Use this sandwich panel line startup checklist before every shift and after every recipe change on a PU, PIR, or rockwool panel line. Start with safety and utilities, prove materials and recipes, run the line empty, then approve one panel by measurement and cut sample before you let the operator increase speed.
Sandwich Panel Line Checklist
A sandwich panel line startup checklist should move in this order: 1) safety and utilities, 2) coil and core loading, 3) heating and glue or foam preparation, 4) dry run, 5) first-piece inspection, and 6) logged sign-off. Don’t start saleable panels until thickness, adhesion, edge shape, and cut length match the project sheet.
| Startup stage | Operator action | Do not pass if |
|---|---|---|
| Safety walk | Check guards, interlocks, E-stops, walkways, saw area | Any guard is loose, bypassed, or missing |
| Utilities | Confirm power, air, hydraulic oil, heating, cooling, exhaust | Pressure drops or alarms appear on HMI |
| Materials | Check steel coil, film, PU/PIR chemicals, rockwool, adhesive | Batch number or recipe doesn’t match the order |
| Mechanical dry run | Run conveyors, roll former, laminator, cutter, stacker | Edge guide hunts, chain jumps, saw zero is wrong |
| First-piece QC | Measure one approved panel before speed-up | Voids, weak bonding, wrong length, bad edge shape |
| Shift record | Sign off recipe, readings, defects, correction | Values are guessed or copied from yesterday |
One sheet per shift is enough. Don’t make it a binder nobody opens. Put the checklist at the HMI, give the shift leader a pen, and require a real number where a real number matters: tank temperature, air pressure, line speed, cut length, panel thickness.
Panel Line Safety Checks
Start where someone can get hurt. A sandwich panel line has slow-moving sections that look harmless, then sudden hazards at the decoiler, roll forming stands, laminator chain, cross-cut saw, trimming saw, stacker, and hydraulic lift table. The United States Occupational Safety and Health Administration standard 29 CFR 1910.212 requires machine guarding for hazards such as point of operation, nip points, rotating parts, flying chips, and sparks. On your line, translate that into a walk-around check before the first coil rotates.
A bypassed interlock is a maintenance stop, not a production delay. Same rule for a dead E-stop. Press it, reset it, and confirm the HMI sees the signal. Whether your cabinet uses a Siemens S7-1500 PLC, Mitsubishi FX5U PLC, Schneider TeSys contactors, or local electrical parts, the operator’s job is the same: prove the stop circuit works before material enters the line.
Noise gets ignored because it feels normal after week two. It shouldn’t. The Occupational Safety and Health Administration standard 29 CFR 1910.95 sets an 85 dBA 8-hour time-weighted average action level for hearing conservation, and panel lines can cross that during saw cutting, air blowing, and stacker impact. Measure it during commissioning, then again after adding a faster saw blade or air knife.
Daily utility checks should be boring:
- Main voltage: within plant tolerance, no phase loss alarm, cabinet fans running.
- Compressed air: usually 0.6-0.8 MPa at the FRL unit, with water drained from the bowl.
- Hydraulic station: correct oil level, no foaming, no new leaks around lift tables or cutter clamps.
- Heating system: laminator, hot-air circulation, hose heating, and tank heating at recipe temperature.
- Exhaust: working near foaming, adhesive, trimming dust, and rockwool cutting points.
One small habit saves trouble: start the exhaust before heating chemicals or cutting mineral wool. Operators often wait until smell or dust appears. By then, the work area is already dirty.
Material Recipe Checks
PU and PIR are less forgiving than operators think. A small ratio error at 8:10 a.m. becomes a hollow sound inside the panel at 10:30, and by lunch the plant has stacked 80 panels nobody wants to ship. For most export projects, we ask operators to record polyol and isocyanate tank temperature in the 20-25 C range unless the chemical supplier gives a different window. The supplier’s datasheet wins.
