An Introduction to Live Tooling
As jobs change or volume increases and the need arises for new machinery, don’t just accept the standard tooling packages provided by the builder before researching whether live tooling makes sense.
Live tooling, as the name implies, is driven by the CNC and the turret of various spindle and powered subspindle lathes to perform various operations while the workpiece remains in orientation to the main spindle. These devices, whether BMT or VDI, are also called driven tools, as opposed to the static tools used during turning operations and are usually customized for the machine tool builder’s turret assembly.
Most often, live tooling is offered in standard straight and 90-degree configurations with a wide variety of tool output clamping systems, including collet chuck, arbor, Weldon, Capto, whistle notch, hydraulic, HSK, CAT, ABS and others.
As jobs change or volume increases, or as you encounter specific challenges in machining very large parts with deep pockets or very small intricate parts, and the need arises for new machinery, a common error is made by accepting the standard tooling packages provided by the builder. You need to do as much evaluation of your process when determining the proper tooling to be used as you did when you evaluated the various machines available for purchase.
This examination can range from the simple (for example, external versus internal coolant) to the sublime (for example, adjustable or extended tooling configurations) to the truly exotic, an example of which will end this article.
“Live” or “driven” tools, whether BMT or VDI, are usually customized for the machine tool builder’s tool turret assembly.
Tool life is the product of cutting intensity, materials processed, machine stability and parts produced. Two seemingly identical job shops can have vastly different tooling needs because one is automotive, one is medical, one specializes in one-offs and low-volume work, while another has a greater occurrence of longer run jobs. The totality of your operation determines the best tooling for the machines being purchased.
Bearing construction and the resulting spindle concentricity drive the life of any tool, and you might find that a mere 10 to 15% greater investment in a better design can yield both longer-lasting cutters and consistently superior finish on your products. Of course, the stability and rigidity of the machine tool base are also critical factors, especially on large or deep-pocket workpieces, where the distance from the tool base to the cutter tip is greater. Bevel and spur gears that are hardened, ground and lapped in sets are best for smooth transition and minimal runout. Roller bearings are consistently superior to spindle bearings in live tooling applications, so look for a combination system to get the highest precision possible. Also look for an internal versus external collet nut, so that the tool sits more deeply in the tool. Likewise, coolant high pressure might be desirable. Look for 2,000 psi in 90-degree tools and 1,000 psi minimum in straight tools.
You need to ask another question, namely: Is the turret rpm enough to handle the work to be done? It’s possible a speed increaser on the tool would be helpful. Would it be beneficial to move secondary operations to your lathe? Polygon machining can take care of gear hobbing or producing squares or flats.
Standard live tooling is most often suited to production work, where the finish, tolerances and cutter life are critical; whereas quick-change systems may be better suited to the shop producing families of products and other instances where presetting the tool offline is a key factor in keeping the shop at maximum productivity.
This opens the discussion of long-term flexibility, which is the most often overlooked consideration in buying live tooling. What work you have in the shop, what work will be coming and the overall economies of a changeable adapter system on your tooling may be considerations that wind up ignored when the focus is centered on the machine being purchased. Dedicated tools for large families of products may be desirable, but consider a changeable adapter system, and talk to your supplier before making that determination. Likewise, if the future work you’re bidding involves more product families, then think ahead when buying the initial tooling on the machine.
Standard live tooling is most often suited to production work, whereas quick-change systems may be better suited to machining product families.
If standard ER tooling is suitable for the work, there are many good suppliers, but remember to consider the construction aspects noted above. For a quick-change or changeable adapter system, there are fewer suppliers in the market, so seek them out and be sure they can supply the product styles you need for all your lathe brands. Adjustable-angle head systems can be costly but worthwhile, owing to the stability and rigidity of their construction, when producing families of parts with only slight differences in the dimensions.
Now, as promised, one of the exotic live tooling examples. It evidences the value of having test runs performed on alternative tool styles.
One company was doing a cross-milling application on an AL6063 sheave using an ER40 output tool on a Eurotech lathe while running at 10 ipm and 4,000 rpm. They were making three passes with a cycle time of 262 seconds, getting a chatter finish on 20,000 pieces per year. The annual cost of the machining was over $130,000. By using an improved adapter tool design with ER32AX output and the same parameters, they were able to produce the part in a single pass with a smooth finish and cycle time of just 172 seconds. Over the course of the year, this turned into a savings of $45,000, approximately 20 times the cost of the tool. The bottom line is the bottom line, as the accountants tell us.
In the end, you may not need a +135/-30 degree universal adjustable tool or a multi-spindle live holder or even a quick-change adapter system but do consider all the options. Talk to your machine builder and several tool suppliers and the most important people in this equation, your shop personnel, as their input is invaluable.
About the Author
Preben Hansen is president of Platinum Tooling Technologies Inc. (Prospect Heights, Illinois). Contact Mr. Hansen with questions and input at firstname.lastname@example.org.
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