The Slice is Right: A Guide to Cutting-Equipment Selection
Learn about the types of cutting systems that are available, the capabilities each variety provides, and the production issues you need to consider before selecting a system for your operation.
For many screen printers, the decision to invest in substrate-cutting equipment is inspired by the desire to add new products and attract new customers. But far too often, printers purchase cutting machinery with only their current or short-term needs in mind and don't consider how this equipment will fit in with their future products and production goals.
While simple cutting equipment may be all that some screen-printing companies ever require, other shops need equipment that is flexible enough to take on a broad range of applications and fast enough to keep pace if production demands should increase. To ensure that the right machine is selected for the applications and the production environment, it's important to understand the pros and cons of the various cutting machines available today. Finding the right piece of equipment is a key step in streamlining finishing operations and realizing the greatest efficiency--and profitability--from the cutting process.
Available cutting equipment
The term diecutting applies to systems that use a steel-rule or hard-tooled die to cut materials, but other cutting systems are also available that screen printers may consider. The various cutting machinery offered today falls into six general categories:
* clamshell diecutting presses
* flatbed diecutting presses
* rotary diecutting presses
* gap diecutting presses
* cutting plotters
* laser cutting systems
For jobs with relatively loose requirements for cut-to-print registration, clamshell diecutting presses are still quite popular. These presses are generally hand-fed, so high-tonnage presses are most desirable. The high tonnage makes it possible to cut more pieces per press cycle, which helps offset the labor time associated with manually loading and unloading substrates on the press.
Like clamshell presses, flatbed diecutting presses are also good for situations where you need high output but have relatively low requirements for cut-to-print registration. These machines, some of which support automated material-feeding systems, usually use wide-format steel-rule dies and can cut a large number of parts simultaneously. Specific job requirements (the type of material to be cut, internal features such as creases or perforations, part perimeters, etc.) determine if low- or high-tonnage flat-bed presses are required.
Rotary diecutting systems are designed for processing roll-fed material. The tooling on these systems consists of a cylinder that rotates and cuts as material is fed between it and the surface of the press. While rotary systems can offer very high cutting speeds, their cut-to-print accuracy is also limited by the fixed nature of the tooling.
When cut-to-print registration tolerances are tight, image distortion due to printing irregularities (e.g., screen stretch during printing) or substrate dimensional changes (material stretching or shrinkage due to processing or environmental conditions) make it nearly impossible to get the required cutting accuracy from large-format diecutting presses. For these jobs, gap diecutting presses that use electro-optical registration technology and digital cutting systems that don't require fixed dies (i.e., cutting plotters and lasers) are the devices of choice.
The laser cutters and cutting plotters are often the preferred route for shops that deal in short-run cutting jobs or companies that need an effective solution for prototyping. The main advantage of these machines is their repeatability in terms of cutting accuracy. However, unless these devices incorporate vision-registration systems, they have no way to compensate for image or material distortion and gauge where they are cutting relative to the print area. These machines also have some other drawbacks compared to conventional diecutting presses in that they cannot crease materials and may be more limited in the range of materials they can cut (adhesives, for example, tend to be challenging for them).
Optically-registered mechanical gap diecutting presses using either steel-rule dies or hard tooling are hybrid systems that combine the speed of diecutting with the accuracy of a digital cutting system. Gap presses offer high-tonnage cutting in a narrow gap between the tooling head and the press bed.
Unlike clamshell or flatbed presses, gap-diecutting machines have a more limited cutting area and cut far fewer pieces per cycle (usually 2-4 pieces). However, when these presses are equipped with electro-optical sensors and fully automated material-handling systems <B>(Figure 1),</B> they provide minimal labor costs and economies of operation that are equivalent to conventional diecutting equipment. Optically-registered gap presses don't just provide greater accuracy, they are also far more flexible in terms of the range of materials they can handle and the special features they can create, such as creases, embossed areas, and perforations.
