It is the nature of machining to generate heat. The friction between tool and work piece and the acts of cleaving material with a tool and breaking molecular bonds are, in fact, exothermic processes. However, excessive heat generation can shorten tool life, degrade surface finish, cause workpiece and tool warping, and generate toxic smoke.
Follow these tips to mitigate heat buildup in your tools and workpieces
High Efficiency Milling (HEM)
HEM is different from High Speed Milling (HSM) because it is focused on reducing chip thinning and maximizing tool efficiency. The HSM approach is designed to reduce the depth of cut and maximize spindle speed. HEM, on the other hand, aims to optimize tool wear by adjusting the feed rate to maintain chip thickness throughout the operation.
Most notably, HEM mitigates heat build up by cutting with as much of the cutting edge as possible. This distributes the heat over a larger area of the tool. Utilizing the whole cutting edge also reduces tool wear.
Your first instinct for mitigating heat buildup in tools and workpieces might be to crank up the coolant flow. As the thinking goes:
More Coolant = Cooler Parts
This might work in most cases, but the practice is wasteful. It also does not take into consideration the effects coolant has on part finish, chip evacuation and potential material damage or warpage. It is important to select the right coolant (air, mist or liquid) and the best delivery system for the process. Then, the most efficient flow rate can be dialed in for the best part quality.
In some cases, using coolants may not be feasible. Customer requirements or certain procedures dictate machining dry. For these occasions, refer to this article to find tips for alleviating heat buildup during dry machining operations.
Traditionally, milling operations put the feed direction and the tool rotation in opposing directions. This method generates a thin-to-thick chip which has multiple adverse effects. It increases the chances of undesirable surface finishes because of chip re-cutting and tool rubbing. It also pushes heat generation into the tool and workpiece.
On the other hand, climb milling puts the feed and tool rotation in the same direction. This generates a thick-to-thin chip. The heat gets pushed the chips rather than into the tool and workpiece. It also improves surface finish and helps push chips out of the part. This makes coolant flows more efficient for heat removal and chip evacuation.
Implementing these tips can ensure you are producing the highest quality parts while preserving your tools.