Laser Die Cutting: “An Overview of Options for Diecutting”; Industrial+Specialty Printing; July-August 2010

What does your die cutting department look like? Do you have multiple flat bed presses “chunking” along making parts for your mobile phone, automotive part or gasket customers? Are rotary die cutting units rolling along at 450 feet per minute to produce labels?

Over the past several years converting departments have been forced to change along with the rest of the printing world due to the overwhelming demand for shorter runs. Traditional die cutting equipment continues to make up the majority of converting departments. While the types of parts produced have stayed within the general spectrum of the specialty printing, digital printing has become more acceptable forcing die cutting equipment to evolve. Die cutting systems on the market today offer many options such as in-line lamination, uv coating, sheeting, slitting, hot stamping, embossing, etc. Rotary die cutting and galvo laser die cutting equipment act as full converting lines while traditional flat bed die cutting systemsoffer forms of converting depending on the applications.

The goal of this article is to introduce, compare and educate industrial and specialty printers to the many opportunities in their own die cutting or converting departments. By comparing flat bed, rotary and laser die cutting I will attempt to offer solutions for a variety of converting needs. As specialty printer’s we see a proliferation of different material types in a range of thicknesses so finding the right die cutting equipment that positively affects your company’s bottom line can be a massive undertaking.

Laser Die Cutting
Within the laser die cutting circle there are two types of beam delivery: Gantry and Galvonometer (Galvo). Gantry systems use a laser source where the laser head either moves around on an XY plotter system OR remains stationary and the material moves into position under the head. This type of cutting has proven successful for high precision parts like membrane switches where tight tolerance cutting around plug-ins or switches is critical. Gantry systems have also inherent benefits when cutting materials thicker than 800 microns or wide format printing. The biggest complaint about gantry laser systems seems to be the running speed. Since either the material OR the head needs to physically move into position around the cutting pattern the gantry system can be very slow. There are applications in automotive part manufacturing where laser heads are mounted to the end of robots where precision and relative speed work in tandem.

Galvonometer (Galvo) laser systems have made the most significant advancements in the die cutting arena within the past several years, specifically in the label, medical device and nameplate industries. A Galvo head laser remains stationary above the web or sheet of material while mirrors within the head make slight adjustments to redirect the path of the laser onto the substrate. Since the Galvo head is cutting on an angle due to the nature of redirecting a laser source by mirrors, the thinner the material the better. This is in contrast to the Gantry laser that always moves into position directly above the cut area and pointing straight down.

Galvo-laser systems are equipped with camera registration units that offer flexibility in registering off of any color contrast. Cameras are positioned above the printed substrate and send positioning signals back to the Galvo head so corrections can be made on-the-fly in both X and Y axis’. Theta axis registration is achieved through web steering devices in roll applications and near side/far side sheet adjustments in sheet applications. Advances in Galvo operating software have increased speed capabilities and cut quality to the point where cutting larger labels across a 200mm or 350mm web can be achieved at 300 feet per minute. After years of trial-and-error Galvo systems are achieving tool-based system cut quality on polyesters, paper, polycarbonate, magnetic materials with a thickness range of 10-800 microns.

As the trend moves toward shorter runs this means more tooling expenses and more material waste. Laser die cutting removes the need for new and replacement tooling expenditures. Design time is virtually eliminated as vector based files can be imported directly into the laser die cutting system. Optimization software removes the need for the operator to set up cutting paths or optimize throughput speeds so installation of a never-before-seen job takes just minutes. New job die design and production times are usually very good for rotary or steel rule die systems, however, dies still have to be designed and ordered which can slow down production when unforeseen delays or changes to the die are needed.

Tooling expenditures from mid-level printing companies range from $50,000 to $100,000 annually. This is representative of tooling costs alone. Most of the tooling damage reported on traditional steel rule die or rotary die systems occurs during die installation or die removal from inventory. Material waste between job set up and the ability to nest parts closer together using a laser die cutting system add another 20-25% savings to your bottom line.

Galvo-laser die cutting systems are currently being sold in sheet, roll or combination sheet and roll fed systems. They are being used with a variety of materials including polyester, polycarbonate, plastic films, paper, adhesives and abrasive materials. One of the few materials that are not being cut on a regular basis on a laser die cutting system is PVC due to the gases emitted when burning the material and discoloration of the substrate when cutting through the material. Galvo laser systems are also adding rotary die stations and laser marking to their portfolio while running in-line with digital printers. The ability to take a new job in the morning and shipping finished parts by the afternoon is what makes a laser die cutting system a money making proposition for many printers.

