A supplier visit earns its travel cost when it lets you compare what a glass supplier tells you with what is running on the floor, and when you come home with a process map, a capability statement, a risk register and a dated evidence file. Plan the route against the material flow, from batch handling through forming, annealing, inspection and packing to the warehouse and laboratory, and put the same short questions to every station. A two-hour walkthrough only confirms that a process exists; allow half a day for a screening visit and a full day when your own container is on the line.
Identify the supplier model before planning the route
The itinerary depends on what sort of business you are about to walk through. Reports from two visits cannot be compared unless each one says which model it describes.
| Supplier model | What it does | Where the evidence sits | Questions that matter |
|---|---|---|---|
| Glass works | Melts, forms and anneals the container | Furnace and forming machines: number of lines running, forming process, single or double gob, inspection equipment per line, an on-site laboratory or none | Changeover discipline, sampling frequency, scrap handling, how a defect trend is caught before the customer catches it |
| Decorator or secondary processor | Buys containers and adds printing, coating, frosting, hot foil or sleeves | Decoration line, colour control routine, curing or firing method | How a colour is matched and verified, cleaning between jobs, segregation of rejects, whether the sample process is the production process |
| Trader, agent or consolidator | Coordinates a network of suppliers, often with packing and shipment in house | A system, not a machine: upstream sources, specification control, incoming inspection | How many sources are really used, who answers when two shipments differ, whether a factory-level record can be produced for a complaint |
Plenty of suppliers are two of these at once, and a few are all three. That is acceptable as long as the itinerary assigns each station to a model and the report marks the boundary. An in-house decoration line carries different risk from an outsourced one, even if the finished container looks the same.
With a trader, insist on the upstream question. A visit that stops at the office proves the office is competent, and office competence was never the risk you travelled to assess.
Outputs that justify the trip
Do not plan the day as an inspection with a pass or fail at the end. Plan it to produce four artefacts:
- A verified process map showing which stages happen on site, which are subcontracted, and where the container physically travels between them.
- A capability statement based on what you saw, separating routine work from work the site does occasionally by arrangement and from work it claims but could not demonstrate.
- A risk register naming the points where this supplier could fail your project, each with an owner and a follow-up action.
- An evidence set of documents, photographs and measurements that goes into the supplier file and can be set beside the next visit or the next supplier.
How much of this one trip can deliver depends on four things. Duration sets the upper limit. Timing matters more than buyers tend to assume, since a plant in normal production is representative and a plant in a scheduled shutdown, a holiday period or a quiet season is not. The make-up of your party shapes what you are shown: a lone commercial visitor gets the showroom table, while a group with a technical or quality person gets the line. Access settles the rest, namely whether you walk past running machines or sit in a sample room, and whether production records are opened or merely described.
Arrangements to make before you travel
Three requests cost almost nothing and lift the value of the day. Find out which lines will run on the date and at what hours, then build the schedule around production instead of the meeting room. Ask whether measurement records, calibration records and retained samples can be shown, so that a refusal reaches you as information ahead of time. Send the agenda with every station listed, which lets a supplier decline an area before you arrive instead of inventing a reason at the door.
When we help a buyer plan a visit, two inputs come first: the supplier model and the risk the buyer wants reduced. The model decides which stations exist at all, because a glass works with no decoration line has nothing to show there and a trader has no forming hall. The risk decides the depth. Worry about dimensional consistency points you at forming, inspection and the laboratory; worry about breakage in transit points you at the packing hall, the pallet pattern and the warehouse.
A useful briefing therefore covers:
- the supplier type, or the shortlist of types;
- the container or container family;
- destination market and transport mode;
- the annual or seasonal volume band;
- the project stage;
- the failure you fear most: dimensional variation, colour consistency, surface defects, transit damage, documentation or continuity of supply.
From that we can propose a half-day or full-day agenda, rank the stations in material-flow order, list the documents to request at each one, and supply a recording template that keeps observation, question and evidence in separate columns.
