How to Build a Bag BOM: Fabrics, Components and Trims

The reason for working in passes is that each class of item is bought in a different unit from a different kind of supplier and arrives on a different clock. Fabric comes in rolls by the metre from a mill. Foam comes in sheets or die-cut parts from a converter. Hardware comes in pack quantities from a component supplier. Writing them in one list makes the BOM hard to action and easy to get wrong.

There is also a sequencing argument. Fabric is usually the longest lead item and the largest cost line, so it gets resolved first, and the answers it produces — the width, the yield, the shade — constrain the passes that follow.

How Do You Build Pass One: Fabric and Lining?

Start from the panel list on the pack, not from the bag. Every panel has a cut size; the sum of the panel areas, divided by the marker efficiency and the fabric width, gives the linear metres per bag. Then add the cutting allowance and the defect allowance and multiply by the order quantity.

State the width explicitly. A consumption figure without a width is meaningless, because the same bag cut from 150 cm material and from 110 cm material uses different lengths. Where the marker has not been made yet, state the assumed efficiency and revise the line when it has.

How Do You Build Pass Two: Foam and Interlining?

As an area, with the sheet size stated. Foam is cut from sheet or die-cut to a profile, and the yield depends on how the profiles nest. State the area per bag, the sheet size, and the number of parts per sheet, rather than a single thickness figure that nobody can buy against.

Where the foam is laminated to the shell or the lining, the line changes character: it becomes a converted material bought by the metre rather than a sheet bought by the area. Say which it is, because the supplier, the lead time and the allowance are all different.

How Do You Build Pass Three: Hardware?

Straight from the callout list. Every balloon on the drawing that points at a buckle, a ring, a slider, a snap, an eyelet or a stud becomes a row with a count per bag. Then multiply by the order quantity and add the defect allowance.

The two extra columns that matter on hardware are the pack quantity and the finish. Hardware is sold in pack quantities — a hundred, five hundred, a thousand — and an order for 1,040 pieces buys 1,500. And a plated finish carries a longer lead time than a moulded colour, which is the difference between a component that fits the bulk window and one that does not.

How Do You Build Pass Four: Trims and Packing?

Trims are webbing, binding, cord, elastic, hook-and-loop, labels, print and transfers. Each is a cut length or a piece count, and each needs the turn-back included: a webbing handle is not 180 mm of webbing, it is 180 mm plus what is folded under at each anchor.

Packing is the pass most often left off the BOM entirely, and it is a real material cost. Polybags, cartons, tape, desiccant where the destination needs it, and the insert or hangtag where the programme has one. State the polybag gauge and whether it is perforated, because both are purchasing decisions with a cost attached.

Labels and printed matter belong in this pass as well, and they are the items most often forgotten until packing week. The care label, the fibre content label, the country-of-origin marking, the tracking label where the product is a children's product, and any barcode or hangtag each have a supplier, a minimum run and a lead time of their own.

Where a label carries a compliance claim, the certificate reference goes on the same line. A recycled-content claim needs a GRS transaction certificate number, and a restricted-substance claim needs the REACH statement reference, and neither can be produced at short notice once the goods are packed.

How Do You Handle a Component With No Second Source?

Flag it on the BOM as single-source and give it a lead-time buffer. A component bought from one supplier in one place is a single point of failure for the whole run, and the failure does not have to be dramatic: a mill running two weeks late on a single-source shell moves the entire bulk window.

Where a single-source component is also long-lead, the buffer has to be in the order plan rather than in the window. Ordering it earlier than the rest of the BOM costs storage and working capital, and it is still usually the right call against a 35-50 day bulk commitment that has already been promised to a customer.

How Do You Put Prices and Lead Times on the Lines?

Prices go on as a unit price with a break level and a currency, and lead times as working days from order to delivery at the production site. Both should be dated, because both move. A BOM with undated prices is a snapshot that will be quoted as if it were current several months later.

The lead-time column is the one that decides the order plan. Work out the longest line and count backwards from the date bulk is due to start. On a 35-50 day bulk window, a component with a four-week lead time has to be ordered before the sample is approved, which is a decision the buyer should make knowingly rather than discover.

How Do You Handle a Component That Is Bought in Two Places?

As two lines with a split stated, not as one line with two suppliers. A programme that buys a stock buckle from one source and a branded puller from another has two different lead times, two different minimums and two different substitution rules, and collapsing them into one row hides all three.

Where a genuine second source exists for the same part, that is different: it is one line with an approved-substitute column naming the second source and the person who approves its use. The distinction is between a split buy, which is two commitments, and a fallback, which is one commitment with a contingency.

How Does the BOM Handle Colourways and Size Runs?

By multiplying rather than by adding rows. One BOM covering all colourways, with a column per colourway giving the quantity of that component in that colour, is easier to check than a separate BOM per colourway and far easier to change. Where a colourway uses a different material entirely, it becomes a separate style with its own BOM.

Size runs work the same way: one BOM, with the quantity per size taken from the grading sheet. The trap is personalisation, which is not a size issue and does not scale with the grading. A run of 500 pieces across three sizes and forty names is forty personalisation units, and that line has to be counted separately from the piece count.

What Does the BOM Say About Packaging Weight and Freight?

Enough to model the freight before the price is agreed. The packing lines give the polybag and carton specification; the packing section of the pack gives the pieces per carton; and the two together give the carton count and the carton weight. Those are the inputs a freight quotation needs.

Where they are missing, the freight is estimated on a guess about the carton, and the guess is usually optimistic because an unstuffed bag packs tighter than a stuffed one and nobody has said which applies. State the fold method and whether the bag is stuffed, and the freight per unit stops being a surprise.

How Do You Check the BOM Before It Is Issued?

Three arithmetic checks and one completeness check. The arithmetic: does every row have a quantity and a unit; does the sum of the material lines reconcile with the quoted material cost; do the allowance percentages produce a plausible order quantity. The completeness check: does every callout on the pack have a row.

One more check that is worth the five minutes: read the BOM as if the order quantity were ten times larger. Lines that are fine at 500 pieces and break at 5,000 — a component with a long lead time, a dye lot with a minimum, a part from a single source — are visible at that scale and invisible at this one, and they are the constraints the programme will hit if it grows.

Then one sanity check that catches most errors. Multiply the total material weight by the order quantity and compare it with an estimate of the finished bag weight. If the material weighs less than the finished bag, a line is missing. It is a crude test and it works.

How Does the Finished BOM Feed the Cost and the Calendar?

Both downstream documents inherit the BOM's errors and neither can correct them. A cost sheet built on a BOM that missed a trim produces a unit price that is wrong by the cost of that trim, and a plan built on a BOM that missed a lead time produces a date that is wrong by the length of it. Neither error is visible downstream, because both read as arithmetic that has already been checked.

The cost sheet applies prices to the BOM quantities, adds labour from the operation list, adds overhead and margin, and produces a unit price. The calendar takes the longest lead-time line and counts backwards. Both are only as good as the BOM underneath them.

From there the programme runs on the standard windows: sampling 6-10 working days from the signed pack, bulk 35-50 days from written sample approval, inspection at AQL 2.5 under ISO 2859-1, FOB Xiamen. The BOM is what makes those windows real rather than nominal, because it says what has to arrive before the first day of bulk. Model the result in the landed cost calculator.

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