Cutting-system selection and run length
The make-ready considerations associated with each of the different cutting systems can have significant bearing on which type of device a screen shop should select. But these considerations are frequently overlooked by screen printers.
When applications don't involve challenging substrates or adhesives and run lengths are short, digital lasers and cutting plotters clearly offer the best return for the investment. However, as run lengths increase on these systems, consumables costs (replacement laser heads and blades for cutting plotters) can become uneconomical, and the slower op-erating speeds of these machines can begin to hinder productivity. For longer run lengths, flatbed or gap diecutting presses deliver the best value.
Focusing on diecutting systems, the primary economic concerns relate to the cost of making die adjustments and maintaining run lengths to offset these adjustment costs. Typically, tooling-adjustment issues arise when screen printers are working with materials that they have not used before or recently. Adhesives, for example, may present some nasty surprises the first time they are cut. These materials can lead to significant downtime when dies must be cleaned and readjusted repeatedly to achieve the proper cut. On occasion, the adjustments become so dramatic that the tooling must be completely remade.
With a smaller-format gap press, however, such adjustments become significantly easier as the tooling features far fewer cavities than the dies on larger-format clamshell and flatbed systems. Where these larger systems may have 40 cavities, the smaller gap press may have only 2-4. Also, the optical-registration feature on high-end gap presses ensures that die position is always accurate. This means that tooling adjustments are required far less frequently, and when they do occur, the adjustments do not have to be repeated. Once the tooling is adjusted, shops using these machines can easily handle periodic short-run repeat orders of the same job and don't have to worry about repeating their make-ready tooling adjustments.
Overcoming production bottlenecks
All manually-fed cutting systems are prone to cause production bottlenecks. These bottlenecks stem from the amount of time it takes to feed and unload materials and to remove cut pieces from sheets and rolls, which is typically far slower than the screen-printing process that is churning out the printed material. For shops using manual cutting equipment, making sure that sufficient labor is on hand is the only way to avoid such delays.
For high-volume production with flatbed, rotary, and gap diecutting presses, the best option is to incorporate automated material-handling systems that feed and unload materials as well as remove the cut parts (Figure 2). Parts collection and batching can also be automated.
Trying to accommodate every application with its own sheet size to optimize material usage is not an effective approach to diecutting. Sheet (or roll) size variations lead to excessive tooling adjustments and require other modifications in prepress and printing, all of which increase downtime and reduce productivity. A better route is to gear all of the plant's production for a minimum number of standard sheet or roll sizes and to plan production so that you are changing from one material size to another as few times as possible. The reduced down-time this approach provides will far off-set any resulting increase in scrap costs.
Production bottlenecks can be avoided further if you plan diecutting jobs with all of your facility's cutting equipment in mind. This means that all printed materials must contain correct registration marks that correspond to all the diecutting presses in your operation. With this sort of standardization, you always have the option of running jobs on two or more machines to meet delivery schedules. Such standards also let you optimize capacity or simply make switches to find diecutting machines that work better for special job requirements.
Art departments also need to know how to gang images and otherwise create designs that keep scrap to a minimum on all the shop's equipment. Standard design layouts should accommodate the minimum scrap-area requirements around the perimeter of a sheet and between pieces for all the cutting equipment in the shop, not just for specific machines. Since art departments are generally not aware of which diecutting machine will be used for any given job, artists need to design graphics so that they accomodate the largest scrap areas required by their equipment.
Managing die inventory
Few high-volume printers can support their cutting needs solely with lasers and/or cutting plotters, and most have some form of diecutting solution at their disposal. Those that do employ diecutting face a common challenge in making sure that the right dies are on hand when they're needed.
Tooling-availability problems are a very common source of bottlenecks. Either the tool is not delivered on time or there is something wrong with the tool that becomes clear when production begins, making it necessary to replace the die. Cultivating close working relationships with skilled diemakers will help you get the right dies when you need them and will make it much easier to have dies adjusted on short notice. In some screen-printing operations, the volume of dies required may be high enough to justify creating an in-house diemaking department and employing full-time diemakers.