Depth by stage: screening visit, project visit, re-audit
One standard itinerary for every stage leads to over-inspecting strangers and under-inspecting partners. Match the depth to where the relationship stands.
| Stage | Purpose | What it should end with | Who should attend |
|---|---|---|---|
| First visit (screening) | Establish the supplier model, confirm the process your container needs exists on site, test whether answers hold up under a follow-up question | A list of open questions, not a verdict; half a day is enough on a compact site | A commercial buyer, with a technical advisor reachable by phone |
| Second visit (project) | Test the supplier against your project while your container is running or has just run | A sealed retained sample, and any outstanding complaint investigated on the spot | Technical or quality representation, because the deciding questions concern curves, gauges and sampling plans |
| Re-audit (maintenance) | Detect drift since the last visit | Confirmation that agreed actions were carried out | The buyer alone, provided the earlier report is detailed enough to check against |
On the project visit, check four things specifically: that the mould exists and is the one agreed, that an annealing curve has been set for this container, that the inspection stations are set up for the defects this shape tends to show, and that the packing configuration suits your destination.
Build a re-audit agenda from the previous risk register plus the complaints and deviations logged since. If it yields the same generic report as the screening visit, it has missed its only job.
Walking the site against the material flow
Judge the plant by what is running, not by what was laid out for you. A sample room can be curated. A running line cannot, unless production stops, and nobody stops production for a visitor. Use the showroom to look at finished references and take the assessment from the working areas.
A practical route begins with raw materials and batch handling, continues through melting and forming to the annealing lehr, passes the inspection stations and the packing hall, and closes in the warehouse and the laboratory. The order lets you trace a defect seen at inspection back to its origin, and lets you pin a later complaint to a place on the map without starting the investigation from nothing.
The three questions for every station
A long questionnaire does not survive the noise of a working plant. These do:
- What is this station there to ensure?
- How does the site know, right now, that it is doing so: which measurement, how often, against which limit?
- When it is not, where does the material go and who gets told?
Fluent answers to the first and vague answers to the other two say a good deal about the whole management system, and no catalogue will show you that.
Two things that are hard to stage
Look at the space between the machines. Spills, loose cullet, tools on the walkway, blocked emergency routes and unlabelled containers show how the process runs when no visitor is present. Then watch the operators when a defect turns up. Any site can produce a checklist. A site that responds to an abnormal container with a defined action, and can tell you who was informed and what followed, is running a control loop and not just a document.
If your own technical knowledge is limited, take a technical or quality specialist or an inspection body with you. That is more honest than accepting a tour which leaves nothing verifiable behind.
Station checklist for a glass container supplier visit
Carry this table onto the floor. Its rows follow the walking order from forming to the laboratory. Keep entries in the recording column short, since a note or photograph made at the station beats a long description written from memory at the hotel.
