Production Scheduling for Reactive 2-Part Adhesives

Production planners and operations managers in reactive 2-part adhesive formulation can use Schantt to model hybrid batch-and-flow production lines with parallel dispensing, pot-life-constrained handoff windows, and directional changeovers between chemistry families. This guide walks through configuring the stages, machines, routings, and calendars needed to schedule epoxy, polyurethane, and acrylic products on a shared multi-stage line.

This guide follows a fictional composite company built from industry research on reactive 2-part adhesives; all names, parameters, and figures are illustrative.

Industry context

Reactive 2-part adhesives cure through a chemical reaction between a resin base and a hardener, mixed immediately before dispensing. Manufacturers produce three main chemistry families — epoxy, polyurethane (PUR), and acrylic — each with distinct cure profiles, pot-life windows, and equipment requirements. Epoxy structural adhesives cure through heat in an oven. PUR adhesives set through ambient moisture over several hours. Acrylic fast-set adhesives cure in minutes at room temperature.

The production line follows a sequential multi-stage flow: resin batching in large reactors, metering and mixing in dedicated dispensing lines, filling into cartridges or pails, curing (for epoxy), then packaging and labelling. Batch stages process discrete loads on fixed cycles. Flow stages run at a continuous rate. Three product classes share the line, but each follows its own routing — epoxy passes through all five stages, while PUR and acrylic skip the curing stage, with their ambient dwell modelled as bridging transfer times.

A representative SMB formulator, CrossBond Formulations, runs approximately 65 people at a facility of roughly 2,800 m², making three product classes across five production stages, scheduled by a two-person planning team. The plant produces around 1,800 tonnes of reactive 2-part adhesive products per year. Its resin reactors batch 1,200 kg per cycle — 150 minutes for epoxy and acrylic on the shared reactor, 210 minutes for PUR on its dedicated reactor. Metering and mixing lines dispense in 10-minute cycles. Cartridge filling runs at 700 units per hour, pail and drum filling at 250 units per hour. The epoxy curing oven holds 240 units on a 45-minute cycle. Packaging runs at 800 units per hour.

Changeovers between chemistry families require purge cycles on shared equipment — 20 minutes for epoxy-to-acrylic or acrylic-to-epoxy transitions on the resin reactor and the shared metering line, and 10 minutes for format and label changes on the cartridge filler and packaging line. Transfer times of 30 minutes connect consecutive stages, with a 240-minute quality-hold buffer between dispensing and curing. PUR ambient cure adds a 1,440-minute bridging transfer from dispensing to packaging (1,440 minutes standard, manually extended to 2,160 minutes during Q2–Q3 summer months). Acrylic sets in 15 minutes after dispensing.

The plant runs Monday through Friday, 06:00 to 22:00, with filling lines also operating Saturday morning, 06:00 to 14:00. Three calendar exceptions apply — New Year's Day, International Workers' Day, and a year-end shutdown window starting 24 December. An annual summer shutdown closes the facility from 14 July to 18 July for maintenance. The PUR-dedicated metering line receives a six-hour quarterly maintenance in January.

CrossBond Formulations runs roughly 65 people at a facility of approximately 2,800 m², making 3 product classes across 5 production stages, scheduled by a 2-person planning team.

Process overview

flowchart LR
    S1["Resin Batching<br/>2 reactors"]
    S2["Metering & Mixing (MMD)<br/>2 lines"]
    S3["Dispensing & Filling<br/>2 fillers"]
    S4["Curing<br/>1 oven (epoxy only)"]
    S5["Packaging & Labelling<br/>1 line"]
    S1 --> S2 --> S3 --> S4 --> S5

Production flow at CrossBond Formulations — resin batching through five stages to packaging.

Polyurethane (PU-400) and acrylic (AC-10) classes skip the curing stage entirely — their ambient cure and set times are modelled as bridging transfer times from dispensing directly to packaging.

Scheduling challenges and how Schantt handles them

Reactive 2-part adhesive scheduling is driven by customer demand for mixed product classes across shared equipment — the planning team receives orders for epoxy, PUR, and acrylic products, each requiring different processing routes and cure treatments on the same production line. Demand is assumed to be a weekly mix of all three classes; some readers whose operation runs long campaigns of single chemistries will find their scheduling simpler than what this guide describes. Schantt schedules forward from a start date and minimizes total production time the schedule requires, within the configured shift calendars and machine availability. The practical horizon for this scenario is one to two weeks. Two scheduling modes are available: Auto mode, where the algorithm optimises both job sequence and machine assignments, and Semi-Auto mode, where the planner sets the job order and the algorithm selects the best machine for each operation.

