How Does a Sanitary Pad Machine Work? — A Plain-Language, Step-by-Step Guide

Problem → Solution → Case, with a simple flowchart, hands-on steps, external resources, and ready-to-paste schema

What you really want to know (Problem)

You’re looking at a sanitary pad machine for the first time and you need straight answers:

• How do materials travel through the line and become finished pads?

• How do I get speed up without yield down?

• Why are changeovers slow and waste high—and how do I fix it fast?

This guide explains the line in plain English. You’ll see the path from rolls to bags, the few settings that matter most, what to check first when defects spike, and a short routine you can teach to new operators.

What you’ll take away (Solution)

• A simple process flow that matches most brands/models

• A “first 10 checks” list for quick stabilization

• Practical targets for changeover, pass rate, and uptime

• Links to reliable resources if you want to go deeper

Who this helps (Case)

• First-time investors building a new pad line

• Supervisors training a new shift

• Engineers comparing full-servo vs. half-servo choices

1) See the whole line at a glance (from roll to bag)

Flowchart

Why this matters (Problem)
New lines usually struggle with registration drift, glue stringing, and long changeovers. Everyone chases speed, but yield is what pays the bills.

What to do first (Solution)
Lock the flow above, then watch these critical process parameters (CPPs):

• Web tension by material and width

• SAP add-on amount and distribution

• Seal temperature/time and nip pressure

• Knife phase and pad pitch

• Small registration offsets in servo stations

Quick example (Case)
A startup was stuck at 88–90% pass with side-leak fails. They lowered topsheet tension ~10% and reduced seal temperature by 8–12 °C. Without touching line speed, pass rate climbed to ~97% in one week.

Deeper reading: EDANA (nonwovens knowledge) – https://www.edana.org/
Hot-melt basics (Nordson) – https://www.nordson.com/
Web guiding (BST) – https://www.bst.elexis.group/

2) Station-by-station: the 10 checks that fix most problems

2.1 Unwind, splicing, tension (Problem)

If tension jumps at roll change, everything downstream goes out of tune.

Hands-on fix (Solution)

1. Add buffer/accumulator on key webs (topsheet, backsheet, air-laid).

2. Use zero-time splicing for high-volume webs; fix overlap length and glue pattern in the recipe.

3. Save tension set-points per material lot; softer webs need lower targets.

4. Calibrate load cells weekly and write it down.

Case
A line with ~12 splices/shift lost 3–4 minutes per splice. Servo unwind + accumulator removed dips and saved ~45 minutes/day—about +1% OEE.

2.2 Core forming + SAP dosing (Problem)

SAP clumps or dust cause uneven absorbency and swelling.

Solution

• Keep humidity stable; pulp and air-laid behave differently when damp.

• Dose SAP with closed-loop feeding; aim for CV ≤ 7–10%.

• If you wrap the core, make sure edge overlap is enough so SAP doesn’t escape.

Case
Switching to a feeder with mass-flow feedback cut SAP CV from 14% to 6.8%. Left-right absorbency complaints vanished.

2.3 Lamination and shaping (Problem)

Wrinkles and pitch errors start here.

Solution

• Tune nip pressure together with seal temperature/time. Save a window (min-target-max).

• Do a pitch audit: measure 30 pads; track mean and stdev.

• After every blade change, re-phase the rotary; don’t rely only on camera offsets.

Case
Great cameras but still skewed pads. Root cause: blade concentricity. Re-grind holder + re-phase fixed it in one shift.

2.4 Wings, sealing, and edge trim (Problem)

Edge wicking and wing tear-off are common customer issues.

Solution

• Ultrasonic: link amplitude to line speed. Thermal: pair temperature × dwell.

• Remove trim with vacuum + blockage sensors; a clog makes a lot of hidden rejects fast.

Case
After syncing ultrasonic amplitude with speed, wing peel strength became consistent without changing materials.

2.5 Inspection, counting, bagging (Problem)

You can still lose good pads at the packer: miscounts, scuffs, static.

Solution

• Use soft transfer belts and anti-static bars.

• Re-teach count/stack logic after every size change; manually verify every 50 bags.

• Link bag length and jaw pressure to product size via recipe.

Case
Adding one extra anti-static bar and vacuum assist cut short-pack complaints by ~80%.

Quality systems: ISO 9001 overview – https://www.iso.org/iso-9001-quality-management.html

3) Full-servo vs. half-servo: what’s the real difference?

Common belief (Problem)
“Half-servo is cheaper. We’ll tune our way to the same output.”

Reality (Solution)

• Full-servo = size changes are recipe-based; new shifts can repeat yesterday’s run.

• Servo unwind + buffer = smoother roll changes, fewer micro-stops.

• Vision + servo offsets = small drifts self-correct.

Case
Two new plants launched together.

• Full-servo hit 96–97% pass by week 4 and <25 min size change.

• Half-servo needed 2× the changeover time and stalled at 92–94% without senior techs.

