Why Plastic and Rubber Manufacturers Outgrow Spreadsheets
Picture a mid-sized injection moulding plant: twenty presses running around the clock, each fitted with a different mould, each consuming its own mix of resin and colour masterbatch. At the end of every shift the plant manager wants three numbers: how many good parts were made, how many kilograms of material were lost, and what each part actually cost. In many plants those answers arrive a week later, assembled from supervisor sheets and spreadsheets, and they are estimates rather than facts.
Plastics and rubber are high-volume, low-margin businesses. A difference of one halala on a bottle cap is tens of thousands of riyals a year when you make millions of them. Accurate data is not a nice-to-have here. It decides whether you know where you make money or find out from the annual accounts.
The stakes are rising in Saudi Arabia. The National Industrial Strategy, launched by the Crown Prince on 19 October 2022, aims to triple industrial output and reach 36,000 factories by 2035. Competition for packaging, food, construction and automotive contracts will only get tighter, and the converter that knows its true cost per part is the one that can quote with confidence.
This article walks through the problems specific to the sector, how an ERP handles formulations, moulds, scheduling, quality, scrap and costing, a worked cost example for a moulded part, and a practical rollout plan.
The Problems Specific to Plastics and Rubber
Volatile resin prices
Polyethylene, polypropylene and other polymers move with petrochemical markets. Resin is often the largest single cost in the part, so every price movement goes straight to margin. A plant still quoting from a standard cost set a year ago may be selling some lines at a loss without knowing it.
Moulds are expensive, complex assets
A mould can cost tens or hundreds of thousands of riyals. It has a fixed number of cavities, a life measured in shots, and needs regular maintenance. Some belong to customers, not to the plant. Managed in a notebook, moulds fail in the middle of rush orders or simply go missing between the toolroom and the shop floor.
Scrap and regrind
Runners and sprues, rejected parts, start-up purge and colour-change waste can be ground and reused up to an allowed ratio. If none of this is recorded, it disappears from stock and resurfaces as unexplained variances at the next count.
Changeovers eat capacity
Moving from a light colour to a dark one is easier than the reverse, and a mould change can take an hour or more. Running orders in random sequence wastes press hours every day.
Quality is measured in tight tolerances
Part weight, dimensions, wall thickness, Shore hardness for rubber, colour match. A packaging customer may reject a full shipment if container weights drift outside specification.
Rubber adds a compounding stage
Rubber goods go through mixing, then forming, then curing. Each compound has a precise recipe, a cure time and temperature, and a limited shelf life before it must be moulded. That adds a planning layer most industries never deal with.
How an ERP Handles Each Problem
Formulations and bills of materials
A plastic part has a formulation: base polymer, colour masterbatch, additives such as UV stabilisers, and a maximum regrind percentage. The ERP stores this as a percentage-based bill of materials and calculates exact quantities for any production order. Assembled products, such as a container with its cap and label, use multi-level structures. Our guide to the bill of materials covers the fundamentals.
Moulds as tracked assets
Each mould gets a unique asset code, a location, a status (available, in use, under maintenance, disposed) and links to the parts it makes and the presses it fits. Transfers to and from the toolroom are recorded and depreciation is calculated. Tracking shots completed against expected life lets you schedule maintenance before a failure. For more on that, see our article on preventive maintenance.
Production scheduling
Once you can see every open order with its mould, press and colour, you can sequence work to minimise changeovers: group orders that share a mould, run colours light to dark. The schedule shows available capacity per press and flags conflicts before they happen.
Quality at every stage
Resin inspection at receipt, first-article checks at each start-up, periodic in-process checks, and final inspection before dispatch. Results are stored against the production order and material lot, so a customer complaint leads straight to the press, mould, shift and resin batch.
Scrap and regrind recording
Every production order closes with three numbers: good output, rejects and regrind. Regrind enters stock as its own item at a defined cost and is issued to later orders within the permitted ratio. Scrap becomes something you can manage instead of a general feeling that it is "too high".
Inventory that matches reality
Resin arrives in 25 kg bags or bulk containers, sometimes feeding silos shared by several presses. Masterbatch is used in small quantities but is expensive. Finished parts ship in cartons, bags or pallets, sometimes in different pack sizes for different customers. You need multiple units of measure with clean conversions, lot tracking for each resin delivery with its certificate of analysis, clear locations (raw store, press-side staging, finished goods, rejects and regrind) and a proper return movement for material issued but not used. Issuing 500 kg to a press, using 460 kg and never returning the other 40 kg is the most common way plants distort their own costs.
Integrated finance
Material issues, production receipts, scrap and sales post directly to the ledger. Cost of goods sold, inventory value and work in progress are right without month-end journal fixes.
Worked Example: Cost of an Injection-Moulded Cap
The figures below are hypothetical. A plant makes 4 g caps on an 8-cavity mould with a 12-second cycle. Each shot also produces 6 g of runner.
- Shots per hour: 3,600 / 12 = 300.
- Caps per hour: 300 x 8 = 2,400.
