Machining parameters

The selection of appropriate machining parameters such as feed rate, spindle speed, and cutting depth has a direct impact on the final product. Therefore, every CNC machine operator should thoroughly analyze this issue.

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A person starting their journey with CNC milling services, due to a lack of experience, probably doesn’t realize how crucial it is for an operator to understand the parameters of their machine. Therefore, an experienced CNC operator likely recognizes the significance of this field and understands that selecting machining parameters plays a crucial role in daily work with numerically controlled machines. For instance, overly aggressive parameters can lead to rapid tool wear and may contribute significantly to machine malfunctions. On the other hand, overly conservative settings, in contrast to sharply defined configurations, will undoubtedly prolong the processing time, resulting in higher costs for CNC services.

Machining parameters are undoubtedly helpful in work

Palgio is a company providing CNC milling services, and as such, it possesses extensive knowledge regarding the selection of milling parameters. Drawing on its experience, the company has compiled a set of sample parameters used for machining aluminum. Therefore, the parameters presented below can serve as a starting point for setting adjustments for those embarking on their journey into the world of numerically controlled machines, while also facilitating the work of moderately experienced operators. It should be noted that the presented machining parameters are examples, and they should be adapted to the specific characteristics of the work arising from the particular features of a given milling machine.

Machining parameters for aluminum, values for a good start

Sample machining parameters for aluminum, specifically tailored for a 2-flute carbide end mill. Additionally, it’s important to note that these parameters are recommended primarily for roughing and finishing operations.

diameter [mm]cutting depth [mm]cutting width [mm]feed [mm/min]spindle revolutions [RPM]
Examples of CNC milling parameters used primarily for end mills

Machining parameters primarily used for working with a 2-flute ball nose end mill, made of carbide, and undoubtedly intended for machining aluminum with 6% Si content. Typically employed in finishing operations for 3D surfaces and mold-making for injection molding.

diameter [mm]side step [mm]cutting depth [mm]feed[mm/min]spindle revolutions [RPM]
CNC milling parameters designed primarily for ball end mills

Parameters determined primarily for the 1-flute milling cutter used to perform chamfering. Additionally, it is worth noting the cone angle is 90 degrees.

diameter [mm]cutting depth [mm]cutting width [mm]feed [mm/min]spindle revolutions [RPM]
Machining parameters used primarily for chamfering

Concepts related to machining parameters that are certainly worth knowing

Cutting speed – the basics of CNC milling

Cutting speed is the linear speed of movement of the blade relative to the material during machining, therefore this value is expressed in m/min. This parameter should certainly be known by every CNC machine operator and is undoubtedly needed for everyday work on a CNC machine. Knowing the cutting speed, we can calculate what the correct set spindle revolutions should be.

Below we present the method of calculating cutting speed, i.e. the mathematical dependence of this parameter

Vsk = (Pi * d * n) / 1000

 d – tool diameter [mm]

n – spindle revolutions [RPM]

Below we have made sample cutting speed calculations for a cutter with a diameter of 6 mm and a spindle speed of 24,000 RPM.

Vsk = (3.14 * 6 * 24000)/1000 = 452 [m/min]

By transforming the formula into cutting speed, we are able to calculate the spindle speed, which will certainly be useful in the operator’s work.

Vobr = (Vsk*1000)/(pi*n) = (400*1000)/(3.14*6)= 21230 RPM

Depth of cut, an important machining parameter

The depth of cut can be described as a value measured in millimeters and corresponding to the depth of immersion of the cutter in the material during a single pass of the tool. An important rule is that when rough milling, where we mill the entire width of the tool, the maximum recommended milling depth should not be exceeded. Therefore, make sure that the milling depth does not exceed half the diameter of the cutter.

Cutting width, i.e. how much the cutter can collect

The cutting width is a value expressed in millimeters, so it can be figuratively described as the length of the wall collected by the cutter during one pass. Several basic rules regarding this parameter should be followed, one of them is to use a cutting width ranging from 60 to 100% for roughing movements, as opposed to finishing machining, for which the cutting width should not exceed 10% of the tool diameter.

Feed per tooth at the end of the article

Feed per tooth, i.e. the linear distance of material collected by a single tool blade, is another parameter related to machining. Therefore, using simple mathematical relationships, we can calculate the cutting speed, which in turn will allow us to calculate the spindle revolutions.

Formula for feed per tooth [mm] = (cutting speed) / (number of teeth * set spindle revolutions)

Using the above formula, we can calculate the feed per tooth for a cutter with 2 blades and moving at a cutting speed of 500 [m/min] at a speed of 24,000 RPM.

Feed per tooth [mm] = (500)/(2*24000) = 0.01 [mm]

In summary, it can be noted that for sintered carbide cutters, the feed per tooth is assumed to be no greater than 0.02 mm in the case of a cutter with a diameter of 3 mm, as opposed to a 6 mm cutter where this value should not exceed 0.04.