How to Evaluate a Plastic Packaging Supplier: Evidence, Not Adjectives
The signals that separate a factory from a reseller, scored the way a quality team would score them rather than the way a brochure claims them.
Score the evidence, not the presentation
Six dimensions decide whether a supplier can carry your programme: capability, mould control, process control, quality system, document integrity and commercial behaviour. Each one is scored on evidence you can ask for, not on what a supplier says about itself.
The point of a scorecard is not to rank suppliers against each other. It is to find the one or two dimensions where the answers do not hold up, before you commit a tool and a first order to them.
This guide is the evaluation framework. If you are choosing a sourcing route rather than a supplier, start with sourcing plastic bottles from China. The document system behind the answers is on quality & compliance.
Six dimensions, and the evidence that scores each one
Each dimension below is scored on something a supplier has to produce, not something they can assert. If a dimension cannot be evidenced, it scores zero rather than average.
| Dimension | What it decides | Evidence to ask for |
|---|---|---|
| Capability | Whether the process your product needs actually runs on their floor, at the volume and the tolerance you need. | Which process your part would use and why, the machine types involved, the moulds held in your material, and a monthly capacity figure. |
| Mould control | Whether tooling is cut and maintained on site, because that decides how fast a correction happens and whether a repair stops production. | Where the mould would be made, whether the mould shop is on site, and a tool number read off a bottle they already produced. |
| Process control | Whether the tolerance you specified is held batch after batch, not only on the sample. | The in-process check interval, the wall-thickness check points per cavity, the weight tolerance, and how a drift is caught before a pallet is built. |
| Quality system | Whether inspection is a written process with records, or a habit. | The ISO 9001:2015 certificate and its scope, the names of the inspection gates, the AQL plan, and a QC report from a previous lot with the commercial data removed. |
| Document integrity | Whether what they call a certificate is a certificate, and whether your market file will stand up. | Request one test report and one certification separately, and check that each is labelled accurately rather than bundled as “certificates”. |
| Commercial behaviour | Whether the commercial relationship will survive a problem. | What the quote states and what it leaves out, what happens when a lot fails, and whether they have ever declined a project. |
A supplier that scores well on capability and process control but cannot produce a QC report is a risk. A supplier that scores well on quality but cannot explain which process your part needs is a reseller.
Factory or reseller: the questions that are hard to answer without a factory
Prices and lead times can be answered by anyone. These questions require physical capability, which is why they separate a factory from an intermediary more reliably than an audit of the website.
Ask these, and listen to how the answer arrives
- ▸Which process would you use for my bottle, and why? A real answer depends on your material and wall; a rehearsed answer does not.
- ▸What dot would you read off the mould for my part? A factory can describe the tool number engraved on a bottle they produced.
- ▸What neck tolerance do you hold, and how do you check it? The neck is the highest-precision feature on the part, so this is where engineering knowledge shows up first.
- ▸What happens to a resin delivery before it reaches a machine? Resin identity, grade and moisture content are checked before drying.
- ▸Where would my mould be cut, and what happens if it needs a repair mid-run?
- ▸What percent of your production is subcontracted, and which stages?
- ▸Which projects do you decline? A supplier that never says no has not understood the requirement.
Cross-check the answers against a physical sample where you have one. A bottle they made can be measured, and a measured claim is worth more than a described one.
Reading a quality system rather than accepting its name
ISO 9001:2015 is a management-system standard, not a product approval. What it tells you is that the processes are written, audited and maintained — which is worth having, as long as you read what it actually covers.
What to read, and what it means
The document request that exposes the most
The most revealing question in a supplier evaluation is a simple one: please send the test report and the certification as two separate files.
| What you ask for | What a good answer looks like | What a bad answer looks like |
|---|---|---|
| A certification | A named certificate, from a named accredited body, with a scope and a validity period. | A logo on a letterhead, a claim in a brochure, or a certificate belonging to a different legal entity. |
| A test report | A specific result on a specific sample or lot, with the method and the acceptance limits shown. | A general statement that the product “meets” a standard, with no limit and no sample identified. |
| A material declaration | The resin supplier declaration, traceable to the resin grade actually used. | A generic data sheet for the material family, with no supplier or grade. |
| Recycled-content records | A supply-chain record behind the percentage claimed, and confirmation that the claim on pack is permitted. | A percentage quoted verbally with nothing behind it, offered after the artwork was approved. |
| A QC report | The inspection result for the lot, with the acceptance basis shown. | A pass or fail stamp, or a report with no limits stated. |
Ask for these before the purchase order rather than after it. A supplier who can produce them quickly is telling you that the documents exist as documents; one who cannot is telling you something equally useful.
