The OEM Waterproof Bag Sampling Process, Step by Step

Why the Sealed Sample Decides the Whole Programme

Everything that follows a sampling round is a comparison against it. The pre-production sample is checked against the approved prototype, bulk is checked against the pre-production sample, the pre-shipment inspection is checked against the specification written at approval, and a warranty claim two years later is checked against whatever the brand can still find in a cupboard. A programme with a vague sample has no reference at any of those four points, and disputes get resolved by opinion rather than by measurement.

This is why we insist that the approved sample be a physical object held by both parties, tagged with a revision letter, rather than a set of photographs and a satisfied email. Photographs do not show hand feel, they do not show how a closure behaves when it is wet, and they cannot be re-measured when a question arises in bulk. The cost of shipping and storing two reference units is trivial against the cost of one argument about what was actually approved.

It is also why the sampling round should be treated as an experiment designed to break the design rather than as a preview of the product. A first prototype that comes back perfect usually means it was not tested properly, because a welded bag with any novelty will have at least one place where the film bridges instead of bonding. Finding that place in the sample room costs days; finding it in bulk costs the season. Start the file through the custom programme page with the test method stated, and the round is built around proving it from day one.

Day Zero: What Must Be in the File Before Sampling Starts

The 6-to-10-day clock starts when the file is complete, not when the first email arrives, and the distinction is the source of most perceived sampling delays. A complete file contains a dimensioned drawing with tolerance bands, a shell specification with the required hydrostatic head, a closure specification with class and pull type, a hardware list with finishes, artwork with Pantone references if decoration is involved, and an acceptance test with method and pass mark. Six items. Missing any one of them puts the round on hold while somebody asks a question.

• Dimensioned drawing with tolerance bands: critical fit dimensions at plus or minus 2 mm, structural at plus or minus 3 mm, cosmetic at plus or minus 5 mm.
• Shell specification: face fabric denier, film type and gauge, and the hydrostatic head required under ISO 811, typically 10,000 mm for light duty and 20,000 mm or above for loaded wet use.
• Closure specification: closure class, tape width, pull type, and the ingress code the finished bag is expected to reach under IEC 60529.
• Hardware list: every buckle, D-ring, slider and eyelet with material and finish, since plated zinc inside a sealed bag will bloom within weeks.
• Artwork: vector file, Pantone references, placement drawing with dimensions from the nearest weld, and a minimum stroke width of 0.8 mm.
• Acceptance test: the method, the duration, the sample size and the pass mark, written before the sample exists rather than negotiated after it arrives.

The acceptance test is the item that buyers omit most often and the one that decides whether the round ends. Without it, approval becomes a matter of taste: the sample looks right, feels right, and nobody can say whether it passed. With it, the round has a defined exit and the brand's own quality team can repeat the test on their side and get the same answer. We supply a template and we ask for it back filled in before the round begins.

Sample Room Sequence From Cut to Welded Body

The sample room does not work the way a production line does, and knowing the sequence helps a buyer read a progress report. Day one is pattern release and nest check, confirming every panel fits the roll width. Day two is cutting, usually by die for repeat panels and by hand or laser for a first build. Days three and four are the weld trials, where the electrode, the dwell and the pressure are set on coupons before any panel is committed. Day five is body assembly, day six is hardware and trim, and days seven to ten are decoration, ingress testing and packing.

The weld trial is the step that decides whether the rest of the schedule holds. Running it on coupons first means the parameters are proven before the actual panels are used, which is why the trial appears early and why it sometimes consumes a day that a buyer expected to be spent on assembly. Skipping it saves a day and risks the panels, so we do not skip it. Where a programme has an unusual laminate, the trial widens to include a peel test at two parameter settings and the sample window moves toward the 12-to-15-day end.

Hardware fitting comes after the body is closed, not during, and the reason is the wet zone. Fitting a D-ring or an anchor before the final weld means the fitting operation has to reach past or through a joint that should be left alone. Fitting after closure means the anchor lands on a reinforcement patch welded in the right place, and the patch is part of the drawing rather than an afterthought. This is the single sequencing rule that most distinguishes a clean sample from one that needs a second round.

First Article Inspection at the Bench

First article inspection on a sample is a measurement exercise, and it takes about forty minutes. Every dimension in the critical band is measured and recorded, the seam width is measured at five points along each weld, the closure is cycled fifty times dry and fifty times wet, the hardware is pull-tested by hand against the specified load, and the whole bag is inspected under a lamp turned inside out. The output is a one-page record with the revision letter on it, and it travels with the sample.