What Schantt handles well

• Sequential multi-stage routing — ordered stage chain with per-class routing, forward-only transfer times between consecutive stages, shown as one operation per stage per product on the Gantt.
• Multi-machine stages (parallel-line contention) — multiple parallel machines per stage; Auto and Semi-Auto modes explore machine assignments to minimise total production time.
• Sequence-dependent changeovers — directional per-machine changeover matrices capture cross-chemistry purge cycles and format changes; the scheduling algorithm clusters similar chemistries to reduce total changeover time.
• Shift-aware availability — calendars per machine group (reactors on standard day, filling lines on extended shift); operations advance through working minutes only, with non-working gaps on the Gantt.
• Per-class routing with stage skipping — product classes share the common line but skip stages where realistic, with bridging transfer times to model the handoff across the gap.
• Mixed batch-and-flow pipeline — the route mixes batch stages (reactors, metering mixers, curing oven) and flow stages (filling, packaging), correctly applying batch-cycle physics and linear-rate physics with automatic pause segments where downstream outruns upstream supply.

How Schantt handles each challenge

1. Pot-life limited handoff.

• Reactive 2-part compounds begin curing the moment the resin and hardener are metered together at the mixing stage. Acrylic compounds have a usable pot-life window of approximately 4 minutes, PUR of 15 minutes, and epoxy of 30 minutes — if mixed compound sits beyond its window before reaching the dispensing head, it degrades and must be discarded. The scheduling reality is that the mixing-to-dispensing gap must stay inside these tight windows, especially for fast-set acrylic.
• Schantt models the metering and mixing stage as a batch step with a 10-minute cycle duration and enables partial transfer for the acrylic class — the metering line can pass 5 syringe units to dispensing as soon as they are ready, without waiting for the full batch to complete. This stamp-fed handoff reduces the exposure gap between mixing and dispensing. The planner can verify the gap on the Gantt by checking that the end of the metering operation and the start of the dispensing operation stay within each class's pot-life window for every scheduled job.

2. Sequence-dependent changeovers and parallel-line contention.

• Cross-chemistry transitions on shared equipment consume significant production time. Switching the shared resin reactor from epoxy to acrylic or back requires a 20-minute purge, as does the shared metering line. On mixed-class days these changeovers accumulate — a single reactor running a full epoxy-acrylic-epoxy sequence incurs 40 minutes of changeover time before any production. At the same time, three product classes compete for two dispensing fillers, and contention on the filling stage can cascade into queue delays upstream.
• Schantt captures each changeover as a directional, per-machine time matrix — from every class to every other class that machine processes — so the 20-minute epoxy-to-acrylic purge and the 10-minute filler format change are configured exactly where they apply. The scheduling algorithm clusters same-chemistry jobs together to minimise the total changeover time across the shared reactor and metering line. In Auto mode it can reorder jobs to find this lower-changeover sequence; in Semi-Auto mode it holds the planner's order fixed and manages changeover time by assigning jobs across the available parallel machines.

3. Three-way cure modelling and seasonal calendar diversity.

• The three product classes cure through three fundamentally different mechanisms. Epoxy cures in an oven at 80 °C on a 45-minute cycle with a batch capacity of 240 units — an effectively finite bottleneck capped at roughly 320 units per shift. PUR cures through ambient moisture over 24 hours, extending to 36 hours in humid summer conditions. Acrylic sets in 15 minutes at room temperature. Two shift patterns cover the line — a standard Monday-to-Friday day for reactors, metering, curing, and packaging, and an extended day including Saturday morning for filling lines. The planning challenge is modelling three cure regimes with different physics on the same line while respecting two distinct calendars.
• Schantt models the epoxy cure as a batch stage with the oven's finite batch capacity and 45-minute cycle, so the schedule respects the oven's throughput limit automatically. PUR and acrylic cure are modelled as bridging transfer times from dispensing to packaging — 1,440 minutes for PUR (manually adjustable to 2,160 minutes during Q2–Q3 summer months), 15 minutes for acrylic — which apply the correct dwell delay without adding an operation on a modelled curing stage. Per-class routing skips the curing stage for PUR and acrylic entirely. Calendar assignment is per machine group: filling lines use the extended shift, all other stages use the standard day. The planner switches the PUR transfer time seasonally by editing the configured duration.

