An automation user requirement specification (URS) states what the machine must achieve, the conditions it will operate under and how each requirement will be verified. Start with the product range, sustained output, quality criteria, site interfaces and handover records. Number each requirement and give it an acceptance method so competing proposals can be compared against the same task.
Motionwell reviews URS documents for custom machines built and tested at Woodlands Link. On a filling project, for example, fill range, accuracy, utilities and footprint each become a requirement before mechanical design begins.
The short version comes first. A URS for a machine states the need. Every line carries an identifier, a verification method and an acceptance criterion written at the same time as the requirement, so the document can be tested. Ranges are the ones you will really run, because the widest range prices the machine. Your site, your existing line and your data rules are requirements too. And the traceability matrix starts from the URS instead of being reconstructed at the end, because numbering every requirement from the start is also what makes competing quotations comparable.
What each qualification stage proves once the machine exists is on our computer system validation page.
What Is a URS Actually For, and What Goes Wrong Most Often?
It exists so the people who know the process and the people who know machinery are arguing about the same thing. You own the product, the rate, the site and the consequences of getting it wrong. The builder owns kinematics, drives, tooling and control architecture. The URS is the boundary between those two bodies of knowledge, and its job is to carry your half across intact.
A common failure, and an expensive one, is a URS that specifies a solution. It happens for a good reason: naming a robot, a feeder or a camera feels like precision, and a document full of part numbers reads as though somebody has done the engineering. What it does instead is delete the better answer before a layout exists, quietly, because a tender gives a bidder who can see the cheaper route little room to propose it.
| What the URS said | What it quietly ruled out | What it should have said |
|---|---|---|
| A six-axis robot shall load each machine on the row | A single beam over the row, where one steel single-beam gantry serves more than ten CNC machines | The load point at each machine door, the shortest machine cycle on the row, and the parts per hour the row has to hold |
| Closures shall be fed by vibratory bowl feeder | A dedicated sorter or a robot pick from a tray, which is what a trigger spray with a tangling dip tube needs | Every closure on the list, including the one arriving next year, with a physical sample of each |
| Inspection shall use a smart camera at the station | One vision controller sharing its processing across three heads, where a job needs three views | The defect classes to be caught, per zone, with the smallest defect that must be detected |
| A collaborative robot shall be used so no fencing is required | Every safeguarding route the risk assessment might have chosen, since safeguarding follows the assessment | What a person does in that space, how often, and whether the workpiece or tooling is itself hazardous |
| Every axis shall be servo driven | A closed-loop stepper, where the axis is light, slow and forgiving | The positioning accuracy, duty cycle and settling behaviour each axis has to deliver |
Every good version in that right-hand column is a statement about your process that only you could have made, and every bad version is one about machinery the builder is better placed to make. So the test on any line you are unsure about is this: could our supplier have written this sentence without talking to us? If yes, it probably does not belong in your URS.
Which Sections Does a Workable URS Need?
It needs fewer than most templates suggest, and each one has to settle a question that would otherwise be settled by accident.
| Section | What it has to settle | What happens when it is missing |
|---|---|---|
| Scope, boundaries and exclusions | Where the machine’s scope starts and stops, who supplies the tie-in at each end, and what you will supply yourself | Both parties price a gap that neither owns |
| Product and variants | Every part number with dimensions, weights and real tolerances, plus the ones arriving next year | A variant appears after the frame is welded |
| Process description | The sequence as performed today, manual steps included, with what the operator judges by eye | The machine misses the step that decided quality |
| Throughput and availability | Sustained rate, shift pattern, and how rate will be measured and over what window | A peak figure gets designed to, and never holds |
| Quality and acceptance | What is checked, against what limit, on what sample, and what happens to a reject | Verification depth is decided by the quotation |
| Interfaces | Mechanical height and pitch, electrical connections, and the data signals with an owner named for each | An unowned handshake on your floor |
| Utilities, site and environment | Power, air, extraction, network, footprint, access route, ceiling, floor, and whether a particle class or washdown applies | The machine is right and the building is not |
| Safety and regulatory scope | The market the machine is placed on, your plant safety standard, and who signs the declaration | Conformity work arrives as a change order |
| Data and records | Which values are retained, who may change them, where they go and for how long | A logging requirement arrives as a redesign |
| Operation, spares and training | Who runs it, the training level assumed, service access, spares and changeover expectations | A machine that runs well at handover, badly in year two |
| Acceptance and documentation | What is tested at factory acceptance, what at site, who witnesses, and what counts as a pass | Test scope is negotiated while the machine stands there |
Two notes on the document’s shape. One requirement per numbered line, because a paragraph holding three requirements gets traced once and tested once. And keep the reason for a requirement in a separate column from the requirement, so a supplier can offer something better against the line without arguing with your explanation.