PLC platforms you’ll meet: Mitsubishi – https://www.mitsubishielectric.com/ , Siemens – https://new.siemens.com/

4) “First run” routine you can follow today

Before turning the first roll

• Power 380 V 50 Hz three-phase; air 0.6–0.8 MPa with <10% pressure drop.

• Calibrate load cells, temp sensors, encoders, cameras.

• Build Recipe v1: tensions, seal temp/time, nip pressure, SAP add-on, knife phase.

First 60 minutes

1. Start at 70–75% target speed for 10–15 min.

2. Check 30 pads for length + pitch; adjust phase, not speed.

3. Go to 90%; remove stringing/delam by temp/nip tweaks.

4. Settle at your stable point (~800–900 pcs/min for new teams).

5. Begin hourly SPC: weight, SAP, peel, visual.

Changeover drill

• Swap knives, load new pitch, re-phase.

• Load bag settings for the new size; run 30 packs with manual count checks.

• Target 25–40 minutes total, depending on stations.

5) Six common headaches → one-step fixes (with mini-cases)

1. Registration drift

   • Fix: Re-zero encoders; check unwind brake; raise web-guide gain; stabilize heater zones.

   • Case: Drift vanished after re-wiring an encoder and lowering topsheet tension 10%.

2. High scrap at roll change

   • Fix: Zero-time splice; add 10–15 mm overlap; increase buffer.

   • Case: Scrap per splice fell from 35 m to 8 m.

3. Glue stringing / delamination

   • Fix: +5–10 °C or less add-on; correct nozzle-to-web distance; align gun timing.

   • Case: Changing to a spiral pattern killed strings at the same add-on.

4. Leaks at crotch/side

   • Fix: Slightly higher seal pressure; re-center core; push SAP to edges.

   • Case: A 2 mm core shift fix cut complaints by 40%.

5. Wing tear-off

   • Fix: Sync ultrasonic amplitude to line speed; check laminate; adjust perf line.

   • Case: Amplitude-to-speed follow removed tears—no material change.

6. Short-pack / miscount

   • Fix: Re-teach sensors; add debounce; slow infeed 5–10%; add anti-static.

   • Case: Short-packs disappeared; stacks became stable.

6) Materials and traceability (easy mode for small teams)

Problem
Retailers want traceability and consistent feel; you don’t have MES yet.

Simple solution

• Use a barcode/QR log: material lot, shift, recipe number, operator.

• For feel/softness, lock GSM, MD/CD tensile, softness with suppliers and keep a materials sheet at the HMI.

• Use AQL sampling for weight, absorbency (gravimetric), and peel.

Case
A team started with a Google Sheet + barcode gun. When a buyer asked about one lot, they matched it to Recipe v1.3 and the material lot in minutes—no debate, just facts.

ISO 2859 AQL overview – https://www.iso.org/

7) Speed, cost, and ROI — what really pays back

Trap (Problem)
Chasing catalog top speed while scrap grows.

Win (Solution)

• Pick a stable set-point (~800–900 pcs/min) and reach ≥97–98% pass first.

• At 900 pcs/min, +3% pass = +27 good pads/min = +1,620/hour.

• Multiply by cost/pad and hours/day; weekly savings often fund servo unwind, better guiding, and vision.

Case
After two weeks of “speed chasing,” a plant froze at 880 pcs/min, tightened CPP windows, and hit 97.5% pass. Saved scrap funded a bagger upgrade in one quarter.

8) Environment and safety (don’t skip)

• Keep ambient 10–35 °C and ~55% RH so air-laid/tissue stay stable.

• Watch noise near ultrasonics; add damping if needed.

• Train on lockout/tagout, hot surfaces, and pinch points.

9) Quick FAQ your team will ask

• Design speed vs. stable speed?
  Design = mechanical/servo limit. Stable = where you get repeatable yield. For new teams, lock stable speed + ≥97–98% pass first.

• What utilities do we need?
  Commonly 380 V 50 Hz three-phase, ~400 kW running load, 0.6–0.8 MPa compressed air. Confirm with your vendor layout.

• How many operators per line?
  Typically 4–6 for converting + packing at the start; fewer with more automation and experience.

• Delivery and ramp-up?
  Many vendors quote ~120 working days after deposit; then a 30-60-90 ramp on site.

10) A six-step blueprint you can start today

1. Put the flowchart on the wall; map each station on your line.

2. Write Recipe v1: tensions, temps, time, pressure, SAP, knife phase.

3. Train the first 60-minute run and the 25–40-minute changeover.

4. Start hourly SPC on 3–5 quick tests: weight, SAP, peel, visual.

5. Review OEE + loss tree daily; kill one root cause per shift.

6. Link lot → recipe → shift; audit weekly.

External resources to bookmark

• EDANA nonwovens knowledge – https://www.edana.org/

• ISO 9001 quality management – https://www.iso.org/iso-9001-quality-management.html

• Nordson hot-melt application – https://www.nordson.com/

• BST web guiding basics – https://www.bst.elexis.group/

• Mitsubishi PLC – https://www.mitsubishielectric.com/

• Siemens PLC – https://new.siemens.com/