Production Scheduling for Printing Inks Manufacturing

This guide walks production planners and scheduling managers at printing ink manufacturers through configuring Schantt for a typical mid-market plant — modelling directional colour-change changeovers, parallel bead mills with dedicated and flexible machines, QC-hold delays, and partial transfers across a mixed batch-and-flow pipeline.

This guide follows a fictional composite company built from industry research on printing inks; all names, parameters, and figures are illustrative.

Industry context

Printing ink manufacturing is a batch-and-flow process that transforms pigments, resins, solvents, and additives into finished ink through five sequential stages. Premixing blends pigment powder with resin and solvent into a wet millbase using high-speed dispersers. Dispersion & Milling grinds the premix to target fineness — typically Hegman 6–8 — in horizontal bead mills that consume the bulk of the batch cycle time. Letdown & Colour Matching dilutes the milled base with additional resin and solvent, then adjusts the shade through tinting iterations until it matches the standard. Filtration removes oversized particles and debris through bag or cartridge filters. Filling & Packaging runs the finished ink into pails or drums on semi-automatic fillers, with inline labelling and palletising.

A typical mid-market ink plant produces roughly 4,500–5,000 tonnes annually, split across three broad product classes: high-volume Process CMYK base inks (about 55 % of volume), custom Spot Colours (about 30 %), and Pre-dispersed Bases — high-pigment concentrates sold to smaller ink houses (about 15 %). Changeover times vary significantly by colour transition: cleaning a bead mill or letdown tank from a dark colour to a light one takes 45–120 minutes, while the reverse light-to-dark direction takes only 15–30 minutes. A black-to-yellow changeover, for instance, runs roughly 90 minutes. Every batch also waits for quality-control (QC) release between letdown and filtration, a passive hold of 1–4 hours that adds forward delay but no machine work.

Pinnacle Printing Inks runs about 85 people at a 4,200 m² facility, making three product classes across five production stages, scheduled by a three-person planning team.

Process overview

flowchart LR
    PM["Premixing <br/>(BATCH)"]
    DM["Dispersion & Milling <br/>(BATCH)"]
    LD["Letdown & Colour Matching <br/>(BATCH)"]
    FL["Filtration <br/>(FLOW)"]
    FG["Filling & Packaging <br/>(FLOW)"]

    PM --> DM
    DM --> LD
    LD --> FL
    FL --> FG

Process flow through the five production stages at Pinnacle Printing Inks, from raw material premixing through to finished goods.

Pre-dispersed Bases skip both premixing and dispersion, entering at the Letdown stage.

Scheduling challenges and how Schantt handles them

Schantt assumes production is driven by a fixed demand schedule — a list of products with quantities to be produced over a horizon. If your plant is driven by make-to-order releases or kanban pull, the same configuration works; you enter jobs as they are released. The optimizer minimises total production time (makespan) across all jobs and schedules forward from a chosen start date. For this scenario, a one-week horizon with roughly 15–20 jobs is typical. Schantt offers two optimisation modes: Auto mode, where the algorithm decides both job sequence and machine assignments from scratch, and Semi-Auto mode, where the planner sets the job order and the algorithm optimises machine assignments within that fixed sequence.

What Schantt handles well

• Directional changeover matrix — Per-machine, per-pair changeover times where dark-to-light and light-to-dark durations differ, so the algorithm favours sequences that group similar colours together.
• Multi-machine stages with dedicated and capability-restricted machines — Parallel bead mills, letdown tanks, and fillers where each machine's eligibility for a product class is expressed by which rate entries exist; a light-dedicated mill simply has no entries for dark colours.
• Per-class routing with stage skipping — Each product class follows its own path through the stages; Pre-dispersed Bases skip dispersion entirely and enter at letdown, with a bridging transfer time across the skipped span.
• Mixed batch-and-flow pipelines — Batch stages (premixing, dispersion, letdown) and flow stages (filtration, filling) in one route, each typed correctly so the algorithm applies the right duration physics to each step.
• Partial transfers between stages — A downstream stage can start on the first usable portion while the upstream stage is still running, configured per class at each handoff.
• Shift-aware availability with multiple calendars — Machine-level calendar overrides let bead mills run unattended overnight while fillers follow standard day shifts; calendar exceptions and downtimes adjust working windows.

