What is Depth of Cut in Machining - Depth of Cut (DOC) Effect and Selection

The selection of cutting parameters will have a significant impact on the machining result. Today we’ll talk about the depth of cut in CNC, what is it and how it works and how to choose it.

What is the Depth of Cut?

The basic purpose of machining operations is to gradually remove extra material layers from the blank to give a basic shape and size and a reasonably smooth surface finish. For any machining process, three relative motions between the workpiece and the tool are essential, which are actually the main cutting parameters, the depth of cut is one of them. So let’s take a look at these three parameters.

1. Cutting speed

Provide the most important cutting parameters for the necessary cutting movements. It can be transmitted to the cutting tool or workpiece through rotation or reciprocating motion. For a rotating tool (such as milling, drilling, grinding) or a rotating workpiece (such as turning), the peripheral speed of the tool or workpiece is considered the cutting speed. However, when neither the workpiece nor the tool rotates, the translation speed of the tool or the workpiece gives the expected cutting speed.

2. Feed rate

The auxiliary cutting movement is provided by the feed speed. Generally, the feed speed direction is perpendicular to the cutting speed direction. The main objective of the feed rate is to remove material from the large surface. Basically, it helps to cover the entire surface of the workpiece by moving the tool or workpiece.

3. Depth of cut

Three cutting movements provide the necessary depth of material to be removed by machining. It is expressed in millimeters. It is usually given in the third vertical direction (speed, feed, and depth of cut usually act in mutually perpendicular directions).

Effect of Depth of Cut (DOC)

As cutting depth is one of the three major cutting parameters, its value also affects the overall machining performance and machining economy. Some common impacts of DOC are listed below.

1) Higher cutting depth indicates a higher material removal rate (MRR) because MRR is proportional to speed, feed, and cutting depth. Therefore, the machining productivity can be improved by using greater cutting depth, thus reducing the machining cost.

2) The cutting force depends on the chip load, which is proportional to the cutting depth. Therefore, a large cutting depth value will increase the cutting force, which may affect the machining performance and cause vibration.

3) Higher cutting depth may also lead to tool damage, which is very undesirable.

4) It also affects chip thickness, chip type generated, shear deformation, etc., which are all indicators of machinability.

Selection and Value of DOC

Because the depth of cut is an important parameter that affects the overall machining performance and economy, it is necessary to select the optimal value after considering many related factors. In general, in normal machining operations, the value of the depth of cut varies between 0.1 and 1.0 mm. The following properties should be noted when selecting its value.

– Productivity requirements. Since the material removal rate is expressed by the product of cutting speed, feed rate, and cutting depth, using a larger depth of cut will improve MRR. This in turn reduces processing time, thereby increasing productivity.

– Required cutting quality. For fine cutting, a lower cutting depth shall be provided; For rough cutting, a larger value can be used to shorten the processing time.

– Machining operation. Various machining operations can handle a wide range of cutting depths. For example, using a side milling cutter and a face milling cutter for milling operations can handle greater cutting depth. At the same time, its value is limited in the knurling operation.

– Strength of workpiece material. When machining hard and brittle materials, it is recommended to use a lower cutting depth value, otherwise the force may be very large and the tool may break.

– Machine tool performance. Since the depth of cut will increase the cutting force and vibration, the machine tool performance should also be considered.

What is Depth of Cut in Machining – Depth of Cut (DOC) Effect and Selection

What is the Depth of Cut?

Effect of Depth of Cut (DOC)

Selection and Value of DOC

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