By Wang Yongjie, Production Manager at ZTRFM | Last Updated: September 15, 2026
In March 2025, one of our C-purlin lines went down for four days. The cause was a bearing seizure on stand 14 -- a $40 part that nobody had greased in six weeks. Four days of lost production, a $2,800 emergency bearing replacement, and a very unhappy customer waiting for 12 tons of purlins.
That failure was entirely preventable. I'm Wang Yongjie, production manager at ZTRFM's Botou facility, and I want to share the maintenance routine we now follow on all 14 of our roll forming lines. This isn't theory -- it's the checklist my operators run every single day.
Daily Maintenance (5-10 minutes per shift)
Every operator does these checks at the start of their shift, before turning on the machine:
| Check | What to Look For | Action |
|---|---|---|
| Gearbox oil level | Oil level between the MIN and MAX lines | Top up with ISO VG220 gear oil at once |
| Coil strip feed | Strip edges undamaged, decoiler aligned | Realign the decoiler if strip walks off |
| Roller surfaces | No chips, rust, or scratches on rollers | Wipe with a clean rag, no emery cloth |
| Flying saw blade | Teeth not chipped, blade mounted tight | Replace blade once 3+ teeth are missing |
| Emergency stops | E-stop buttons click and release freely | Tag out the line and report the fault |
The biggest mistake new operators make is skipping the oil check. Gearbox oil doesn't disappear quickly, so people stop checking. Then one day the oil is low, the gears overheat, and you're looking at a $4,000 gearbox rebuild.
Weekly Maintenance (30-45 minutes, usually Sunday shift)
This is the routine that prevents 80% of breakdowns:
1. Lubricate all bearing points. Our machines have 24-30 grease fittings (Zerk fittings) across the roller stands. Use a grease gun with NLGI #2 lithium grease. Two to three pumps per fitting -- don't over-grease, or you'll blow the seals. This takes 15 minutes and is the single most important maintenance task on the entire machine.
2. Check chain tension. The drive chains between stands should deflect 10-15mm when pressed in the middle. Too loose and they skip teeth; too tight and they wear the sprockets fast. Adjust the tensioner bolts as needed.
3. Inspect roller gaps. Run a feeler gauge through each stand. If the gap has drifted more than 0.1mm from spec, recalibrate. This is especially important after running thicker material -- the rollers can get pushed apart slightly over time.
4. Clean the cutting area. Metal chips accumulate around the flying saw. Vacuum them out (don't blow with compressed air -- it pushes chips into bearings). Check the saw guide rails for burrs.
5. Check hydraulic pressure. The hydraulic decoiler and any hydraulic cutting systems should hold pressure within 10% of the rated value. If pressure drops, look for leaks at fittings and hose connections.
Monthly Maintenance (2-3 hours, schedule during changeover)
| Task | Details |
|---|---|
| Gearbox oil inspection | Check for metal particles with a magnet dipstick; particles mean the gears are wearing, so send an oil sample for analysis. Change oil every 2,000 hours or 6 months. |
| Roller profile inspection | Run a test piece and measure the output profile against the drawing; drifting dimensions mean the rollers are wearing unevenly. Catch it early -- a worn set costs $3,000-$8,000. |
| Electrical cabinet check | Vacuum dust from the cabinet with the machine off and locked out; check for loose terminals on the VFD and PLC, and confirm the cabinet fan works -- heat is the enemy. |
| Leveling head rollers | Leveling rollers take the most abuse; check the surfaces for grooving or pitting. Grooves deeper than 0.2mm mean the rollers need regrinding or full replacement soon. |
| PLC program backup | Export the current PLC program to a USB drive labeled with the machine ID and date. If the PLC ever fails, this backup is the fastest way to get the line running again. |
Seasonal / Annual Tasks
Once a year, do a full deep-dive:
- Change all gearbox oil (not just top up). Drain, flush, refill.
- Replace all V-belts and timing belts. They look fine but lose tension over time.
- Check machine alignment with a laser alignment tool. The stands can shift slightly over years of vibration.
- Calibrate all sensors (photoelectric, proximity, encoder).
- Have the electrician megger-test all motors for insulation degradation.
The Maintenance Log
Every machine on our floor has a maintenance logbook hanging on the control panel. Every check, every issue, every part replaced goes in the log. When a machine develops a recurring problem, the log tells the story. When we sell a used machine, the log goes with it -- buyers pay 10-15% more for a machine with a complete maintenance history.
If you're buying a used roll forming machine, ask for the maintenance log. No log = no maintenance. Walk away.
Quick Q&A
How often should I grease the roller bearings?
Weekly under normal use (one shift, 8 hours). If you run two or three shifts, grease every 3-4 days. Use NLGI #2 lithium grease -- not whatever's sitting in the shop.
What's the most common maintenance failure?
Bearing seizure from lack of grease. It accounts for about 60% of our unscheduled downtime. The fix is simple: weekly greasing, no exceptions.
Can I use any gear oil in the gearbox?
Use ISO VG220 (or the grade specified in your machine manual). Thinner oil won't protect the gears under load; thicker oil won't flow properly at startup in winter.
How do I know if my rollers need replacing?
Three signs: output profile dimensions drifting beyond tolerance, visible grooving or pitting on roller surfaces, or surface scratches appearing on the product. Regrinding can extend life by 1-2 years; after that, replace.
Frequently Asked Questions (FAQ)
How often should roller bearings be greased?
Grease them weekly under normal one-shift operation. For two or three shifts, grease every 3-4 days, using NLGI #2 lithium grease.
What is the most common maintenance failure?
Bearing seizure caused by insufficient grease accounts for about 60 percent of the facility's unscheduled downtime, according to the article.
What gear oil should be used?
Use ISO VG220 gear oil or the grade specified in the machine manual. The article warns that oil that is too thin or too thick will not protect or flow correctly.
How can an operator tell when rollers need replacement?
Watch for profile dimensions drifting beyond tolerance, visible grooves or pits on roller surfaces, and scratches appearing on the product. Regrinding may extend service life before replacement.
