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.
Ohio manufacturer of oil field equipment saves 184 hours on one high-precision cutting tool head made of Nitralloy®
PMC-Colinet has a long history in the pipe and tube market, having started in 1912 and introduced the world’s first carbide-tooled pipe threading machine in 1958. Today, the company is established as a primary supplier of machines to the OCTG sector. Its customers include integrated steel mills that sell finished pipe and couplings to the oil and gas industries, specifically using the company’s machines for threading products for downhole drilling applications. PMC-Colinet also supplies cutting tools, consumable tooling, aftermarket parts and field service to the industry.
Recently, PMC-Colinet did an assessment on one very challenging job, namely, cutting keyways into large sections on a high-precision cutting tool head made of Nitralloy. For many years, the production had involved the use of a shaper to produce the keyway in the bore of the die head. Typically, the bore ranged from 6” to 13” in diameter and more than 12’ in length. These keyways have extremely tight tolerances, with location at +/- 0.0005”, width at +/- 0.001” and depth to +/- 0.0025”.
One style of cut is a 3-step keyway that does not run all the way through the bore, stopping at a window that is milled from the outside diameter. This situation prevented the PMC machining department from using a ram EDM to produce the keyway. The only options previously used were to rough the keyway on an old shaping machine, then send it out for ram EDM. This process required 50 hours on the shaper, plus approximately a week for the ram EDM. Another option was to do the job entirely on the shaping machine. Roughing the keyway had to be much more precise and usually required about 61 hours. Plus, an additional 145 hours were required to finish the part, normally. These times included 10-12 hours for set-up.
The team at PMC, led by Milling Foreman Rick Kokish, decided to explore other methods to produce this part on its Monarch 175B VMC. They conducted an exhaustive search on the Internet, turning up over 133,000 hits for 90º angle heads. After more than 30 hours of gleaning out the unsuitable products, they narrowed the search to just two vendors. Both manufacturers visited the facility and brought out their standard angle head designs. One of the companies, Heimatec, quickly realized this job would require a custom 90º head design to satisfy all the requirements.
One competitor brought a standard 40 taper tool, while Heimatec presented a larger, heavier 50 taper unit.
A week later, Preben Hansen, Heimatec’s president, supplied a drawing for the proposed custom product. PMC engineering reviewed both the standard and custom designs and awarded the project to Heimatec.
The angle head supplied was designed to perform a wide variety of cutting tasks on the various end products produced by PMC. On the keyway in a bore 6” in diameter and 12” in length, using the Heimatec 90º head, PMC spent 6 hours in setup, 3 for roughing and 3 for finishing, plus 12 to 16 hours of actual cutting time. This represented a total savings of 184 hours on a single part. Though the head appeared too slender to remain rigid during the entire cutting cycle, according to PMC sources, the performance was deemed very successful.
Heimatec’s head design for this custom radial drilling and milling head features an adjustable tool stop, 3 support pins for stabilizing the tool, CAT 50 taper style, 360º indexable pivot on the angle head and inclined tooth gear design for maximum rigidity.
During the project, Preben Hansen from Heimatecc supervised the installation. After the stop block attachment and grinding of the supports pins for the head were accomplished in just one day, the head was mounted and several experimental cuts were performed. Hansen spent time with Rick Kokish as well as CNC programmer Barry Spence at PMC, discussing various options for programming the head on the Monarch VMC. The very next morning, the setup was performed and an actual keyway was roughed.
Results ongoing have continued to satisfy all requirements, according to PMC sources.
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