How Schantt handles each challenge

1. Directional colour-change changeovers.
- A typical 20-job week across three bead mills spends 12–15 hours on changeover time — roughly 15–20 % of available mill capacity. Dark-to-light cleanouts are two to four times longer than light-to-dark transitions, so the job sequence directly drives how much mill time is lost to cleaning.
- Schantt models each changeover as a directional, per-machine entry: you enter the measured cleanout time from every product class to every other class on each bead mill and letdown tank. The algorithm folds these durations into the total production time it minimises, so it naturally sequences jobs to group similar colours together — placing a light-yellow batch after another light colour rather than after black — because that sequence carries a shorter changeover penalty. On the Gantt, changeovers appear as labelled segments ahead of each processing bar, so the time impact is visible.

2. Parallel bead mill assignment across colour families.
- Bead mills consume 60–70 % of total batch cycle time, yet current whiteboard-based scheduling achieves only 70–75 % mill utilisation, with 8–12 hours per week of mill-idle time caused by assigning jobs to colour-incompatible mills. A dark-dedicated mill forced to run a light colour triggers a long changeover that may have been avoidable on the flexible mill.
- Each bead mill's capability is expressed simply by which rate entries it carries. Bead Mill 1 (the light-dedicated mill) has entries for Process CMYK and light Spot Colours only; Bead Mill 2 (the dark-dedicated mill) has entries for dark Spot Colours only; Bead Mill 3 (the flexible mill) has entries for all three classes. In Auto mode, the algorithm matches each job to an eligible mill and sequences jobs to minimise changeover penalties across all three mills simultaneously. In Semi-Auto mode, it preserves the planner's job order but still chooses the best mill for each job, recovering utilisation without requiring the planner to reassign machines manually each week.

3. QC-hold forward delays.
- Every batch sits idle for 1–4 hours between letdown and filtration while QC verifies the shade and viscosity. On a typical 15-batch week, this creates 15–30 hours of passive forward delay that upstream stages cannot see and downstream stages must wait through. The hold is a scheduled gap, not a machine doing work, and it shifts the entire downstream schedule.
- Schantt models the QC hold as a transfer time — a fixed forward delay between the letdown and filtration stages, set to 90 minutes for this scenario. The delay applies to every job crossing that handoff and appears on the Gantt as a gap between the two stage bars with no machine assigned. Upstream stages schedule in the full knowledge of this delay, and downstream stages start only after the hold elapses. The value is a planner-set baseline per product class; if your plant data shows systematic differences — for instance, Spot Colours needing a longer hold — you can adjust the duration on the Stage detail page.

4. Filler changeover variety.
- The two fillers — one dedicated to pails (1–20 L) and one to drums and totes (200 L and 1,000 kg) — face three kinds of changeover: format-only (e.g. 1 L to 5 L pails, 15–45 minutes), ink-type change on the same format (15–30 minutes), and a full format-plus-ink switch (30–90 minutes). These transitions cause 2–4 filler-idle events per week, totalling 2–5 hours of lost throughput that is invisible in a simple changeover average.
- Each filler carries a directional changeover matrix with entries for every product-class pair, so the algorithm uses the correct duration whether the switch is between two Process CMYK jobs (minimal cleanout) or from a dark Spot Colour to a light Pre-dispersed Base (longer). The pail filler's changeovers for CMYK-to-Spot (22 minutes), Base-to-Spot (22 minutes), and other transitions are all entered as distinct values. Because the algorithm sees the real durations, it can sequence filler jobs to minimise transition time — for instance, grouping pail runs by type to avoid a full format-plus-ink change mid-shift.

5. Letdown-to-filler flow mismatch.
- Process CMYK batches finish letdown at 1,000 kg, but the filler throughput rates (340 kg/hr for pails) mean a full batch cannot finish filling in one shift if it arrives late in the day. Currently each CMYK batch creates roughly 90–120 minutes of avoidable filler idle time as the filler waits for the next batch to arrive from letdown, totalling 6–10 hours per week. The filler starves while letdown tanks hold finished-but-unreleased product.
- For Process CMYK, the routing enables a partial transfer at the letdown-to-filtration handoff: 500 kg transfers from the letdown tank to filtration as soon as that portion is ready, while the remaining 500 kg continues processing. This lets the downstream stages — filtration and filling — begin on the first portion while the second half finishes. The partial transfer quantity is set per class (500 kg for Process CMYK; Spot Colours and Pre-dispersed Bases use full-batch transfers), and the algorithm schedules the overlap automatically, recovering filler throughput that would otherwise sit idle waiting for a complete batch.

