Sepasoft Track & Trace on Ignition: lots, operations and lot genealogy for tracing

Track & Trace is the Sepasoft, Inc. module for Ignition, the platform from Inductive Automation, that records each operation which moves or transforms material: which lots went in, which lots came out, where, when, on which equipment and by whom. Linked together, these records form the lot genealogy that answers both recall questions: which finished lots contain a given raw-material lot (a forward trace), and which raw-material lots went into a given finished lot (a backward trace). Sepasoft aligns the module with ISA-95. Most of the work before configuration is deciding how lots are numbered, where a lot changes and where it is scanned.

What Track & Trace records

Sepasoft's features page lists the scope:

• material followed from raw materials to finished goods, including consumables and by-products;
• lot genealogy, and serial numbers for items and sub-assemblies;
• on-hand inventory (which material is where), WIP inventory and inventory history;
• work orders and operations scheduling;
• per product, the parts consumed and their suppliers, the people and equipment involved, times, lot and serial numbers, measurements and rework.

The module creates and maintains its own database structure. Its components exist for both Vision and Perspective, and Sepasoft's pricing page licenses it per physical production site, perpetual, with unlimited active operations at that site; redundant, development and test licences are add-ons. Trace data can be linked with historian, OEE, SPC and recipe data. Which other modules fit beside it is covered in which Sepasoft module for which plant need.

The ISA-95 objects behind it

Sepasoft's ISA-95 overview describes production in terms of segments. A segment is a production task: it takes input resources (material, equipment, personnel) and produces an output, and several segments can be grouped into an operation. Process segments and operations definitions describe how the work is done; a request represents scheduled work, and a response segment holds what actually happened. The levels and objects of ISA-95 itself are in the ISA-95 article.

The objects a lot trace is built from:

• Material definitions and classes. Each material is a material definition, filed under a material class. The same definitions serve OEE Downtime runs, Track & Trace records and the material parameters of Batch Procedure.
• Material lot. The lot number is generated when the lot is created; a CreateLotNumber event can override it, for example to take numbers from ERP. The number stays the same as the lot moves through the plant. When a new lot is created with a number that already exists, its lot sequence number goes up, so each instance stays unique. A lot has a status (Active while in process, then Complete) and an availability (Available or Used), and it points to the storage unit or equipment where it sits.
• Quantities live in the operations. A material lot object does not hold its quantity: consumed and created quantities are stored in the response segments, and the net quantity is calculated from them.
• Sublots. Serialized items can be recorded as sublots of a lot, and the trace graph can highlight them.
• Equipment. Lines, cell groups and cells from the production equipment model, plus two items that the model lists for Track & Trace: the Storage Zone, an area such as a warehouse, and the Storage Unit inside it, such as a numbered bay. Supplemental equipment such as pallets, bins and dies sits outside the production model and is set up in the MES Object Editor. Renaming an item creates a new item, and data recorded against the old name is not available under the new one.

Recording an operation

Since MES 3.81.6 RC 3, one scripting call, system.mes.trace.recordOperation, records an operation with its begin and end times, the equipment path, an optional work order (the output quantity is added to it), arrays of materials in and out (lot number, material, quantity, unit, status), personnel, supplemental equipment and custom properties. Output lots are created automatically by default. The equipment path of an input must match the place that holds the source lot, and modifyOperation adds final quantities or the end time later. Sepasoft presents this call as the successor to the older method built on ISA-95 operation objects, which needed more setup and scripting. Its own step-by-step tutorial is marked as largely legacy as of 2023, with a design consultation suggested for new cases, so confirm the current method with Sepasoft before designing.

Sepasoft's operation pattern framework sorts operations into six shapes by the ratio of inputs to outputs. The examples below follow Sepasoft's, in our words:

Each recorded operation takes its inputs off the source locations and credits its outputs to their destinations, so inventory stays current.

Lot handling decides what happens when material enters a place that already holds material. Sepasoft's lot handling page lists Single Lot (one lot at a time), Random Lot (the default, any order), FIFO, LIFO, Same Lot (lots of the same material are combined and only the total quantity is tracked) and Blend Lot (one lot at a time; each addition mixes with the contents and creates a new lot, so the history is kept). The methods are configured for a line in the Equipment Manager and apply to storage units and equipment. A zero lot threshold, set as a quantity or a percentage, zeroes a lot when only a small remainder is left, for example in a silo.