How Do You Write a Requirement That Can Be Tested?
You write the verification method and the acceptance criterion in the same sitting as the requirement, on the same line. Do it now, and do it yourself. If you cannot say what test would prove a line and what result would fail it, you have not finished writing the line.
Four methods cover almost everything, and choosing one forces the requirement to become specific. Inspection looks at the built machine or its documents. Demonstration watches it do the thing. Test runs a defined procedure and records numbers against limits. Analysis is a calculation where a physical test is impractical. A requirement that resists all four is an aspiration wearing a shall.
| Requirement as first written | Why it cannot be tested | Verification method | The acceptance criterion it needs |
|---|---|---|---|
| The machine shall be fast | No measure, no window, no product named | Demonstration over a timed run | Sustained units per hour on a named product across a defined run length, with the counting rule agreed |
| The vision system shall detect all defects | “All” cannot be demonstrated, and a rate with no named sample set cannot be re-run at acceptance | Test against a held-back sample set | Escape and false reject rates stated against that named set, including the marginal parts |
| The machine shall hold a tight tolerance | No dimension, no datum, no share of tolerance allocated to the gauge | Test against a master or known artefact | The dimension, its tolerance, the datum it is taken from, and how much of the tolerance the measurement may consume |
| The HMI shall be user friendly | An opinion, and both parties hold one | Demonstration by an operator who has not seen the machine | Basic operation reached after a stated training period, with the tasks that count as basic listed |
| The machine shall run unattended overnight | No definition of a stoppage and no definition of the night | Test over a defined continuous run | Input magazine depth and output buffer expressed in minutes at your rate, plus what the machine does on a fault |
| The machine shall be 21 CFR Part 11 compliant | Compliance is machine capability plus your procedures plus a validation record, so no test on the machine alone settles it | Inspection against each named control | The specific controls required, clause by clause, as capabilities the machine must provide |
Three of those rows lean on work covered elsewhere here: detection rates against a named sample set on our surface defect inspection page, the datum and gauge tolerance argument on our inline dimensional measurement page, and the machine-side controls behind 21 CFR Part 11 on our electronic batch record page.
How Should You State a Range or a Tolerance?
State the range you will actually run. Getting this line wrong is expensive in a way that never appears on an invoice, because the widest range prices the machine.
Every range becomes a design constraint at both ends, and the two ends are usually solved by different hardware. A filling platform covering a wide volume span is a different machine from one covering three fixed volumes, because a dosing element sized for the small end has to be repeated or replaced to reach the large one. A capping head with a wide programmable torque range is a servo head with torque feedback, which is the right buy when the range is real and an expensive one when three closures share a single torque window.
So write ranges in three parts. What you run today. What you are committed to running, with a date. And what somebody would like to run one day, marked as options and priced separately so the base machine is not quietly built for them. That third category is where the money leaks, and it leaks politely, because nobody wants to be the person who left something off the list.
Tolerances work the same way in the other direction. A tolerance is not free precision: it decides the guides, the drives, the fixture and the measurement system. State the one you have to police, and never the drawing’s tightest number, and state where in the envelope it has to hold, because a figure that applies at one station and a figure that applies everywhere are different machines.
Rate and format range also pull against each other, and on a tray-fed machine the container envelope settles it. That trade is worked through on our filling line changeover page, worth reading before you write a rate line and a variant list as if they were independent.
What Do We Need to Know About Your Existing Line, Utilities and Space?
Everything the machine touches that you already own, written as numbers. This part of a URS is often written as background, and it produces expensive surprises, because a machine that is wrong about the building cannot be fixed by adjusting the machine.
