Production Scheduling for Rubber Products (Non-Tire)

Production schedulers and operations managers at non-tire rubber plants know the difficulty of coordinating a hybrid batch-and-flow pipeline where compound cleanout times, press cure cycles, and multi-machine stages all pull the schedule in different directions. This guide walks through scheduling a representative non-tire rubber facility in Schantt — modeling directional changeovers for polymer and filler swaps, parallel extruders and presses with capability restrictions, and separate calendars per stage area — so you can set up your own plant and see a realistic schedule in minutes.

This guide follows a fictional composite company built from industry research on rubber products (non-tire); all names, parameters, and figures are illustrative.

Industry context

Non-tire rubber manufacturing produces a vast catalogue of engineered goods — extruded weatherseals and hoses, molded gaskets and oil seals, compression-mounted engine and anti-vibration components — all sharing a common family of processes. A typical mid-market plant runs a hybrid pipeline that begins with compounding (mixing raw polymers, fillers, curatives, and plasticisers in an internal Banbury mixer, then sheeting off on a mill), followed by warming, forming (extrusion, pre-forming, or both), curing (vulcanisation by continuous vulcanisation line or press), and finishing (deflashing, trimming, inspection, packaging). What makes rubber scheduling distinct is the sequence-dependent changeover landscape: every polymer, filler, and cure-system combination carries a different cleanout duration, and presses incur additional mold-swap and temperature-recovery penalties between product families. A non-tire plant running three product classes — an EPDM weatherseal profile (extruded, CV-line cured), an NBR oil seal (pre-formed, press-cured), and an NR engine mount (full route, press-cured) — across seven production stages with fifteen machines needs a schedule that respects these constraints simultaneously.

Apex Elastomer Products runs approximately 85 people at a 3,200 m² facility, making three product classes — EPDM profiles, NBR oil seals, and NR engine mounts — across seven production stages, scheduled by a small planning team. The plant operates a predominantly engineer-to-order model (approximately 75 % of orders) with the balance made to stock, quoting lead times of 4 to 6 weeks at a planning horizon of the same span. Order quantities range from 1,000 to 15,000 pieces for moulded goods and 500 to 3,000 linear metres for extruded profiles. Compound batches weigh 120–180 kg with Banbury mix cycles of 5–8 min per batch; warming mills run at 3–5 min per batch. Extruder throughput spans 80–140 kg/h, the salt-bath CV line runs at 6–12 m/min, and press cure cycles range from 8–15 min depending on section thickness and compound. Cure temperatures sit between 160–180 °C for sulfur-cured compounds and 170–200 °C for peroxide-cured grades.

Process overview

flowchart LR
  CO["Compounding<br/>(BATCH)"] --> WM["Warming Mill<br/>(BATCH)"]
  WM --> EX["Extrusion<br/>(FLOW)"]
  EX --> CV["CV Line Curing<br/>(FLOW)"]
  CV --> FI["Finishing & Inspection (FLOW)"]
  EX --> PF["Pre-forming<br/>(BATCH)"]
  PF --> PC["Press Curing<br/>(BATCH)"]
  PC --> FI

The production process at Apex Elastomer Products moves through seven stages — compounding, warming mill, extrusion, pre-forming, CV line curing, press curing, and finishing — with each product class following its own route through the line.

The NBR oil seal class enters the process at pre-forming, skipping compounding and warming, with a 20-minute bridging transfer time from goods-in receipt to the pre-forming stage.

Scheduling challenges and how Schantt handles them

This scenario assumes orders as the primary demand driver, consistent with the plant's predominantly engineer-to-order profile. Plants running make-to-stock can substitute a finished-goods replenishment trigger — the scheduling mechanics are identical once the job list exists. The scheduling algorithm minimises total production time — the overall completion window from the first operation to the last — by optimising job sequence across the seven-stage pipeline. It schedules forward from a start date and respects every modelled constraint (changeovers, calendars, transfer times). For this guide the practical horizon is 4 to 6 weeks. Schantt offers two modes: Auto mode, where the system selects both job sequence and machine assignments, and Semi-Auto mode, where the planner fixes the job order and the system optimises machine assignments within that sequence.

