HSK Force Gage

CAT/DIN/BT Force Gage

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HSK standard and parametric CAD/CAM—What do they have in common?

                                             Eugene Kocherovsky, Ph.D.

    HSK (which means "Hohl Shaft Kegel" in German or in literal English means "Hollow Shank Taper") is an abbreviation of the new tooling standard developed in Germany in the early 1990s. Many of the machine tools imported from Europe already have built-in HSK spindles. Companies in the U. S. have also started to adopt this revolutionary connection, especially for high speed machining applications. Makino Inc. pioneered the implementation of HSK spindles on the Western side of Atlantic, and others have followed.

The history of HSK's development is interesting, starting with a retrospective glance at the introduction of the CAT (an abbreviation of the traditional steep taper shank) standard for machining centers and the VDI (also a tooling shank, standardized in Germany) standard for turning machines. Before HSK, the pattern was to standardize products that already were proven on the market and just required some formal "legislation" to became a standard.

HSK's birth was a totally different story. End users, machine tool builders and tooling manufacturers in the middle 1980s started to experience lackluster performance of traditional interfaces. The end users demanded a brand new solution that would be widely available, free of patent infringement and capable of addressing high-speed machining as well as traditional operations.

A working group was established, with representatives from the academic world, machine tool builders, end users, cutting tool manufacturers and the standardization community. After about five years of development and testing, a brand new standard was published. It was not a single solution but rather a set of standards, which included six types of HSK shanks and 35 sizes. Exactly the same matrix was generated for spindle receivers to match each type of shank. Table 1 illustrates a variety of these products.

Table 1. illustrates variety of products.

Table 1. Available nomenclature of HSK Shanks per DIN 69893 and Receivers per DIN 69063

A generic feature of the full spectra of shanks is a hollow taper with ratio 1:10. All other features of the connection vary, depending on the type and severity of application. Figure 1 shows an overview of all the shanks. Some have drive slots, V-grooves for automatic tool change, I.D. chip cavities, internal coolant channels and so on; some do not. Each feature addresses a particular issue, the total giving a range of choices to end users. If a connection, for example, will be used on a machine with an automatic tool changer, then an A, B, E or F shank can be used. If a connection will be used for a manual tool change (for example, on transfer lines), the C or D style may be purchased for a much lower price. If extremely high torque has to be transferred, shanks B and D would be better solutions. For the majority of general applications, shanks A and C will make the job.

One of nuances of HSK development is that it is not carved in stone. Because the first official document was published in 1993, many changes and alterations of dimensions and form of features have been announced. This ongoing evolution requires tooling manufacturers to build special sensitive systems that will allow fast reaction to any correction. Such systems can guarantee that the end user will have at any time the latest and greatest product in accord with the standard specification.

Valenite, Inc. has participated from the very earlier steps in the development of the HSK interface. Our first offer of a comprehensive HSK program goes back to 1992, when HSK was under the name STS (Standard Tooling System). From the very beginning, we envisioned a CAD/CAM system for HSK that would store all information all at once in one place. In this case all corrections or changes would have to be performed once. Also, we recognized that our HSK product line is a perfect example of an extensive Family Part (Figure 2), and we had to handle it by using advanced parametric CAD/CAM: Pro/ENGINEER.

Fig. 2. Available sizes of HSK-A Shanks

We started from analysis of all possible features that we could foresee. We had in mind that some current features may eventually be gone and, vice versa, some features that do not exist now may be added in the future by a working committee as the result of an end user's request. Therefore, we established design rules that minimized parent-child relations between features and made possible easy interventions inside a solid parametric model at any time.

After that, we built a single solid model, which included all possible situations—all slots, grooves, holes and so on. Using the advanced functionality of Pro/ENGINEER’s Family Tables, we established a complete matrix of shanks (again, see Table 1). This was expanded not only to have geometric information for the shanks, but also for bill of materials for each shank, history of changes, manufacturing information and specific company-related information. Everything was stored in compact ASCII format in one "spreadsheet" file.

Each line of this tabulated file represents a complete DNA profile for one type of shank from the family. We used every shank as a separate virtual component in thousands of models—standard and special HSK adapters and special boring, milling and drilling tools, etc. However, information for a shank is stored only once, in the Family Part file. When it is used in other places, it is only retrieved with on-the-fly passes of information for a particular job and then made to disappear when the job is completed. The only record or pointer is where the shank is retrieved.

This approach has tremendous advantage. For example, that HSK63A shank was used in 1500 jobs, which were manufactured and shipped. Each of these jobs only pointed to the shank HSK63A, but did not copy the shank. Now an International Standards Organization (ISO) working group decides to make slight modifications—it changes tolerances of the hollow taper and adds some features, which improve the static balance of connection. In traditional technology, the designer has to visit all 1500 jobs and make all the necessary changes in order to be up-to-date. In our case, we retrieve only one file—Family Part—make the necessary changes and store them. From this point on, each time we retrieve any of the 1500 jobs made earlier, the information will be updated automatically. Also, the numeric control (NC) code in the CAM model will be modified accordingly, following geometric information retrieved from the Family Table.

This has an excellent effect on the maintenance of high volume jobs for middle and large companies.

Eugene Kocherovsky is a project specialist with Valenite Inc., Madison Heights, Mich. He is also the author of the HSK Handbook. He can be reached at intelcon@hskworld.com or www.hskworld.com.

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