A REVIEW OF THIS MACHINING METHOD, THE BASIC CONCEPTS AND SOME EXCITING DEVELOPMENTS IN THE TECHNOLOGY
by Preben Hansen, President, Platinum Tooling Technologies Inc.
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. This short article is meant to give you a set of parameters to consider when evaluating the live and static tooling to use in your 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 fact is often overlooked and that can be a critical error, in the long run.
Your examination can 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. Finding a supplier who has an in-house machine shop for the preparation of special tools is a great value-add.
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. Taper 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 vs. external collet nut, so the cutting tool seats more deeply in the tool, as superior performance will result.
Likewise, high pressure internal coolant might be desirable. Look for 2000 psi capabilities in 90º tools and 1000 psi in straight tools.You need to ask another question, namely, 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 manner, 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 key 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.
Dedicated tools for large families of products may often be desirable for some applications, but do consider whether a flexible changing system would 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.
Now, an application example showing clear evidence of 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, as their input is invaluable to keeping you up and running in a profitable, customer-satisfying scenario.
The author welcomes questions, comments and additional input from readers. Please contact Preben Hansen at 847-749-0633 or firstname.lastname@example.org. Mr. Hansen has over 30 years in tooling and is considered a leading authority on the topic in the North American machine tool market.
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We are very excited to announce that we are now able to offer on-site technical training to YOUR machinists at YOUR location! This is offered at no charge to customers who use any of the manufacturer's whom we represent in California and Nevada.
However, just because you don't purchase things from us, don't feel left out! We also offer on-site topic specter training on any of the following topics for $150/hour.
Each presentation lasts about 2 hours. The presentations last approximately 45-60 minutes with the remaining time for Q&A and discussion about unique applications in your facility.
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by, Preben Hansen is President of Heimatec Inc.
Live tooling is 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 and are usually customized for the particular machine tool builder’s turret assembly.
A common error is often made by accepting the standard tooling packages provided by the builder. This is not a criticism of the standard packages from builders, but this article is meant to give you a set of parameters to consider when evaluating the tooling and toolholding devices to use in your shop or production department. 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.
Identical Job, Different Tooling Requirements
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-offs and low-volume work, while the other has a greater occurrence of longer run jobs. The totality of your operation determines the best tooling for the machines being purchased.
Bearings & Gears
Bearing construction and the resulting spindle concentricity drive the life of any tool and you might find a 10-15 per cent greater investment in a better design can yield longer lasting cutters and consistently superior finish
on your products.
Coolant, RPM & 2nd Op Considerations
Also look for an internal vs. external collet nut, so the tool seats more deeply in the tool, as superior rigidity will result. Likewise, coolant high pressure might be desirable. Look for 2000 psi in 90o and 1000 psi minimum in straight tools.
Standard live tooling 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 instances where the tool presetting offline is a key factor in keeping the shop at maximum productivity.
Dedicated tools for large families of product may be desirable, but consider a changeable adapter system and talk to your supplier before making that determination.
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.
Originally Printed Wednesday, October 17, 2012
Modern Machine Shop, Preben Hansen, President, Heimatec Inc.
The smarter you are when choosing the live tools for your job, the more efficient your lathe becomes.
When any metalworking manufacturing facility, whether captive operation or job shop, makes the substantial investment in a new lathe, it is often looking for ways to streamline the manufacturing process. The smarter you are when choosing the live tools for your job, the more efficient the machine becomes. The key is to find a supplier of live tools that offers high-quality, high-performance products that will provide more flexibility on the first big job and into the future.
The first tool feature to consider is the output needed. Should that be standard ER output or quick change? Do you need coolant through the tool capabilities? Does the tool meet your requirements for precision and performance, including the necessary torque output to complement the machine? Are the tools designed according to the specifications of the lathe manufacturer?
When you look at an ER output, does it give you enough flexibility or do you need a more flexible machining system that will allow you to use the same tool for different applications? If more flexibility is required, then you may want to consider tooling with a system that features adapters for a variety of tools to avoid the cost of new complete toolholder assemblies for each tool needed. However, when you look at such systems, be sure they feature a rigid polygon drive system design to prevent power transmission and alignment issues. Such systems seem appealing, because the live tool stays in place and only the adapter and collet get changed out with each new tool. However, less-sophisticated though inexpensive systems will compromise the accuracy of your work. At that point, the few dollars saved will mean very little, compared to the resulting scrap and downtime.
If change-over time is critical, such as when working on a “family of parts,” the option of a true “quick-change system” might be more beneficial. Adapters can be set offline and ready to go for minimal change-over time.
When coolant-through tools are selected, it is imperative that you first check the machine specifications to be sure your tool is capable of handling the coolant pressure of the machine. In general, your internal coolant live tools should be able to handle 1,000 psi or more.
If your live tool is constructed with large, high-accuracy bearings, the tool will have excellent rigidity and premium cutting performance with minimal runout (0.0002" or 0.006 mm is a desirable goal). The bearings, combined with ground, paired and high-accuracy gears, make for tools that are consistent and long-lasting. Bore tolerance is absolutely key in maintaining proper bearing load and this factor should never be compromised.
In addition, you should consider the many applications that can be accomplished with the proper live tool. You can purchase speed increasers for higher rpm, gear reducers for added torque, adjustable angle tools for compound angles, multiple-spindle tools for additional capacity, or gear hobbing tools for spline or gear cutting. While most of those items are standard catalog devices, consider one more piece of advice: Never shy away from the custom tool, when appropriate and justified by the job you have in-shop today, as well as the ones you might have tomorrow. A good tooling supplier will work with you to produce custom tools at reasonable prices, but the supplier must be very reliable, so look for one with grinding, finishing and perhaps even heat treating in-house or very closely monitored, to do such work. Additionally, be certain the supplier has local support and tools can be repaired or reworked quickly and correctly.
The workpiece materials are always a driver. Those of you doing medical machining know this well. Buying a less expensive tool or one with fewer features to work cobalt chromium and titanium is a really bad idea, to be blunt.
On a practical level, always check the supplier for inventory and source of supply. Today, when your customers are demanding faster response times and more cost off-loading, you can expect the same from your tooling supplier. Likewise, application and engineering assistance should be available from local sources to support your tool choices.
The bottom line is the bottom line for most of us today. However, always consider the future jobs when purchasing tooling systems for your new and existing lathes. What might seem a bargain might not be, after the first big job is completed.
Technical Support Blog
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