Two measurements carry more information than the rest combined. Seam width variation along a single weld tells you whether the electrode was held consistently, and it is the earliest predictor of a leak at bulk, where hundreds of welds are made at speed. Closure effort when wet tells you whether the product will be used correctly in the field, because a closure that needs two hands and a dry grip will be left half closed by a user in the rain, and the resulting return will be logged as a waterproof failure.

Water Ingress on the Sample: Bench Rig and Pass Mark

The bench rig for a sample is deliberately simple so that a brand can replicate it. For spray and rain claims the bag is mounted in its normal carrying attitude, loaded to a third of its rated capacity, and exposed to a spray head at a fixed distance for the stated duration, after which the interior is inspected with tissue paper rather than by eye. Tissue finds a damp patch that a visual check misses, and the difference matters when the pass mark is zero ingress.

For immersion claims the bag is loaded, closed, and submerged to the stated depth for the stated duration with the closure uppermost and then lowermost, because a closure that survives one orientation often fails the other. The pass mark is written in the acceptance test before the sample exists: typically no water on the interior tissue for a spray claim, and no more than a stated number of millilitres for an immersion claim, since a welded bag that has been correctly closed will take in nothing at all.

Two formal methods sit alongside the bench work and are worth naming in the file. AATCC 22 and AATCC 35 cover spray and rain exposure on the finished product rather than on a fabric swatch, which is the distinction that makes a retail claim defensible. ISO 811 covers the shell's hydrostatic head on its own and belongs in the material specification rather than in the product test. A sample round that reports all three gives a brand everything it needs for a hangtag.

Revision Rounds: How Many a 500-Piece Run Justifies

At 500 pieces per style per colour, the economic answer is two rounds for a standard build and three for a genuinely novel one. Beyond that the calendar cost exceeds the value of the improvement, because each round repeats a 6-to-10-day or 12-to-15-day window and pushes the bulk booking back by the same amount. A brand that is still changing the drawing at round four is usually no longer developing a product, it is deferring a decision.

The rule that keeps rounds to two is one variable group per round. Geometry in round one, materials and hardware in round two, decoration in a third if needed. Change two groups at once and a new leak has two possible causes, so the next round changes both again and the cycle repeats. This sounds slower and finishes faster, and it produces a tech pack that can go to bulk without caveats attached.

Deciding what is worth a round at all is the harder judgement. A handle that rolls in the grip is worth a round. A pocket that sits 4 mm off centre inside the cosmetic band is not, and the brand should be told so plainly. We give a recommendation on every finding at the end of a round, including the recommendation to accept and move, because the most expensive outcome is a round spent on something a customer will never notice.

Pre-Production Sample Versus the Approved Prototype

The pre-production sample is the last gate before bulk cutting, and it is not a second prototype. It is built on the production tooling, from the booked material lot, by the line that will run the order, at production speed. Its job is to prove that the prototype can be reproduced rather than to improve it. Any design change requested at this stage pushes the bulk window out, because the tooling or the nest has to be revised and the gate has to be run again.

What the gate checks is therefore specific to reproducibility: shade against the approved swatch, weld width consistency across every seam, closure effort on the production jig, print registration on the production screen or transfer, and the packed carton count. Those five are the things that drift between a sample made by one technician and a run made by a line, and each of them is cheap to verify at the gate and expensive to discover at inspection.

The gate is also where the inspection criteria are confirmed in writing, because it is the last moment at which they can be agreed without affecting a delivery date. AQL 2.5 under ISO 2859-1 sets how many minor deviations are tolerated in a drawn sample; the defect classification is what decides which deviations count as critical. Agreeing the classification at the pre-production gate, with the physical sample on the table, is far easier than agreeing it over photographs of a finished shipment.

Trim, Webbing and Colour Swatch Boards Sent With the Body

Every sampling round ships with a swatch board, and the board is as important as the bag. It carries the face fabric, the film, the webbing, the binding, the print strike-off and each hardware finish, all mounted flat with the revision letter on the back. A brand approving a bag without approving the board has approved a shape and not a material, and the first disagreement in bulk will be about shade or hand feel rather than about construction.

Hardware on the board should be the actual production part, not a catalogue image. Finishes photograph identically and behave differently: an acetal buckle and a plated one look the same in a picture and diverge completely after a season in salt air. Approving the physical part at sampling costs nothing and removes a category of complaint that no inspection standard catches, because a buckle that blooms in month six passed every check at shipment.

The board is also the reference for the repeat order. It is retained alongside the sealed unit, and a re-order is matched against both, which is the only reliable way to hold shade and hand feel across a twelve-month gap between runs. Digging out the board and comparing it under controlled lighting takes ten minutes and settles questions that would otherwise be argued from memory on both sides.

