Think “unattended machining,” and the image in your mind is probably complex—that is, some machining process that relies on automation more than the typical machining process does.
But does going unattended have to involve this complexity? Instead of requiring automation, allowing the operator to step away from the machine tool might just be a matter of addressing the sources of worry that keep that operator engaged.
Bob John, a product manager with cutting tool maker LMT-Fette (Cleveland, Ohio), sees exactly this elimination of worry as one of the principal benefits of his company’s “Point Blank” tooling. These lathe toolholders apply a simple idea for delivering coolant more directly. Instead of leaving the coolant to an overhead nozzle that rains down the fluid from relatively far away, a Point Blank toolholder permits the coolant line to be directly connected. The coolant then exits the toolholder through ports located just above the insert.
“When you use an external nozzle for coolant, you have to worry about a stringing chip knocking the nozzle away,” Mr. John says. Often the most important role of operator oversight in turning is simply to keep glancing at the process to make sure the coolant remains correctly directed. Remove this worry, he says, “and maybe that operator can turn away from the machine.” He or she can then devote attention to deburring parts, for example, or preparing for the next job.
But the impact on how labor is used is not the only benefit of the coolant delivery. The cut itself is affected, too. “I do not believe we have had a user of one of these toolholders who has not seen some improvement in tool life,” Mr. John says. Precisely how the physics of the cut are affected has never been formally studied, so any attempt at an explanation would only be speculative. However, the contributing factors are apparent. The toolholder delivers coolant through three ports that, even in total, offer less exit area than the orifice of a conventional nozzle. As a result, the coolant velocity increases (as when you put your thumb over the end of a garden hose). In addition, the toolholder’s built-in coolant channels are able to direct this coolant much closer to where the chip is forming and building its heat. When the toolholders are used to deliver high-pressure coolant around 1,000 psi, these streams can even become effective instruments for chip breaking.
The toolholders come in standard sizes, made to ANSI and ISO specifications. LMT-Fette’s development efforts currently focus on expanding the range of toolholder types that support this coolant delivery. The latest offerings for through-toolholder coolant are boring bars. Toolholders for Swiss-style machines are set to become available in early 2005.