| Station | Look at | Ask and request | Record | Red flag |
|---|---|---|---|---|
| Forming area | Count of lines running and their forming process; whether your container size is on a machine; frequency of line stops | Which moulds are mounted today and whose they are. Changeover record for the current job; sampling frequency for dimensional checks | Lines running, process, container being made, time of day, stops and restarts seen | A line stopped, cleaned or slowed for your benefit; a machine producing something outside your shape family |
| Annealing lehr | Which lehr is in use, the loading pattern, whether entry and exit temperatures are monitored or simply set | How the annealing curve is set and verified for this container. The recorded curve or temperature log for the current run | Curve exists for your container or not; recorded or assumed; who checks it | A curve called standard and recited from memory, with nothing on record for your container |
| Inspection and retained samples | Stations on the line; automatic versus visual checks; position of light boxes and gauges; quarantine of defects at the station | What becomes of a rejected container the moment it is found. Defect classification, reject rate record, where retained samples are kept | Methods seen, quarantine arrangement, sampling plan in plain words, retained samples present and labelled or not | Rejects returned to the flow; no labelled retained samples; an AQL or ISO 2859-1 plan claimed without a written plan |
| Mould management | Storage and identification; cavity numbering and its link to the container; state of the working set | Who owns the mould, how cavities are marked, how wear is spotted, the refurbishment interval. Mould register and maintenance record for the mould in use | Mould identifier, cavity count, marked ownership, last maintenance date if shown, route from finished container back to cavity | Loose unlabelled moulds; no cavity traceability; an ownership claim that conflicts with a written statement elsewhere |
| Packing and warehouse | Packing method, inner partitions and layer pads, pallet build and wrap, separation of finished goods from work in progress | Standard pack configuration per container and whether your destination needs another. Packing photograph or drawing; container stacking test if there is one | Pack configuration, pallet pattern, edge protection, any mixed or unlabelled stock | Unidentified finished goods; unbonded pallets; packing on the day that differs from the drawing |
| Laboratory | Instruments operated on site versus sent out; laboratory inside the production building or elsewhere; calibration method | Tests run in house and tests outsourced; frequency of external calibration. Calibration register, test report format, one redacted report | In-house tests, outsourced tests and to whom in general terms, calibration interval, report format in use | A brochure laboratory that is not on the site; calibration with no record to support it |
Ownership questions raised at the mould store usually need a contract as well as a register; our page on who owns the mould and what the tooling agreement must state covers where the pattern is held and what a supplier may do with it if the relationship changes.
Comparing the meeting-room account with the floor
You will hear one description of the site in the meeting and see another on the floor. Nearly all the value lies in setting them side by side, so keep them as separate records and resist merging them into a general impression.
Put the same question to two different roles at two points in the day. If a capacity figure or sampling interval shifts between the sales conversation and the production conversation, nobody has necessarily lied, but there is a gap and it needs an explanation.
Sort every statement into one of three classes. "We test wall thickness on every line" is a claim. The record for today's run, shown to you, is evidence. A record that exists but cannot be shown because its keeper is away is unverified, and should be logged that way, neither accepted nor dismissed.
Ask for specifics. Which measurement, how often, by whom, against which limit and what happens when it is exceeded gives you concrete facts. "Is quality good?" gives you a reassuring paragraph with nothing in it. When an answer has to wait for a manager, note that too; it tells you where authority and knowledge sit.
Two biases distort visit reports. Confirmation bias makes a buyer who has already chosen a supplier write down only supporting observations. The halo effect credits a tidy, well organised plant with capability it never showed, or condemns a slightly untidy one whose records are excellent. One habit counters both: three columns for what was seen, what was asked and what was evidenced, with the risk register drawn from the third.
Photographs, notes and the evidence file
A photograph is useful later only if it can be dated, located and compared with another taken at a different time. Context is what does that:
- a packing configuration with pallet label, container and layer pad in one frame, which can be checked against the next shipment where a close-up of a lone container cannot;
- a mould with its identification legible and its storage position recognisable, which settles a traceability question better than any spoken answer;
- the hall shot from one end, showing which machines are working and what is on them, as a record of the site at that moment.
A supplier may refuse photography inside the plant. That is a legitimate position, not an admission. Substitute a written observation that both sides sign or acknowledge; it is weaker than an image but still has value.
Write notes at the station. Capture the time, the station, the observation and the question it raised, and keep the last two apart: the observation is evidence, the question is work still to do, and a report that blends them cannot be acted on. Log each document you are shown with its title, its date and whether you received a copy, since a paper seen carries less weight than a paper handed over.
Assemble the file the same day. It should hold the itinerary as it really unfolded, the deviations from plan, documents requested and received, requests declined, timestamped photographs and any measurements taken on site. Note the instrument behind each of your own measurements. A reading from an uncalibrated hand tool is a helpful indicator, but it does not replace a certificate of analysis. For what such certificates and declarations of compliance can and cannot prove, see our notes on quality documents for glass containers.