What Schantt handles well

• Sequence-dependent changeovers — model directional compound cleanout durations (polymer-to-polymer, filler-directional, cure-system-swap) so the algorithm favours sequences with lower changeover overhead.
• Thermal recovery as changeover time — model the predictable wait when a press transitions between differing cure-temperature set-points as a directional changeover, so the algorithm groups same-temperature runs.
• Multi-machine stages with capability-restricted machine assignment — assign jobs across parallel extruders, curing presses, and CV lines while restricting each product class to only the machines that can physically run it (dedicated extruders for specific compound types, presses sized by tonnage).
• Per-class routing with stage skipping and mid-route entry — define each product class's own route through the stage sequence, skipping compounding or warming for pre-compounded stock, with bridging transfer times for the skipped span.
• Separate calendars per stage area with calendar exceptions and downtimes — assign different shift patterns to each stage (24/5 continuous mixing and CV line, two-shift curing presses, day-shift finishing) and schedule planned maintenance windows and shutdowns.
• Mixed batch-and-flow pipelines — route a product class through both batch stages (compounding, press curing) and flow stages (extrusion, CV line, finishing) in a single ordered path with correct stage-type timing.

How Schantt handles each challenge

1. Directional compound changeovers across polymer and filler families.

• Every polymer swap on the mixing line carries a different cleanout duration: EPDM to NR compound on Banbury Mixer 1 takes 75 min of purge and sweep-out; warming-mill changeovers between the same classes add 15 min for residual-strip clearing. A scheduler working manually or with a spreadsheet tends to apply a single average changeover penalty to all transitions, losing the opportunity to group compatible runs.
• Schantt models each directional changeover as a per-machine, per-pair duration on the Machine detail page. The planner enters the minute value for each direction — 75 min for both EPDM→NR and NR→EPDM on the Banbury, 15 min for each direction on each warming mill — and the algorithm automatically favours sequences that keep like polymers together, reducing the total time spent in changeover.

2. Press mold changes and temperature recovery between cure set-points.

• On a shared press such as Press 2 (medium-duty, 200 ton), switching from an NBR oil seal to an NR engine mount requires changing the mold (25 min including the swap and platen adjustment) and recovering the cure temperature if the set-points differ (12–18 min of thermal stabilisation rolled into the same changeover window). Without directional modeling, the planner applies a flat changeover penalty and either overestimates or underestimates the actual delay.
• The same per-pair changeover mechanism on the Machine detail page captures the combined mold-swap and temperature-recovery duration. The planner enters 25 min for both NBR→NR and NR→NBR on Press 2. The algorithm then groups same-temperature product runs where that shortens total production time, and the combined penalty for a switch is reflected accurately in the schedule.

3. Parallel extruders and presses with capability-restricted machine assignment.

• Extruder 1 is dedicated to EPDM compounds (100 kg/h throughput); Extruder 2 runs at 120 kg/h but can also handle EPDM. Press 1 (300 ton) is the only press rated for heavy engine mounts; Press 3 (100 ton) is dedicated to small NBR oil seals; Press 2 (200 ton) can run both oil seals and engine mounts. A planner manually assigning jobs across these machines must track each machine's eligibility and balance load — a time-consuming constraint check that is easy to get wrong under pressure.
• Schantt models machine capability through rate entries: a machine that cannot run a product class simply has no throughput or processing-time entry for that class. The planner enters values only on compatible machines — Extruder 1 gets throughput only for the EPDM class, Press 1 gets processing times only for the NR class, Press 3 only for the NBR class — and the algorithm automatically assigns each job to a capable machine in Auto mode. The resulting schedule shows every job on a verified-compatible machine.

4. Pre-compounded stock entering mid-route with a bridging transfer.

• The NBR oil seal class skips compounding and warming entirely; pre-compounded NBR stock arrives from an external supplier and enters the line at the pre-forming stage. Without an explicit handoff delay across the skipped span, the schedule would assume the material arrives instantaneously at the pre-form cutter as soon as the job starts.
• Schantt requires a bridging transfer time for mid-route entry. The planner configures a 20-minute transfer from compounding (the implied upstream boundary) to pre-forming on the Stage detail page. That 20-minute window models the goods-in receipt, inspection, and staging delay before the pre-compounded stock reaches the cutter. The routing for the NBR oil seal class defines only three active stages — pre-forming, press curing, and finishing — and the bridging transfer fills the timing gap naturally.

5. Calendar gaps between continuous mixing and shift-based downstream stages.

• The compounding and CV line areas run 24 h per day, five days per week (continuous three-shift rotation), while the press-curing area operates two shifts (06:00–22:00, Monday to Friday) and finishing runs a single day shift (07:00–15:30). A compound batch finished on the Banbury at 23:00 on Thursday is ready for pressing, but no press operator is available until 06:00 Friday. A planner tracking these calendar boundaries manually must advance every handoff across the gap — a tedious reconciliation step that is easy to miss at volume.
• Schantt assigns a distinct calendar to each stage or area: 24/5 continuous to compounding, the CV line, and warming mills; two-shift to curing presses; day-shift to finishing. The schedule automatically computes that a job finishing compounding at 23:00 cannot begin press curing until the next working shift opens. The Gantt shows a wait-material segment spanning the calendar gap, and the planner sees the reason in the operation tooltip — no manual shift arithmetic required.