What to model in Schantt

The five first-class entities a planner creates as top-level objects in Schantt for this scenario:

Step-by-step setup

1. Create the stages in order. Set up the five stages on the Stages page in the order they appear on the production line: Resin Batching (batch, position 10), Metering & Mixing / MMD (batch, position 20), Dispensing & Filling (flow, position 30), Curing (batch, position 40), Packaging & Labelling (flow, position 50). Then, on each stage's detail page, set the transfer times between consecutive stages — 30 minutes from Resin Batching to Metering & Mixing, 30 minutes from Metering & Mixing to Dispensing & Filling, 240 minutes (the quality-hold buffer) from Dispensing & Filling to Curing, and 30 minutes from Curing to Packaging & Labelling. Add bridge transfer times on the Dispensing & Filling stage detail page for the classes that skip Curing:

• Product class: Polyurethane Flexible → Packaging & Labelling — 1,440 minutes (standard), adjustable to 2,160 minutes during Q2–Q3
• Product class: Acrylic Fast-Set → Packaging & Labelling — 15 minutes

2. Add the machines to each stage. On each stage's detail page, create the machines that belong to it:

• Resin Batching: reactor-1 (shared, epoxy and acrylic), reactor-2 (PUR-dedicated)
• Metering & Mixing: mmd-1 (shared, epoxy and acrylic), mmd-2 (PUR-dedicated)
• Dispensing & Filling: filler-1 (cartridge), filler-2 (pail and drum)
• Curing: oven-1 (tunnel oven)
• Packaging & Labelling: packer-1

3. Create the product classes and define each class's routing. Set up three product classes on the Product Classes page — Epoxy Structural, Polyurethane Flexible, and Acrylic Fast-Set. For each class, define its routing by selecting the stages it passes through in order:

• Epoxy Structural: Resin Batching → Metering & Mixing → Dispensing & Filling → Curing → Packaging & Labelling (full five-stage route)
• Polyurethane Flexible: Resin Batching → Metering & Mixing → Dispensing & Filling → Packaging & Labelling (skips Curing)
• Acrylic Fast-Set: Resin Batching → Metering & Mixing → Dispensing & Filling → Packaging & Labelling (skips Curing). On the Acrylic Fast-Set routing, enable partial transfer at the Metering & Mixing stage and set the quantity to 5 units, so the dispensing line can begin on the first syringe units before the full MMD batch finishes.

4. Add one product per class. Create one representative product for each product class — EP-200 (Epoxy Structural, cartridge), PU-400 (Polyurethane Flexible, cartridge), AC-10 (Acrylic Fast-Set, syringe). Set the product class on each.

5. Set each machine's capacity parameters and changeovers. For each batch-stage machine, enter its batch cycle time and batch size on the machine's detail page. For each flow-stage machine, enter its throughput rate. These need the product classes from step 3 to already exist so the per-class values can be configured.

• Resin Batching (batch):
• reactor-1: 150 minutes cycle, 1,200 kg batch size (epoxy and acrylic)
• reactor-2: 210 minutes cycle, 1,200 kg batch size (PUR)
• Metering & Mixing (batch):
• mmd-1: 10 minutes cycle, 60 units batch size (epoxy) / 35 units batch size (acrylic)
• mmd-2: 10 minutes cycle, 50 units batch size (PUR)
• Curing (batch): oven-1 — 45 minutes cycle, 240 units batch size (epoxy only)
• Dispensing & Filling (flow):
• filler-1: 700 units per hour (epoxy and PUR)
• filler-2: 250 units per hour (acrylic)
• Packaging & Labelling (flow): packer-1 — 800 units per hour (all classes)

Then set the directional changeover times on each machine where transitions between product classes apply:

• reactor-1 (shared): epoxy ↔ acrylic — 20 minutes (both directions)
• mmd-1 (shared): epoxy ↔ acrylic — 20 minutes (both directions)
• filler-1 (cartridge): epoxy ↔ PUR — 10 minutes (both directions)
• packer-1: epoxy ↔ PUR — 10 minutes; epoxy ↔ acrylic — 10 minutes; PUR ↔ acrylic — 10 minutes (all directions)

6. Configure calendars, exceptions, and downtimes. Create two shift calendars:

• Standard day (default): Monday to Friday, 06:00 to 22:00 — assign to reactors, MMD lines, curing oven, and packaging line.
• Extended fill: Monday to Friday, 06:00 to 22:00, plus Saturday 06:00 to 14:00 — assign to both filling lines.

Add three calendar exceptions as non-working days: New Year's Day (1 January), International Workers' Day (1 May), and the year-end shutdown (24 December). Add two machine downtime events: a factory-wide summer shutdown (14–18 July, 06:00–22:00) and a six-hour quarterly maintenance on mmd-2 (20 January, 06:00–12:00).

