Gear Production
Issue link: http://gear.epubxp.com/i/262216
16—GEAR Production Supplement F E A T U R E pace of change has increased, and new model launches, often based on entirely new platforms, are more frequent than ever. Unfortunately, history shows that it has been diffcult for spline manufacturers to react quickly to frequent design changes. An Intrinsic Drawback For every suite of spline cutting depth, confguration and geometry, there's a single HSS hob, broach or rack designed almost exclusively for that job. For long runs in a single batch, these processes serve quite well, producing highly repeatable results to tight specifcations. The drawback has been the need for redundancy in such hobs, as regular maintenance such as regrinding and recoating takes them away from the machine or out of the shop. To keep chips fying on a spline operation, shops historically had to have at least two of each individual HSS tool in inventory at any given time in order to accommodate scheduled regrinding/ recoating or recover from possible failure. As the pace of change increased in heavy construction equipment, the only way to remain fexible enough to handle spec or design changes, as well as to make prototypes, was to own a complete set of hobs of all shapes and sizes to cover any contingency. Likewise, in production situations, owning two of each tool was prudent. For years, this has kept a lot of the spline and gear work in specialized, dedicated shops. Smaller Batch Flexibility A leap forward on the fexibility continuum is happening now, because multi-axis and multitasking machines enable disc cutters to perform operations given exclusively to hobs, broaches, spline rolling racks and other tools in the past. Gashing or disc milling external or internal spline teeth can now be an extremely economical way to approach splines. With multitasking machines and new insert developments, it is possible to have a single cutting tool accomplish several operations. This is especially crucial for small- to medium- batch production, which often requires frequent changes throughout the machining and handling process. Instead of producing 10,000 identical components to gain effciency and economy of scale, shops can be capable of producing 100 of one type of spline, then 200 of another, without long delays or excessive diffculty. The key is to exploit the fexibility of a disc cutter such as the CoroMill 172 from Sandvik Coromant. Using a disc cutter takes advantage of the adaptability of a multitasking machine and other non-dedicated types of machine tools. However, the inserts for the cutter are dedicated to a given spline size and tooth count. The user is then trading the fexibility of having a full inventory of hobs for fexibility inherent in machine design, whether it be a multitasking machine, a lathe with driven tools and a Y axis, or a machining center with a rotary table. For example, instead of having a machine for the turning process and a hobbing machine for generating the spline, a multitasking machine can make the complete part. Another possibility is a cell that integrates a turning machine with a three-axis machining center equipped with a rotary table. The benefts of machining the part complete in one machine are reduced setup times and improved feature-to-feature tolerances. By using a machining center and rotary table, the user is not locked into a dedicated machine. The machining center could be used for other Disc cutters of different sizes can be used on CNC machining centers and multitasking machines to complete transmission components for trucks and other heavy vehicles in one setup. 0314_MMS_Gear_MarkFeature.indd 16 2/13/2014 2:44:08 PM