JPS6149068B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a rough machining control method in an NC lathe. In general, rough machining with a lathe is the process of cutting a material into a shape that approximates the product shape.In this rough machining, the tool tip is positioned at a specified machining starting point, and the tool is cut a predetermined amount from this position. The operation of moving the tool in the cutting direction and moving the tool in the feed direction from that position to the designated machining end point is repeated multiple times. In rough machining using an NC lathe, the cutting path of the tool described above, that is, the machining start point, machining end point, depth of cut, and return point for each time, are given numerical values and the machining is performed automatically. There are currently two types. One method is to give it with NC tape,
This method requires a lot of time and effort to create the NC tape, and although various simple NC tape creation methods have recently been proposed, even with this method it is necessary to create the NC tape in advance. Another method is to input data via various operation buttons on the control panel of the NC lathe and perform calculations within the control device, without creating an NC tape.
This is a method of performing NC machining. This method is currently attracting the most attention, but conventional methods cannot process complex shapes with uneven surfaces and are limited to open shapes. In view of the above points, the present invention provides a rough machining control method for an NC lathe that can machine even complex shapes with irregularities with simple operations. Hereinafter, the configuration of the present invention will be explained with reference to the drawings. This invention provides common data consisting of the original position (the position at which the tool is indexed), the finishing allowance δ, and the cutting angle α, front cutting edge angle β, nose radius γ, etc. of the tool corresponding to a preset tool number. and machining shape, X and Z coordinates of the cutting point, X and Z coordinates of the starting point, X and Z coordinates of the end point, radius R when machining an arc shape, depth of cut γ, finishing tool number m, rough tool number
By simply inputting process data consisting of m', rotational speed N, feed rate V, etc., the workpiece is automatically machined into a complex shape as shown in Figure 1 in the order of roughing, rough finishing, and finishing. This is the way to do it. Since the rough finishing dimensions are the finishing dimensions remaining the finishing allowance, they may be automatically calculated by a computer, or may be input separately from the finishing dimensions. However, inputting the rough machining dimensions one by one is very time-consuming, so this invention uses a computer to calculate the rough machining dimensions and automatically performs the rough machining. FIG. 2 is a block diagram showing an overview of the control method for the NC lathe according to the present invention, in which the finishing dimensions described above are inputted through an input medium, converted into electrical quantities at the input section, and introduced into the control section. Necessary calculations are performed between the control section and the calculation section and stored in the storage section, and between the storage section and the control section, the information stored in the storage section is sequentially output to the output section to control the NC lathe. be. The storage unit mentioned above is composed of three types,
To memorize finishing dimensions, rough finishing dimensions, and rough finishing dimensions, use finishing buffer, rough finishing buffer,
It has a rough machining buffer. The rough finishing buffer stores the machining shape, starting point A, ending point F, center point P, radius R, depth of cut γ, roughing starting point M, and others (rotation speed, feed rate, etc.) for each process as shown below. Configure it to get it.

[Table] The finishing buffer is constructed in the same manner as the rough finishing buffer described above. The positional coordinates of the above starting point, etc. are determined by using orthogonal ZX coordinates with one end of the material as the origin, the axis of rotation of the material as the Z axis, and the X axis in the direction orthogonal to this, and using the input medium shown in Figure 2 above. The values of the starting point, end point, and center point of the finishing buffer and rough finishing buffer are calculated and stored based on the finish machining dimensions input from . The above process numbers are explained with reference to Figure 1.The first process is the parts 1 and 2, the second process is the parts 2 and 3, and similarly, the final processes are 9 and 10. In Figure 1, the process is divided into nine steps, and the start and end points of each process are calculated, and in the case of the machining shape and circular arc of each part, the center point is calculated and stored in the buffer. In the above, the contents stored in the finishing buffer will be explained in a little more detail using FIG. 1 as an example.
