What is the working principle of PV Ribbon Rolling Mills

      The PV Ribbon Rolling Mills belongs to the cold precision two roll/four roll reversible continuous rolling mill, which specializes in cold rolling oxygen free copper round rods and coarse copper flat billets into ultra-thin photovoltaic interconnect strips and converging copper strips. The core relies on the principle of metal cold plastic deformation, combined with constant tension closed-loop control to achieve micrometer level ultra-thin precision molding.

1、 Core Principles of Basic Physics (Cold Rolling Deformation)

Roller seam extrusion plastic deformation

The upper and lower pairs of high-precision hard alloy rolling rolls rotate synchronously in reverse, and the round copper wire/copper flat billet passes through the preset small roller gap; Hydraulic/nitrogen gas springs provide constant rolling pressure, causing metal to experience thickness reduction, width extension, and length extension under compression. In the solid cold state, the grains are refined without the need for heating and melting.

Friction realizes feeding and forming

The contact between the surface of the rolling mill and the copper material generates static friction, dragging the wire at a constant speed while radially compressing and thinning it; Multi pass step-by-step pressing, with strict control over the amount of single pressing, to prevent copper strip cracking, edge burrs, and dimensional deviations.

Law of volume invariance

The total volume of copper material before and after rolling remains constant: thickness decreases → length is significantly elongated, and the stretching speed is matched with the unwinding, traction, and winding before and after the rolling mill.

2、 Complete and continuous workflow of the whole machine (integrated production line)

1. Wire laying, pre drawing and pre-treatment

The oxygen free copper rod with a diameter of about 3mm actively releases the wire, which is pre drawn fine by the drawing die. The tension sensor provides real-time feedback on the tension, and the variable frequency motor adjusts the release speed to ensure that there is no shaking or knotting of the incoming wire.

2. Multi pass graded precision rolling (core process)

Multiple rolling mills are used in series for multi-stage rolling (usually 3-4 passes):

Rough rolling: With a large gap between the rollers and a large amount of pressure, it quickly presses round copper into coarse flat strips;

Mid rolling: gradually reducing the roll gap, correcting the width, and eliminating waves;

Precision rolling: extremely small roll gap, constant pressure rolling, producing 0.2-0.5mm ultra-thin photovoltaic strips;

Install tension frames and online thickness/width detectors between each rolling mill, transmit real-time dimensional data to the PLC, and automatically fine tune the rolling mill pressing oil cylinder with a tolerance control of ± 0.03 to ± 0.04mm.

3. Constant tension closed-loop collaborative control

The front and rear traction, rolling mill, and winding motor are synchronously linked, and the tension sensor continuously collects the tension of the strip:

Too low tension: copper strip deviates and bends;

Excessive tension: copper strip is stretched thin and broken;

The servo system dynamically adjusts the speed, maintaining a slight tension and smooth rolling throughout the entire process, ensuring that the strip is straight and without warping.

4. Online cooling and lubrication

Circulating water cooling inside the rolling mill takes away the frictional heat of cold rolling; Special copper rolling oil for roller gap spraying plays a role in lubricating, reducing wear, cooling, preventing oxidation, and improving surface smoothness, ensuring the adhesion of tin coating on the welding strip in the later stage.

5. Annealing, winding and forming

The rolled hard copper strip enters a continuous bright annealing furnace to eliminate internal stress during rolling, improve conductivity and bending toughness; After cooling, the finished photovoltaic copper base tape is obtained through storage line buffering and dual station precision wire winding, and can be directly coated with tin to make solder strips.

3、 Special shaped photovoltaic strip forming principle (triangle/arc welding strip rolling mill)

The new high reflective triangular welding strip and arc-shaped welding strip rolling mill have corresponding arc-shaped/triangular grooves processed on the surface of the rolling rolls. During extrusion, not only does it reduce the thickness, but it also constrains the cross-sectional profile of the strip, forming concave convex arc-shaped sections in one go, reducing the shading area and improving the power generation efficiency of photovoltaic modules. The cold pressing forming of irregular sections is completed by forcibly shaping the rolling roll grooves.