Automotive Production Planning: The Line Hit 100% of Target. The Customer Still Stopped

The shift report is green: 1,000 brackets made against a target of 1,000. Then the phone rings. The customer's assembly line is about to stop. They needed 500 left-hand and 500 right-hand brackets. The plant made 700 left and 300 right, because left-hand was already set up and the operators kept it running.

So the plant hit 100% of volume and delivered 80% of what was needed: 500 left plus 300 right is 800 usable parts. The other 200 left-hand brackets go to the warehouse, and the customer is 200 right-hand short. Automotive production planning is deciding what to make, in what quantity, mix and sequence, so that each day's shipment matches what the vehicle maker's line will consume. Volume is the easy part. Mix and timing are the job.

Automotive production planning starts with call-offs

Most suppliers don't receive a classic purchase order for each delivery. They have a long-term agreement, often a scheduling agreement, for a part, and the customer sends call-offs (also called releases) against it, usually electronically through EDI. In Europe these are often EDIFACT DELFOR and DELJIT messages; in North America the ANSI X12 830 planning schedule and 862 shipping schedule.

A call-off typically has two parts:

• A firm near-term portion: quantities and dates you must ship.
• A forecast further out: quantities that will change, sometimes a lot.

How many days or weeks count as firm, and what the customer will pay for if they cancel, is set in your contract, not by a general rule. Read it before you plan.

JIT and JIS in plain words

Just-in-time (JIT) means the customer keeps almost no stock of your part. You deliver small quantities often, sometimes several times a day, timed to their consumption.

Just-in-sequence (JIS) goes one step further. You deliver parts in the exact order the vehicles will come down the assembly line: a black leather seat, then a gray fabric one, then another black leather. The sequence often arrives only a few hours before the parts must be at the line. A seat in the wrong position in the rack is as bad as a missing seat.

The everyday picture: ordering pizza for a party. Ten pizzas arrive on time, but you asked for five margherita and five pepperoni and got seven and three. The delivery was "complete". Half the guests still aren't happy.

What a ±15% daily change does to a weekly plan

Say the call-off is 1,000 parts a day, 500 of each variant, and daily changes of ±15% are normal.

• Volume swing: 15% of 1,000 is 150 parts a day. If the customer runs high all week, that is 5 × 150 = 750 extra parts. At 250 parts an hour on the press, 3 hours of press time you never planned.
• Mix swing: worse is when left-hand goes up 15% and right-hand goes down 15%. Total stays at 1,000, so the volume report shows nothing. But you now need 575 left and 425 right a day, and the press has to change over at a different point every day.

Plants absorb this in three ways: a small finished-goods buffer per variant sized to the typical swing (here, about 150 parts of each), spare press hours kept free rather than filled with "extra" production, and a short firm zone in the master production schedule so the plan changes on purpose, not every hour. Short changeovers help most, because they let you run each variant every day; see changeover optimization.

Two presses, one tool: capacity counted twice

A classic automotive trap. Two presses, each with 80 available hours a week. Several parts can run on either press, but they all need the same die, and there is only one die.

The capacity sheet adds up 2 × 80 = 160 hours. The demand for parts using that die is 110 hours, so load looks like 69%. But the die can only be in one press at a time. Real capacity is 80 hours, minus the time to move the die. Real load: 110 / 80 = 138%. The plan looked comfortable and was impossible from day one. The constraint was a tool, not a machine, which is exactly the kind of hidden bottleneck described in manufacturing optimization.

Myth: hitting the output target means we delivered

The customer doesn't measure your output. They measure whether the right parts arrived at the right time, and they count it per part number and per delivery. That is why a plant can post record volume and a poor OTIF in the same month. In our opening example, the left-hand line of the order shipped in full and the right-hand line didn't: 50% of order lines on time and in full, next to a 100% volume report.

And the cost of a miss is not the price of 200 brackets. It is premium freight to rescue the delivery and, if the customer's line stops, possible charge-backs for their downtime under your supply agreement. Those numbers are usually far bigger than the value of the parts.

How it looks in factory.online

In factory.online, call-offs brought in as sales orders (for example from SAP or Dynamics 365) create manufacturing demand per variant, so the planner sees 575 left and 425 right for tomorrow, not 1,000 brackets. The finite-capacity Gantt shows when each variant runs on each press, and a planning scenario can test a daily left-right rhythm against the current long-campaign plan before anyone moves a die.

If your line hits target and your customer still calls, book a demo and bring last month's call-offs.