Direct Answer
A spare parts kit is a hedge against the gap between a failure and a delivery, so it should be built from criticality and lead time rather than from a percentage of the machine price. Classify every part as a wear item, a long-lead component or a commodity; stock the first and second, and buy the third locally as needed. When ordering a paper cup machine, ask for the spare parts list with part numbers, quantities per machine, wear classification and lead times, then order the kit that covers the first year of normal consumption plus one change set of any part whose failure stops the line. The expensive mistake is not a modest kit; it is a line stopped for two weeks waiting for a component that could have been on a shelf for the price of one day of lost output.
Opening Hook
The machine ran for eleven months without a problem, and then the sealing heater failed on a Thursday afternoon before a large order. The part cost less than a restaurant meal. It arrived nineteen days later, because it was a proprietary component with a factory lead time and an air-freight option nobody had priced. The plant lost the order. Nothing about the failure was unusual: heaters fail, and proprietary parts have lead times. What was unusual was the absence of a kit list, which is the cheapest insurance available at the moment of purchase. At yoco-group, we issue a classified spare parts list with every machine so the buyer can decide what to hold rather than discovering it during a breakdown.
Classifying Parts So the Kit Makes Sense
Every spare part decision follows from two questions: how likely is failure, and how long does replacement take to arrive.
| Class | Characteristics | Stocking rule |
|---|---|---|
| Wear parts | Consumed in normal operation, predictable life | Stock several change sets |
| Long-lead criticals | Failure stops the line, delivery measured in weeks | Stock at least one |
| Commodity items | Available locally within days | Buy on demand |
| Consumables | Fast-moving, low value, frequent replacement | Stock to a reorder point |
| Proprietary parts | Single source, model-specific | Stock deliberately or accept risk |
| Insurance items | Very low probability, very high consequence | Decide with the plant manager |
The classification exercise is short and it changes behaviour. A plant that knows which six components can stop its line for three weeks will stock those six and stop worrying about the rest. A plant that has never done the exercise usually buys a percentage kit, which over-stocks cheap consumables and under-stocks exactly the parts that matter. Buyers should ask the supplier which components they see replaced most often on that model, because a supplier's service experience is the best available predictor, and should record that answer next to each part number.
Contents of a Practical First-Order Kit
The first-order kit should be a decision, not a default, and it is worth negotiating at the same time as the machine price.
| Kit category | Typical items | Notes |
|---|---|---|
| Forming and sealing | Heating elements, sealing media, forming tools | Highest impact on output |
| Cutting | Blades, die components, trim parts | Consumable and predictable |
| Drive and transmission | Belts, chains, couplings, bearings | Moderate lead time |
| Pneumatic | Seals, valves, cylinders, filters | Small value, high stop risk |
| Electrical | Sensors, relays, contactors, fuses | Locally available or not |
| Control | Boards, drives, displays | Long lead, high cost |
| Auxiliary | Lubricants, cleaning materials, filters | Low value, easy to forget |
Two negotiating points are worth raising before the order is placed. First, ask whether the spare parts prices quoted at machine purchase can be held for a period, because parts bought at commissioning are usually cheaper than parts bought in an emergency. Second, ask for the list in a structured electronic format rather than a printed page, so that it can be loaded into the plant's inventory system and reorder points can be calculated. A parts list that lives only in a commissioning folder is rediscovered every time a part is needed.
Interchangeability and the Proprietary Trap
Interchangeability decides how much leverage a buyer keeps after installation.
| Question | Why to ask it | What a good answer looks like |
|---|---|---|
| Is the part standard or proprietary? | Determines sourcing options | Named standard or explicit proprietary |
| Which manufacturer supplies it? | Enables local sourcing where allowed | Component brand and model |
| Does the warranty require their part? | Affects sourcing freedom | Clear statement in writing |
| Are there equivalents? | Gives fallback options | Documented equivalent list |
| Is the part serialised to the machine? | Affects spares sharing | Yes or no, stated |
| What is the resupply lead time? | Sets the stocking level | Weeks or days, in writing |
The proprietary trap is not that proprietary parts exist; it is that the buyer discovers them at the worst moment. Two practices reduce exposure. Maintain a controlled free-issue and returns process so that a failed part under warranty is replaced without argument, and keep a small buffer of the parts that only the original builder supplies. Where a component is a common industrial item, obtain the manufacturer and model so that the plant can source locally during an emergency, subject to any warranty conditions the supplier states in writing.