What to model in Schantt

The table below lists every first-class entity you create as a top-level object in Schantt, with counts drawn from this scenario.

Step-by-step setup

1. Create the stages in order. Create five stages with production type set to BATCH for the first three (Premixing, Dispersion & Milling, Letdown & Colour Matching) and FLOW for the last two (Filtration, Filling & Packaging). Set the stage positions from 1 to 5. Then, on each Stage detail page, add the transfer times between consecutive stages:

• Premixing → Dispersion: 10 minutes
• Dispersion → Letdown: 20 minutes
• Letdown → Filtration: 90 minutes (the QC hold)
• Filtration → Filling: 10 minutes
• Premixing → Letdown: 45 minutes (the bridging transfer for Pre-dispersed Bases that skip dispersion)

2. Add the machines to each stage. Assign thirteen machines to their respective stages:

Premixing stage: Premix Disperser 1, Premix Disperser 2
Dispersion stage: Bead Mill 1 (light-dedicated), Bead Mill 2 (dark-dedicated), Bead Mill 3 (flexible)
Letdown stage: Letdown Tank 1 (light-dedicated), Letdown Tanks 2–4 (general-purpose)
Filtration stage: Bag Filter 1, Cartridge Filter 1
Filling stage: Pail Filler 1, Drum Filler 1

3. Define the product classes and their routings. Create three product classes. For each class, set the routing — the ordered list of stages it passes through:

• Process CMYK: all five stages, with partial transfer enabled at the letdown → filtration handoff (500 kg).
• Spot Colours: all five stages, full-batch transfers only.
• Pre-dispersed Bases: letdown → filtration → filling only. Premixing and dispersion are absent from the routing; the bridging transfer time (45 minutes from premixing to letdown) already accounts for the skip span.

4. Add one representative product per class. Create Process Cyan (Process CMYK), Pantone 185 Red (Spot Colours), and Carbon Black Base (Pre-dispersed Bases). Assign each a display colour for Gantt visibility.

5. Set machine capacity parameters and changeovers. On each machine's detail page, enter the rate entries and changeover times.

Batch-stage rate entries (batch size and cycle duration):

• Premix Dispersers 1 and 2: 750 kg, 38 min (Process CMYK); 350 kg, 26 min (Spot Colours)
• Bead Mill 1 (light-dedicated): 750 kg, 175 min (Process CMYK); entries for light Spot Colours only
• Bead Mill 2 (dark-dedicated): 750 kg, 165 min (Process CMYK); 350 kg, 175 min (dark Spot Colours only)
• Bead Mill 3 (flexible): 750 kg, 185 min (Process CMYK); 350 kg, 235 min (Spot Colours)
• Letdown Tanks 1–4: entries for all product classes their routing reaches — 1,000 kg, 55 min (Process CMYK); 500 kg, 95–100 min (Spot Colours); 800 kg, 65 min (Pre-dispersed Bases)

Flow-stage throughput entries (kg/hr):

• Bag Filter 1: 680 (CMYK), 460 (Spot), 520 (Base)
• Cartridge Filter 1: 570 (CMYK), 390 (Spot), 440 (Base)
• Pail Filler 1: 340 (CMYK), 285 (Spot), 4 (Base)
• Drum Filler 1: 8 (CMYK), 16 (Spot), 12 (Base)

Changeover entries: Add directional changeover times on every machine that processes multiple product classes. The key entries are on the bead mills (asymmetric dark-to-light vs light-to-dark, ranging from 35 to 68 minutes on different mills) and the letdown tanks (25–52 minutes). The premix dispersers carry a symmetric 10-minute changeover for batch-to-batch class transitions. The filter units use a symmetric 15-minute changeover. Both fillers carry the full matrix of product-class pairs with durations ranging from 22 to 45 minutes.

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

• Standard calendar (default, all machines): Monday–Friday 07:00–16:00, Saturday 07:00–12:00. Non-working days have no entry.
• Night-shift mill override (bead mills only): Monday–Thursday 22:00–06:00. Assign this calendar to Bead Mill 1, Bead Mill 2, and Bead Mill 3 so they can run unattended overnight while the rest of the plant follows the standard day shift.