What to model in Schantt

The five first-class entities below are the building blocks every planner creates as top-level objects. Sub-configuration — routings, changeovers, transfer times, calendar exceptions, and machine downtimes — is set on each entity's detail page and is described in the step-by-step setup that follows.

Step-by-step setup

1. Create the seven stages and set transfer times between them. Define each stage in the order material flows — Compounding, Warming Mill, Extrusion, Pre-forming, CV Line Curing, Press Curing, Finishing & Inspection — and set the production type (BATCH for compounding, warming, pre-forming, press curing; FLOW for extrusion, CV line, finishing). Then configure the transfer times between each successive pair on the Stage detail page:

• Compounding to Warming Mill: 10 min (batch-off cooling conveyor)
• Warming Mill to Extrusion: 5 min (warmed strip transfer)
• Warming Mill to Pre-forming: 5 min (warmed strip transfer to cutter)
• Extrusion to CV Line: 2 min (inline profile-to-CV entrance)
• CV Line to Finishing: 10 min (cool-down spray and transfer)
• Pre-forming to Press Curing: 10 min (tray transfer of blanks)
• Press Curing to Finishing: 15 min (parts moved to deflashing)
• Compounding to Pre-forming: 20 min (bridging transfer for mid-route NBR entry)

2. Add the fifteen machines to their respective stages. Assign each machine to its stage: two Banbury mixers and two warming mills to the batch stages, two extruders to extrusion, one pre-form cutter to pre-forming, the salt-bath CV line to curing, three presses to press curing, and four finishing-station machines to finishing (cryogenic deflasher, trimming bench, inspection bench, packaging station).

3. Create the three product classes and define each class's routing with stage skipping. Start with EPDM Weatherseal Profile (unit: piece), NBR Oil Seal, and NR Engine Mount. On the Product Class detail page, configure the per-class routing — EPDM passes through compounding → warming → extrusion → CV line → finishing (five stages). NR engine mount passes through compounding → warming → pre-forming → press curing → finishing (five stages). NBR oil seal enters at pre-forming, skipping compounding and warming (three stages). The bridging TransferTime from compounding to pre-forming (set in step 1) ensures the skipped span has a non-zero handoff delay. All partial-transfer toggles remain off — material flows at full batch completion.

4. Add one representative product per class. Create one product for each class with a display colour for the Gantt. This is enough to build and run a schedule that demonstrates the full routing and changeover logic. In your own plant you would add all active SKUs, each inheriting its class's routing and rate entries.

5. Set each machine's capacity parameters and changeovers on the Machine detail page. After the product classes exist, enter batch parameters for batch-stage machines and throughputs for flow-stage machines:

• Banbury Mixer 1 — compounding: batch size 150 kg, cycle 6.5 min (EPDM) and 7 min (NR). Directional changeovers: 75 min both directions between EPDM and NR.
• Banbury Mixer 2 — compounding: leave the rate entries for EPDM, NBR, and NR absent. This second mixer is reserved for light-coloured and food-grade compounds outside this scenario's three classes — the same capability-restriction pattern used for Extruder 1, Press 1, and Press 3, applied here to a machine that currently serves none of the demonstrated classes.
• Warming Mills 1 and 2 — warming: batch size 150 kg, cycle 4 min for both EPDM and NR. Changeovers: 15 min per direction between EPDM and NR on both mills.
• Extruder 1 — extrusion: throughput 100 units/h (EPDM only — no entry for other classes, so Extruder 1 is dedicated to EPDM).
• Extruder 2 — extrusion: throughput 120 units/h (EPDM only).
• Pre-form Cutter 1 — pre-forming: batch size 25 kg / cycle 4 min (NBR) and 50 kg / cycle 5 min (NR). Changeovers: 10 min each direction between the two classes.
• Salt-Bath CV Line — curing: throughput 220 units/h (EPDM).
• Press 1 — heavy-duty press curing: batch size 50 kg, cycle 15 min (NR only — no NBR entry, dedicated to engine mounts).
• Press 2 — medium press curing: batch size 25 kg / cycle 12 min (NBR) and 50 kg / cycle 15 min (NR). Changeovers: 25 min each direction between the two classes.
• Press 3 — small press curing: batch size 25 kg, cycle 12 min (NBR only).
• Finishing machines (cryogenic deflasher, trimming bench, inspection bench, packaging station): throughputs ranging from 35 to 350 units/h per class, entered only on machines each class can reach.

