Flexible finishing19 September 2003
Bob Trkovsky, vp sales and marketing, Spartanics, on the versatility of die cutting equipment
Tackling growing market opportun- ities for new types of packaging, such as those made from more elastic plastics like Teslin, sometimes has less to do with the press and more to do with the finishing equipment on hand. The various types of die cutting equipment available to converters each have their plusses and minuses, such that combinations of one or another type of die cutting technology should be considered. This article will define the varied niches of flatbed, rotary, and gap die cutting presses and discuss how maximum versatility may be achieved by combining two or more types.
For many jobs, the inferior cut-to-print registration of flatbed and rotary die cutting presses is not a problem. However, a growing number of new package designs, especially for high end items such as perfume, do require tight cut-to-print registrations. To effect these type of tolerances, converters need to have electro-optically registered gap die cutting presses available. Better electro-optically registered gap die cutters deliver consistent precision registration accuracy in the X, Y, and Theta axes within 0.1 mm.
Flatbed and gap die cutters differentiate by their ability to handle a wide range of substrates that are at best messy and at worst non starters for rotary die cutting presses. Adhesives, for example, may present some nasty surprises the first time they are cut, and sometimes might even require the remake of tooling in order to achieve needed adjustments on a system. Smaller format gap presses may have the same problems if they are of inferior design.
As long as gap press die cutting equipment registers in the X, Y planes and rotation (Theta-axis) with each stroke of the die cutting or punching press, it can handle material elasticity with greater ease. Where one gets into problems is by trying to get gap die cutting systems that only correct for cut-to-print registration in the Y and rotation axis once per sheet.
Various die cutters are further limited in the size format of the jobs they can handle. While flatbed types are ideal for large format sheet-fed jobs, they cannot handle small sheet formats. Rotary machines cannot do the largest format jobs. Electro-optically registered gap die cutters can accommodate both sheet-fed and reel material in sizes that cover the full range of rotary cutters as well as the smaller end of flatbed press formats.
Neither rotary nor gap die cutters can deliver the type of throughput that is the forté of the flatbed system. Usually these machines use wide format steel rule dies and can cut a large number of parts simultaneously. Whether one uses a low or high tonnage flatbed press is usually a function of part perimeters, internal features, material being cut, and other aspects of a job. While gap and flatbed presses run at the same press strokes per minute (120), the large flatbed systems would typically have 40 cavities compared with two-four for the gap presses.
Rotary die cutters are also relatively fast, with speeds of 300ft/min and a corresponding high throughput. This often makes them the most economical option if the job specifications can be handled by the reel-fed configurations of the rotary die cut system. This is a big "IF", given the creative new package designs that are being introduced to the marketplace and the special features they often involve.
Both customers' requirements for just-in-time deliveries and the growing demand for short runs of speciality designs demand new focus on being able to accommodate both long and short runs. Electro-optically registered gap presses differ most from rotary and flatbed die cutters in this regard.
The greater throughput of flatbed and rotary die cutters has the downside of higher material costs for scrap during job change-overs. Until you can align registration properly, these types make a lot of bad parts quickly. Both flatbed and rotary machines' tooling designs also involve relatively longer times to fit and remove tooling during change-overs. For small runs of 50,000 units, for example, it would typically take longer to do this on a flatbed die cutter than to use the tooling for the run.
In contrast, tooling set-ups and change-overs are relatively instantaneous on electro-optically registered gap die cutters, especially the better models that position steel rule dies in the same place every time for a given job and require no make-ready adjustments. If you are running a series of short order jobs, these savings in change-overs will significantly impact the bottom line.
Tooling costs also come into play when one considers run length. Tooling for flatbed die cutters can typically cost two-four times the cost of that for rotary die cutters and even more disproportionate to the low cost steel rule dies for many jobs on electro-optically registered models. It simply requires more engineering to create tooling for flatbed die cutters and this usually makes them too expensive for short run jobs.
Consider, for example, the difficulties of levelling the die for a large sheet from right to left compared with levelling the die for a much smaller sheet. For long runs, one amortizes the high cost of flatbed tooling over many units making it the most economical option most of the time. For short runs, flatbed die cutters are rarely, if ever, competitive.
In today's marketplace, holding on to customers increasingly involves being able to meet changing job requirements for package design innovations. If you don't want to send customers seeking out competitors' services, it is best to have tooling on hand that has the flexibility to handle changing job requirements. That usually means adding die cutters whose main advantage is also flexibility for varying job requirements - electro-optically registered die cutters, to existing flatbed or rotary die cut equipment in a finishing department.
Converters should understand the strengths of each type of die cutter — flatbed machines handle long runs of large format sheet-fed jobs; rotary models handle long runs of reeled materials without need for special features beyond their reach; and electro-optical systems are ideal for short runs.
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