Failure Findings That Send a Sample Back to the Room

Five findings account for most second rounds, and each has a specific cause rather than a general one. A bridging weld shows as a line where the film joined but did not bond, usually at a corner with too tight a radius. A closure that closes under tension usually means the mouth dimension drifted outside its 2 mm band. Water inside the bag after spray usually means the mouth or a pocket mouth, not the body. A handle that rolls means the webbing is too narrow for the load. A print that lifts means it crossed a weld.

The Sign-Off Sheet We Ask Brands to Return

Approval is a signed sheet, not a reply to an email, and it records eight things: the revision letter, the date, the dimensions measured, the ingress result with the method named, the shade approval reference, the trim approval reference, the acceptance criteria agreed for bulk, and the name of the person approving. Eight lines, one page, and it is the document that ends the sampling stage and starts the bulk clock.

The sheet matters most in the two places buyers do not expect. The revision letter prevents a later argument about which version was approved when a change is made in bulk. The named acceptance criteria prevent the argument at inspection, because the pass mark was agreed when the sample was on the table rather than when a shipment was already packed. Both are obvious in hindsight and both are routinely skipped in a hurry.

We also ask the brand to state on the sheet whether the sample is approved as-is or approved subject to listed changes. Approved subject to changes is a legitimate answer and it is common at round two, but it has to be written as a list of specific items with the revision they will appear in. Approved-but-change-this-oral-instruction is the version that produces a bulk shipment nobody agrees on.

Booking Bulk Production After the Sample Is Signed Off

Once the sheet is signed, the order moves to material booking, which is the step that actually starts the 35-to-50-day bulk window. The film lot, the face fabric, the webbing, the hardware and any printed packaging are all booked against the approved references, and the lead time on those items, not the assembly time, is what sets the earliest possible delivery date. A brand that signs the sheet three weeks late has not lost three days of production, it has lost three weeks of material position.

Payment follows the same logic. Terms are T/T 30 per cent deposit and 70 per cent before shipment, and the deposit is what releases the material booking. Shipments leave FOB Xiamen. The deposit date, not the approval date, is the one that should go on a buyer's own critical path chart, because that is the date that converts an approved sample into a booked production slot.

Capacity is rarely the constraint at this stage, but it is worth stating. The validated production partner facility runs 4,950 square metres across 7 lines with 149 machines and 137 people, verified by SGS, at 200,000 pieces a month. A 500-piece programme does not compete with catalogue volume for a slot; it is booked into its own window, which is why the deposit date rather than the queue position decides the delivery.

Retained Reference Units and the Two-Year Sample Store

We retain two sealed units from every approved pre-production sample, plus the swatch board, for two years. One unit stays with the production partner as the line reference and one is available to the brand on request. The retention period is not arbitrary: it covers the typical interval between a first order and a second-season re-skin, which is exactly when the question of what was originally approved comes up.

Retention is also what makes a warranty conversation possible. When a claim arrives, the question is whether the bag as shipped matched the bag as approved, and that can only be answered if the approved bag still exists. Brands that keep their own reference unit and their own board are the ones who resolve claims in days rather than quarters, and we recommend it as standard practice regardless of who the production partner is.

Two years is also roughly the point at which the material itself becomes an unreliable reference. Films age, coatings change slightly and shade drifts, so a unit older than that should be used for construction reference and not for colour matching. Colour matching always goes back to the swatch board and the recorded delta, which is why both are retained rather than one.

Sampling Cost, Round Count and Calendar

The calendar arithmetic for a waterproof bag programme is simple and worth writing down before a launch date is promised: 6 to 10 working days for a standard prototype or 12 to 15 for a complex one, multiplied by the number of rounds, plus 35 to 50 days of bulk from the approved pre-production sample, plus transit and customs. A two-round standard programme is therefore roughly 50 to 60 working days before goods are on the water.

Sampling charges are usually credited against the bulk order once it is placed, which is the arrangement we use, and they are always disclosed before the round starts. What buyers should watch is not the charge but the round count, because the calendar is the scarce resource. Two rounds inside a season is comfortable. Three is tight. Four means the launch date moves, and the cost of that is larger than any sampling fee.

To open a sampling round, send the drawing, the shell requirement and the acceptance test to service@junyuanbags.com or WhatsApp +86 177 5002 0688. Test method detail sits on the water ingress test methods page, the inspection gate is described on the quality page, and the wider development sequence is on the product development cycle page.

Frequently Asked Questions

Q1: How long does a waterproof bag sample take?