6. Configure calendars, exceptions, and downtimes. Create three calendars and assign them:

• 24/5 Continuous: three rotating eight-hour shifts, Monday 00:00 through Saturday 00:00. Assign to compounding, warming, extrusion, and the CV line.
• 2-Shift Curing: shift A 06:00–14:00, shift B 14:00–22:00, Monday through Friday. Assign to the three curing presses.
• Day-Shift Finishing: single shift 07:00–15:30, Monday through Friday. Assign to all finishing machines.

Add three calendar exceptions for team-wide non-working days: New Year's Day (1 January), International Workers' Day (1 May), and a year-end shutdown beginning 24 December. Then add three machine-downtime entries: a weekly press-maintenance window (Saturday 06:00–14:00, factory-wide), a bi-weekly Banbury teardown cleanout (Saturday 06:00–14:00, Banbury Mixer 1 only), and the annual facility shutdown (24 December through 31 December, factory-wide).

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

Common mistakes

1. Using a single blanket changeover duration instead of directional per-pair values. Applying one average changeover penalty to every transition on the Banbury or the presses ignores the real directional variance between different polymer and cure-system pairs. The algorithm sees the same time penalty for every swap and loses the ability to group compatible runs. Fix: enter a distinct duration per directional pair on the Machine detail page — 75 min for each direction between EPDM and NR on the Banbury, 25 min for each direction between NBR and NR on Press 2 — and let the algorithm reward shorter transitions naturally.

2. Putting products with different routes into a single product class. If the EPDM profile (5-stage route through the CV line) and the NR engine mount (5-stage route through press curing, skipping the CV line) shared one class, the routing would be identical for both and neither would reach its correct curing stage. Fix: create a separate product class per distinct routing — one for the CV-line profile, one for the press-cured oil seal, one for the press-cured engine mount — even if the compounds share a polymer family.

3. Forgetting the bridging transfer time for a mid-route product class. Without an explicit transfer time spanning the skipped stages, the NBR oil seal's handoff from goods-in receipt to the pre-forming stage defaults to zero minutes — the schedule assumes the material teleports to the cutter. Fix: configure a bridging TransferTime from the skipped span's boundary (compounding) to the first active stage (pre-forming), set to 20 min to model receipt, inspection, and staging delay.

4. Assigning the same calendar to the mixing area and the press area. A single 24/5 calendar for every stage ignores the reality that presses run two shifts and finishing runs one. Compound finished on the night shift has no press operator available for hours, but a single-calendar schedule would let it proceed immediately. Fix: assign separate calendars — 24/5 continuous to mixing, warming, extrusion, and the CV line; two-shift to presses; day-shift to finishing — and let the schedule compute the correct calendar-gap pauses.

5. Populating rate entries on a machine that cannot physically run the product class. If a throughput entry exists for the NBR oil seal on Press 1 (heavy-duty, 300 ton), the algorithm may assign an oil seal to a press that is oversized for the job and needed for heavier engine mounts. Fix: leave the product class's throughput and processing-time rows absent on incompatible machines — Extruder 1 carries only EPDM entries, Press 1 carries only NR entries, Press 3 carries only NBR entries — and the algorithm will never assign a job to a machine that lacks the matching rate entry.

What a good schedule looks like

A well-configured schedule in Schantt shows each product class flowing through its correct route, with changeover-driven sequences, calendar-respecting handoffs, and machine assignments that match floor capability.

Before (manual scheduling or spreadsheet): The planning team spends significant effort sequencing jobs to minimise cleanout penalties, tracking which extruders and presses are available for each product class, and manually advancing handoff times across calendar shifts. Common symptoms include:

• Changeover times estimated as flat averages, resulting in either optimistic timelines or excessive buffer padding
• Presses idle while the Banbury produces compound on the night shift that no one is staffing until morning
• Occasional mismatched machine assignments that are caught only during shift handoff or pre-production review
• Schedule updates that take most of a day because every downstream operation must be manually re-shifted when a single job changes

After (Schantt Auto mode): The schedule is built in seconds from the same job list, with all constraints evaluated simultaneously:

• The algorithm groups same-polymer runs on the Banbury to minimise the 75-minute cleanout between EPDM and NR, and sequences press runs so NBR-to-NR transitions (25 min) do not interrupt a long EPDM production block
• Compound finished at 23:00 on Thursday enters the press stage with an automatic wait-material pause until the two-shift calendar opens at 06:00 Friday — no manual advance needed
• EPDM jobs are assigned only to Extruder 1 or 2 (both throughput-configured), engine mounts only to Press 1 or 2, oil seals only to Press 2 or 3 — verified automatically by the absence of rate entries on incompatible machines
• The Gantt shows each operation on its assigned machine with changeover, processing, and wait-material segments clearly colour-coded, and calendar exceptions and downtime windows render as non-working overlays