Live tooling, as a component on a lathe, is specifically manipulated by the CNC to perform various milling, drilling and other operations while the workpiece is being held in position by the main or sub spindle. These components, whether BMT or VDI, are also called driven tools (as opposed to static tools) that are used during turning operations.
All live and static tools are built per the machine tool builder’s specification for each of the various models they produce. A key to running a successful job shop or production department is to partner with a supplier who can meet the tooling needs for all or most of the machines on your floor.
Most often, live tooling is offered in standard straight- and 90º-angle head configurations with a wide range of tool output clamping systems, including ER 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.
When the need arises for a new machine tool, careful consideration should be made to determine which live tools are appropriate for your application. While a standard machine tool package will help you get started, it is important to anticipate job and volume changes, as well any unforeseen machining challenges from the beginning, in order to avoid machine downtime.
Simply stated, when determining the proper tooling to be used, you need to do as much evaluation of your process as you did when you evaluated the various machines available for purchase. While this often is overlooked, it can represent a critical error in the long run.
Considering tooling options. Your examination may range from the simple (external vs. internal coolant, for example) to the sublime (adjustable or multi-spindle configurations), to the custom tool that may be required and built to suit your special application. A supplier who has an in-house machine shop for preparing special tools can offer additional value to your selection.
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 the one-off and low-volume work, while the other has a greater occurrence of longer running 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. You might find that just a 10-15% 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 are always critical factors. Bevel and spur gears that are hardened, ground, and lapped in sets are best for smooth transition and maximum torque output.
Tapered roller bearings are consistently superior to spindle bearings in live-tool milling applications, so look for a combination system to get the highest rigidity possible. Also, look for an internal versus external collet nut, so the cutting tool seats deeper in the tool; this will result in superior performance.
Likewise, high-pressure internal coolant might be desirable. Look for 2,000 psi capabilities in 90º tools and 1,000 psi in straight tools.
Consider the work requirements. You need to ask another question too: Is the turret RPM sufficient to handle the work to be done? It’s possible that a live tool with a built-in speed increaser, often called a speed multiplier, would be helpful. Would it be beneficial to move secondary operations to your lathe? Gear hobbing can be accomplished in this way, as can producing squares or flats, through the use of polygon machining.
Standard live tooling most often is best suited to production work, where the finish, tolerances and cutter life are critical, while quick-change systems may be better suited to the shop producing families of products and other applications where the tool presetting offline is a factor in keeping the shop at maximum productivity. It’s a given in our industry that when the machine isn’t running, the money isn’t coming.
This opens the discussion of long-term flexibility and it’s the most often overlooked consideration in buying live tools. You might wonder, what work do you currently have in the shop and what work will be coming in the future?
The overall economies of a changeable adapter system on your tooling may not be part of your consideration when a machine being purchased. Often, dedicated tools for large families of products often may be desirable for some applications, but a flexible changing system could be more appropriate. Talk to your tooling supplier for the various options, before making that determination.
If standard ER tooling is suitable for the work, there are many good suppliers. It is important though, to pay close attention to 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.
The value of testing live-tool performance. One company was performing a cross-milling application using an ER 32 output tool on a Eurotech lathe, running 10 ipm at 4000 rpm. They were making three passes with a cycle time of 262 seconds and were having difficulties with chatter on the finish, while producing 20,000 pieces per year. The annual cost of the machining was over $130,000.
By using an alternative live tool with an ER 32AX output, internal collet nut design, with 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 yielded a cost savings of $45,000, approximately 20x 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 universal adjustable tool or a multi-spindle live holder, or even a quick-change adapter system, but do consider all these options. Talk to your machine builder and several tool suppliers, plus the most important people in this equation: your shop personnel … their input is invaluable to keeping you up and running in a profitable, customer-satisfying scenario.
Preben Hansen is the president of Platinum Tooling Technologies Inc., Prospect Heights, Ill. Contact him at [email protected]