Data: ISO publishes asset management and maintenance standards that set out how organisations plan maintenance, define asset criticality and manage the resources required to sustain equipment performance.
Judgment: Base spare parts holdings on documented criticality rather than on a fixed percentage of machine value, because criticality analysis directs limited capital to the components that actually stop production.
Source: ISO — Asset Management and Maintenance Standards (2024)
Stock Levels, Storage and Reorder Discipline
Stock level is an economic calculation, and storage conditions decide whether the stock is usable when needed.
| Part type | Storage consideration | Common failure |
|---|---|---|
| Rubber seals and belts | Dark, cool, away from ozone sources | Shelf-life degradation |
| Electronic boards | Anti-static packaging, moisture control | Static or humidity damage |
| Cutting blades | Protected edge, moisture control | Corrosion before use |
| Lubricants | Sealed, within shelf life, labelled | Wrong grade used in haste |
| Assemblies | Complete, paired, labelled | Missing small parts at use |
| Sensors | Original packaging, calibration intact | Damaged during storage |
Two rules keep a store functioning. The first is labelling that ties every item to the machine and the part number, because an unlabelled bin creates wrong-part installation, which is worse than waiting for delivery. The second is a reorder discipline linked to a defined minimum, so that stock is replenished when it reaches a level rather than when someone notices an empty shelf. Buyers who record consumption will be able to adjust stock levels from evidence rather than from feeling, which reduces both stockouts and idle capital. Our spare parts inventory planning guide covers the calculation in more detail.
Data: The U.S. Occupational Safety and Health Administration publishes machine safety and maintenance requirements describing how equipment must be maintained in a safe condition and how maintenance work must be controlled.
Judgment: Treat the parts store as part of the safety system, because correct parts fitted correctly and documented are what keep a guarded machine within the condition it was assessed in.
Source: U.S. Occupational Safety and Health Administration — Machine Safety and Maintenance Requirements (2025)
Documentation That Makes Reordering Trivial
Documentation is what converts a kit into a system, and it takes an afternoon to prepare properly.
| Document | Minimum content | Owner |
|---|---|---|
| Spare parts list | Part number, description, quantity, class, lead time | Maintenance |
| Recommended stock list | Minimum, reorder point, current holding | Stores |
| Consumption history | Parts issued by date and machine | Stores |
| Supplier contacts | Named contact, lead time, terms | Purchasing |
| Warranty and returns procedure | What is covered and how to claim | Purchasing |
| Machine serial link | Ties every document to the asset | Maintenance |
The document that pays for itself fastest is the consumption history, because it turns stock policy into arithmetic. After a year of records, the plant knows which parts are genuinely fast-moving and which were bought in a nervous moment. Buyers should also keep the spare parts list tied to the machine serial number, especially in plants that run several similar machines, because a part that fits one model may not fit another in the same family. Our total cost of ownership guide for spare parts sets out how holding cost, downtime cost and ordering cost balance against each other.
Data: The Lean Enterprise Institute publishes total productive maintenance and standard work resources describing how planned maintenance, operator involvement and documented standards reduce unplanned equipment losses.
Judgment: Link spare parts planning to planned maintenance activity, because parts consumed by a schedule are predictable, while parts consumed by breakdowns are expensive and arrive at the worst time.
Source: Lean Enterprise Institute — Total Productive Maintenance and Standard Work Resources (2024)
The Bottom Line
Classify parts by criticality and lead time, order a kit that covers the first year of wear plus one change set of every line-stopping proprietary component, store items so they are usable when needed, and keep a consumption record that turns stock policy into arithmetic. Spares are insurance, and the premium is always smaller before the failure.