Principles for determining feed speed:

1) When the quality requirements of the workpiece can be guaranteed, in order to improve production efficiency, a higher feed rate can be selected. Generally, it is selected within the range of 100-200m/min.

2) When cutting and processing deep holes or processing with high-speed steel tools, it is advisable to choose a lower feed rate, generally within the range of 20-50m/min.

3) When the processing accuracy and surface roughness are required to be high, the feed speed should be selected smaller, generally within the range of 20-50m/min.

4) When the tool travels empty, especially when "returning to zero" at a long distance, the highest feed rate set by the CNC system of the machine tool can be selected.

4. Determination of the spindle speed

The spindle speed should be selected according to the allowable cutting speed and workpiece (or tool) diameter. Its calculation formula is:

Machining center tool cutting parameter list, including 45# steel, stainless steel, aluminum alloy, etc.

n=1000*v/π*D

v----cutting speed, the unit is m/min, determined by the durability of the tool;

n----Spindle speed, the unit is r/min;

D----workpiece diameter or tool diameter, the unit is mm.

The calculated spindle speed n should finally select the machine tool's own or close speed according to the machine tool manual.

In short, the specific value of the cutting amount should be determined by analogy method according to the performance of the machine tool, related manuals and practical experience. At the same time, the spindle speed, cutting depth and feed rate can be adapted to each other to form the best cutting amount.

5. Reference formula

1) back cutting amount (cutting depth) ap

The vertical distance between the machined surface of the workpiece and the surface to be machined is called the back cut amount. The back engagement is the amount of engagement measured through the base point of the cutting edge and perpendicular to the working plane. It is the depth at which the turning tool cuts into the workpiece during each feed, so it is also called the depth of cut. According to this definition, if the outer circle is turned longitudinally, the back cutting amount can be calculated according to the following formula:

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ap = (dw-dm)/2

In the formula, ap----the amount of the knife on the back (mm);

dw--the surface diameter of the workpiece to be processed (mm);

dm ---- workpiece has been machined surface diameter (mm).

Example 1: It is known that the surface diameter of the workpiece to be processed is Φ95mm; now feed the machine to the diameter of Φ90mm at one time, and find the back cutting amount.

Solution: ap=(dw-dm)/2=(95-90)/2=2.5mm

2) Feed amount f

The relative displacement between the tool and the workpiece in the direction of feed motion when the workpiece or the tool rotates once. According to the different feed directions, it can be divided into longitudinal feed and cross feed. Feed rate.

Feed speed v f refers to the instantaneous speed of the selected point on the cutting edge relative to the feed motion of the workpiece.

vf=f*n

Where vf----feed speed (mm/s);

n ---- spindle speed (r/s);

f----feed rate (mm/s).

3) Cutting speed vc

The instantaneous velocity of a selected point on the cutting edge relative to the main motion of the workpiece.

vc=(π*dw*n)/1000

Where vc----cutting speed (m/min);

dw----the surface diameter of the workpiece to be processed (mm);

n----workpiece speed (r/min).

The calculation should be based on the maximum cutting speed, such as the value of the diameter of the surface to be processed during turning, because the speed is the highest here and the tool wear is the fastest.

Example 2: Turning the outer circle of a workpiece with a diameter of Φ60mm, the selected lathe spindle speed is 600r/min, find vc

Solution: v c=( π*d*w*n)/1000 = 3.14x60x600/1000 = 113 m/min

In actual production, the diameter of the workpiece is often known. The cutting speed is selected according to the workpiece material, tool material and processing requirements, and then the cutting speed is converted into the lathe spindle speed to adjust the lathe. The following formula is obtained:

n=(1000*vc)/π*dw

Example 3: Turning a Φ260mm pulley outer circle on a CA6140 horizontal lathe, select vc as 90m/min, and find n.

Solution: n=( 1000*vc)/ π*dw=(1000x90)/ (3.14x260) =110r/min

After calculating the spindle speed of the lathe, the value close to that on the nameplate should be selected, that is, n=100r/min should be selected as the actual speed of the lathe.

6. Summary

The three elements of cutting amount refer to the general term of cutting speed vc, feed rate f (or feed rate vf), and back cutting amount ap.

1. Amount of back cut ap(mm)

ap = (dw-dm) / 2

2. Feed amount f(mm/r)

vf=f*n

3. Cutting speed vc(m/min)

vc=(π*dw*n)/1000