About 10 years ago, Modern Machine Shop published a special issue on high speed machining—the first of what would become a succession of special issues on this topic. Machining centers with higher spindle speeds were becoming broadly accessible then, and something seemed to be happening. The higher speed let various types of shops do their work in different ways. The changes included replacing custom machines with fast machining centers, milling solid monoliths instead of building assemblies and milling parts to completion that once required EDM. These changes led us to the best definition for high speed machining that we have found: not any particular rpm value, but instead the speed at which a change in the process becomes possible. It seemed legitimate to wonder whether some such threshold was waiting to be crossed in most of the shops the magazine reached.
Now, our cover story profiles another shop that crossed a performance threshold through higher spindle speeds. The speed wasn’t the only factor, but it was the core ingredient. Cutting faster let the shop make parts better and more quickly in a way that answered its customers’ changing demands. Does this shop’s example suggest it may be time again to reconsider your speeds?
Not necessarily. High speed machining never stopped being important, but we know more about it today. Taking fast, light cuts at high spindle speeds is particularly useful in two applications—die/mold machining being one. Through HSM, a shop can efficiently mill complex surfaces in hard steels to a level of precision capable of finishing the part at the machining center. The other application, machining pockets and similar features in aluminum, relates to aircraft components and parts such as the ones in the cover story. Here, the speed lets one small tool hog out a large volume quickly, potentially machining the part both faster and better, and (in the case of aircraft parts) allowing the design of the part to improve. These are thresholds that high machining center spindle speeds can cross.
In other applications, this speed may not be the key. The machining center may not be the best machine for the job, for example. Multitasking turning machines do more today, and so do machining systems that might once have been considered too dedicated. In still other applications, the answer may not be to change either the speed or the type of machine, but instead to change the organization of the shop or the communication with customers. In short, HSM has changed from a topic of general importance to become an established solution for specific challenges.
And in a way, this is fitting. The industry has moved in a direction from general to specific as well. Shops and plants thriving today tend to be those that have learned to serve the needs of some specific type of customer. Many of these shops and plants no doubt have thresholds waiting to be crossed, but the shops are more different than ever, and the ways across those thresholds are as different as the shops.
The manufacturer on our cover needed spindle speed to get to its own next level. However, “How fast should I machine?” is not the question to take away. The question instead is this one: Where does your own threshold lie?