Raw Material Inspection: Why Received Doesn't Mean Usable

The steel arrived Monday. The lab will have hardness results on Wednesday. The cutting job that needs it starts Tuesday at 6:00. The stock report shows 12 t on hand, so the plan looks fine. It isn't.

Incoming inspection is the check a plant makes on raw materials after goods receipt and before they are released for production: identity, documents, dimensions, key properties. Until it is done, the raw materials are in the building but not usable. A plant that treats "received" and "usable" as the same word will sooner or later send suspect material to a machine.

The four decisions after incoming inspection

Every inspected batch of raw materials ends in one of four outcomes. Decide ahead of time who can make each one.

• Release. The batch meets the specification and becomes available to production.
• Hold. Something is unclear: a missing certificate, a borderline result, a test still running. The batch stays unusable until someone decides.
• Return. The batch fails. It stays blocked until it leaves for the supplier, and the shortage it leaves behind needs a replacement order.
• Concession. The batch is out of spec, but engineering or the customer approves its use for a named purpose. Say hardness is 5 HB below the range, which is fine for a bracket and not for a shaft. A concession is written down and limited to that use.

A hold is not a rejection. Think of airport security. Your bag is at the airport, but it can't board until it is scanned. A bag pulled aside is not confiscated. It just isn't going anywhere until someone looks inside.

Why a quality hold is a planning event

Back to Tuesday. The cutting job needs 4 t of 42CrMo4 bar. The new 12 t batch is on hold. From an earlier heat, 2.5 t are released and on the rack. What are the options?

1. Run on the held steel "at risk." If the hardness is out, you have cut 4 t of scrap blanks. At $1,100 a ton, that is $4,400 of material plus a day of saw time.
2. Cut what you can from released stock. 2.5 t covers about 62% of the job (2.5 / 4 \= 0.625). Then switch the saw to another order whose material is released, and finish the first job on Wednesday afternoon once results are in. The cost is one extra changeover.
3. Ask the lab to test this heat first. If results come Tuesday at 10:00, you lose four hours instead of a day.

Notice that none of these is a quality decision. They are scheduling decisions triggered by a quality status. The planner needs to see the hold the moment it is set. Quality management covers what happens when inspection itself becomes the bottleneck.

Sampling and AQL in two paragraphs

For a delivery of 1,000 machined bushings, the common sampling tables (ISO 2859-1, or ANSI Z1.4 in the US) at normal inspection level II say: take 80 pieces. With an AQL of 1.0, you accept the lot if you find 2 or fewer defectives and reject it at 3 or more.

AQL stands for acceptable quality limit. It is the worst average defect rate you are willing to live with over many lots. It is not a guarantee about this lot. A lot with 2% defects still passes this plan about 78% of the time, simply because 80 pieces can miss the bad ones. If one bad piece can stop a customer's line, sampling is the wrong tool, and you need 100% checks or a supplier who controls the process.

Myth: "It came with a mill certificate, so it's fine"

A mill certificate (a 3.1 certificate under EN 10204) reports the steel mill's tests on the heat, the melt the steel was made from. It tells you about the heat, not about the bars on your rack. The check that catches most problems is simple: does the heat number stamped on the bars match the number on the certificate? Mixed bundles and wrong paperwork are far more common than bad chemistry.

Keep the heat number with the batch through cutting and into the finished part. If a certificate turns out to be wrong six months later, that link is what lets you find every affected part, as described in batch traceability.

Returns: don't lose the shortage

When a batch is returned, two things must stay visible. First, the physical return, with the original receipt and batch number. Second, the gap it leaves in the plan. A supplier credit note does not put steel on the rack. The replacement order needs its own date, and that date must include inspection time again, or you repeat Monday's problem next week. Procurement in manufacturing walks through the options when replacement supply is late.

Don't count the loss twice, though. If the held stock was already excluded from usable stock, returning it lowers the physical balance but creates no new shortage. The difference between on-hand and usable stock is the core idea of inventory management for manufacturers.

What the planner sees in factory.online

In factory.online, the 12 t batch is received with its heat number and put on quality hold. MRP no longer counts it as available, so Tuesday's cutting order shows a shortage of 1.5 t linked to that order, while the released 2.5 t from the earlier heat is still visible. The planner can see the gap on Monday afternoon and resequence the saw before anyone arrives on Tuesday.

If held material regularly surprises your shop floor, book a demo and we'll trace one of your recent holds together.