Rotary Die Cutting
When you are looking for in-line converting of roll products at high speeds then rotary die cutting equipment is the most widely used. The use of rotary die equipment has been a staple in many label, textile and adhesive tape manufacturing operations for years due to overall speed and relative flexibility. A full cylinder rotary die cutter uses a cylinder that holds a die plate for making an impression during each revolution. The problem with shorter runs is there is no flexibility of changing the size of the step and repeat. In order to change the step-and-repeat you need a completely different cylinder which can be expensive. Over a decade ago, the introduction of semi-rotary die cutting equipment controlled by servo motors revolutionized the technology. The cylinder and substrate react in tandem to provide a lot of flexibility in terms of part layouts and step ups. A full cylinder rotary die makes for a laborious changeover when removing a full 20” wide cylinder that can weigh 400 lbs. A 25” full rotary die cylinder requires every print job to have the same step and repeat of approximately 23”. A 25” semi-rotary cylinder gives the user the ability to run, for example, a 12” step up therefore providing more reasonable die costs and much more flexibility on shorter run jobs.

Web steering control systems and semi-rotary X correction allow rotary die cutting systems to fit nicely in many applications. Web speeds for many label applications using full cylinder rotary systems can reach over 500 feet per minute while semi-rotary systems run between 100-150 fpm. In either case, most rotary die applications are considered thin material applications up to 20-30 thou. When tight cut-to-print accuracy (+/- 0.005”) in X, Y and Theta axis is necessary then rotary die cutting may fall short, however, there are plenty of printing applications where the step and repeat registration of rotary die systems are acceptable.

There are two types of rotary dies that are used for these systems 1) Hard tool and 2) Flexible die. The hard tool die uses a male/female cutting principle that generally works better on thicker substrates or very long runs. The flexible die consists of a magnetic plate that mounts directly onto the die cylinder. Since the cost for a flexible die is much less than a hard tool, flexible dies provide much more flexibility for shorter runs. Changing over a job when using the same material can take minutes if the step ups from job to job are identical and assuming the tooling has already been designed and only needs to be removed from inventory. Changeover can be delayed when there is a need to shim a die for a kiss cutting application but an experienced operator can usually reduce the time needed between jobs.

Flat Bed Die Cutting
On a very basic level, traditional flat bed die cutting involves a C-Frame or hydraulic press (tonnage ranges from 5 to 100+) and a die. Clam shell presses corner register a sheet of material so cut-to-print accuracy is determined by the relationship between the edge of the sheet and the print on the sheet. Optical or camera registration systems provide true cut-to-print registration because they register the die cut to the print on the substrate using print marks to register the image prior to the die cut. Some optical registration flat bed systems register prior to each press stroke which serves automotive, medical and plastic card applications very well. This differs from semi-rotary registration where the registration occurs prior to each revolution. Registration flat bed die cutting equipment offers both steel rule die and hard tool (machined steel) capabilities holding accuracy tolerances of +/- 0.005”. The advantage of steel rule die cutting is the tools are less expensive ($200 -$1,000) so changing to a new layout is relatively cheap. Hard tool systems require more steel and more expensive equipment to machine these tools so changing part designs can be expensive ($5,000-$40,000) depending on the application.

The plastic card and nameplate industries have embraced both steel rule die and hard tool technologies since cut-to-print registration is important and substrates are generally thicker than substrates used in rotary or laser applications. More force (press tonnage) is needed to physically cut the part. For example, manufacturers of insurance cards or loyalty cards find a 30 Ton press with a steel rule die design optimal since they may be using a teslin core (synthetic paper product) and polyester thermal laminate to make a part that is 400-760 microns thick. These cards are called carrier cards because they often include two CR80 (credit card size) cards within an overall mailing carrier design. The same card manufacturer can remove their steel rule die and place a hard tool in the press to produce standard CR80 size identification, financial transaction or hotel key cards. Due to the standard size requirements of many different types of cards a manufacturer might purchase one hard tool for $20-$30,000 and achieve up to 3,000,000 hits per sharpening and be able to sharpen the die 12-15 times.

Who’s the winner?
There is no clear cut winner since the specialty printing market incorporates so many different material types, material thicknesses and applications. Flat bed steel rule die systems and rotary die cutting systems offer relative flexibility while full cylinder rotary die cutting offers tremendous speed potential. Flat bed hard tool systems provide more accuracy in specialty cut-to-print applications due to the machining and durability of dies made from steel.

The one benefit for a digital finishing solution (laser die cutting) that can eliminate setup is a bar code reading device that differentiates jobs on-the-fly. A printed roll of material containing multiple jobs, geometries and step ups can changeover in minutes without any mechanical adjustments. Since flat bed hard tool systems and full cylinder rotary systems require approximately ½ hour for changeover, machinery for lifting heavy tools and higher cost to purchase and replace dies these solutions are reserved for longer run jobs.

Still Confused? There are more choices available for today’s converting professionals than there were only a few short years ago. Rest assured that there are many professional consultants and equipment manufacturers available to work with you on the best technology choices for your specialty product.

Mike Bacon is vice president of sales and marketing for Spartanics, which manufactures laser die cuttingsystems, steel rule die and hard tool cutting systems, screen printing lines, automated counters and other equipment. Spartanics is available for technology demonstrations and contract manufacturing services.