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As more cutting tool manufacturers concentrate development efforts on the burgeoning Swiss-type turning market, numerous new and interesting cutter configurations are available for shops. Quick change is a watchword for these tools, as changeover flexibility is a crucial consideration.
Kennametal’s KM tool lock system has been available to general turning shops for many years. The Micro model is scaled down for screw machining but still provides a rigid coupling between tool shank and cutter head. A twist of the connector screw frees only the tool head. Repeatability is generally sufficient to eliminate re-qualification of the tool.
The productivity of new Swiss-style machines has increased in recent years as faster spindles, more rigid bases and improved controls have made it possible to dramatically increase metal removal rate. But while cycle times have been substantially reduced, the time required to change cutting tools has stayed largely the same.
The result is that machines spend a greater and greater proportion of their time sitting idle while inserts are indexed and toolholders are set up. Just recently, cutting tool manufacturers have begun to address this problem with a new generation of quick-change systems designed specifically to meet the requirements of Swiss-style machines. Because today’s faster machines proportionately spend so much time waiting for tools to be changed, these new tooling systems can deliver dramatic cost savings on the order of $20,000 in added revenues per machine per year.
While the concept of quick-change tooling systems is far from new, cutting tool manufacturers have long neglected the Swiss-style market, probably because they were concentrating on the much larger and more lucrative market for turning centers. Several quick-change tooling systems have become very popular in the marketing for larger toolholders because they typically provide productivity gains on the order of 80 percent by increasing the proportion of time dedicated to productive metalcutting from 30 percent to 55 percent.
Today, 13 percent of new machines are equipped with quick-change tooling, and this number can be expected to rise to 50 percent in the next 5 years because the economics are so compelling. Of course, these systems are not designed for nor can they be used on Swiss-style machines.
A number of small cutting tool manufacturers have attempted to fill this void by developing systems that make it faster to change the inserts on Swiss-style machines. Since access to the insert is generally from the side, there’s no way to get at the screw that is normally used to fasten the insert from the top. So, these companies have typically developed special clamping systems that allow side access.
The problem with the systems that have been developed up until now is that they require special inserts that are only available from the toolholder manufacturer. This means that the purchasers of these systems are locked into a single insert manufacturer that they must buy from regardless of cost, and they are unable to take advantage of advancements in cutting tools and chip control geometries offered by other companies. As you might expect, the market acceptance of these systems has been relatively weak.
That’s why it’s so exciting that major cutting tool manufacturers have begun to address the Swiss-style machine market with quick-change tooling systems that are similar in design to the systems that address the larger machine market. A typical design consists of a clamping unit that is attached to the gang plate like a conventional Swiss-style toolholder. The clamping unit locks a special toolholder that uses a coincidental cone arrangement to provide three-point contact between the clamping unit and the toolholder. The operator indexes the inserts on a toolholder while the machine is running. Then, when the insert in the machine needs indexing, the operator simply switches one toolholder for another, which only takes about 30 seconds.
The new tooling systems can provide dramatic increases in revenue generated by Swiss-style machines by reducing tool-change downtime. Changing inserts on a Swiss-style machine is normally time-consuming because the tools are arranged so closely together that it’s usually necessary to take the tool out of the gang plate. This means that a simple insert change typically takes about 5 minutes, considerably more time than is required on a conventional turning center.
If we assume that an average of five tools needs to be changed per 8 hour shift and the plant works three shifts per day, 5 days per week, and 46 weeks per year, then the machine is sitting idle a total of 287 hours per year during toolchange. By cutting the time to change a tool to only 30 seconds, the newest generation of quick-change tooling systems can reduce annual downtime to only 29 hours per year. In a typical case, quick-change toolholders also can substantially reduce setup time from 30 minutes to 5 minutes by eliminating the need to strip the gang plate.
The new quick-change tooling is available in a wide range of sizes and styles to suit nearly every common operation on virtually all Swiss-style machines. For example, one manufacturer offers clamping units to fit 12 mm, 16 mm, ½ inch, and 5/8 inch gang plate slots. Special gang plates and clamping units are also available that can make it possible to upgrade some machines to hold seven tools rather than the normal six.
Toolholders are offered for screw-on inserts as well as pin-and-clamp toolholders that use negative rake inserts to provide cutting edges on both sides. Available styles include threading and grooving tools, on-edge grooving tools, integral and modular cutoff tools, back turning tools for turning away from the chuck, and collet chucks for drills and taps.
Operators of Swiss-style machines are migrating toward this new generation of quick-change toolholders because the systems can provide hundreds of hours per year in additional production capacity. The savings are typically enough to pay for the cost of the new tooling in a matter of a few weeks.
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