Production Machining - Your access to the precision machining industrial buyer.
Issue link: https://pm.epubxp.com/i/827352
The Next Step in Setup Reduction Edited by Chris Felix W hen machining tough materials such as titanium, machinists are challenged to maximize metal removal rates to achieve production efficiencies, yet they face low cutting speeds and considerably higher cutting forces. In response, and with advances in FEM and other analysis tools, machine tool builders have improved stiff- ness and damping on spindles and machine structures through the years to minimize undesirable vibrations that deteriorate part quality and tool life. ese advances add to higher productivity, but the weakest point has often been the spindle connection itself. e KM quick-change system from Kennametal Inc. was designed to address concerns about this weak point in the process. Quick-change modular tooling is a clear way to increase productivity, shorten setup time and generally improve the bottom line for job shops and large manufac- turers alike. While the KM system has proven effective in this area for quite a while, the company has been expanding its lineup to address a broader machine tool platform. Primary Advantages Some systems may be able to transmit a considerable amount of torque, but cutting forces also generate bending moments that will exceed the interface's limits before torque limits are exceeded. e combination of the KM4X system's high clamping force and controlled interference levels lead to a robust connection, extremely high stiffness and restrained bending moment for improved performance in titanium machining. e system is engineered for three times the bending moment resistant capacity compared with other tool systems. is design allows shops to use their high-perfor- mance machining centers to increase speeds and feeds in difficult machining applications, thus gaining the full potential from the machine tool. Moreover, the ability to retrofit the spindle connection to an existing machine tool offers the added advantage of increasing throughput without having to invest in expensive additional capital equipment. Existing Spindle Connections e tool spindle interface must withstand high loads, yet maintain its rigidity. In most cases it will determine how much material can be removed on a given operation until tool deflection is too high or the onset of chatter is reached. Several different types of spindle connections have been developed or optimized over the last few decades. Because of a good cost/benefit position, the 7/24 ISO taper became one of the most popular systems on the market. While it is used successfully in many appli- cations, it has limitations in its accuracy and speed. e advent of face contact represented a step forward over the standard 7/24 taper. e combination of face contact with 7/24 solid taper provides higher accuracy in the Z axis, but it lacks stiffness at higher speeds or with high side loads. Most of these tools on the market are solid, and the spindles have relatively low clamping force. Connection stiffness is limited, as radial interference needs to be kept to a minimum. Required tolerances to achieve consistent face contact are thus very tight, leading to higher manufacturing costs. In the early 1980s, Kennametal introduced the KV system, which was a shortened version of CV tooling with a three-ball mechanism acting on a conical surface of a bore. Later versions were designed and sold with face contact. In 1985, Kennametal and Krupp Widia initiated a joint program to develop a universal quick-change system, now known as KM and recently standardized as ISO 26622. e polygonal taper-face connection known as PSC, now also standardized as ISO 26623, and the early 1990s HSK system started being employed on machines in Europe and later became standardized as DIN 69893, then ISO 121. :: KM and KM4X work on stationary applications as well as in this centerline turning toolholder for multitasking machines and mill-turn lathes. :: Because of its inherently balanced design, KM4X63 can achieve "out of the box" spindle speeds 30 percent higher than HSK, and almost twice that of comparably sized polygon-style toolholders. TECH BRIEF 28 PRODUCTION MACHINING :: JUNE 2017