The shape of the product and the dimensions of each part can be determined by looking at the design drawing, and the continuous outline drawn on this design drawing is divided into simple shapes starting from one end as shown in Figure 1, and each division is divided into simple shapes. Divide it into one process and give process numbers sequentially starting from one end. Then, the processing shape of each process (straight line, taper, convex circle, concave circle, etc.), the dimensions of the starting point and end point (this is the actual dimension from one end of the product), and in the case of an arc, the radius are the dimensions written in the design drawing. The ZX coordinates are read from the ZX coordinates and set in the digital switch in the order of the process, given the origin of the ZX coordinates, converted to ZX coordinates internally, and stored in the finishing buffer. Once the finishing roughness data is obtained, adding the finishing allowance δ to that data will give the rough finishing data,
These are also immediately calculated internally and stored in the rough finishing buffer. Next, all you need to do is find the rough machining data.
Hereinafter, how to obtain rough machining data will be explained. Rough machining can be performed by slicing from the shape of the material to the rough finishing data obtained in the above manner by slicing it with a single cutting depth γ as shown by the rough machining line in Figure 1. The movement command pattern of the tool during machining can be fixed. In this invention, the rough machining pattern is divided into two types: an open type as shown in Figure 3 and a concave type as shown in Figure 4, and the tool movement command pattern for rough machining is as shown in Figure 5. As shown, the patterns are divided into three types and fixed, and one of the patterns is automatically selected and determined in the manner described later. In Figure 5 above, Gi is the rough starting point and Hi
is the rough ending point, Ji is the rough return point, and from Gi
From Hi to Ji, cutting is fed in parallel to the Z-axis direction, and from Hi to Ji there is a quick return. Rough machining can be performed by sequentially calculating the ZX coordinate values of Gi, Hi, and Ji for each machining process. It is also possible to calculate and store Gi, Hi, and Ji for each machining cycle in advance for all processes in the same manner as the finishing and rough finishing data described above, but in this invention, in order to reduce the storage capacity of rough machining data, Calculations are performed once at a time, and rough machining is performed immediately using the data obtained each time. Next, the previous data is erased and the next data is calculated to perform rough machining, and this is successively repeated for the entire process. The memory data is updated one after another. Therefore, in this invention, it is sufficient to use a rough machining buffer that stores rough machining data basically with a capacity that can store three points for one process: rough start point Gi, rough end point Hi, and rough return point Ji. It is something. However, in reality, in order to calculate the above three points, a buffer for storing the previous rough starting point Gi-1 and a buffer for storing the rough starting point X(M) for each process are used. Furthermore, in order to move the rough return point Ji to the rough start point Gi+1 of the next process without wasting feed, it is necessary to calculate a buffer to store the next rough machining data and a buffer to temporarily save and store the current rough machining data. Use a proper batshua. The rough processing buffer used in this invention is as follows.

[Table] The specific calculation method for Gi, Hi, and Ji is explained below. X (Gi) = X (Gi-1) - γ (γ is depth of cut) X (Hi) = X (Gi), so Z (Gi), Z (Hi), X (Ji)
Only Z (Ji) and Z (Ji) matter, and these are determined as follows based on the machining shape and the rough starting point of the next process.

[Table] In other words, Z (Gi) in the concave taper is the 6th
Taper start point A and end point F of rough finishing dimensions in the figure
It is determined from the ZX coordinate value and given by considering the finishing allowance δ. The reason for considering the finishing allowance δ is to prevent the tool from cutting into the tool trajectory during rough finishing and to make the finish smooth during rough finishing. It's not a thing. Further, Z (Hi) at the taper is calculated in the same manner as above, as shown in FIG. In addition, for Z (Gi) in a concave and convex circle, the ZX coordinates Z (P) and X (P) of the center point P are calculated from the arc start and end points and radius R of the rough finishing dimensions, and from this It is calculated and obtained as shown in . Further, Z (Hi) of the convex circle is calculated in the same manner as shown in FIG. Further, Z (Gi) of the concave and concave circles is calculated as shown in FIG. 10, and Z (Hi) is calculated as shown in FIG. 11. Therefore, if we give the machining shape, starting point A, ending point F, arc center point P, arc radius R, depth of cut γ, finishing allowance δ, and the X coordinate X (Gi-1) of the previous rough starting point, then Z
(Gi) and Z (Hi) can be calculated. For the above A, F, P, R, γ, and δ, it is sufficient to give the process number N of the rough finishing buffer, so in the end, it is sufficient to give the process number N and X (Gi-1) of the rough finishing buffer. Next, X (Ji) and Z (Ji) are Z (Hi) and Z
The magnitude relationship with (Hi+1) is determined and determined as follows.

