Automatic oil film feeder: matching one feeder to different materials

An automatic oil film feeder pushes stock forward on a thin film of oil rather than dragging it across dry steel. A pump wets the lower surface, a pair of feed rollers or a belt applies light pressure, and the film separates the stock from the guide plates. Friction drops, so thin or soft material does not buckle at the entry.

Film thickness is the control variable. Too thin and the stock scratches the guides; too thick and the rollers lose grip, so feed length drifts. Most units run 5–20 μm wet film, set by oil viscosity and roller pressure. That window shifts with material hardness and surface finish.

The feeder itself does not care what alloy is on the coil. What changes is how the stock behaves under pressure: stiffness, surface hardness, springback after the rollers, and how well oil clings to the surface. Those four properties decide whether one feeder setting covers a mixed-material run or whether you need separate recipes.

• 1
  Rigid stock, light filmCold-rolled steel and stainless hold shape with minimal support.
• 2
  Soft stock, wider guidesAluminium and copper mark easily; plastic needs the widest clearance.
• 3
  Wet vs dryOily stock suits drawing and forming; dry stock suits clean assembly.

Cold-rolled steel and stainless steel are the easy case. Both are stiff enough to bridge the gap between feeder and die, and a 10 μm film gives stable feed length. Stainless 304 and 316 work, but they work-harden at the roller nip if pressure is set too high, so we keep roller load low and let the film do the separating.

Aluminium is where most feeder problems start. 5052 and 6061 are soft, and a hard roller leaves marks that show after anodizing. Use urethane-covered rollers and lower pressure. Copper and brass behave the same way and also pick up oil unevenly, so the film has to be re-applied closer to the die.

Plastics are the hard limit. ABS, PC and POM have low stiffness and high thermal expansion, so a feeder tuned for 1.5 mm steel will over-feed a 1.5 mm PC sheet. PEEK and carbon-fibre sheet are stiffer but abrasive; they wear rollers fast. For these, a belt feeder with a wider contact patch usually beats a roller pair.

Below roughly 0.3 mm, most metals lose the stiffness to bridge the feeder gap and sag into the guides. You can still run them, but you need a support plate under the stock and a shorter unsupported span. Above 6 mm, roller pressure has to rise enough that the film squeezes out, and feed accuracy drops.

Width matters as much as thickness. A narrow strip under 20 mm tends to rotate in the guides, so add edge guides or run the stock through a channel. Wide sheet over 600 mm needs a crowned roller to keep the film even across the face; a flat roller leaves the centre dry and the edges flooded.

Perforated, lanced or pre-notched stock breaks the film. Oil escapes through the holes and the feed length wanders. In that case, switch to a grip feed or add a second oiling point after the first station. Pre-formed parts with bends rarely feed on film at all.

The parts that decide feeder life are the roller shafts, guide plates, pump housing and the metering needle seat. Roller shafts need concentricity and a ground finish so the roller runs true; we hold ±0.005 mm and Ra 0.8–1.6 μm on the bearing journals. Guide plates take the most wear, so we cut them from 440C or 17-4PH and harden the working face.

Pump housings and valve bodies are usually 6061-T6 or 303 stainless. Aluminium keeps weight down on moving assemblies; 303 machines cleanly for the small internal bores. Metering needle seats need a fine finish so the film thickness stays repeatable, which is where Ra 0.2–0.8 μm matters.

We machine these on 3-axis and 4-axis mills for the plate work, and on our 5-axis centers when a housing has angled ports or a curved oil channel. Mill-turn handles the roller shafts in one setup, which keeps the journals concentric. From one prototype to 10,000+ part runs, no minimum order quantity.