Quoting should own the price and the buyer’s first contact; ERP should own the commercial record (customers, orders, stock, invoices, accounts); MES should own the work on the floor (schedules, routings, progress, traceability). They connect at two points: an accepted quote becomes an order in the ERP and a job in the MES, and the actual times the MES records flow back to correct the quoting model.
Key points
- One system is the master of each fact. The price belongs to quoting; the order and invoice to ERP; the job’s progress to MES.
- ISA-95 puts ERP at level 4 (business planning) and MES at level 3 (manufacturing operations).
- The hand-off is an order, sent once, with a stable identifier, so a retry never creates a duplicate.
- Actual machine time and labour from the floor are the data that make quotes accurate. Close that loop.
- Most problems come from two systems both believing they own the price or the customer.
What does each system do?
Three systems, three questions. Quoting answers “what will this cost the buyer?”. ERP answers “what have we sold, bought, made and invoiced?”. MES answers “what is happening on the floor right now, and what happened to this job?”.
The ISA-95 standard, which most manufacturing software follows when it describes itself, places business planning and logistics (ERP) at level 4, working in months, weeks and days, and manufacturing operations management (MES) at level 3, working in shifts, hours and minutes (Siemens on the ISA-95 layers). Quoting is not a level of its own in that model. In practice it sits in front of the ERP: it is the part of selling that happens before there is an order.
| System | Owns | Does not own | Time frame |
|---|---|---|---|
| Quoting | Part analysis, estimate, price, options, manufacturability checks, the quote itself | Customer accounts, invoices, schedules | Seconds to days |
| ERP | Customers, sales orders, purchasing, stock, invoices, accounts | How a part is priced from its geometry, what a machine is doing now | Days to months |
| MES | Work orders on the floor, routings, machine assignment, progress, quality, traceability | Prices, invoices | Minutes to shifts |
Where should the price live?
In one place. If the quoting system computes a price and the ERP recomputes it from its own routing, they will disagree, and someone will spend an afternoon finding out why. Decide which system is the master of the price and make the other one store it.
For a shop that sells custom parts from uploaded files, the master is usually the quoting system: it has measured the geometry, applied the machine-hour rate and the material price, and recorded every line of the price breakdown. The ERP receives the price as part of the order and stores it as the sales order value. It should not reprice.
For a shop that sells mostly repeat parts against long-standing routings, the ERP may already be the master, and quoting adds value only for new parts. CPQ for manufacturing explains where configure-price-quote tools fit in that picture.
What should cross from quoting to ERP?
The accepted order, once, with everything needed to make and invoice it.
| Field | Why the ERP needs it |
|---|---|
| Quote identifier | To match the order with the quote and to ignore a duplicate delivery |
| Customer and contact | To find or create the customer account |
| Part files | For the job folder and the floor |
| Chosen process, material, finish, quantity | To create the routing or pick an existing one |
| Price lines and total | To set the sales order value and, later, compare cost |
| Promised lead time | To schedule and to check the promise is being kept |
| Settings version used | To reproduce the price if it is ever questioned |
Three ways to move it, in order of preference:
- A signed webhook sent by the quoting system when an order is placed, with retries until the receiving system acknowledges it. The signature proves it came from your quoting system; the identifier makes a retry safe.
- An API the ERP or a small script calls to fetch new orders on a schedule.
- E-mail with the order attached, read by a person. It works, but it is data entry with extra steps.
Quotometry, for example, stops at the order on purpose: it delivers orders by signed webhook with retries, by e-mail and to an inbox with manual review, and leaves scheduling, stock and invoicing to the systems built for them. Its orders page and the webhook documentation show the payload.
What should flow back from MES to quoting?
The truth about finished jobs. A quote is an estimate; the MES records what happened.
- Actual machine time per job, against the estimated time.
- Actual material used, including failed and reprinted parts.
- Actual labour for set-up, removal and finishing.
- Scrap and rework, with reasons.
Comparing estimates with actuals over a few dozen jobs shows where the quoting model is wrong: a material that always runs slower, a finishing step that takes twice as long as assumed. Calibration fits the model’s coefficients to those jobs, so the correction is made once in the rates, not remembered by an estimator for every new quote.
Worked example: estimate against actual for one material (figures assumed for illustration)
| Job | Estimated machine time | Actual machine time | Ratio |
|---|---|---|---|
| A | 4.0 h | 4.6 h | 1.15 |
| B | 7.5 h | 8.4 h | 1.12 |
| C | 2.0 h | 2.3 h | 1.15 |
| Total | 13.5 h | 15.3 h | 1.13 |
In this example the model underestimates this material by about 13 %. At a rate of €4.00 an hour, a 10-hour estimate would leave about €5.20 of machine time unpriced on every such job (10 h × 0.13 × €4.00). One correction to the material’s speed fixes every future quote.
What about capacity?
Quoting promises a lead time; the MES knows whether the floor can keep it. In a small shop, a lead-time choice with a surcharge for express work is usually enough. As the shop grows, the quoting system benefits from knowing roughly how full the next weeks are, so it can stop offering a lead time the floor cannot meet. That is a capacity planning question owned by the MES or ERP; quoting only needs the answer. Measures such as OEE belong to the floor too, but they tell you whether the hours your machine-hour rate assumes are the hours you actually get.
What goes wrong when they are joined badly?
- Two masters of the price. The ERP reprices an order and the invoice does not match the quote.
- Duplicate customers. Every web order creates a new account because the match is on e-mail address only. Agree a matching rule before the first order flows.
- Duplicate orders. A webhook retried after a timeout creates a second sales order. Use the quote identifier to ignore a delivery the ERP has already seen.
- No way back. Actuals stay in the MES and the quoting model never learns. Quotes stay as wrong as they were on day one.
- Everything in one system. An ERP stretched to answer buyers in seconds, or a quoting tool stretched to schedule the floor, does both jobs badly.
How do you start?
Write down, for each fact, which system owns it: price, customer, order, stock, schedule, actual time. Then connect the order hand-off first, because it removes the most typing, and the feedback loop second, because it makes quotes better. If you are choosing a quoting system with this in mind, the buyer’s checklist includes the integration questions, and quote win rate covers the measurements the quoting side should keep for itself.
Questions people ask
What is the difference between ERP and MES?
ERP runs the business: customers, orders, purchasing, stock, invoicing and accounts, planned over weeks and months. MES runs the shop floor: which job is on which machine, routings, progress, quality records and traceability, over shifts, hours and minutes. The ISA-95 model puts ERP at level 4 and MES at level 3, with standard interfaces between them.
Can my ERP do instant quoting?
Most ERP systems hold a quote record and can price from a routing that an estimator enters, which suits repeat parts and drawings. Few can measure an uploaded 3D file, estimate machine time from its geometry and answer a buyer on a website in seconds. Shops that want both usually run a quoting system in front of the ERP and pass accepted orders into it.
How should a quote reach the ERP?
As an order, not as a quote, once the buyer has accepted it. The cleanest route is a signed webhook or an API call carrying the customer, the part files, the chosen options, the price lines and the quote's identifier, so the ERP can create the sales order and the job without anyone typing it again. E-mail is a fallback, not an integration.
Why should shop-floor data flow back to quoting?
Because the quote is an estimate and the MES records what actually happened. Comparing estimated and actual machine time, material and labour for finished jobs shows where the quoting model is wrong. Feeding that comparison into calibration corrects the rates and coefficients, so the next quote is closer to reality.
Quotometry prices every part from your own machines and rates, on your website, in seconds.