[Table] The above three types of patterns correspond to FIG. 5. The overall rough machining control (concave type) system of the present invention based on the rough machining data described above is shown in a flowchart as shown in FIG. 12. To start rough machining in Figure 12, first erase the X(M) and flags (details will be described later) for all processes in the rough machining buffer, and then perform rough machining while sequentially calculating from the final process n. Have them do it. In the first operation, X(Gi−1)
is not determined, but since it is sufficient to give the X coordinate value of the end point (F ₁ ) of the first step of the rough finishing buffer, it is given as X(Gi-1)=X(F ₁ ). Then, as for the process number N, rough machining is performed from the final process n, so N=n. As a result, Gi, Hi, and Ji of the process are calculated from the data stored in the rough finishing buffer of the n process using the calculation method described above. However, the calculation here is

[Table] This is a temporary setting.
Z(Ji)〓Z(Gi)〓
Let's calculate it as Z (Gi) and Z
For (Hi), it is sufficient to sequentially give one of the process numbers N and have the other process number selected.If Z (Gi) is to be given sequentially, Z by the method shown in Figure 13.
(Hi) is calculated. To explain this specifically, Z (Gi) is the 6th
In order to calculate Z (Gi) of the n-th process, which is calculated by any of the methods shown in Fig. 8, Fig. 10, the starting point stored in the rough finishing buffer of the process, It is determined from the position coordinates of the end point and center point, the radius, and X (Gi). Regarding Z (Hi), as shown in Figure 13, X (Gi), Z (Gi), X (Hi), X (Ji), Z
After (Ji) is determined as above, the students are asked to determine whether or not the X coordinates of the starting and ending points of all processes of the rough finishing buffer are larger than X (Gi), thereby determining Z (Hi). This determination is made in block 10 in FIG. When Z (Hi) is obtained in this way, as shown in Figure 13, it is determined whether the process number is "1" or not, and if it is "1", the process is changed to the next one, and if it is not "1", it is It is determined whether X(M) is present or absent in the process of (N-1), and when it is "present", the process is moved to the next one, and when "absent", X(M _N-1 )=X(Gi-
1) Memorize. The above FIG. 13 shows the reference numerals 11 and 11 in FIG.
