Machine builders and users of machine tools have realized in order to get the most optimized cycle times and throughput, the machining process must be controlled. Chip contamination is a major deterrent to controlling the process. Over the years, while the processing of steel and other alloys has greatly improved, the properties of these materials, for the most part, have not changed. No matter how we program the cutting speeds and feeds, certain materials cause chip control problems during the machining process. Tooling manufactures have addressed chip problems by improving insert technology and design. While this new technology has been a factor in cycle time reduction, it does not solve the chip control problem.
Standard machine flood coolant systems do not have the ability to consistently control chip problems that occur during many machining processes. This applies not only to drilling and boring operations, but also to turning and cut off operations. Fast cycle times are meaningless if the machine operator has to continually interrupt the machining process to remove chips that have “bird nested” on the part, the turret or the tool slide. In the case of machining centers, chips get nested on the fixture, get packed into small holes in the machined part, or wrap around the tool. When this happens, the required throughput cannot be achieved. That is why during the past few years the use of high pressure coolant systems during the machining process has increased dramatically. (Typical high pressure systems manufactured today vary from 500 to 2,000 psi and from 3 to 10 gpm. The machine manufacturer and the machining application, however, will dictate system specifications.) Increased throughput and tool life improve dramatically when high pressure coolant is applied to the machining process.
We know high pressure coolant improves throughput and tool life, but is a single coolant line enough? Does directing a single coolant line to a lathe turret or through the spindle of a machining center totally solve the chip control problem?
Today’s machine tools are more complex than ever before—especially turning machines. Five- to nine-axis machines provide the capability to complete complex parts in a single operation. The pressure to keep inventory levels in control and the demand for quicker deliveries has required all sectors of manufacturing to produce smaller lot sizes of complex components in a single setup. This requires the use of multi-axis machine tools.
Knowing that a high pressure system improves throughput and tool life, it makes sense to incorporate multiple high pressure coolant lines to multiple axis machine tools. With many operations occurring during the machining cycle, it is extremely important to maximize the benefits of high pressure. Independent lines can be directed to multiple turrets and cutting tools and used when and where required. Do not have the system running continuously. Incorporating multiple independent lines allows coolant to be used when it is required for each specific operation during the machining cycle. Activation of each independent line is accomplished by using specific programming codes.
Many of the new multi-axis lathes incorporate a secondary spindle called a pick off or subspindle. After the work is completed on the main spindle, the part is transferred to the subspindle where the part is completed. Subspindles or pick off spindles can be adversely affected by chip contamination. During the cut-off operation as the subspindle collet opens to pick off the completed part, chips can get trapped in the collet. When the collet clamps on the part, chips get imbedded into the part and damage the surface finish. Additionally, when chips get caught in the collet at the moment of pick off, the part does not seat properly. This can adversely affect tolerance when performing the back working operations on the part. The collet can also be affected when chips get imbedded into the collet damaging the surface. Damage in the subspindle can occur even when machining soft materials such as brass. High pressure may not be required for the turning or drilling operations but simply to prevent damage during pick off.
In many cases the use of an air blast to control chips during pick off will not be effective. Incorporating a high pressure coolant in place of or in addition to the air blast can greatly diminish chip problems created during the part transfer. Another benefit of high pressure through the subspindle is realized when drilling and boring operations are performed in the subspindle. Many applications require that a drilled through hole must be done in the subspindle. Activating the high pressure line during this operation can force chips out of the subspindle and back into the machining area, eliminating chip build up in the subspindle.