Turning the record into decisions
Act within days. Detail fades fast, and so does the supplier's readiness to respond to findings.
Start with a short shared document for the supplier setting out what was observed, what was agreed, what is still open and the date for each item. It turns spoken assurances into written commitments and gives the supplier a fair chance to correct something you misread. Next comes your internal risk register: the specific ways this supplier could fail this project, each with an owner, a mitigation and a likelihood expressed as a judgement, not a number. Last is the sourcing decision itself, whether this supplier becomes a single source, one of two, or a source for a limited range, based on what you saw and not on how broad the catalogue is.
A specific record is also fair negotiating material. Saying that the packing observed on a given date departed from the drawing in a given way puts a fact on the table. Saying quality seemed inconsistent offers an impression, and impressions do not move a commercial discussion. Keep the follow-up list to three to five dated items; a list of twenty actions gets half done and then forgotten.
Findings that bear on supply continuity belong in that programme, not in the visit file. Our guide to qualifying and holding a second glass source explains how to split a specification between two plants and keep them comparable. Buyers who are still settling a purchase pattern across several containers, and are not yet auditing a site, can start from the glass container ranges available at volume.
Keep the report structure fixed from one visit to the next, station by station with identical columns. Drift then appears as a difference between two documents instead of a shift in somebody's memory. A report that changes shape each time is a diary, whereas one that keeps its shape works as a measurement.
Frequently asked questions about supplier visits
How long should a factory visit last?
Half a day is the minimum for screening, and a project visit needs a full day where the site has more than one building or a decoration line. The limit is coverage. On a large or scattered site even a full day may reach only the stations that matter, so name those in the agenda and state plainly that the others were not visited, so nobody later assumes they were verified.
Can a packaging supplier be evaluated without travelling?
In part. Documents, samples, test reports, calibration records and video calls with the production team establish a lot, and for a low-risk part they are often sufficient. What stays unknown is the condition of running equipment, how operators react to a defect, the state of the storage areas and the physical identity of the goods being made. Where travel is impossible, write that gap into the risk register and cover it with a stricter incoming inspection plan.
Is a third-party inspection or audit body worth bringing?
Someone in the party must be able to read an annealing curve, check a gauge against a drawing and tell a specific answer from a general one. That person can come from your own organisation or from outside. A third-party body is especially useful when the audit has to be in a format other parties will recognise. It does not replace your commercial judgement, and the itinerary should still follow your particular risks instead of a generic checklist.
What do buyers most often overlook?
They study the container and ignore the process around it. The sample room shows a good day; the running line, the floor between machines, the reject quarantine, the labelling of retained samples and the identification of moulds show an ordinary one. The next most frequent omission is failing to write down which requests were declined. A refused document or closed area tells you something about the supplier, and it vanishes from the file unless someone records that it was asked for.
How can a capacity claim be tested on site?
Test the arithmetic, not the headline figure. Ask how many machines are installed, how many were running during your visit, each machine's rated speed, the hours worked per day, and how changeovers and maintenance cut into the theoretical output. Then ask what share is already committed to other customers, because that determines whether your volume will be scheduled. A confident answer on installed capacity paired with a vague one on committed capacity is true without being an answer.
What should not be photographed?
Leave out other customers' branding, private documents and people's faces unless you have agreement. Beyond the contextual shots described above, the quarantine area and the retained sample rack are worth a frame each.
How often should a visit be repeated?
Let risk and history set the interval, not the calendar alone. A new supplier usually warrants a screening visit, a project visit once your container is running, and a re-audit after the first significant shipment or the first complaint. A supplier with a long clean record and a stable process may need a maintenance visit only every one or two years, or after a change of mould, of raw material source or of personnel in the quality function. The trigger should be an event or a clock, never an intention.