Forward and backward trace

Sepasoft's operation pattern framework describes the linked operations as a genealogy graph that can be traced forward or backward for recalls and quality investigations. The tools:

• MES Trace Graph (Vision and Perspective) draws lots and segments as alternating nodes, laid out in time order from left to right, so raw materials sit on the left and finished goods on the right. A Max Fan Count limits how many nodes fan out from one node, a sublot name can be highlighted, and clicking a node passes its lot, material, equipment and times to scripts.
• Lot Trace returns the same data as a dataset, with each row linked to its previous and next segment and lot, and marks each lot's use as In, Out, Consumable or By-product.
• system.mes.trace.getTraceabilityData returns forward lot tracing from a given lot, with optional fan-out and depth limits; lot quantities can be included from 3.81.11 SP0. Sepasoft's tutorial builds a trace report that walks both upstream through the materials in and downstream through the materials out.

How data gets in

• Operator screens. Sepasoft's built-in trace components reduce the need for custom entry screens. On Perspective, Ignition's Barcode Scanner Input component listens for keyboard-wedge scanners without needing focus and can pick out the code with a prefix and suffix or a regular expression.
• PLC events. recordOperation is a script function, so any Ignition script event can call it. A gateway tag change script runs on the gateway with no client open and fires when a listed tag changes value, quality or timestamp, for example a transfer-complete bit in the PLC. Sepasoft notes two limits: tracking driven by tag values, such as pumps and valves switching on, follows material transfers more loosely than operations entered through a user interface, and production control (where an operation may run, who may run it, which materials it accepts) can only be implemented through a user interface.
• ERP. Business Connector moves data between Ignition and business systems, triggered by a schedule, a tag change, a web service call or a script. It uses B2MML, the XML form of the ISA-95 object models, and its mapping tool turns business data into MES data such as schedules and material definitions for Track & Trace. SAP and web-service links go through the Interface for SAP ERP and Web Services modules.
• Batch. With Batch Procedure, an equipment phase can carry Material_In and Material_Out parameters, and the batch's lots appear in the trace graph; see Batch Procedure on Ignition vs FactoryTalk Batch.

What the plant must decide first

• Lot numbering. Who issues the number at each step: the supplier, ERP or the MES. Whether the supplier lot is kept as a property of an internal lot. What happens when a number is reused, given that the lot sequence number then rises.
• Where a lot changes. Decide which operations create a new lot (recordOperation creates output lots by default). Mark the points where lots merge, such as silos, tanks and hoppers, and choose the lot handling method for each.
• Scan points. Each place where material identity enters the system or changes, who scans there, and what happens when a scan is missed.
• Quantities. Whether consumption is weighed, counted by the PLC, taken from the recipe or entered by hand, and in which units.
• Granularity. A finished lot per order, per shift or per pallet, and whether serialized units are recorded as sublots.
• The production model. Storage zones, storage units, lines and cells, named once before the first operation is recorded.
• Two test questions. Write one forward and one backward trace question in the plant's words and run both at acceptance.

Worked example: a generic food packing line

A generic line, not a customer's: flour, sugar and oil are mixed in batches, the mix goes through a hopper to a filler, and packs are cased and palletised. Lot names are examples.

A backward trace from one pallet runs pallet, FG-01, the filling operation, the hopper lot and film lot, MIX-01, then the flour, sugar and oil lots and their supplier lots. A forward trace from one flour lot finds every mix lot that consumed it, every finished lot made from those mixes and every pallet shipped from them. We would choose Blend Lot for the hopper, because each new mix then creates a new hopper lot and the hand-over between two mixes stays visible; with Same Lot only a running total is tracked, and a trace through the hopper would widen to every mix that passed through it.

TDL's role

TDL Industrial Automation is a Sepasoft MES Certified Integrator and an Ignition Certified Integrator. TDL's related work so far is on Rockwell Automation platforms: barcode and OCR checks, vision, checkweigher and reject stations on packing lines, and barcode material integration in a FactoryTalk Batch system. Where a plant uses or chooses Track & Trace, TDL connects it to the line PLCs, as described on the MES on Ignition page; stop and count data for the same lines are covered on the OEE and downtime monitoring page. For when a plant needs an MES at all, see what MES is.