Regardless of where dies are made, printers that have developed systems for maintaining die inventories face far fewer production hang-ups than those with sloppy die-management policies. Some users rationalize that steel-rule dies are relatively inexpensive and throw them away shortly after each job, despite the fact that many of the dies can be reconfigured and reused for other applications. Maintaining a die library can help avoid the expense of continually buying new tooling. Such libraries or die-storage areas can be arranged in some sort of numerical sequence by job and/or customer. More sophisticated shops use bar-coding systems on dies with scanners to ensure that the correct dies are selected. Some high-end gap presses are equipped with memory features that allow you to input a die number so that the system can automatically recall all job settings for use with that die, greatly minimizing setup time.
Because of the great number of dies that shops can have on hand, they also should have procedures in place for double checking that the artwork for a given job has not changed. One of the most common production glitches that occurs is when printers set up tooling for a job that they think is a repeat order when, in fact, the customer has made slight revisions to the design that require tooling changes, too.
Additionally, procedures need to be in place to ensure that dies are handled and stored properly. Steel-rule dies can be nicked relatively easily. Hard tools also need to be properly stored, inventoried, and monitored for wear. If you try to push the use of a hard tool too long without sharpening it properly, you will eventually find yourself in the midst of a run that the tool can no longer cut with clean edges. A successful backup strategy that many screen printers employ for hard tooling is to always have a steel-rule die or a spare hard tool made that can be used as a backup if the primary tool needs to be refurbished or recreated.
Successful die management also includes making cost-effective decisions about which types of dies to use with which jobs. For example, consideration should be given to the life cycle costs of various types of dies because up-front cost is usually a poor indicator of lifetime costs for the tooling.
A typical sourcing scenario for a hard-tooled die might turn up two options, including a high-end die and a lower-cost die. Assuming identical die configurations, the high-end die might have a price tag twice as high as the lower-cost option, but withstand 3,000,000 cycles before requiring sharpening and support resharpening 12-15 times during its lifetime. The lower-cost die may also allow resharpening 12-15 times, but could require resharpening after 1,000,000 cycles. So for twice the initial cost, the high-end die would support 3 times the number of cutting cycles as the less-expensive tool. However, if you wouldn't expect to use the die for more than 15,000,000 cycles, buying the more costly tool would be an unnecessary expense.
Maintenance and training
It always pays to follow maintenance procedures recommended by equipment and die manufacturers. Most of these maintenance procedures require very little time, and when compared to the costs of downtime, their expense is negligible. One of the most fundamental maintenance habits that you should get into with diecutting equipment is to track the number of cycles that the press has been in operation. You can establish regular maintenance routines, such as sharpening of dies, based on the cycling history of the press, much like you schedule maintenance on your car based on accumulated mileage.
In selecting equipment, you should also consider how long it takes to make repairs and whether loaner equipment is available from manufacturers. Modular equipment enables manufacturers to provide loaner modules that help ensure continued uptime when equipment repair becomes necessary. Also, it usually pays to keep important spare parts for the equipment in house.
To realize a full return on your cutting-equipment investment, it makes good sense to properly train employees on how to operate the machinery. Some users believe that operating cutting equipment involves little more than turning the power switch on and off. But the fact is that when screen-printing companies take time to train workers on proper equipment operation, the companies see more throughput and fewer equipment breakdowns. Before committing to a new cutting system, find out what type of training options the equipment manufacturer offers.
Cutting to the chase
Whether you wish to support new products or enhance your current production process, the perfect system awaits you. It may be a fast flatbed diecutting system, an economical cutting plotter, or a high-end gap press augmented with optical-registration features. To match your needs with the right piece of equipment, give careful attention to your current goals and future production plans. Make sure the equipment you select offers the level of speed, accuracy, and flexibility you need to help your business profit and grow. By understanding all the options in cutting technology and the advantages and drawbacks of each, you'll be able to ask educated questions and find the machine that's the right fit for your operation.