Die-less cutting -Part 1 (Knife cut)
What is Die-less cutting?
Die less cutting, otherwise known as continuous cutting is used for cutting both leather and synthetics. In this method, computer controlled cutters (either mechanical knives or high-pressure waterjet) will cut the material of single or multiple layers, from a previously prepared computerised lay plan. The action is to cut around each piece with a continuous tracing motion, rather than a press action. Because conventional knives and dies are not needed with this method, it is possible to produce faster with new styles and to make modifications quickly and easily. Usually CAD data can be fed directly to the lay planning software. With mechanical cutting knife versions there may be difficulties while cutting some very intricate shapes as allowance has to made for the shape and size of the blade.
Over the years there have been several investigations of the technology associated with novel cutting techniques such as ultrasonic knives and plasma jets. Bust there remain only 3 cutting techniques till today used in the Footwear industry. They are
1. Knife cutting (Reciprocating or drag knife)
2. Water jet.
3. Laser jet
Why go dieless?
→ No need to wait for cutting dies.
→ Reduce the costs of dies required for cutting patterns.
→ Pattern development costs:No need of preparation of patterns dies etc. You can completely remove the development costs
→ Maintenance of Dies/Spares: Depending on the toughness or density of the material you cut, you may have to periodically sharpen and replace your dies. Some may keep spare dies. You can avoid all these costs by using the cutting system.
→ Reduce material waste.
→ Can cut all type of thickness i.e Very thick or thin.
→ Accurate cutting is possible.
→ No cutting by hand or with templates.
→ Nesting can be done to suit today’s production mix.
→ Material handling: Because of no dies involved, the cutting room can switch from product to product without any effort. No rack of dies to be found and moved into position and there is no material handling need for this. So indirect labor cost can be reduced.
→ Reduce lead times-design a component and produce it in seconds.
→ Floor space needed to store Dies will be reduced.
→ Change over time: If any changes in the design the whole process (dies preparation) has to be repeated. In case of computers you can reduce them. Possible to cut simple or too complex shapes.
Types of Die-less Cutting Systems
1. Knife Cutting Systems:
Mechanical knife cutting systems are used to samples and small production runs. In mechanical system the material is pulled down against a cutting bed and held in position during cutting by a powerful vacuum system. (Ex. Atom’s FlashCut series). The cutting device is usually a special knife blade reciprocating at very high speed. Todays machines also include oscillating knife, fixed ‘drag’ knife, electrical oscillating knife, punch’s, Pricker, creasing tool, rotary cutter and pen. A Lay planning is usually carried out to interactively on the leather to be cut using computer aides and incorporating an overhead image projection system. Operator control the image on the surface of the leather, then operator builds up a complete lay plan piece by piece before activating the cutting action.
This approach used the traditional skills of cutting operatives in similar way to manual cutting. The cutter uses visual and tactile skill to assess the skin and identify the position and seriousness of flaws, unusable area and lines of tightness. Then he uses his special skills to plan the nesting of shapes to be cut from the skin using above parameters. Systems are available from a number of suppliers with either single or double workstations (Ex. Procam Procut twin cutting system,). With double workstations, while cutting at one station, lay planning cabin be carried out at the other, then the roles are immediately reversed for fast, flexible production.
The latest leather cutting systems captures the hide shape and up to four flaw grades in seconds using a digital camera. It then analyzes the image and automatically nests parts to maximize hide yield. Cutting is fast and extremely accurate with Precision Knife Technology. Ex: Gerber :Taurus II Leather cutter.
Advantages of Knife Cutting Systems:
→ Economic Price
→ Ideal for woven, non-wovens, industrial fabrics, technical textiles, laminate, corrugated materials, etc.
→ Cost of running the system is much less.
→ Sheet or rolled goods can be processed. ·
→ Conveyorized beds available. ·
→ Replacement knives are inexpensive.
Cover image : Atom Flashcut 222/888 series
Source: Class notes prepared by A.V.Suresh, Ex.Sr . Technical officer, CFTI, Agra for students, while he was working in CFTI, Agra