JPS58217247A - Supervisory method of abnormal phenomenon at cutting - Google Patents

Abstract

PURPOSE:To surely detect damage of a tool, by considering the cutting tool as the damage if component ratio and back component/main component of the three components of cutting resistance exceed a preset value and if a differential coefficient of the component ratio to the time with the main component above the preset value exceeds the preset value. CONSTITUTION:A feed component Ft, back component Fn and a main component Fc of cutting resistance during cutting are measured by a dynamic distortion meter 4, respectively input to comparators 6-8 via an amplifier 5 and compared with a preset value for an initial value of cutting. While ratios Ft/Fc and Fn/Fc are respectively obtained by dividers 9, 10 and compared with a preset value determined by machining tolerance in comparators 11, 12. Further the ratio Fn/Fc is differentiated to a differential coefficient for time in a differentiator 13 and compared with a preset value in a comparator 14. Then outputs of the comparators 6-8, 11, 12 become a level H, and if the level H lasts for a prescribed time of a timer in a wearing decision device 15, replacement of a worn tool is indicated. While if the ratio Fn/Fc exceeds a prescribed value and if a differential coefficient with the component Fc above the prescribed value exceeds the preset value, a damage decision device 16 stops a machine tool 17 as the damage of the cutting tool.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for monitoring chipping of a cutting edge during cutting of a cutting tool.

Conventionally known methods for in-process monitoring of abnormal phenomena such as tool chipping and chipping during cutting include a method based on the current value of the main motor and power consumption without using a special sensor, and a method using a cutting dynamometer to measure cutting resistance. A method using an increase in the principal component force has been tried, and a method using an AE sensor, which is said to be able to test the occurrence and propagation of cracks within a tool, is being researched.

However, the method using current, power, and cutting resistance may output a signal similar to that of tool damage due to the effects of changes in cutting conditions, Jlif shape of the workpiece, rotational runout, etc. In addition, with the AE sensor method, the acoustic radiation from the mechanical elements of the machine tool during operation and the acoustic radiation when cutting chips during cutting may be similar to the AE multiplied signal when the tool is damaged. It is difficult to fully utilize the force, and it is not yet satisfactory in practical use.The applicant has previously proposed the three-component force for cutting based on Japanese Patent Publication No. 52-55154, which was previously proposed in order to find a method for monitoring abnormalities in vine tools that can be put to practical use. Various studies using the factors of 2-component force ratio ('n/Fc, 't/pc) have shown that when the cutting edge is chipped, it is possible to continue cutting and it is not necessarily necessary to stop the machine immediately, but the cutting edge As a result of analyzing the phenomenon of defects, we found that it is necessary to minimize the time delay from occurrence to stopping the machine in the case of large defects or defects that mean destruction of the entire chip. When the blade breaks, there is a sudden change in the above factors ■The cutting resistance is higher than the value during steady cutting ■The cutting force ratio is higher than the wear judgment standard value ■The cutting force ratio 'n/
The positive differential coefficient of po with respect to time is greater than or equal to a certain value.
They found that these two events occur simultaneously and confirmed that they can be detected using these six composite signals.

Therefore, the present invention has been made based on the results of the above-mentioned research, and aims to provide a method for monitoring abnormal phenomena during cutting that can issue commands to the machine in a short time in response to chipping of cutting edges. Component force ratio of 6 component forces applied to the tool inside The component force/principal force exceeds the set value When the principal component force exceeds the set value, the differential coefficient of back force/principal force with respect to time exceeds the set value And ^
This feature is characterized by the fact that it is assumed that the cutting edge is defective and the necessary signal is sent to the machine.

Hereinafter, embodiments of the present invention will be explained based on the drawings.A workpiece 6 supported by a chuck 1 and a center 2 of a tailstock of a lathe is measured by a cutting dynamometer 4 installed in a tool post to reduce cutting resistance by 3 minutes during cutting. The force feed component Ft, the back force Fn, and the principal force Fc are measured and taken out via a dynamic strain meter. The measured value of the 6-component force is amplified to the required level by the amplifier 5, and the outputs of the feed component force Ft, the back force Fn, and the main component force F are respectively input to the comparator 6.7.8. It is compared with the set value for each initial cutting value, and the feed component force Ft
and the principal force Fc are sent to the divider 9, and the back force Fn and the principal force F are sent to the divider 10 to obtain the cutting force ratio Ft/
Fc, F, /FC are each divided. This divided value Ft/Fa is input to the comparator 11 and is determined from the initial cutting value by a set value (Jl
The divided value Fn/Fc is input to the comparator 12, and is compared with a set value (I! Wear judgment reference value) determined by the machining tolerance of the workpiece with respect to the initial cutting value. The force ratio #″n/Fo is input to the differentiator 16 and is calculated as the differential coefficient a(”/po)/with respect to time ゛.
Compute at. The calculated value ""Fa)At is the comparator 14
is input and compared with the set value. Comparators 6°7.8 for each of the 6 component forces, comparators 11 and 12 for the cutting force ratio
, the respective setting values in the differential coefficient comparator 13 are such that, for example, Ft is an initial value of 411N and a setting value of 65c/l/F.
The initial value of n is 286N, and the set value is 65ONFc, and the initial value of force is 982/V, whereas the set value is 1050jv'/po.
The initial value is 40.1% and the set value is 56%"/p0 is the initial value is 28.2% and the set value is 41.2%"/p, the differential coefficient a ("/po), /dt of The setting value is '50%/
It can be determined as 20m5ec.

6 component force comparators 6, 7.8 and cutting component force ratio comparator 1
1.12 outputs A, B, C, D, E are wear judger 1
5 is input. When each comparator exceeds the set value, its output becomes H level.

