Here is a test. Send “please quote your best automatic packaging machine for 500 g powder” to five suppliers and see what comes back. You will get five machines, five price structures, and no way to tell which one fits, because you did not actually ask a question. You described a category.
A specification is not paperwork. It is the difference between five comparable quotes and five sales brochures.
Start with the product, not the machine
Suppliers cannot size a machine without product data, and most buyers underestimate how much of it matters. Give them these, numerically, even if some are estimates:
- Product name and a photo, including one photo of a single piece next to a ruler
- Bulk density in g per litre, measured, not guessed from a datasheet
- Piece dimensions and weight range
- Product temperature at the moment of packing
- Moisture or surface oil, and whether the product is sticky, dusty, or abrasive
- Flow behaviour: free-flowing, sluggish, or bridging in a hopper
- Fragility: can it survive a 300 mm drop into a bag
- Whether the product is food, pharmaceutical, or industrial, and which contact approvals apply
Bulk density is the one buyers most often skip and the one that decides whether the machine needs 40 litres of hopper or 120.
Draw the bag, do not describe it
A bag drawing with dimensions, in millimetres, answers twenty questions at once. Include:
- Bag type: pillow, gusseted, quad seal, stand-up pouch, flat bottom, sachet
- Finished width, length, and gusset depth
- Seal width and seal pattern, including whether you need a crimped or flat seal
- Fill weight and target fill volume
- Tear notch, hang hole, valve, zipper, or spout, with positions
- Eye mark position and repeat length, if the film is printed
- Whether the bag must stand up on a shelf, and at what fill level
If you do not have a drawing, cut a bag open, measure it flat, and photograph it on graph paper. That is enough for a supplier to quote, and it prevents the most expensive mistake in the whole project: a forming shoulder machined for the wrong width.
Specify the film, not just the product
Give the structure and thickness: for example, 12 micron PET / 9 micron foil / 60 micron PE, total 81 micron, or “40 micron BOPP, cold seal”. Add the roll width, core diameter, and maximum roll diameter your machine must accept.
If the film is not chosen yet, say so and ask the supplier to recommend two structures, one for cost and one for barrier. Do not let this stay blank, because seal jaw coatings, knife type, and even the pull belt choice depend on it.
Write speed as sustained output
“Up to 120 bags per minute” is a peak number measured for ten minutes with perfect film. What you need is a sentence like: “sustained output of 80 bags per minute at 85 percent efficiency over an eight-hour shift, with a reject rate below 1.5 percent.”
That is a testable claim, and you can put it in the acceptance criteria. Suppliers who cannot hit it will tell you so before you sign, which is exactly when you want to hear it.
Utilities and space, in numbers
| Item | What to give the supplier |
|---|---|
| Power | Voltage, phases, frequency, available breaker size |
| Compressed air | Pressure available, dryer type, whether the line is oil-free |
| Floor | Available footprint, ceiling height, floor loading, door width |
| Environment | Room temperature range, humidity, washdown or dry area |
| Layout | A sketch showing infeed, outfeed, and where operators stand |
That layout sketch is worth more than a page of text. Half of all installation problems are discovered when the machine arrives and the outfeed conveyor points at a wall.
Compliance and documentation
State your market and the standard you need: CE for the EU, UKCA for Britain, UL or CSA components for North America, and for pharmaceutical work, GMP construction with 21 CFR Part 11 data handling. Say which surfaces must be food contact approved and whether you need a material certificate.
Then specify the documents: electrical schematic, pneumatic diagram, PLC and HMI backups with passwords, manual in your language, spare parts list with part numbers, and calibration certificates. Ask for them as deliverables in the purchase order, not as favours after delivery.
What to lock, and what to leave open
Lock the things that affect your product and your building: bag dimensions, film structure, fill weight, output, utilities, and compliance. Leave open the things the supplier knows better than you: jaw coating, servo brand, guarding design, and the internal layout of the frame.
Buyers who specify every component end up with a machine nobody has built before and a support conversation that starts with “that is not our standard design”.
Include the acceptance criteria
One paragraph is enough: which product and film will be used, how long the run lasts, what the tolerances are for bag length, fill weight, and seal strength, and what the reject rate must stay under. Our FAT checklist goes deeper, but the principle is simple: if it is not in the specification, it will not be measured.
For the technical vocabulary on the spec sheet itself, see decoding packaging machine specifications. And before you send the enquiry, check the material compatibility notes in film and machine compatibility, because a machine that cannot run your film is not a bargain at any price.
Frequently asked questions
How long should a specification be?
Two pages plus a bag drawing. One page of product data and requirements, one page of utilities, compliance, and acceptance criteria. Longer documents get skimmed, and skimmed documents produce vague quotes.
Should I tell suppliers my budget?
Give a range, not a number. It stops them quoting a machine you cannot afford and stops the other extreme, where they quote something too light for your volume and you waste a month finding out.
Do I need a bag drawing if I am buying a standard machine?
Yes, because “standard” still needs a width, a length, and a gusset. Suppliers will draw it for you if you send dimensions and a photo, but you should approve the drawing before any tooling is made.
What is the most common specification mistake?
Leaving the film structure blank. Seal quality, jaw coating, knife type, and running speed all depend on it, and suppliers will quietly assume the easiest film to run rather than the one you will actually buy.