Commercial behaviour: how the supplier answers when the answer is inconvenient
The commercial evaluation is about what happens on the day the programme goes wrong, and the signals are visible in the quotation stage.
What to score commercially
- ☐Does the quote state what it covers, with tooling separate from the unit price?
- ☐Does it state the MOQ for the specific SKU, the Incoterm and the validity period?
- ☐Does it answer the questions you asked, or the questions they would prefer?
- ☐Do they say when a stock mould is the better answer, even though a tool would earn more?
- ☐Do they decline work they cannot do well, and say why?
- ☐Do they say clearly which documents they cannot provide, before the order rather than after?
- ☐Can they describe what happens when a lot fails inspection?
- ☐Will they sign an NDA before receiving drawings, as standard rather than as an exception?
- ☐Do they offer a route to a second supplier if your risk policy requires one?
- ▸A price that arrives without a single question about your specification or your market.
- ▸A quote that changes between two emails while the specification stays the same.
- ▸Pressure to place a large first order before sampling, described as a resin-price opportunity.
- ▸No answer to the question of what happens when a lot fails inspection.
- ▸Certification claims that cannot be produced as an auditable document from the issuing body.
Scoring, and what to do with the result
Score each dimension as evidenced, partially evidenced or not evidenced. The result is not a ranking; it is a list of the questions to resolve before you commit.
| Result | What it means | What to do |
|---|---|---|
| All six evidenced | The supplier can carry the programme and can evidence it. | Move to sampling, and write the agreed specification, acceptance basis and document set into the order. |
| One or two partial | There is a specific gap, usually in documentation or process control. | Resolve the gap in writing before the purchase order, because it will not improve once the tool is cut. |
| Capability good, documents weak | The goods may be fine, but your market file may not stand up. | Ask for the specific document your market requires, and accept that some of it may have to be arranged with a third-party laboratory. |
| Documents good, capability unclear | The system is real but may not cover your process. | Check the scope of the certification against the process your product needs, and ask which stages are subcontracted. |
| Several not evidenced | The answers are not coming from a factory floor. | Treat the quotation as a lead rather than an offer, and use it to find the factory behind it. |
Ask us the same questions you would ask anyone
- ▸The product, the process you believe it needs, and the material.
- ▸The market it will be sold in, and the documents your buyer or regulator will ask for.
- ▸The volume you expect over the life of the pack, not only the first order.
- ▸Whether exclusivity of the shape is a requirement.
- ▸Any standard your own quality system has to apply to a new supplier.
Send the six-dimension list and we will answer it in the same terms — including the dimensions where the honest answer is partial, such as third-party testing that has to be arranged with an external laboratory.
Supplier evaluation, sourcing and quality
Evaluating a packaging supplier: buyer questions
How do I evaluate a plastic packaging supplier?+
Score six dimensions on evidence rather than claims: capability, mould control, process control, quality system, document integrity and commercial behaviour. A dimension that cannot be evidenced scores zero rather than average.
How can I tell a factory from a trading company?+
Ask which process your part needs and why, what tool number is engraved on a bottle they produced, what neck tolerance they hold and how it is checked, and where the mould would be cut. Those answers require physical capability rather than a sales reply.
What certifications should a packaging supplier have?+
ISO 9001:2015 for the quality management system is the certification we hold, and it is a system statement rather than a product approval. Everything else — test reports, material declarations, recycled-content records and market-compliance files — is a document, and a supplier should label it that way.
What documents should I ask for before ordering?+
The ISO 9001:2015 certificate and its scope, a QC report from a previous lot with the commercial data removed, one test report for the test your market requires, and the material declaration for the resin grade. Ask for the certification and the test report as two separate files.
How do I check process control without visiting?+
Ask what is checked in process, how often, and at how many points per cavity: visual defect inspection at a 30-minute interval, wall thickness at four points per cavity, weight within ±2%, and neck finish tested against your actual closure. Then ask to see the record rather than the description.
Should I use one supplier or two?+
A single supplier carries the interface risk, which is worth a great deal when the bottle and the closure have to seal together. A second qualified supplier is a risk-management decision, and it is worth making deliberately rather than after an incident.
Does ISO 9001 mean the product is approved?+
No. ISO 9001 is a management-system standard. It certifies that processes are written, audited and maintained. It does not certify an individual bottle or closure, and it is not a food-contact or market approval.
What happens if a supplier cannot provide a certificate I need?+
A supplier should say so at quotation stage rather than after the order is placed. Where a test is required that we do not run in-house, we prepare samples and supply the material and process data the third-party laboratory asks for, so the test can be arranged rather than left open.
Ask the six questions before you commit a tool
Send the dimensions your own quality team scores, and we will answer them in the same terms — including the places where the honest answer is partial.