Set by the timer in the wear detector 15 for stable detection of work materials that cause dry cutting or cracks.

If the H level continues for a certain period of time from 1 to 12 seas, the outputs G and H1J of the wear determiner 15.

When K and L become "H" level, the machine tool 17Tt-feeds and stops the feed of the tool rest, and if necessary, commands the tool replacement of the worn tool according to the wear indication. Then, the tool is replaced with a new tool, and feeding of the machine tool 17 is continued again. Note that the output of the wear judger 15 is the cutting force ratio output G, H, or 3.
Combining component force and cutting force ratio. On the other hand, the output F of the comparator 14 is input to the defect determination unit 16, and the differential coefficient d(""
/FQ)/dt exceeds the set value, the output F becomes
It becomes H level. Deficiency determiner 16 is constituted by an AND circuit in which output E of comparator 12 of principal force FC, output C cutting force ratio of comparator 8 of comparator 8 / pc, and output F are manually operated, and principal force value F, has exceeded the set value.H level and cutting force ratio Fn/F0 have exceeded the wear judgment reference value.H level and differential coefficient d(Fn/F0)/mu have exceeded the set value.
"H" of the output that satisfies the AND condition with the 3 outputs with the level
"Stop the feed of the machine tool 17" or completely stop the machine at the level.

Next, experimental results using the above detection device will be described.

Cutting workpiece '4A's45 to easily cause tool breakage.
0(6) The spot weld is set at cutting speed' = ” ” ”l
'aec.

Depth of cut: 2 mm, feed f = 0.6 mm/ro
Dry cutting was performed using vT tool P20. It is assumed that the wear judgment is performed only based on the cutting force ratio. Cutting resistance 6 component force Ft, Fn, FC, cutting force ratio Ft before and after fracture occurrence
/ p, , n / p, , Fn / pc
In Figure 2, which shows the change in the differential coefficient with respect to the poem,
As the cutting progresses, chipping of the main cutting edge due to the weld occurs first, and the feed force Ft increases from the initial cutting value of 411.6 A', and the cutting force ratio Ft/Fo increases from the initial cutting value of 40.1%. When the cutting force ratio Ft/Fo exceeds the wear judgment reference value of 53% for side flank wear detection, the comparator 11 determines that tool wear is severe and does not fall within the machining tolerance of the workpiece.
The output level becomes 1°H5) level. This EI H5
) level continues for the timer set time 18θe, the output G of the wear determiner 15 becomes the ErHt' level, and the tool post feed of the machine tool 17 is stopped to perform the necessary tool exchange. As cutting progresses further, wear due to chipping of the main cutting edge progresses, leading to feed force Fθ and cutting force ratio Ft/F.
o increases and chipping occurs on the front cutting edge, resulting in principal force FC1
The thrust force Fn and the cutting force ratio Fn/F0 also begin to increase. However, the cutting force ratio Fn/Fo does not exceed the wear criterion value of 41.2% for detecting front flank wear until the front cutting edge breaks, but chipping increases as cutting continues. When the front cutting edge breaks, the back force Fn
and the cutting force ratio F21/Fo increases rapidly. Therefore, the cutting force ratio "/pa" exceeds the wear criterion value for detecting front flank wear, and the output E of the comparator 12 becomes "H".
'This level becomes the level and is set by the timer i'
If the operation is continued for a period of 30 seconds, the output H of the wear determiner 15 becomes H level and sends a signal to the machine tool 17. In addition, the differential coefficient d(”/F
c) /at becomes 100% and the setting value is 30%/20
maee is exceeded and the output F of the comparator 14 becomes H level. On the other hand, the cutting force ratio Fr1/F0 is set at 41.2%.
Since the output E of the comparator 12 has exceeded the set value 1050#t- and the output E of the comparator 12 has reached the H level, and the principal force FC has exceeded the set value 1050#t-, the output E of the comparator 12 has reached the H level. Then, the AND condition of the AND circuit is satisfied, and the output power becomes H'' level and the machine tool 17 is completely stopped.

As described in detail above, the present invention detects a sudden change in the cutting force ratio Fn/F0 using a differential coefficient with respect to time, and performs a pre-cut using a composite signal of the principal force exceeding a set value and the cutting force ratio "/pc". Since the chipping of the cutting edge is known, it is possible to reliably detect the chipping of the cutting edge within a short period of time, which makes it impossible to continue cutting.Also, this can cause damage to the workpiece or tool post, etc. It has the characteristics of being able to eliminate secondary damage such as, and improve the reliability of unmanned operation.

[Brief explanation of the drawing]

Figure M1 is a block diagram of the detection device used to implement the present invention. Figure 2 is the 3-component force of cutting force due to chipping and chipping of the tool during cutting, the ratio of cutting component force, and the ratio of cutting component force to time of "/pc". It is a diagram showing changes in the differential coefficient. 4... Cutting dynamometer 9, 10... Divider (9) 6.7, 8, 11.12.13... Comparator 15...
Wear judgment device 16...Defect judgment device Patent applicant Okuma Iron Works Kashi Co., Ltd. Tatsu Sashi, - Osamu Kato Yumi Kato 5.
″(10)

Claims (1)

[Claims] The independent component of the 3-component force of the cutting resistance applied to the cutting tool during cutting, the cutting component force ratio of the backing force to the principal component force, and the differential coefficient of the component force ratio with respect to time are determined, and the component force ratio is set. When the principal component force exceeds the set value and the differential coefficient of the component force ratio with respect to time exceeds the set value, it is assumed that the front cutting edge of the tool is broken and the necessary signal is sent to the machine. Features a method for monitoring abnormal phenomena during cutting.