Take utilities literally and write them as numbers. Our tray-fed filling and sealing machine runs on a 220 or 380 V AC supply. On the cleanroom automated test equipment, air preparation units at each valve bank regulate the supply separately, because the pressure each station needs follows the test force it applies. The 5-axis shot peening machine carries its own dust collection box and ducting, a service the building has to accept somewhere. Extraction, drainage and network access are utilities as surely as power is.
| Site item | Why it changes the machine | Where it is usually found too late |
|---|---|---|
| Electrical supply | Voltage, phases and available capacity decide the panel, and a plant at its limit changes the project scope | At installation, when the switchboard cannot carry it |
| Compressed air | Pressure, flow and quality; a machine sized for clean dry air behaves differently on a starved ring main | During commissioning, as intermittent faults nobody can reproduce |
| Extraction, drainage and bunding | Dust, fume, washdown water and spill containment are building services | When the machine is on site and the drain is not |
| Footprint and access route | The machine has to arrive through the doors and around the corners, in the sections it ships in | On delivery day |
| Ceiling and overhead volume | Crane, ducting, sprinklers and roof structure occupy the same volume an overhead machine needs | On a concept drawing that assumed clear height |
| Floor level, flatness and loading | A long machine on a floor with a fall in it is either shimmed or built to follow the floor, and those are different machines | At levelling, which is the worst time to discover it |
| Conveyor interface height and pitch | A new station has to accept product at the height and spacing your line already runs at | When two machines meet for the first time |
| Control signals and their owners | Part ready, cell ready, buffer full, fault and reject asserted each need one owner agreed in writing | On your floor, as a signal neither party built |
The last row decides more on a retrofit than people expect, and the fix is administrative: name an owner per signal in the URS, and the argument happens on paper. Your PLC and robot platform belong beside it as a requirement, since spares, training and a programming environment already exist for one platform, and telling us at enquiry stage means it lands in the concept, as set out on our robot integration services page.
On a retrofit, add one line: what the existing machine does today, what it must keep doing, and what evidence of its behaviour exists. Establishing what the existing circuits actually do before anything is replaced is regularly the largest single line in a retrofit safety scope, and it belongs in your specification.
What Does a Regulated Line Add to the URS?
Three things, and none of them is the qualification protocols, which come later and are covered on the validation page.
A named regulatory scope. Write which rules apply and to which product: GMP, the cleanroom class if there is one, the predicate rule behind any electronic record you intend to keep, and the markets the pack is sold into. Singapore’s HSA is a PIC/S member, so a line built here for a local site and one built for export are usually held to the same specification set. The scope line is short, but it has to be explicit.
Data and records as requirements. On a regulated machine the record is part of the product, and a logging requirement that arrives during testing is a redesign. State which values are retained per unit or per batch, who may change a parameter and at which authority level, whether a signature is required and what it means, where the record goes, in what format, and for how long. On our delivered machines these are signals the process already produces: a fill volume against its target on the filling and sealing machine, a test result against a serial number on the cleanroom test equipment. Deciding early which become retained records keeps the validation effort proportionate.
Materials, finish and environment as specifications. On a GMP build these are URS lines: product-contact material and surface finish, weld treatment, gasket compliance, and cleaning access. Our tray-fed filling and sealing machine carries a named product-contact alloy, a named surface finish and a stated enclosure rating, built for an ISO Class 7 or 8 room, and each of those was a line in a specification before it was a drawing. A tighter finish, a different alloy or a harsher cleaning regime is a different machine with a different price, and the URS is where you choose which risk you are buying against.
One line applies to every project, regulated or not, and it is one people leave out and argue about later: which market the machine is placed on, and on a retrofit, how far the modernisation goes.
How Do Requirements Get Traced Through Design and Test?
They get traced through a matrix built from the URS as it is written, one row per numbered requirement, growing as the project moves. That last point is the whole argument. Reconstructing traceability at the end means reading test records backwards to guess what each was proving, and the requirements nobody tested are exactly the ones that exercise will miss.