This is a detailed version of part 12. As described above, the calculations of Gi, Hi, and Ji were performed in the part 11 in Fig. 12, and then the judgment of "yes" or "no" of X(Gi)>X(A _N ), (Gi)>X(F _N ) and Z(Gi)>Z(Hi) are respectively performed for confirmation, and based on the results, processing as shown by the arrows is performed. If there is no problem in the above confirmation judgment, the obtained Gi,
The ZX coordinate values of Hi and Ji are stored in a temporary save buffer indicated by reference numeral 13 in FIG. 12, and then the next calculation of Gi, Hi, and Ji is performed in the same manner. In this case, X (Gi-1) is the previously calculated X
It goes without saying that (Gi) must be included. When the next Gi, Hi, and Ji are determined, they are stored in a buffer for storing the next rough machining data, which is indicated by reference numeral 14 in FIG. In the above process, when N=1 is "yes" as shown in Figure 12, "end flag set" is displayed because the rough machining process is calculated in reverse order starting from n. In the calculation, the step number becomes ``1'' and there is no need to repeat the calculation thereafter, so an ``end flag signal'' is output. When the rough machining data for the next process is calculated as described above, the rough machining data for the current process stored in the temporary save buffer is again called and stored in the buffer 15 in FIG. Then, it is determined whether or not there is an "end flag", and when "NO", a determination is made that Z(Hi)>Z(Hi+1), and the rough return point Ji is correctly determined for the first time. The setting of Ji is divided into three types 1, 2, and 3, as shown in FIG. 5 and described above. In FIG. 12, numerals 1, 2, and 3 mean that the determination results correspond to those in FIG. In the above Ji determination, when a type 1 determination is made, an "initial flag i+1" signal is set to distinguish it from others. In this way, when Ji is determined considering the next time, the current rough machining can be carried out, and the cutting conditions for the relevant process (common data such as spindle rotation speed, cutting speed, etc. and process data) are set. , this time, it is determined whether the "initial flag i" signal is set, and if "yes", the signal is erased, and at the same time the tool is set to Z (Gi) +
Fast forward in the Z-axis direction to X(Gi-1)-X(Gi)+a/tan(β ^-3 ), and when "NO", move the tool to the obtained Gi, Hi, Ji. In this case, Gi from the current position (Gi−1)
and from Gi to Hi is the cutting feed,
It is a quick return from Hi to Ji. When this is completed, the process moves on to the next step, but before that, it is determined whether the "Initial flag i+1" signal was set last time, and if "yes", the signal is erased, and at the same time, the "Initial flag i+1" signal is set. The signal of "Flag i" is set to proceed to the determination of the presence or absence of the next "End flag", and when the signal is "NO", the procedure immediately proceeds to the determination of the presence or absence of the "End flag". Then, if the "end flag" is "present" or "yes", it means the end of the process, so the "end flag signal" is erased and the tool is
Move it to (F ₁ )+a to finish rough machining. However, the "end flag signal" is not set in processes other than the final process, so the above judgment is made as ``none'', that is, ``NO'', and in this case, the next process rough start point Gi + 1, rough end point Hi + 1
And the rough return point Ji+1 is already at 14 in FIG.
Since it has been stored in the buffer shown in FIG. 12, it is called up and stored in the temporary save buffer shown at 16 in FIG. This buffer 16 is the same as the buffer indicated by reference numeral 13 in FIG. 12, and is used to erase the memory of the buffer 13 (the previous one) and store new data. Next, set X(Gi-1) to X(Gi+1), set the process number as the next process, and repeat the 12th process.
Proceed to the front of the arithmetic section 12 in the figure as indicated by *, and repeat the same process. In short, in Fig. 12, the period between the * mark and the * mark is repeated from the second time to the final time. Now, as a specific example, a case where a shape as shown in FIG. 14 is controlled by the rough machining control method of the present invention described above will be described. In the case of Fig. 14, the rough finishing buffer process consists of six steps, the first step has A ₁ as the starting point and F ₁ as the ending point, and similarly, the sixth step has A ₆ as the starting point and F ₆ as the ending point.
is the end point, and rough machining is the sixth and final process.
Started from the process, the first rough starting point in that case
G ₁ , rough end point H ₁ , and rough return point J ₁ are as follows. First, for X(Gi-1), enter X(F ₁ ). Since X(G ₁ ) is X(Gi-1)-γ, X(G ₁ )=X(F ₁ )-γ. X(H ₁ ) is the same as X(G ₁ ). Since Z(G ₁ ) can be calculated using the formula shown in Figure 6, Z(G ₁ )=Z(A ₆ )−Z(A ₆ )−Z(F ₆ )/X(A
₆ )-X( _F6 ){X( _A6 )-X( _G1 )}-δ. Next, Z (H ₁ ) is determined, as shown in Figure 13. That is, looking at the contents of block 10 in FIG. 13, N=N-1, that is, in the step of FIG. 14, _{the magnitude of the X coordinates X(A 5 )} and As is clear from Figure 14, X(G ₁ ) is larger than X(A ₅ ), so next we compare X(G ₁ ) and X(F ₅ ), In figure 14, X
(G ₁ ) is larger than X (F ₅ ), so N=N-1 again
That is, X (A ₄ ) and X (F ₄ ) in the fourth step
(G ₁ ) and searches for a process with a value of X greater than X (G ₁ ). In the example of FIG. 14, the process having such a value of X is the first process. Therefore, the data from the rough finishing buffer process is used to calculate Z(H ₁ ).
