CNC Knowledge: Problems and solutions for the machining of deep holes using machining centers

In fact, the use of a vertical machining center for the treatment of holes is the most common treatment method, but when the deep treatment of the holes is carried out, it will encounter great difficulties. However, there are many effective ways to solve this problem.
The objective is to treat these holes with precision and obtain good positioning precision and surface precision as well as good economy. The most important factor in the success of the treatment of deep holes is understanding the principles of treatment. It is necessary to understand what is happening inside the hole during drilling and knowing how to apply this knowledge to guide you at the most effective technical approach.
Based on the long -term accumulation, three main problems of treatment of deep holes are resolved: discharge drilling chips and cannot damage the surface of the room; Other important factors include the precision of machining, repeated positioning precision and surface roughness. In general, the deep holes are defined by the ratio of the diameter to the depth of the hole. It is considered that it is a treatment of deep holes which is greater than or equal to 5: 1.
In general, there are two methods of treatment of deep holes using vertical machining centers. We use an equally divided retraction depth to reach the final depth. The other is different retraction depths and the depth gradually decreases each time.
First, the elimination of cutting fleas is not limited to the treatment of deep holes. The time for the cuttings to be removed determines the length of the borehole. These drilling shavings will drain the cooling liquid of the holes as is, which means that the heat of the forest is achieved and causes excessive wear of the tool. This situation will eventually lead to complete damage to the tool. The disadvantage of the treatment of deep holes and the elimination of tools and the elimination of fleas is that it takes too long to finish the machining of each hole.
In this method, time will be devoted to feeding the tool and rapid retraction, then to rapid retraction and advancement. Multiply the time required for a single cutting cycle of the cut by the number of holes to be treated more the delayed time. Even if each hole is only added for a few seconds, drilling efficiency is considerably reduced. In the processing of products with many processes, this ineffectiveness will become a serious constraint.
In addition, let the cooling liquid reach the bottom of the hole – When the cooling liquid cannot reach the bottom of the deep hole, the chips can block the drilling groove, causing the accumulation of heat and damaging the tool drilling and room.
The control system for most treatment equipment provides drilling for the machining of deep holes, which controls the drilling tool to completely leave the hole after being drilled in the material at a specific distance, then drilled in the hole. This type of drilling cycle, when the drilling bit comes out, the boreholes fall into the hole under the cooling liquid. This situation occurs in particular in the treatment of steel materials. When the drilling bit enters again, it will hit the drilling chips located at the bottom of the hole. The drilling cuttings begin to turn under the action of the tool in the vertical machining center, cuts or melt the drilling cuttings. During manual drilling, the operator may feel that the chips block the rotation forest and stop treatment to clean the drilling fleas. In any case, such a treatment cycle can be written in the program, and the treatment can be interrupted before the last cut and the elimination of fleas to avoid such situations.
In the example of different depth retraction cycles, the treatment reaches 1 inch to make the first retraction and the elimination of fleas. 0.05 inches deeper than the last time they withdraw. The more deeply pierced in the hole, the reduced retraction depth will help eliminate the stack of drilling chips around the tool. The more deeply pierced the holes, the harder the cooling liquid, so the delay is used to empty the drilling chips and allow more cooling liquid to flow up of the drilling tool.