Nobody plans to buy a twenty-year-old drive for four times its original price. It happens because a product change notice arrived in 2019, went to an address nobody reads, and the machine that depends on that drive was never linked to it. Obsolescence management is the unglamorous work of closing that gap.
What obsolescence actually means
Manufacturers of industrial control gear use a lifecycle vocabulary that is more precise than it looks, and the words matter when you are deciding whether to act.
Active means the part is in production and orderable on normal lead times. Phase-out (Siemens and others call it "cancelled for new designs", Rockwell calls it "end of life") means a date has been announced after which new orders stop. Discontinued means production has ended; what exists is stock, surplus and repair. Some vendors add classic or mature for a part that is still built but no longer recommended for new machines.
The important number is not the discontinuation date. It is the last time buy date — the last day the manufacturer will accept an order — and the repair service end date, typically seven to ten years after production stops. Between those two dates your spare comes from a distributor's shelf or a refurbisher's bench, and the price is set by how many people kept one.
Build the list before you need it
An obsolescence programme is a list, not a project. Three columns get you most of the value:
- Which parts are in which machine. If you have no bill of materials per line, start with the parts that stop production when they fail: CPUs, drives, HMIs, safety relays, servo amplifiers, encoders on the main axes. Fifty rows per line is usually enough to cover 90 % of the downtime risk.
- What each part's lifecycle status is today. Manufacturer lifecycle pages carry this, and so does every part page on this site. Re-check quarterly; status changes are announced, not negotiated.
- What it would cost you to be without it. Not the price of the part — the cost of the line standing still for the time it takes to get one. That number is what justifies holding stock.
The third column is the one people skip, and it is the one that makes the case. A €900 contactor that idles a €40,000-per-day line is not a €900 decision.
Deciding: buy, stock or migrate
Once a part is announced for phase-out, there are exactly three honest answers.
Last-time buy. Work out the remaining life of the machine, divide by the observed mean time between failures for that part, add one, and order that many. This is the cheapest option when the machine has a defined end date within roughly ten years. Store the units properly: keep drives and anything with electrolytic capacitors in a dry, temperate store, and power them up periodically if the manufacturer recommends re-forming.
Live off the surplus market. New surplus, refurbished and tested-used stock exists for most industrial parts for a decade or more after production ends, and it is dramatically cheaper than a panic purchase. This is the right answer when a last-time buy is not affordable or the quantity is hard to predict. It needs an active supplier relationship and a willingness to accept a supplier warranty instead of a manufacturer one.
Migrate. Replace the part, and usually its neighbours, with the current generation. Migration costs engineering time and production downtime, so it is the answer when the whole family is discontinued, when spares have become genuinely scarce, or when you would have to re-engineer for another reason anyway — a new safety standard, a control system upgrade, a line extension.
The mistake is treating these as a sequence. A plant that always defers ends up migrating in an emergency, which is the most expensive version of all three.
Storing what you bought
A last-time buy that degrades on the shelf is a last-time buy you did twice.
- Keep electronics in their ESD packaging, in a dry store between roughly 5 °C and 30 °C, away from vibration and direct sun.
- Electrolytic capacitors in drives and power supplies dry out and lose capacitance in storage. Manufacturers of larger drives publish re-forming procedures — typically applying reduced DC bus voltage for a period every one to two years. Follow the vendor's own procedure; there is no generic one.
- Record what you have where, in the same system as the machine. A spare nobody can find during a breakdown is not a spare.
- Rotate batteries. Backup batteries in older CPUs have a shelf life measured in years, and a stored CPU with a dead battery loses the program it was stored with.
What to do this quarter
If none of this exists in your plant yet, the smallest useful step is one spreadsheet per production line with the twenty parts that stop it. Look each one up, mark the status, and put a date in the calendar to check again. That alone will surface the two or three parts that are quietly in phase-out right now, while a last-time buy is still an option rather than an auction.
When you find one, get a price for the successor and a price for surplus stock on the same day. The gap between them is your decision, and it is usually much clearer than it felt before you had both numbers.