Cutting polyurethane foam is a topic we’ve discussed before, and Change– The process of cutting foam into shapes – is an integral area of the polyurethane foaming industry. We know this because cutting machines often make up more than 75% of Sunkist’s annual sales. Many of our loyal customers started out as a simple conversion plant with only two or three types of cutting machines.
Because they are so common, cutting machines are often overlooked. They don’t require the chemical expertise of continuous foaming, but they are still a school of knowledge in their own right.
So Sunkist has decided to collaborate with Albert Bandknives Germany, We’re bringing you the expert knowledge about cutting polyurethane foam from both the machinery end and the blade end. Together, we’ll answer every question you may have about bandknives and foam cutting. Want all upcoming articles delivered straight to your inbox? Subscribe to our mailing list now!
cutting machines 101
Here at Sunkist, we have nine different types of foam cutting machines:
- vertical cutting
- horizontal cutting
- long split
- block cutting
- CNC Cutting
- hydraulic press
The two most common types are vertical and horizontal cutting machines. Their names refer to the orientation of the blades, so vertical cutters have blades that extend from floor to ceiling while horizontal cutters have blades that run from left to right. These cutting machines need to be the most versatile in terms of what they cut because they take care of everything from flexible to rigid to viscoelastic foam.
Long splitting refers to the production of a long and relatively thin cut of foam, often stored and sold as a roll. The thinner your foam product, the more precise the cutting mechanism must be so that there are no bunches, tears, or uneven thickness.
Block cutters are used to cut slabstock into blocks. Their blades can be either horizontal or vertical, and machines are often installed on a conveyor line for continuous material flow. We prioritize rigidity here because with the foam block in motion, we want to avoid breaking the bandknife during cutting as much as possible.
Trimming can be done on any vertical or horizontal cutting machine, but it is often too laborious to be cost-effective. Trimming stations are often added on slabstock lines to automate and speed up foam conversion.
Convolutors, or foam profile cutters, make up a large percentage of Sunkist’s production. A sheet of foam is pressed between two patterned rollers, while a bandknife cuts through the center of the foam, dividing it into two sheets with interlocking topographies.
Peeling also produces long thin sheets of foam sold in rolls. Unlike long splits, however, peeling continuously removes the outer layer from the foam cylinder (like peeling the skin from a carrot or potato). Long splits, on the other hand, cut off the top layer of long rectangular foam blocks.
CNC cutting makes curved and highly detailed cuts possible, allowing preprogramming the bandknife to run along a computer-drawn path. Bandknives need to be precise and thin in profile for CNC to perform tight turns. They also want to reduce the amount of sawdust and destroyed material.
And finally, the hydraulic press. This is the only Sunkist cutting machine that does not use a knife to cut. Instead, it punches the shape of the foam with a metal mold.
Closed Knife 101
Written in collaboration with George Hank from Albert
Knife cutting is a big part of our daily lives, and everyone knows kitchen knives, razor blades, and wood saws. Throughout history, swords with mythological qualities have become famous in many places.
Here we talk about industrial knives.
The criteria that determine the selection of a cutting machine also apply to the correct selection of knives. Precision, efficient cutting, and durability are major factors. Bandknives used on foam and rubber cutting machines are made of carbon spring steel. They are optimized in structure, hardness and type of steel to maximize cutting ability and edge strength. In addition the steel must be sharp, weldable and shock-resistant.
The cutting machine determines the blade dimensions (length, width and thickness).
In general the following are: Categories to stab:
1. CNC Contour Bandknives:
As contour cutting leads to a 3-dimensional tight and precise shape, the contour bandknives are narrow (3.0–4.5 mm in width) to allow for easy winding. There are both dentate and dentate types, with different tooth sizes to be determined by the material.
2. Horizontal wide bandnives
Horizontal cutting machines such as loopers, splitters, peelers, convoluters and carousels/loopers use bandknives 30-100 mm wide. In most cases closed knives move between tight blade guides. The thickness tolerance of the blade should be less than 0.04mm to guarantee accurate cutting.
3. Vertical bandsaw and bandsaw
Vertical cutting machines with 6-35 mm wide blades come in smooth-edged (no teeth) or toothed varieties in various shapes. Single or double-edged versions, twisted welding, tooth setting and tooth hardening are all available options for cutting in one or two directions which will be discussed in an upcoming article.
company alberto Focuses on the knowledge of more than 100 years of experience in producing knives and saws in Germany.
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