Wood working26.08.2015

Die cutting cardboard boxes

When opening a cardboard package, we rarely stop to think about the long and complex process involved in making a cardboard box out of wood. The wood raw material is first processed into cardboard at pulp and board mills after which the box itself is manufactured by cutting the shape of the box out of a large roll of cardboard using a die cutting tool. Some plywood also comes in handy.

Manufacture of a die cutting tool for producing round cardboard end pieces.

Manufacture of a die cutting tool for producing round cardboard end pieces.

Polytronic Oy: Managing Director Jani Kaunisto

Polytronic Oy: Managing Director Jani Kaunisto

Polytronic, located in Valkeakoski, is Finland’s largest industrial manufacturer of die cutting tools, producing both flatbed and rotary die cutting tools for use in the packaging industry. The company’s net sales in 2014 came to just over EUR 2 million and, in addition to its three owners, the company employs 12 people. Next year, the company will be celebrating its 30-year anniversary.

“During the past two years our order book has been growing and we have invested in knife automation and a second laser cutter. And more investments are in the works,” says the company’s Managing Director, Jani Kaunisto.

Knife mounter Heikki Nikkanen servicing a die cutting tool.

Knife mounter Heikki Nikkanen servicing a die cutting tool.

Manufacturing tools requires precision

The die cutting tool is assembled from flat or semi-cylindrical plywood, various knives and several grades of rubber. Numerous work stages are required and it is important to be careful with the die cutter once the knives have been installed – if you want to keep all your fingers.

First, a groove is burnt into the surface-treated plywood panel, which can be enlarged from the back using a CNC machine for the removal of cardboard scraps. Koskisen supplies Polytronic with the semi-cylindrical KoskiLaser rotary cutting panel, in particular.

“Koskisen’s die board is a perfect fit for the die drum,” says knife mounter Heikki Nikkanen.  

Lasering of a die board.

Lasering of a die board.

The width of the groove created through laser cutting is adjusted by altering the height and speed of the laser nozzle. After this, the knife is mounted using a plastic hammer, without damaging it, but hard enough to ensure that the knife sits firmly in the groove.

“Durable and precisely dimensioned Finnish birch plywood is an excellent surface for attaching the knives,” says Nikkanen, mounting a knife using a plastic hammer.

The knife cuts the shape of the box out of the cardboard and the scoring rule forms the box’s creases. In addition to knives, ejection rubbers are installed in the die cutting machines for removing scraps. 

Knives are mounted securely into the grooves in the die board.

Knives are mounted securely into the grooves in the die board.

“Rotary die cutting tools are gaining in popularity among packaging manufacturers. Due to their round shape they can be used to continuously and efficiently cut out cardboard boxes, while flat die boards are better suited for manufacturing smaller batches,” explains Managing Director Jani Kaunisto.

Meticulous work

One die cutting tool is used to manufacture hundreds of thousands of boxes, which means that the plywood die boards, knives and rubbers need to be durable.

“As a Finnish company we of course wish to purchase the wood raw material for our die boards from Finland. However, due to availability issues, we purchase the knives and ejection rubbers from abroad,” says Kaunisto.

Polytronic serves its customers through fast die cutter deliveries and by servicing used die cutting tools. 

Fact box

  • Polytronic Oy, Valkeakoski. Established in 1986.
  • Finland’s largest manufacturer of die cutting tools. Manufactures both flatbed and rotary die cutting tools.
  • Net sales just over EUR 2 million, 12 employees
  • Owners: Jani Kaunisto, Harri Koivisto and Juho Kuusinen
  • Combined, the owners have more than 70 years’ experience in the business.
  • Koskisen supplies KoskiLaser rotary die boards for the manufacture of die cutting tools.