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CUSTOM SOFTWARE · MRP AND MRP II

MRP and MRP II: Material and Capacity Planning

Working from your bill of materials (BOM), we calculate which material is needed, in what quantity and by when; then we deduct stock on hand, open orders and lead times to produce dated order proposals for purchasing. With the MRP II layer we also test the same plan against machine capacity and labour.

Purchasing's hardest question is always the same: what should I order, how much of it, and by what date at the latest. In most factories the answer comes out of a foreman's experience, the production manager's guess and an Excel file kept on someone's desktop. This method carries the business for a while, but it turns out expensive in both directions. On one side the line stops because a single ancillary material was ordered too late; the team then brings it in on an emergency order, at a high price and sometimes by air freight. On the other side, raw material bought in excess on the reflex of never running short again piles up in the warehouse and cash is locked into stock. Both situations come from the same gap: the requirement was never calculated, only estimated.

What is missing is not really software, but the data the calculation rests on. Material requirements planning (MRP) is built on the bill of materials (BOM) and on lead time data. On the shop floor, however, the BOM is usually out of date; the product has changed, the recipe has been updated in someone's head but never written into the system. Scrap rates are not recorded, the alternative material is knowledge only the buyer holds, and lead times shift according to whatever the supplier promises. That is why in many companies the MRP module in the ERP does exist but is never run: it was tried once, the proposal list it produced did not match reality, confidence was lost and the file was closed. The source of the problem is not the module itself, but the data feeding it.

At its core the MRP calculation is a simple chain. Sales orders and the production plan give the gross requirement; the BOM explodes that requirement down to the component level. Stock on hand, open purchase orders not yet received and quantities reserved for other jobs are then deducted; what remains is the net requirement. In the final step the system counts back by the lead time and finds the latest date on which the order must be placed. Safety stock, minimum order quantity and lot sizing rules are layered on top. The output is not a list but a dated action plan: which material, in what quantity, from which supplier and by which day at the latest it must be ordered.

MRP II, that is manufacturing resource planning, adds the resource dimension on top of that calculation. The material may well be sufficient; but are the machine hours, the tooling and the shifts available to do the work? MRP II tests the plan for rough-cut capacity: which work centre is overloaded in which week, and can the delivery date you quoted actually be met. The boundary has to be drawn clearly here. MRP and MRP II answer the how much and by when question; which job runs on which machine, in what sequence and with which tooling changeover is a matter for advanced planning and scheduling, and that is separate work. Finally, an honest warning: MRP on its own does not reduce stock, and no calculation repairs bad data. If the bill of materials and the lead times are not correct, the proposal that comes out will be wrong too.

Who is it for?

Who is Material Requirements Planning (MRP / MRP II) a good fit for?

Manufacturers with multi-item bills of materials

Companies in machinery, metalworking, furniture and assembly-led production, where a single product is made up of dozens or even hundreds of sub-components. In this structure a single missing fastener stops the shipment. Calculating the requirement by hand is practically impossible; the margin for error grows with the number of parts and nobody can find where the error is.

Businesses using long lead time materials

Businesses that import their raw material or use components made to order. Here a delay cannot be made up: when an order is placed a week late, production does not slip by a week but by the full lead time. Recording the lead time per material and feeding it into the calculation is the single change with the highest return in these companies.

Businesses using the same raw material across many products

Textile, plastics, food and packaging operations where a shared raw material circulates through different products. In these businesses the same stock is counted towards more than one order, and material assumed to be in the warehouse has in fact been allocated to another job. The problem is usually noticed not at month end but on the day of shipment. Bringing reservation logic into the system removes this double counting.

Companies with an MRP module in their ERP that they cannot use

Companies running Logo, Mikro, Netsis (Turkish business software products) or a similar system where the production and MRP modules have never been switched on, or were tried once and then dropped. What is needed here is not a new program, but making the bill of materials and the supply data usable and setting the calculation up around the company's real rules.

What we build

What we deliver within Material Requirements Planning (MRP / MRP II)

Bill of materials (BOM) and revision management

A multi-level bill of materials is built; quantity, unit of measure, scrap rate and alternative material can be defined for each item. BOM revisions are kept with dates, so which order was produced against which revision is never lost. For variant production, a parameterised structure can be built instead of opening a separate BOM for every variant; in companies with a wide product range this noticeably reduces the maintenance burden.

Gross and net requirement calculation

Sales orders, the production plan and the demand forecast are converted into gross requirements; the bill of materials is exploded down to the lower levels. Stock on hand, open purchase orders, work orders in production and quantities reserved for other jobs are deducted to give the net requirement. Line by line, you can see what was deducted from which input; the result is not a black box.

Lead times and backward planning

For each material, the lead time by supplier plus goods receipt and quality control time are defined. The system counts back from the required date and calculates the latest day on which the order must be placed. Which production order and which customer delivery date a late order will affect is shown as a chain; that way, which delay is urgent stops being a matter of debate.

Order proposals and handover to purchasing

At the end of the calculation, dated order proposals are produced; proposals can be grouped by supplier, material group or the person responsible. The planner accepts, defers or amends a proposal; every intervention is recorded with its reason. An approved proposal becomes a purchase requisition and is passed into your existing purchasing flow. MRP does not take the decision; it prepares the decision and shows the reasoning behind it.