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 through 2 January, entered as a single exception for 24 December).

Add three machine downtimes: a monthly bead charge inspection on Bead Mill 1 (four hours), a quarterly all-mills maintenance window affecting all three mills (eight hours), and a weekly filler line flush on Pail Filler 1 (two hours). These windows are subtracted from working capacity before scheduling so the algorithm routes work around them automatically.

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

Common mistakes

1. Entering symmetric changeover durations on bead mills. A single average cleanout time across all colour transitions loses the directional information the algorithm needs. The algorithm will not penalise a dark-to-light sequence correctly, so the optimiser may produce a sequence that looks good on paper but requires a 90-minute cleanout between two jobs that could have been grouped differently. Fix: Enter the measured cleanout time for each direction — dark-to-light separately from light-to-dark — as distinct changeover entries on each bead mill and letdown tank.

2. One product class for all colour families. Defining a single "Ink" product class forces every product through the same routing and applies uniform changeover values, so the stage-skipping behaviour of Pre-dispersed Bases is lost and changeover times across incompatible colour families are averaged. Fix: Split product classes by routing and colour-family behaviour — Process CMYK, Spot Colours, and Pre-dispersed Bases each as their own class — so each inherits the correct stage path and changeover matrix.

3. Missing per-class rate entries on dedicated machines. Bead Mill 1 (light-dedicated) should carry entries only for Process CMYK and light Spot Colours. If you mistakenly add entries for dark Spot Colours as well, the algorithm may assign dark jobs to the light-dedicated mill, triggering a long changeover that undermines the dedication strategy. Fix: Review each machine's rate entries to ensure they reflect actual floor capability. If a machine cannot process a product class, leave that rate entry blank — the algorithm will not assign jobs to it.

4. Modelling the QC hold as a stage rather than a transfer time. If you create a QC stage with a long cycle time, the algorithm assigns a machine to it, creating an artificial resource bottleneck and consuming capacity that does not exist. The hold is a passive wait, not a machine step. Fix: Use a transfer time of 90 minutes between Letdown and Filtration on the Stage detail page. No machine is consumed, and the hold appears as a scheduled gap on the Gantt.

5. Using a single blanket calendar for all machines. Assigning the same Monday–Friday day-shift calendar to every machine loses the overnight running capacity of the bead mills. A single bead mill running overnight adds roughly 32 hours per week of mill capacity that the algorithm can use. Fix: Create a separate night-shift calendar (Monday–Thursday 22:00–06:00) and assign it to the three bead mills via the machine-level calendar override on each mill's detail page.

What a good schedule looks like

Scroll through the Gantt for a typical 20-job week built in Auto mode. The schedule shows a coherent production flow where colour-group sequencing and machine assignments work together rather than against each other.

Before (baseline whiteboard scheduling):
- Bead mill utilisation holds at 70–75 %, with 8–12 hours per week of avoidable mill-idle time from colour-group mismatch — a dark Spot Colour sitting on the flexible mill while the light-dedicated mill finishes a CMYK job, then the flexible mill needing a long changeover for the next light-colour run.
- Changeover time consumes 12–15 hours per week across the bead mills alone.
- The filler sits idle for 6–10 hours per week while upstream letdown batches finish and QC holds expire, with no mechanism to release product in partial quantities.
- The QC hold of 15–30 hours of forward delay per week is invisible — it shows up only as unexplained gaps between letdown end-times and filtration start-times on the whiteboard.

After (Schantt Auto mode):
- Bead mill colour-group sequencing improves utilisation above 80 %: light colours route to Bead Mill 1, dark colours to Bead Mill 2, and the flexible mill handles overflow and class-spanning jobs, with changeover durations folded into the optimisation so the algorithm naturally groups similar colours.
- Changeover time across the three bead mills drops measurably — the optimiser avoids the long dark-to-light transitions where possible by sequencing light-colour jobs consecutively on the light-dedicated mill.
- The filler begins working earlier in each cycle because the 500 kg partial transfer at the letdown-to-filtration handoff releases product in two halves: the first 500 kg flows downstream while the second half completes, recovering the 6–10 hours per week of avoidable filler wait.
- The QC hold is visible as a scheduled gap on each job's Gantt row, so the planner knows exactly when each batch will reach filtration and can communicate release timing to the QC lab.