It is calculated using the formula shown in Figure 7 using A ₁ and F ₁ . That is, Z(H ₁ )=Z(A ₁ )−Z(A ₁ )−Z(F ₁ )/X(A
₁ )-X( _F1 ){X( _A1 )-X( _G1 )}+δ. X(J ₁ ) and Z(J ₁ ) are Z(H ₁ ) obtained above
and Z(H ₂ ) obtained in the same way, and in the case of Fig. 14, Z(H ₁ ) < Z(H ₂ ).
And since N ₁ = N ₂ , it becomes type 2, and in the end, X(J ₁ )=X(G ₁ )+a Z(J ₁ )=Z(G ₂ )+X(J ₁ )−X ( _G2 )/tan
(β−3°)

[Table] 〓
〓Z(J ₄ )〓Z(G ₄ )
Since the process ends, the end flag appears and the next operation is not performed, and X(F ₁ ) + a
The tool is moved to the point where the rough machining shown in FIG. 14 is completed. In FIG. 14, the tool path indicated by a solid line indicates cutting feed, and the tool trajectory indicated by a broken line indicates rapid feed. Thereafter, rough finishing and finishing are performed successively based on the data stored in each buffer. The above explanation is for a partially concave machined shape, but for an open shape, Z (Gi) = Z
(A _o )+b, so only Z(Hi) needs to be calculated.In this case, the process number can be given sequentially from the first process, so the flowchart is as shown in Figure 15. This is extremely simple compared to the concave type. In this way, the combination of two types of rough machining methods, the partially concave type and the open type, enables machining of complex shapes, and also allows for the rough return point during rough machining.
Since Ji is selected from three types and determined based on the next rough machining data, unnecessary feed of the tool can be eliminated. In addition, in this invention, A, B, as shown in FIG.
The machining shape given by C, D, K, E, and F can also be rough-machined as one process. In other words, X(M) is used separately from X(M) for in-process use.
If (M') can be memorized, X in Figure 12
Calculations within the process can be performed using a flowchart in which (M) is replaced with X(M'). As explained above, the present invention divides the machining shape pattern into an open type and a partially concave type and inputs it into the control device of the NC lathe, and sequentially processes the machining shape from one end in the direction of the lathe's main axis parallel to the lathe main axis. Divide into simple shapes such as straight line, taper, convex circle, or concave circle, each shape is treated as one process, and divided into n processes from one end to the other end in the direction of the lathe main axis, and the type of machined shape, starting point, and ending point for each process. , the center point, radius, etc. of the arc are input into the control device of the NC lathe as dimensions from the reference point in the direction of the main axis of the lathe and dimensions from the center of the main axis of the lathe in the direction orthogonal to the main axis, and along with this, the dimensions of the material , common data regarding tool specifications, process data, and depth of cut are input into the control device, and the tool movement command pattern within the control device is set to make one cut in the direction perpendicular to the main axis of the lathe from the machining start point. Then, the cutting feed is moved parallel to the main axis of the lathe until the machining end point, and then the next machining start point is ahead in the cutting feed direction of the tool along the lathe main axis based on the current machining end point. At this time, the first pattern is to quickly return from the current machining end point in the direction perpendicular to the lathe main axis by the dimension that takes into account the next machining start point dimension and the depth of cut, and then move to the next machining start point; The machining start point is at the same position or behind the current machining end point in the cutting feed direction of the tool along the lathe main axis, and the process input separately for the simple shape is the current machining start point. If it is different from the start point of the next machining, a second pattern is created in which the current machining end point is returned slightly in the direction perpendicular to the lathe main axis and then quickly returned in the direction of the lathe main axis to the next machining start point, and the second pattern is Under the above conditions, if the current machining start point and the next machining start point are in the same process,
