In the mass production of gears, the structural size of the hob will affect its processing efficiency. Whether a hob is easy to use or not can only be used for a certain processing occasion! And no hob can play its highest efficiency in any kind of processing occasions!

When choosing a hob, the structural size of the hob should be determined according to different processing objects, so as to achieve the lowest cost of machine tool consumption and tool consumption, and the processing quality can reach the level required by the process. This should also consider the gear to be processed Materials and heat treatment conditions, the condition of the machine tool used and clamping conditions and other related factors:

Hobs with different structural sizes have great differences in efficiency

Example 1:

Modulus Mn1.35, number of teeth Z59, the outer diameter of the gear is 91.25mm, and the total tooth height is 3.88mm;

Option 1: Hob outer diameter Ø70mm, single head hob with 16 slots, the axial feed is 2.13mm/workpiece revolution, the cutting speed is 73m/min, and the working time for a single piece is 1.5min. The cutting length of one tooth is 2.55m tooth length.

Option 2: Ø70mm, 11 grooves, 4-head hob processing, the axial feed rate is 2.2mm/per revolution, the cutting speed remains the same, and the processing time for a single piece is 0.35min. The cutting length of each tooth of the serial cutter Can reach about 5 meters;

Example 2:

In this example, the gear modulus is 10, the number of teeth is 23, the helix angle is 13 degrees, the outer diameter is 260.4, the tooth width is 290mm, and the total tooth height is 24mm.

Option 1: The outer diameter of the hob is Ø240mm, the single-head hob with 14 slots, the cutting speed is 45m/min, the axial cutting amount is 1.42mm/revolution, and the processing time for a single piece is 85 minutes.

Option 2: The outer diameter of the hob remains unchanged, the number of grooves is increased to 21, and the hob is changed to a double-headed hob. The cutting speed is still 45m/min, and the cutting amount can be 3mm/revolution. At this time, the envelope error of the tooth shape is 0.003mm, and the depth of the machining tool marks does not exceed 0.003mm, which fully meets the requirements of finishing. The processing time of a single piece is shortened to 24 minutes..

From the above two calculation results, it can be seen that there are obvious differences in processing efficiency when processing the same gear, selecting hobs with different structures, and selecting different cutting parameters.

Precautions for selection of cutting parameters

When the rigidity of the process system is not good, the ideal cutting amount cannot be used. Sometimes when the machine tool adopts a cutting amount greater than 2mm, it will generate huge noise, which makes the operator daunted! It also causes serious deviations in the accuracy of the tooth shape and tooth direction.

The hob with multi-groove and multi-head should be equipped with a suitable machine tool, otherwise a large amount of cutting tool cannot be used, and the processing efficiency cannot be improved. The machine tool cannot automatically shift the cutter, or the length of the shifting cutter is very short and the hob has a long blade length. Not all can be fully used, although the cost of the tool has increased, but the number of processed gears cannot be increased, which relatively increases the cost of the tool!

Effect of Tool Structure on Cutting Amount

The impact of tool structure size on the selection of cutting parameters is often overlooked, so how to determine the appropriate hob structure size according to the conditions of the processed gear, so that it can adapt to the machine tool used, and achieve the three goals of processing efficiency, processing accuracy and tool cost Unite?

To achieve this goal, in addition to knowing the structure of the gear, the condition of the machine tool and the clamping of the workpiece, it is necessary to understand the selection principles of the three major cutting parameters of gear cutting:

1. Depth of cut has the least impact on tool durability. First, choose the depth of cut as large as possible. Most hobbing uses one pass to cut to the full tooth depth, unless there is a stricter limit on the tooth surface roughness. Added fine-cut sequence.

2. The amount of cutting. The cutting speed has the greatest impact on the tool life! The cutting speed is related to the material of the tool and its coating and the material, heat treatment and modulus of the processed gear. It is easy to find the hobbing speed recommended according to different tool materials, and it is a very effective and feasible way to choose the hobbing speed according to the above conditions. There are many factors that affect the selection of the cutting amount, and the cutting amount has a great influence on the machining efficiency. At the same time, the selection of the cutting amount is restrained by the structure of the hob. The tool structure for processing the gear is determined according to the gear structure parameters, so that it can Use the largest amount of cutting as possible to improve processing efficiency while maintaining normal cutting tool consumption.