Live Tooling, as the name implies, is specifically driven by the CNC control and the turret of various spindle and powered sub-spindle configurations on CNC 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. Live tools are usually customized for the particular machine tool builder’s turret assembly.
Most often, live tooling is offered in standard straight and 90º configurations with a variety of tool output clamping systems, including collet chuck, arbor, Weldon, Capto, whistle notch, hydraulic, HSK, CAT, ABS and a variety of custom or proprietary systems developed by the many suppliers to the industry.
As jobs change or volume increases or a shop encounters specific challenges in machining large parts with deep pockets or small intricate parts, for example, the need may arise for new machinery. When this happens, a common error is sometimes made—accepting the standard tooling packages provided by the builder. This is not a criticism of the standard packages from builders. Rather, this article is meant to provide a set of parameters to consider when evaluating the tooling and toolholding devices to use in a machine shop or production department.
Simply stated, 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 (external vs. internal coolant, for example) to the sublime (adjustable or extended tooling configurations) to the truly exotic, an example of which is at the end of this article.
Tool life is the product of cutting intensity, materials processed, machine stability and, of course, piece parts produced. Two seemingly identical job shops can have vastly different tooling needs because one is automotive and one is medical, or one specializes in one-offs and low-volume work, while the other has long-run jobs. The totality of your operation determines the best tooling for the machines being purchased.
Investing in a Better Design
Bearing construction and the resulting spindle concentricity drive the life of any tool. A better design that costs just 10–15% more can yield both longer lasting cutters and consistently superior finish.
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 possible precision. Also look for an internal vs. external collet nut so the tool seats more deeply in the tool. This produces superior rigidity.
Likewise, high-pressure coolant may be desirable. Look for 2000 psi (13.79 MPa) in 90º and 1000 psi (6.9 MPa) minimum in straight tools.
Need for Speed?
Another key question needs to be asked: is the turret RPM sufficient 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 a lathe? Gear hobbing can be accomplished or producing squares or flats through the use of polygon machining.
Standard live tooling is most often best suited to production work where finish, tolerances and cutter life are critical, while quick-change systems may be better suited to the shop that produces families of products and other instances where offline tool presetting is a key factor in keeping the shop at maximum productivity.
This opens the discussion of the need for long-term flexibility, the most often overlooked consideration in buying live tooling. Key questions to ask are, what work do you have in the shop, what work will be coming in the future, and what are the overall economies of a changeable adapter system on your tooling?
These questions are often not considered when the focus is only on the machine being purchased. Dedicated tools for large product families 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 on involves more product families, think ahead when buying the initial machine tooling.
If standard ER tooling is suitable for the work, there are many good suppliers but do 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 very worthwhile, owing to the stability and rigidity of their construction, when producing families of parts with only slight differences in the dimensions.
Now, let’s consider the exotic example mentioned earlier. It is a good example of the value of doing test runs 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, running 10 ipm (254 mm/min) at 4000 rpm. It was making three passes, with a cycle time of 262 seconds, and 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, the shop was able to produce the part in a single pass with a smooth finish and cycle time of just 172 seconds. Over the course of a year, this generated 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 +135º/-30 universal adjustable tool or a multispindle live holder or even a quick-change adapter system, but do consider all the options. Talk to your machine builder and several tool suppliers, plus the most important people in this equation, your shop personnel, as their input is invaluable.