For step-by-step instructions on configuring each of these in Schantt, see the Schantt documentation.

Common mistakes

1. A single blanket changeover time instead of per-pair entries. Entering one changeover duration for all transitions on a shared machine ignores the direction-specific reality — the shared reactor and metering line require 20-minute purge cycles between epoxy and acrylic, while the cartridge filler and packaging line need only 10-minute format changes. A single blanket value either overestimates or underestimates every transition. Fix: Enter each directional pair separately on the machine's detail page, using the matrix format — one row for epoxy-to-acrylic and one for acrylic-to-epoxy on the shared reactor, and so on for each shared machine.

2. One product class covering all three chemistry families. Creating a single product class called "2-part adhesives" with all three representative products assigned to it prevents the system from applying their different routings, changeover matrices, and capacity parameters. Epoxy, PUR, and acrylic do not share the same processing route or machine eligibility — their differences are exactly what drives realistic scheduling. Fix: Create three separate product classes — Epoxy Structural, Polyurethane Flexible, and Acrylic Fast-Set — and assign each representative product to its correct class.

3. Forgetting to add the bridge transfer times for stage-skipping classes. Polyurethane and acrylic both skip the curing stage. Without a bridging transfer time on the Dispensing & Filling stage from these classes directly to packaging, the system cannot schedule a correct handoff — it either leaves a gap or applies the wrong delay. Fix: On the Dispensing & Filling stage detail page, add two bridge transfer-time entries — Polyurethane Flexible to Packaging & Labelling (1,440 minutes) and Acrylic Fast-Set to Packaging & Labelling (15 minutes).

4. Using the same shift calendar for all machines. Filling lines regularly need Saturday morning to clear the end-of-week dispensing backlog, while reactors, metering, curing, and packaging do not. Assigning the standard Monday-to-Friday day to all machines forces filling jobs to spill into Monday — or forces an unrealistic start. Fix: Create the extended-fill calendar for the two filling lines and keep the standard-day calendar for all other machines.

5. Setting batch-stage parameters on flow-stage machines and vice versa. Batch stages (reactors, metering mixers, curing oven) need a cycle duration and batch size — these determine how many cycles a given quantity requires. Flow stages (fillers, packaging line) need a throughput rate in units per hour. Confusing the two parameter types produces incorrect operation durations and a schedule that does not reflect floor reality. Fix: On each machine's detail page, enter batch parameters for batch-stage machines and throughput for flow-stage machines, matching the stage's production type.

What a good schedule looks like

A well-configured schedule for reactive 2-part adhesives shows all three classes flowing through the shared line with realistic timing — epoxy passing through the curing oven with its finite batch capacity, PUR and acrylic advancing directly from dispensing to packaging through their bridging transfer times, and each chemistry cluster running together to minimise purge cycles between changeovers.

Before (spreadsheet baseline): A manually planned week that treats the facility as a single continuous pipeline with a uniform 30-minute changeover for every transition.

• Changeover time on the shared reactor totals 80 minutes or more on mixed-class days because the planner treats epoxy-to-acrylic and acrylic-to-epoxy purge cycles identically to all other transitions.
• Acrylic jobs get scheduled back-to-back with epoxy on the shared reactor and metering line without clustering — the 20-minute purge cycles multiply across both stages.
• The filling-stage calendar applies Monday-to-Friday only, so a Friday-afternoon dispensing backlog spills unresolved into the following Monday.
• No bridge transfer times differentiate the 24-hour PUR cure from the 15-minute acrylic set — both are handled as manual calendar blocks, adding planner overhead.
• The curing oven's batch capacity is not tracked explicitly, so the planner must manually count units against the 240-unit limit.

After (Schantt Auto mode): The schedule respects each class's routing, machine eligibility, and calibrated changeover times, and the algorithm clusters same-chemistry runs to reduce transition overhead.

• The scheduling algorithm clusters epoxy runs together on the shared reactor and metering line, reducing the number of 20-minute purge cycles — a mixed week that incurred 80 minutes of reactor changeover now completes those transitions in 40 minutes.
• Per-class routing correctly skips the curing stage for PUR and acrylic, applying their bridging transfer times — PUR moves from dispensing to packaging after 1,440 minutes (24 hours), acrylic after 15 minutes — with no gap in the handoff chain.
• The curing oven's 240-unit batch capacity is modelled explicitly: epoxy quantities that exceed 240 are automatically split into consecutive oven batches on the 45-minute cycle.
• The extended-fill calendar gives filling lines Saturday morning availability, clearing the Friday backlog before Monday.