A: A standard prototype takes 6 to 10 working days from a complete tech pack, and a complex one with new tooling, a novel closure or a bonded badge takes 12 to 15 working days. The clock starts when the file is complete rather than when the first email arrives. Bulk production then runs 35 to 50 days from the approved pre-production sample, plus transit and customs.

Q2: What has to be in the file before sampling starts?

A: Six items: a dimensioned drawing with tolerance bands, a shell specification with the required hydrostatic head under ISO 811, a closure specification with class and pull type, a hardware list with materials and finishes, artwork with Pantone references and placement, and an acceptance test with method, duration and pass mark. Missing any one puts the round on hold.

Q3: Why does the sample need a physical approval rather than photographs?

A: Because photographs cannot show hand feel, cannot show how a closure behaves when wet, and cannot be re-measured when a question arises in bulk. The approved sample is the reference for the pre-production sample, for the pre-shipment inspection and for any warranty claim two years later. A programme with only images has no reference at any of those points.

Q4: How many revision rounds should a programme allow?

A: Two for a standard build and three for a genuinely novel one. Beyond that the calendar cost exceeds the value of the improvement, since each round repeats the sampling window and pushes the bulk booking back by the same amount. The rule that keeps the count down is one variable group per round: geometry first, then materials and hardware, then decoration.

Q5: What is the difference between a prototype and a pre-production sample?

A: The prototype proves the design; the pre-production sample proves the design can be reproduced. It is built on production tooling, from the booked material lot, by the line that will run the order, at production speed. Its job is to confirm shade, weld consistency, closure effort on the production jig, print registration and carton count, not to improve the design.

Q6: What does the water ingress test on a sample actually involve?

A: For a spray or rain claim the bag is mounted in its carrying attitude, loaded to a third of capacity, exposed to a spray head for the stated duration, and inspected inside with tissue paper rather than by eye. For an immersion claim it is submerged to the stated depth with the closure uppermost and then lowermost. The pass mark is written before the sample exists.

Q7: Which standards should be named in a sampling file?

A: AATCC 22 and AATCC 35 cover spray and rain exposure on the finished product rather than on a fabric swatch, which is what makes a retail claim defensible. ISO 811 covers the shell's hydrostatic head and belongs in the material specification. IEC 60529 covers immersion codes where the closure geometry can support one. A round reporting all three supports any hangtag wording.

Q8: What findings most often send a sample back for a second round?

A: Five: a bridging line along a weld from too tight a corner radius, a closure that closes under tension from a mouth outside tolerance, water inside after spray from a pocket mouth below the water line, a handle that rolls in the grip from webbing too narrow for the load, and print lifting because it was placed over or within 10 mm of a weld.

Q9: What is on the sign-off sheet?

A: Eight things: the revision letter, the date, the dimensions measured, the ingress result with the method named, the shade approval reference, the trim approval reference, the acceptance criteria agreed for bulk, and the name of the person approving. The revision letter and the acceptance criteria are the two that prevent arguments later, at change time and at inspection respectively.

Q10: What is the MOQ once the sample is approved?

A: 500 pieces per style per colour. The minimum covers the film lot, the line change and the set-up rather than the pattern, so it applies equally to a new build and to a catalogue shell with new branding. A three-colourway launch therefore commits 1,500 pieces, which is worth confirming at the brief stage rather than at approval.

Q11: How are samples and bulk paid for?

A: Terms are T/T 30 per cent deposit and 70 per cent before shipment, with goods leaving FOB Xiamen. Sampling charges are usually credited against the bulk order and are always disclosed before the round starts. The deposit date is the one that belongs on a buyer's critical path chart, because it releases the material booking that starts the production clock.

Q12: How long are reference samples retained?

A: Two sealed units from the approved pre-production sample plus the swatch board are retained for two years, one held as the line reference and one available to the brand. That period covers the typical gap between a first order and a second-season re-skin. After roughly two years a unit is reliable for construction reference but not for colour matching.

Q13: Why is a swatch board sent with every sample?

A: Because approving a bag without approving its materials has approved a shape and not a product. The board carries the face fabric, film, webbing, binding, print strike-off and each hardware finish mounted flat with the revision letter, and it is the reference used to match shade and hand feel on a repeat order twelve months later.

Q14: What is the full calendar from drawing to shipment?

A: Six to 10 working days for a standard prototype or 12 to 15 for a complex one, multiplied by the number of rounds, plus 35 to 50 days of bulk from the approved pre-production sample, plus transit and customs. A two-round standard programme is roughly 50 to 60 working days before goods are on the water, which is why round count rather than sampling speed decides a launch date.

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