The best startup habit for a custom PU sandwich panel production line is to treat the recipe as a production document, not operator memory. PU wall panel, PIR cold-room panel, and rockwool roof panel may use the same steel coil width and still need different line speed, foam output, laminator pressure, side sealing, and curing time.
Before pressing Run, check four material groups:
- Steel coil: thickness, color, coating direction, protective film, coil edge damage, and whether top and bottom skins match the order.
- PU/PIR system: batch number, expiry date, tank temperature, filter condition, metering pressure, mixing head purge, and shot weight if you use manual verification.
- Rockwool system: density, slab thickness, fiber direction, dust level, joint fit, side alignment, and adhesive viscosity.
- Finished panel spec: panel width, thickness, rib profile, side joint, cut length, protective film direction, and packing label.
Don’t copy a Chinese commissioning recipe into a different climate without checking the chemical supplier’s window. A plant in Riyadh, Manila, and Warsaw can run the same mechanical line, but humidity, steel temperature, and storage conditions change the first 30 minutes of production. The HMI can store the recipe. The operator still has to prove it.
Dry Run Before Foam
Prove mechanical travel before chemicals enter the head. Thread the top and bottom color steel through the decoilers, film rollers, roll former, side guide, laminator, cutting system, and stacker. Then run at low speed for 3-5 minutes. One or two meters per minute is enough. You aren’t testing output yet; you’re looking for drift, rubbing, bounce, and bad timing.
A plant that changes between PU and mineral wool should be stricter here, because a PU and rockwool panel production line has more changeover points than a single-core line. Check rockwool feeding without adhesive first. Slabs should enter square, joints shouldn’t open, and side trimming knives should touch only where planned. If the rockwool dust extraction is weak, clean it before adhesive touches the slab. Glue plus dust makes a weak bond that looks fine for about ten minutes.
Watch sensors during the dry run. A photoelectric sensor near the cutter, such as an Omron E3Z or SICK W12, can misread glossy protective film. The encoder may count correctly at low speed and drift when the line accelerates. Test one dry cut, measure it, and check saw return before foam or adhesive is live.
Stop the dry run if you see any of these:
- The top and bottom skins don’t share the same centerline.
- Roll formed ribs show scratching, oil marks, or uneven depth.
- Side belt pressure leaves a visible mark on the steel skin.
- Laminator chain blocks knock or climb.
- The cutter clamps before the panel is stable.
- The stacker hits the panel edge instead of lifting cleanly.
Don’t adjust five things at once. Move one guide, run again, and watch the same reference point. Fast guessing wastes more time than slow checking.
First-Piece Inspection
The first piece is not a souvenir. It is the plant’s permission to produce.
Cut one short sample after the line reaches stable movement, then cut a full-length panel only when the first sample looks right. For PU/PIR, wait long enough for the foam to finish its early rise and skin bond before final judgment. Five to ten minutes is often enough for a startup check, but the chemical system sheet should decide. For rockwool, inspect bonding and edge shape immediately, then check one cut section after the adhesive has had time under pressure.
Use practical measuring points, not perfect laboratory habits. Measure width at the head, middle, and tail. Measure thickness at four corners and the center. Compare diagonals on a full panel. Cut a 300-500 mm sample and inspect the core. If your QC bench has a Mitutoyo caliper, use it for skin thickness or small edge details; for panel length, a steel tape and trained hands are faster.
| QC item | Practical method | Typical startup target |
|---|---|---|
| Cut length | Measure both sides and centerline | Contract tolerance, often +/-2 mm on standard panels |
| Panel width | Measure head, middle, tail | Usually within +/-1.5-2 mm after guide setup |
| Thickness | Four corners plus center | Often +/-1 mm, no crushed edge |
| Diagonal | Compare corner-to-corner readings | Keep difference small; many plants use <=3 mm on 6 m panels |
| PU/PIR core | Cut section and inspect fill | No large voids, no burnt color, no wet uncured zone |
| Rockwool core | Check slab joints and density label | No open joints, no missing strip at side edge |
| Bonding | Knife pry or peel test | Core should fail before clean skin release |
| Surface | Visual under plant lighting | No scratches through coating, no roller dents |
These numbers are working examples, not a replacement for the buyer’s contract. Cold-room panels, fire-rated PIR panels, export roof panels, and cleanroom wall panels may carry tighter specs. Write the real tolerance on the startup sheet.
