sm

A slip marker (SM) is a physical tag or label attached to material, usually a batch of parts or a roll of stock, as it moves through a manufacturing process. Its primary job is to communicate essential information about that material to the next station, operator, or machine without requiring a separate tracking system. The slip marker travels with the material itself, making it a passive but reliable method of process control in high-volume and batch production environments.

Slip markers take various forms depending on the trade and material type. In textile mills, they may be cardboard tags tied or clipped to fabric rolls, printed with dye lot number, yardage, and destination department. In metalworking shops, they might be adhesive labels on coil stock or sheet bundles, showing alloy grade, thickness, and heat treatment status. In food and beverage production, they are often date codes or batch identifiers on trays or containers. The marker must be durable enough to survive the process temperature, humidity, and handling, but not so permanent that it contaminates the finished product.

Function in process flow

The slip marker serves as a paper-based work instruction and traceability record. It tells the next operator what to do with the material, alerts them to any special handling requirements, and creates a record of which batch passed through which station at what time. In lean manufacturing contexts, slip markers support kanban systems and signal when material is ready for the next pull. They are especially valuable in environments where digital tracking is impractical, such as foundries, textile operations, or job shops with frequent changeovers.

Problems arise when slip markers are damaged, lost, or misread. A faded or torn label can send material to the wrong station or cause operators to miss critical instructions about temperature, speed, or quality checks. In wet processes like dyeing or galvanizing, markers must be protected in waterproof pouches. In high-speed operations, markers can fall off or catch on equipment. For this reason, many manufacturers now use a hybrid approach: a slip marker plus a barcode or RFID tag that can be scanned without removing the physical label.

The term reflects older manufacturing vocabulary. Slip originally referred to a piece of paper itself (a merchant's slip), and the marker is the physical embodiment of a work order or instruction sheet. In modern factories, slip markers remain common in plants with legacy equipment or batch processes, and they remain the default choice where electricity, scanning infrastructure, or network connectivity is unreliable or unnecessary.