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Knowledge of CNC machining

Effects on cutting temperature: cutting speed, feed rate, back feed.


Effects on cutting forces: back feed, feed rate, cutting speed.


Effects on tool durability: cutting speed, feed rate, back feed.


When the back feed is doubled, the cutting force is doubled.


(a) When the feed rate is doubled, the cutting force increases by approximately 70 per cent.


(a) The cutting force decreases as the cutting speed is doubled.


In other words, if you use the G99, the cutting speed gets larger and the cutting force doesn't change much.

It is possible to determine whether the cutting force and cutting temperature are within the normal range based on the discharge of iron chips.


When the concave arc is greater than 0.8 between the actual value X and the drawing diameter Y, the R made by a lathe with a 52-degree sub-deviation (that is, a lathe with a 35-degree blade and a 93-degree main deviation) may wipe the tool at the starting position.


Temperature represented by chip color: white less than 200°C


Yellow 220-240 degrees


290 degrees dark blue.


Blue 320-350 degrees


Black and purple greater than 500 degrees.


Red greater than 800 degrees


FUNAC OI mtc General default G command.


G69: Not quite sure.


G21: Metric size input


G25: Disconnected spindle speed fluctuation detection


G80: Fixed cycle cancellation


G54: Coordinate system default


G18: ZX plane selection


G96 (G97): Constant Linear Speed Control


G99: per transfer of feed


G40: Cancellation of tip compensation (G41 G42)


G22: Memory stroke detection switched on


Male threads are typically 1.3P and female threads are 1.08P.

Thread speed S1200 / pitch * safety factor (typically 0.8).


Manual blade tip R compensation formula: chamfering from the bottom to the car: Z=R*(1-tan(a/2)) X=R(1-tan(a/2))*tan(a) chamfering from the top to the bottom of the car will be changed from minus to plus.


For every 0.05 increase in feed, the rotation speed decreases by 50-80 rpm because lowering the rotation speed means lower tool wear and slower increase in cutting force to compensate for the increased cutting force and higher temperature caused by the increase in feed.


Cutting speed and cutting force are critical to the tool, and excessive cutting force is the main cause of tool collapse. The relationship between cutting speed and cutting force: the faster the cutting speed, the feed remains unchanged and the cutting force slowly decreases, at the same time, the faster the cutting speed will make the tool wear faster, making the cutting force more and more, the temperature will be higher, when the cutting force and internal stresses are too large for the blade to withstand, it will collapse (of course, there are also reasons such as the stresses caused by temperature changes and the decrease in hardness).


When CNC turning, special attention should be paid to the following points.


(1) For the current economy of our country's CNC lathe is generally used ordinary three-phase asynchronous motor through the frequency converter to achieve stepless speed change, if there is no mechanical deceleration, often at low speed spindle output torque is insufficient, if the cutting load is too large, it is easy to boring car, but some machine tools with gears is a good solution to this problem.


(2) As far as possible, so that the tool to complete a part or a working shift of machining work, large pieces of finishing pay particular attention to the middle of avoiding midway tool change to ensure that the tool can be a processing completed.


(3) With CNC turning threads as far as possible when using a higher speed, in order to achieve high quality and efficient production.


(4) As far as possible to use G96.


(5) The basic concept of high speed machining is to make the feed exceeds the heat conduction speed, so that the cutting heat can be discharged with the iron chips to isolate the cutting heat from the workpiece and ensure that the workpiece does not heat up or less heat up, therefore, high speed machining is to select a very high cutting speed and high feed to match the small back eating tooling amount.


G67: Macro modal call cancellation


G64: Not quite sure.


G13.1: Cancellation of the polar interpolation methodWorkpiece material machinability grading scale (small P79)

Gauge for common thread cuts and back feeds (large P587)

Formulas for calculating common geometric figures (large P42)

Inch to millimetre conversion table (large P27)


In the groove will often produce vibration and collapse, the root cause of all this is the cutting force becomes large and tool rigidity is not enough, the shorter the tool outstretched length, after the smaller the angle, the larger the area of the blade, the better the rigidity, with the greater cutting force, but the greater the width of the groove cutter can withstand the cutting force will be correspondingly increased, but its cutting force will also increase, on the contrary, the groove cutter small force it can withstand, but its cutting force is also small.


Causes of vibrations during tanking.

(1) The length of tool extension is too long, resulting in reduced rigidity.

(2) The feed rate is too slow, resulting in the unit cutting force becomes large and thus cause a large vibration, the formula is: P = F / back to eat the tool amount * f P for the unit cutting force F for the cutting force, in addition to speed too fast will also vibrate the knife.

(3) the machine is not rigid enough, that is, the tool can bear cutting force, and the machine can not withstand, to put it bluntly, the machine tool car does not move, the general new bed will not have such problems, there are such problems with the bed is either very old, or often encounter machine tool killers.


But after a period of time, the tool wears out and the cutting force becomes bigger, causing the workpiece to shift on the chuck, so the size is always running and unstable.

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Contact: Jacky Wang

Phone: +86 14714816052

Tel: +86 14714816052

Email: [email protected]

Add: Floor 1, Shixi Industrial area, Canton, Guangdong, China. 510288

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