Magnetic Cylinder for Flexible Die Cutting

Magnetic cylinders are made to order for the machine they will run in. There is no fixed standard size. When you ask for a quotation, RK needs the following from you:

• Machine make and model the cylinder will fit (RK machine name, or the maker and model of another machine)
• Gear pitch and number of teeth of the die cutting unit
• Repeat length required, or the label size and gap you will cut
• Web width of the machine
• Whether you want the flexible dies for your current label shapes supplied along with the cylinder

A magnetic cylinder is a precision-ground steel cylinder with permanent magnets set into its surface. It is mounted in a rotary die cutting station in place of a solid die. A flexible die – a thin, etched or engraved steel plate with raised cutting edges – is wrapped around the cylinder and held in position purely by magnetic force. No clamps, screws or adhesives are involved.

Because the flexible die is the only part that changes from job to job, one magnetic cylinder can serve many label sizes as long as the repeat length of the cylinder suits them. That is the main reason converters prefer the magnetic cylinder and flexible die combination for short and medium label runs: the cylinder stays on the machine, and the dies are stored and swapped as needed.

Firm Magnetic Hold for the Flexible Die

The magnets are arranged across the cylinder face so that the flexible die is held flat over its whole area, not only at the edges. A die that lifts even slightly cuts unevenly, so an even hold is the first requirement.

Ground to Suit Rotary Die Cutting Units

The cylinder body and bearer rings are ground so the die rotates true against the anvil roller. This is what keeps the cutting depth the same across the full web width and around the full circumference.

Made to the Machine's Repeat and Teeth

RK supplies magnetic cylinders to the gear pitch, teeth count and repeat length of the die cutting unit they will run in. An example from the RK range is the wrist band machine, whose rotary die cutting unit runs an 80 teeth magnet cylinder with a flexible die.

Quick Die Change Between Jobs

With the cylinder left in the station, a job change is a matter of peeling off one flexible die and seating the next. That keeps changeover time short on slitting and die cutting machines that run many label sizes in a day.

Fits the RK Die Cutting and Slitting Range

The cylinder is a natural pair for RK's rotary die cutting machines, label slitting machines with die cutting and the die cutting stations on RK flexo presses, as well as for machines of similar construction from other makers.

Supplied With the Matching Flexible Die

RK also supplies the flexible dies themselves, so a customer can order the cylinder and the dies for the current jobs together and be sure they are matched.

The cylinder is mounted in the rotary die cutting station and geared to the machine drive, so it rotates in step with the printed web. The flexible die is placed on the cylinder with its leading edge lined up to a reference mark, and the magnets pull it down flat. The die's raised cutting edges now stand slightly above the cylinder surface.

As the web passes between the magnetic cylinder and the anvil roller, the cutting edges press through the label face stock and adhesive down to the release liner, but not through it. That is kiss cutting: the label is cut, the liner stays whole, and the waste matrix is stripped away and rewound on the next unit. Because the cylinder's circumference matches the label repeat, the same shape is cut on every revolution with no gap error.

• Self-adhesive label die cutting – the everyday use, on rotary die cutting stations of flexo presses and on offline die cutting machines.
• Label slitting and die cutting machines – slitters that also cut label shapes carry a magnetic cylinder in the die station.
• Short and medium label runs – jobs that change often, where swapping a flexible die is faster than changing a solid die.
• Wrist band and special label converting – the RK wrist band machine's rotary die cutting unit is one example of a magnetic cylinder with a flexible die in a dedicated application.
• Converters replacing worn cylinders – a replacement cylinder ground to the original teeth and repeat for an existing machine.

The magnetic cylinder itself does not touch the material; the flexible die does. With the right die, the combination kiss cuts the usual self-adhesive label stocks – paper, chromo, PP, PE, PET and similar film labels on a release liner – and can full cut thin unsupported paper and film where the machine's die station is designed for it. Tell RK your face stock, adhesive and liner so the die and the cutting depth are specified correctly.

• Flexible Diethe thin steel die that the magnetic cylinder carries; made to your label shape.
• Solid Diean engraved one-piece rotary die for long runs of one label shape.
• Printing Cylinderaluminium plate cylinders for RK flexo printing units.
• Powder Brake and Clutchweb tension control for unwinding and rewinding.
• Rubber Rollnip and pressure rolls for printing, pasting and slitting machines.

RK Label Printing Machinery Pvt. Ltd. has built label printing and converting machines in Ahmedabad, Gujarat since 1995, works from three manufacturing units and supplies customers in 23+ countries. Because RK designs and builds the die cutting units the cylinders run in, the accessory is specified against the machine rather than sold as a generic part. The company also supplies flexible dies, solid dies, printing cylinders and other consumable accessories, so a converter can keep one supplier for the machine and the parts that wear.

• Machine first: the cylinder must match the gear pitch, teeth and shaft arrangement of the die cutting unit. Send the machine model, or the details of the existing cylinder.
• Repeat length: choose the circumference to suit your common label sizes. A repeat that divides evenly into your label-plus-gap sizes gives no wasted web.
• Web width: the magnetic face should cover the full width you cut, with room for the bearers.
• Job mix: frequent size changes point to a magnetic cylinder with flexible dies; one shape run in very long quantities may justify a solid die instead.
• Dies along with it: ordering the flexible dies for your live jobs at the same time makes sure die and cylinder are matched.

The price of a magnetic cylinder depends on its diameter and repeat, teeth count, web width and whether flexible dies are ordered with it. RK quotes each cylinder against the machine it will fit. Prices are quoted ex-works Ahmedabad with GST at 18% applicable, and if an engineer visit is needed for fitting or setting, the engineer's transport and stay are borne by the customer. Send your machine details and label sizes to RK for a quotation.