For PU/PIR density, don’t guess by touch. Cut a known-size sample, weigh it on a calibrated scale, and calculate density from volume. A recipe calling for 40 kg/m3 foam can’t be accepted because the panel “feels full.” It either matches the target or it doesn’t. PIR may run with different chemistry and curing behavior, so don’t force a PU habit onto a PIR order.
The most common bad fix is speed. Operators see overflow and raise line speed. Sometimes that hides the symptom, but it can leave weak bonding or uneven fill. Check mix pressure, component temperature, shot output, side sealing, laminator pressure, and steel temperature first. Speed is a production setting after the process is stable.
First-Hour Faults
The first hour tells you more than the clean handover meeting. Stay near the line. Listen for cutter timing, watch edge shape, and cut another sample after the first few full panels. Problems that appear only after heating are still startup problems.
| Symptom | Likely check | Better first correction |
|---|---|---|
| Hollow sound in PU/PIR panel | Foam output, ratio, skin temperature, side leakage | Verify shot weight and mixing pressure before changing speed |
| Panel bends after cutting | Uneven skin tension, laminator pressure, cooling difference | Recheck decoiler brake and top/bottom alignment |
| Rockwool delamination | Dust, adhesive spread, pressure, slab gap | Clean slab path and confirm glue weight per square meter |
| Saw burr or angled cut | Clamp timing, blade wear, encoder pulse, saw travel | Test dry cut, then replace or sharpen blade if needed |
| Edge joint won’t close | Side guide, belt pressure, profile mismatch | Reset guide by panel drawing, not by eye |
| Skin scratches | Dirty roller, film wrinkle, roll former misalignment | Clean contact points and mark the exact stand causing damage |
A good shift leader changes one variable, marks the time, runs two panels, and checks the result. That sounds slow. It is faster than chasing random HMI values while the stacker fills with rejected panels.
Startup Records Matter
A startup record doesn’t need fancy software. It needs honest entries. Record coil batch, chemical batch, rockwool supplier batch, ambient temperature, steel temperature if measured, tank temperature, line speed, laminator pressure, cut length, first-piece dimensions, defect photos, correction, operator name, and shift leader sign-off.
This matters more for overseas plants. When YZ Welding supports a buyer after installation, a photo of the HMI plus a real startup sheet lets our engineer separate recipe trouble from mechanical trouble. “Panel edge open” is too vague. “100 mm rockwool side strip shifted left after speed increased from 2.5 to 3.5 m/min” gives the service engineer somewhere to start.
Keep failed samples for 24 hours when the defect is new. Mark the date, recipe, and coil. If the same fault appears next week, you can compare the cut section instead of arguing from memory.
FAQ
How long should startup take?
On a warm, stable line, daily startup usually takes 20-40 minutes before first-piece approval. After weekend shutdown, chemical change, or cutter maintenance, plan 60-90 minutes because heating, purging, and dry-run checks take longer.
What causes first-panel delamination?
Common causes are low skin temperature, wrong foam or adhesive ratio, dusty rockwool, weak laminator pressure, or running too fast before the reaction reaches stable rise. Check recipe values before changing line speed.
Should failed panels be sold?
No. Mark failed first panels as scrap or internal test material. Selling panels with voids, weak adhesion, or wrong thickness creates site complaints that cost more than one rejected startup panel.
Before your next production shift, print the checklist, add your contract tolerances, and make first-piece approval mandatory. For new PU, PIR, or rockwool panel projects, YZ Welding can review your layout, utilities, target panel specs, and commissioning checklist so the operators start with a production method they can repeat.