- Shot weight: (8 x 4) + 6 = 38 g, so material per hour is 300 x 38 g = 11.4 kg.
| Cost item | Basis | SAR per hour |
|---|---|---|
| Resin | 11.4 kg x SAR 6.50 | 74.10 |
| Colour masterbatch | 2% of material x SAR 25/kg | 5.70 |
| Press and energy | Machine-hour rate | 45.00 |
| Labour | Share of operator and supervisor | 30.00 |
| Mould depreciation | SAR 120,000 over 2 million shots x 300 | 18.00 |
| Total | 172.80 |
With a 2% reject rate, good output is 2,352 caps, so cost is 172.80 / 2,352 = SAR 0.0735 per cap, or SAR 73.50 per thousand.
Now look at what small decisions do to that number:
- Regrinding the 1.8 kg of runner per hour and reusing it within the allowed ratio saves up to SAR 11.70 an hour in virgin resin, bringing cost down to roughly SAR 68.50 per thousand.
- A resin price rise from SAR 6.50 to 7.50 adds about SAR 4.80 per thousand. At 10 million caps a year, that is SAR 48,000.
- Cutting one second off the cycle raises output by about 9% on the same press and labour.
You can do this by hand for one part. A plant with a hundred parts and twenty presses needs a system that pulls actual figures from every production order. Our article on manufacturing costing looks at costing methods in more depth.
Buying Resin When Prices Move
Because resin dominates cost, when and how much you buy are financial decisions. Buying big when prices dip can save money but ties up cash and floor space. Buying only on demand exposes you to price spikes and supply delays. An ERP will not predict prices, but it gives you a firm basis for the decision: net requirements for the coming weeks from confirmed orders and forecast, minus stock and open purchase orders; purchase price history by material and supplier; and a direct link from the new purchase price to product cost.
Hypothetically, a container maker on a fixed-price annual contract sees that a 12% resin increase over two quarters has pushed that contract's margin close to zero. With the numbers documented, it can negotiate a resin-indexed price clause at renewal rather than arguing from impressions.
Rubber Compounding
Rubber parts makers (gaskets, seals, hoses, technical mouldings) share most of these needs but add a critical stage: compound preparation. A compound is mixed from raw rubber, carbon black, oils and curatives in precise ratios and produced in batches. Each batch needs a lot number and test results for hardness and viscosity before release, has a limited shelf life before forming, and carries specific cure parameters. In the ERP, the compound is set up as a semi-finished item with its own bill of materials, used in the bills of the finished parts, and its batches and expiry are tracked much as a food plant tracks sensitive ingredients.
Before and After an ERP
| Area | Without an integrated system | With an ERP |
|---|---|---|
| Product cost | Fixed estimate that ignores resin prices | Actual cost from every order |
| Moulds | Notebook or separate sheet, surprise failures | Asset register with status, location, maintenance |
| Scrap | Shows up as a count variance | Recorded per order and analysed by cause |
| Scheduling | Whiteboard and supervisor experience | Capacity view and changeover-aware sequencing |
| Quality | Paper forms that are hard to retrieve | Results linked to order and lot |
| Purchasing | Order when stock runs out | Requirements calculated from orders and stock |
KPIs Worth Tracking
- Scrap rate by part and press: material issued versus weight of good output.
- Actual versus standard cycle time: persistent drift points to mould or setting problems.
- Changeover time: average minutes lost per mould or colour change.
- Final inspection reject rate: compared across shifts and moulds.
- Output per press hour: a simple way to spot underperforming machines.
- Actual margin by customer: calculated on actual cost, not standard.
A Practical Rollout Plan
- Register every mould first: owner, cavities, parts, presses, current condition.
- Standardise formulations: one approved formulation per part with clear ratios and a maximum regrind percentage.
- Set machine-hour rates: energy, depreciation and maintenance per press so costs are spread fairly.
- Make order close-out mandatory: good, rejects and regrind must be entered or the order cannot close.
- Start with one line: run a group of presses for a full month, fix the setup, then roll out.
- Use barcodes: labels on every resin bag and finished carton cut entry errors and speed up receiving and issuing.
- Record downtime with a reason: breakdowns, waiting for material, mould changes. Otherwise capacity looks higher than it is.
- Review costs monthly: compare actual with standard for your top twenty parts and update prices where needed.
How Tranquil Supports Plastic and Rubber Plants
Tranquil is a cloud ERP whose manufacturing features match what this sector needs: multi-level bills of materials, material planning, production scheduling, quality checks, barcode integration and a production calendar. Moulds can be registered in the asset management module with a unique code, category and status, with transfers between locations tracked and depreciation calculated automatically. All of this connects to inventory, purchasing, sales, financial accounting and ZATCA-compliant e-invoicing.
Every plant runs a little differently, so the team offers customization of screens, reports and approval workflows, plus role-based training. Talk to Tranquil about your plant and get a quote within 24 hours.
Frequently Asked Questions
Is an ERP worth it for a small plastics plant?
Yes, once you make more than a few products and want to know your real cost. Cloud ERP priced per user lets you start with inventory, manufacturing and accounting and add modules later.
How does an ERP handle regrind?
Regrind is recorded as a separate stock item when a production order closes, at a cost set by plant policy, and issued to later orders within the ratio the formulation allows.
Can I track customer-owned moulds?
Yes. Register them in the asset register under their own category so you can track location, status and movements without including them in the plant's depreciable assets.
How do I calculate a machine-hour rate?
Add up a press's annual energy, maintenance, depreciation and floor-space share, then divide by expected running hours. That rate is charged to production orders based on actual hours.
What should I measure first after go-live?
Scrap rate by part and press. It is usually the fastest source of savings and exposes mould and setting problems early.