Features of deep hole machining of rolls

Deep hole processing belongs to the category of machining, and the characteristics of deep hole processing can be analyzed to better choose different processing methods. Compared with ordinary hole processing, the characteristics and difficulties of deep hole processing are mainly manifested in:
1) When drilling, the cutting condition of the tool can not be directly observed, and the cutting process can only be judged whether the cutting process is normal by listening to the sound, looking at the chips and touching the vibration during the working process.
2) The ratio of length to diameter of the hole is large, the drill pipe is thin and long, the rigidity is low, it is easy to vibrate, and the drilling hole is easy to deviate, so the support and guidance are very important.
3) The cutting heat is not easy to dissipate, the working conditions are harsh, and effective cooling methods must be adopted.
4) The deep hole drill pipe is limited by the hole diameter, the diameter is small and the length is large, resulting in poor rigidity and low strength, and it is easy to produce vibration, ripple and taper during cutting, which affects the straightness and surface roughness of the deep hole.
5) The heat dissipation conditions of the tool are poor, and the cutting temperature increases to reduce the tool life.

3. Deep-hole structure analysis
The rubber rolls are high nickel-chromium rolls, and the finished product quality is 6568kg. This kind of drilled rubber roll is to open a plurality of small diameter circular channels along the axial direction below the working surface of the roll body, and at the same time reprocess the oblique holes to make the cavity in the center of the round holes communicate. The holes at both ends of the roll are blocked by a sealing cover plate to form a circulation path, and the general section is composed of 3~5 boreholes to form a circulation hole combination. The center position of the roll in the text has a stepped center through hole of φ90~φ150mm, and the roll body has 24 straight holes of φ30mm and a length of 2130mm, and the aperture is small and penetrates the full length of the roll surface. 8 φ25mm oblique holes are distributed at both ends of the roller body, the angle is 35° with the central axis, the oblique holes are connected with the central through holes, and the φ25mm cross small oblique holes are distributed between the two φ30mm straight holes.
According to the structure of the rubber roll, the process flow of deep hole processing is analyzed. Because deep hole drilling is a labor-intensive and accident-prone process (such as broken bits or hole deflections), it is important to consider the process economy and reasonableness throughout the roll process. The main processing process is arranged as follows: the allowance of each part of rough turning→ the amount of grinding of each part of fine turning, the processing of steps and end grooves of each part is completed→ the end face and stop → drilling center through hole→ drilling deep hole and oblique hole→ drilling end face wire hole and tapping → assembly accessories→ water pressure → grinding face and shaft journal.
4. Positioning of the roll when drilling
Rubber roll deep hole processing is the first time for our company, the deep hole structure is more complex, there is no special machine tool, it is necessary to rely on the existing equipment, and certain measures need to be taken for the installation and alignment of the deep hole structure roll.
For the positioning and installation of the roll, because the heating cooling hole is distributed on the concentric circle of the working surface of the roller, it is more suitable to use the roll body of the roll as the positioning datum. Roll is placed on two supporting rollers, when not compressed, can rotate on the supporting roller, can be pressed with pressing plate after determining the drilling position and aligning the drill bit, in order to prevent the workpiece from producing axial movement during drilling, a locating piece needs to be placed on the roll end face. The horizontal position positioning of the roll depends on the alignment of the drill pipe axis, and the workpiece moves together with the idler to achieve that the workpiece axis and the drill pipe axis are parallel to each other. The positioning of the front and rear height of the roll is based on the alignment of the work table, the height of the roll is detected before and after using the scribing disc, and the axis of the roller can be adjusted to be parallel to the workbench by using the supporting roller. In addition, the mutual position of the roller of different specifications and the drill pipe is not the same, and the axis of the drill pipe should also be on the distribution circumference of the roller hole while correcting the above-mentioned parallel position.
5. Straight and deep hole processing of roller body
The roller body is distributed along the circumference of 24 φ30mm, the length of 2 130mm of straight holes, the hole diameter is small and penetrates the full length of the roller surface, the length-diameter ratio reaches 71, after analysis, the straight hole of the workpiece adopts gun drilling (see Fig. 3) two-way drilling processing, first process one side hole to a certain depth, and then turn around and process the other side hole to drill through. In order to prevent stress concentration, each hole is misaligned by 100mm. When machining, the workpiece is stationary, the tool rotates and is axial feeded, and after each hole, the index is carried out by the drill die until the 24 holes are completely machined. This has the following advantages: (1) The two-way drilling reduces the drilling depth, and greatly reduces the degree of deviation that is common when drilling. (2) The volume and mass of the workpiece are large, and stationary during processing is conducive to simplifying the structure of the machine tool and reducing the volume and quality of the machine tool. The gun drill is made of cemented carbide, with a speed of 70~100r/min and a feed of 0.06~0.1mm/r.