The worked example on our computer system validation page traces one fill accuracy requirement from end to end, and it is worth reading as a description of who writes what.
| Trace step | Content in the worked example | Who produces it |
|---|---|---|
| Requirement identifier | URS-014 | You, at the moment the requirement is written |
| Requirement | Fill volume accuracy within the stated tolerance band across the declared range | You |
| Risk classification | Critical, direct product quality impact | You, with your quality unit |
| Specification reference | FS-3.2 dosing control, DS-7 dosing valve selection | The builder, during design |
| Test reference | OQ-11 volume challenge at range limits, PQ-04 batch performance | The builder, with your quality unit approving the protocol |
| Result and deviation | Pass, or a deviation number with its disposition and approval | Executed jointly, signed by the approver |
Read the right-hand column and the reason for writing the identifier first becomes obvious. Rows two and three are yours and nobody else can supply them. Rows four and five cannot be written until row one exists, because there is nothing to reference. A requirement that was never numbered has no place to be traced to, so it drops out of the design conversation without anyone deciding to drop it.
Keep the same table on an unregulated project, with the test reference pointing at a factory acceptance item. Beyond proving coverage it makes scope changes visible, since a requirement arriving in week nine has to become a row with a test against it, and at acceptance it gives you a list to walk.
Does a Good URS Actually Make Quotations Comparable?
This is the commercial reason to do the work. Two proposals naming the same robot can differ by a wide margin without either being wrong, because the arm is one line on the bill of materials and the engineering is in the other rows. Without a numbered requirement list you are comparing documents that describe different machines in similar language.
Ask for the response in the shape of your document: a line-by-line compliance statement against your numbering, marked comply, comply with comment, or exception. Read the exceptions before the prices. An exception is a supplier telling you where your specification is wrong, and a detailed URS drawing no exceptions at all is worth one more question about how closely it was read.
Five things are easy to leave out of a quotation when the URS leaves room for them, and each can return later as a change order.
- Part presentation and feeding. The station can only work on a part that arrives correctly oriented at the right moment, and feeding difficulty is set by the part.
- Safety scope and its evidence. Guarding, interlocks, the safety circuit and the measurements that prove stopping performance on the built cell, and never a distance asserted on a drawing. That scope is on our machine safety and CE marking page.
- The interface work at both ends. Conveyor tie-ins, signal exchange, and whatever has to be done to an existing controller before it can be extended safely.
- Documentation, spares and training. Drawings, schematics, program archives, manuals, and the training that lets your team run the machine without calling the builder for every adjustment.
- Acceptance testing scope. What is demonstrated at factory acceptance, on whose parts, with whom present, and what is deferred to site.
Then ask every bidder the same question: who owns the cycle time number on our actual parts? A rate from a datasheet and a rate timed on your product are different claims. The wider evaluation framework, including the trap where the lowest-priced proposal often generates the highest total project cost once change orders, rework and extended commissioning are counted, is in our guide to choosing an automation system integrator.
What Should a URS Not Contain?
Seven things, because a document trying to do everything does none of it well.
Not the mechanism, unless the constraint is real. The test is whether you can state the reason. A constraint with a reason attached survives; a preference dressed as a requirement is easy to value-engineer away.
Not another site’s requirements. A borrowed URS carries a borrowed format envelope, a borrowed rate and sometimes a borrowed regulator. Useful as a checklist of section headings, dangerous as a source of content.
Not commercial terms. Payment milestones, liquidated damages, warranty periods and delivery terms belong in the contract. Mixing them in puts commercial negotiation into a technical review meeting.
Not requirements you cannot verify at acceptance. A twenty-year design life cannot be tested at a factory acceptance test. Convert it into things that can be inspected: component ratings, duty classes, material specifications, service intervals and spares availability.
Not a moving product. A schedule risk that recurs on custom machines is late finalisation of the product design, because if the geometry changes after detail engineering starts, the machine design changes with it. Record which product revision the machine is built to, and freeze it before detail engineering begins. The phase structure behind that is in our write-up on special purpose machine design.
Not a custom machine, where a standard one does the job. Write the process description before the equipment description for exactly this reason. If a catalogue machine covers your process at your rate, the URS should be able to reveal it, and any builder worth dealing with will say so.
