Indirect cooling of a rotary cutting tool
An indirect cooling system for a rotating cutting tool uses a cryogenic coolant that is delivered to a cavity formed on the back surface of the cutting element, providing cooling near the cutting edge of the element. Because the total flow rate of the working fluid is low (less than 0.08 Liters/min/cutting edge), the fluid can be safely vented to atmosphere from the cavity, and as a result, no specialized coolant recovery or ventilation equipment is needed. The cavity may be formed with fins to enhance the heat transfer between the cutting element and the coolant, and coolant may additionally be sprayed directly onto the exterior surface of the element to cool the tool-chip interface. The indirect cooling system may be used for hard to machine metals and composites, as well as the machining of conventional materials without the use of traditional cutting fluids.
1. An indirect cooling system for a rotating tool having a tool body and a cutting element, the system comprising:
at least one specific area on the tool body for mounting the cutting element;
an indirect channel in the tool body for conducting coolant that is at a temperature that is less than ambient temperature to the rear face of the cutting element;
a cryogen comprising the coolant;
a cavity formed in the rear face of the cutting element for receiving the coolant from the channel; whereby the coolant in the cavity cools the cutting element; and
an exhaust port in the cavity and an exhaust outlet coupled to the exhaust port on the face of the cutting element, whereby coolant flowing into the cavity can be exhausted to atmosphere through the exhaust outlet, wherein the cutting system uses a flow rate that is less than ten percent of the flow rate required for conventional flood coolants when machining the same workpiece, and wherein the coolant uses the latent heat of vaporization of the cryogen to remove heat from the cutting element.
2. The indirect cooling system of claim 1 further comprising:
fins formed in the cavity, whereby the fins enhance the transfer of thermal energy from the cutting element to the coolant.
3. The indirect cooling system of claim 1 whereby the coolant is able to reduce the temperature of the cutting element when machining a workpiece using a flow rate that is less than two percent of the flow rate required for synthetic coolants when machining the same workpiece.
4. The indirect cooling system of claim 1 further comprising:
an opening on the tool body for spraying coolant on the insert; and,
a direct cooling channel in the tool body for conducting coolant to the opening, whereby the cutting element is cooled by a coolant being sprayed on the element and by coolant being applied to the rear face of the element.
5. The indirect cooling system of claim 1 wherein the cutting tool element is a cutting tool insert.
6. The indirect cooling system of claim 5 further comprising:
at least two pockets formed in the tool body for receiving an insert and an insert mounted in each pocket, each pocket having an indirect cooling channel for conducting coolant to the rear face of the insert, whereby each of the inserts in the tool body are cooled by indirect cooling.
7. The indirect cooling system of claim 6 further comprising:
at least two jet openings mounted on the tool body and spaced from the inserts; and,
a direct cooling channel coupled to each of the jet openings for supplying coolant to the jet openings, whereby the jet openings spray coolant onto the inserts to directly cool the inserts while the inserts are indirectly cooled by the coolant supplied to the cavity on the rear face of the inserts.
8. The indirect cooling system of claim 1 wherein the cutting tool element is brazed or otherwise permanently affixed to the tool body.
9. The indirect cooling system of claim 1 , wherein the flow rate of the coolant is 0.08 L/min for each cutting edge.