Safety stock, lot sizing and ordering rules

Safety stock, reorder point, minimum order quantity and multiple-of rules are defined per material. Critical items and those with long lead times are governed by a separate policy. Safety stock is set per material according to consumption variability rather than by one blanket rule; applying the same number of days' cover to every item is the most common and most expensive simplification.

MRP II: rough-cut capacity and labour planning

In the MRP II layer the plan is tested not only for material but also for resources. Available machine hours, shift patterns and operator numbers are defined per work centre; which work centre the plan exceeds in which week becomes visible. That way, before a delivery date is quoted on an accepted order, it can be checked whether the capacity is genuinely there.

Scenario comparison and variance measurement

What-if runs can be made on the plan: if a new order is accepted, if a supplier is late or if a line goes down, which material and which delivery date is affected. Planned and actual consumption are also compared; how close assumptions such as the scrap rate and the lead time are to reality is measured, and the data is corrected over time.

Technologies

The technologies we work with

  • Multi-level bill of materials (BOM)
  • MRP calculation engine
  • Rough-cut capacity planning (RCCP)
  • Safety stock and reorder point
  • Python
  • PostgreSQL
  • REST API
  • React planning screens
  • Scheduled jobs (cron)
  • Logo / Mikro / Netsis integration
  • Excel import and export
Process

How we move from discovery to go-live

  1. 01

    1. Discovery and data health assessment

    On site we establish how much of the bills of materials are up to date, where scrap rates are held and whether lead times are written down at all. We work out step by step what purchasing actually looks at today when it takes a decision. The output is an assessment report that states the health of the data honestly; without that report we do not give a timeline or a cost estimate.

  2. 02

    2. Building the bill of materials and the supply data

    For a pilot product group, bills of materials are updated, scrap rates and alternative materials are written down, and lead times are entered by supplier. This step is usually the longest part of the project and the one that demands the most internal effort; we say so from the outset and put in writing who is responsible for which data.

  3. 03

    3. Building the calculation engine and running it in shadow

    The MRP calculation is built and for a period run only in shadow: proposals are produced but not acted on. Purchasing compares its own decision with the system's proposal. Every item that comes out differently is examined one by one; the difference usually stems from missing data, and this examination is the most effective way of putting that data right.

  4. 04

    4. The MRP II layer and go-live

    Once the proposals have become reliable, work centre capacities and shift patterns are defined and the plan starts being tested for capacity as well. Order proposals are connected to the purchasing flow and the pilot group goes live. The scope is then widened product group by product group; we do not recommend starting with all products at the same time.

  5. 05

    5. Go-live, measurement and support

    In live use, planned and actual are compared: scrap rates, lead times and safety stock levels are updated with real data. Cases where the reason for a stoppage was a material shortage are tracked separately. We provide monitoring and support under an SLA; as the product structure or the supplier base changes, we review the rules with you.

Frequently asked questions

Common questions about Material Requirements Planning (MRP / MRP II)

Does MRP also schedule the machines?

No. MRP calculates which material is needed, in what quantity and when; MRP II then adds a rough-cut capacity check on top, showing which work centre is overloaded in which week. Which job runs on which machine, in what sequence and with what tooling changeover time is a matter for advanced planning and scheduling; it calls for different calculation logic and a different data set. Mixing the two into a single project leaves both half finished.

We already have an MRP module in our ERP, are you going to rewrite it?

Usually not. First we look at why the existing module is not being used; in the cases we have come across, the problem is generally not in the module but in missing bill of materials and lead time data. If the existing module works once the data is put right, that is the right piece of work and we will tell you so. We only propose new development if the company's rules do not fit the module; for example if you need variant bills of materials, formula-based recipes or a requirement calculation tied to subcontracting.

Our bills of materials are out of date, can we still start?

You can, but it should not be taken lightly. An MRP built while the bill of materials is out of date produces the wrong proposal quickly and destroys the team's trust in the system in the first few weeks. That is why we start with a pilot product group and update that group's bill of materials together first. Trying to correct the whole product range from the outset is, in most companies, the decision that stops the project before it ever starts; keeping the scope narrow delivers results faster.

We do make-to-order production where every job is a one-off. Does MRP fit?

Standard MRP does not fit this kind of production as it stands, because it expects the recipe to have been set up in advance. In project-based one-off manufacturing the bill of materials usually only becomes clear as the work progresses. In that case we build the calculation around the main components and the long lead time items, and run the rest on work orders and actual data. In other words, rather than forcing MRP we narrow its scope; we discuss this openly during discovery and do not make a promise that cannot be kept.

Will our stock fall once we put MRP in?

Usually the shape of the stock changes; total stock does not always fall. For critical items and those with long lead times, safety stock may deliberately increase; against that, items that had accumulated beyond any requirement come down. The real gain is often not in the stock figure but in the reduction of stoppages caused by material shortages and of emergency procurement costs. We will not promise you a percentage reduction; we would advise you to treat any proposal that does so with caution.

What do we end up with?

Updated bills of materials with revision history; lead times, safety stock and ordering rules per material; the net requirement calculation and dated order proposals; a connection into the purchasing flow; on the MRP II side, a rough-cut capacity view by work centre; variance reports comparing planned with actual. Everything, including source code, documentation and data, belongs to you.

Contact

Let us talk about your Material Requirements Planning (MRP / MRP II) project

In a 30-minute discovery call we listen to what you need and tell you honestly whether custom development or an off-the-shelf product is the better answer.

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