Not a sign-off from your machine builder. The same team cannot write your requirements and then be measured against them, which is why approval of the document stays with your quality unit.
How Do You Get a First Draft Written This Week?
Run these in order. An incomplete first draft that admits its gaps beats a polished one from a template, because the gaps are visible.
- Describe the process as it runs today, manual steps included, and mark every point where an operator judges something by eye. Those judgements are easy to leave out of a specification.
- List every variant with dimensions, weights and real tolerances, marked for what runs now, what is committed, and what is aspiration.
- Write the rate twice, sustained across a shift and peak, and say which one the machine is bought to hold.
- Write the acceptance criterion beside every requirement as you go. If you cannot, leave the line marked unfinished.
- Measure the site: power, air, extraction, drainage, network, footprint, access route, ceiling height, floor condition, and the interface height and pitch of the line it joins.
- Name the signals and their owners, and send that list to whoever owns the equipment on either side before it reaches a supplier.
- Settle the regulatory scope and the market, including whether any record the machine creates has to be retained.
- Number everything and start the matrix, even if the only columns you can fill are the identifier, the requirement and the verification method.
Lead time runs 16 to 24 weeks from concept approval to factory acceptance testing on a standard build, and 24 to 32 weeks where cleanroom compatibility or full GMP validation applies, with concept design taking 2 to 4 weeks of that and detail engineering 4 to 6. The URS has to exist before the first window opens, because concept is where the mechanism is chosen and the requirements are what it gets chosen against.
Standards Used in Machine Design and Validation
These references inform the design, testing and documentation described on this page. Each row links to its primary source and records the edition checked.
| Standard | Current edition | What it means for your machine |
|---|---|---|
| Regulation (EU) 2023/1230: the EU Machinery Regulation | (EU) 2023/1230 (changeover pending) | Applies on a mandatory basis from 20 January 2027, replacing Machinery Directive 2006/42/EC. Project planning should align the intended EU market date with the conformity assessment and technical documentation, including relevant software integrity and connected-function requirements. The European Commission permits voluntary declarations against the Regulation before that date, while the Directive remains applicable.Checked 1 Sep 2026 against European Commission, Machinery page (single-market-economy.ec.europa.eu/sectors/mechanical-engineering/machinery_en); EU-OSHA legislation register |
| Modified machinery as new machinery: Machinery Directive 2006/42/EC scope rule | Directive 2006/42/EC (applies until 19 January 2027) | For EU-market retrofits, review the proposed changes to function, performance and safety to establish whether the modified equipment is treated as new machinery. Record that assessment during scope definition and assign responsibility for the risk assessment, technical file and conformity documentation.Checked 1 Sep 2026 against European Commission, Machinery page (single-market-economy.ec.europa.eu/sectors/mechanical-engineering/machinery_en) |
Frequently Asked Questions
What is a URS for a machine, and who writes it?
A user requirement specification is the buyer's document, and it states what the machine has to achieve. You write it because you own the process, the product, the site and the rate; the builder owns the mechanism that meets it. On a custom machine the URS is also where your constraints first exist in writing, before anyone spends money: the variants you actually run, the space the machine has to fit, the signals it has to exchange with the line above and below it, and what has to be provable at handover. Motionwell reviews a URS and challenges its lines for testability before design starts, but the document stays yours and your quality unit approves it.
Should a URS name the technology, or only the requirement?
Only the requirement, with one genuine exception. Naming a robot brand, a feeder type or a camera architecture looks like clarity and usually removes the cheaper answer before anyone has drawn a layout. State the need and let the builders compete on the mechanism. The exception is a genuine site constraint: if your maintenance team stocks spares for one PLC platform and has been trained on it, that is a real requirement and it belongs on the list with the reason attached. Write it as a constraint with a justification, so it survives value engineering.
Does a good URS actually make quotations comparable?
Yes, and little else does. Two proposals naming the same robot can differ by a wide margin without either being wrong, because the design work around the arm is where they differ. Number every requirement and ask each bidder to respond line by line with comply, comply with comment, or exception. That turns a pile of differently shaped documents into one table where the gaps are visible before the order. Then ask each bidder who owns the cycle time number on your actual parts, and read the exceptions before you read the prices.