. “Production Part Approval Process (PPAP).”
- Institute for Supply Management. “Supplier Evaluation Best Practices.”
- Plastics Technology. “Supplier Qualification Guide.” https://www.ptonline.com/
- Thomas Publishing. “Supplier Assessment Checklist.” https://www.thomasnet.com/
- MAPP (Manufacturers Association for Plastics Processors). “Finding the Right Molder.” https://www.mappinc.com/