A command is issued within the control device by distinguishing between a third pattern that causes a slight quick return in the direction perpendicular to the lathe main axis from the current machining end point, and then a quick return in the direction of the lathe main axis to the current machining start point. , the machining allowance in the direction perpendicular to the lathe spindle from the material dimensions to the machining shape is sliced parallel to the lathe spindle with the above depth of cut, and the machining start point of each tool movement command pattern,
The cutting path for rough machining is determined by sequentially internally calculating the machining end point using a calculation method corresponding to each machining shape so as not to interfere with the machining shape, and based on the calculation results, the tool is moved from the machining start point of the material each time as described above. Since the type of movement command pattern is determined and the movement is controlled using the corresponding movement command pattern, when the rough machining cutting path is repeated multiple times from the material to the final machining shape, the current machining end point When moving the tool from the point to the next machining start point, based on these positional relationships, it is possible to automatically determine the appropriate pattern from among the three types of tool movement command patterns and move the tool, thereby reducing wasteful feed. Since it is possible to move in a relatively shortest route by reducing the amount of time required for processing, the time required for processing can be shortened. In addition, it can be applied to both open and concave shapes, making it possible to process complex shapes, further improving the capabilities of this type of NC lathe with easy input operations. and the storage capacity of the rough processing buffer can be reduced.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of a processed shape that can be processed by the present invention, Fig. 2 is a block diagram showing an overview of a processing system for carrying out the method of the present invention, and Fig. 3 is an open type. FIG. 4 is an explanatory diagram showing an example of a machining shape, FIG. 4 is an explanatory diagram showing an example of a concave machining shape, FIG. 5 is an explanatory diagram showing a tool movement command pattern in rough machining of the present invention, and FIG. Fig. 7 is a geometric explanatory diagram showing how to find the rough starting point, Fig. 7 is a geometrical explanatory drawing showing how to find the rough ending point in a concave taper, and Fig. 8 is a geometrical explanatory diagram showing how to find the rough starting point in a concave convex circle. FIG. 9 is a geometric explanatory diagram showing how to find the rough end point in a partially concave convex circle, and FIG. 10 is a geometric explanatory diagram showing how to find the rough starting point in a partially concave concave circle. 11 is a geometric explanatory diagram showing how to find the rough end point of a concave circle with a concave shape, FIG. 12 is a flowchart showing a rough machining control method for a concave shape with a concave shape, and FIG. A subroutine flowchart diagram showing the details of the Gi, Hi, and Ji calculation sections of
FIG. 14 is an example showing the cutting path of the rough machining tool obtained by applying the above flowchart.
FIG. 5 is a flowchart showing an open rough machining control method, and FIG. 16 is a diagram showing an example of a machining shape. Gi...Rough start point, Hi...Rough end point, Ji...Rough return point, A...Start point of machining shape, F...End point of machining shape, X(Gi)...X coordinate value of Gi point, Z( Gi)…
...Z coordinate value of Gi point, N...Process number, n...Final process, P...Circle center, R...Circle radius, X
(M)... Rough machining start point, γ... Depth of cut, δ... Finishing allowance, a, b... Constant, β... Front cutting edge angle of the tool.

Claims (1)

[Claims] 1 The machining shape pattern is divided into an open type and a partially concave type and input into the control device of the NC lathe, and the machining shape is sequentially changed from one end in the direction of the lathe's main axis to a straight line parallel to the lathe main axis, a taper, a convex circle, a taper, a convex circle, etc. Divide into one of the simple shapes of a concave circle, each shape is considered as one process, and divided into n processes from one end to the other end in the direction of the lathe main axis, and the type of machining shape, starting point, ending point, center point of the arc, and radius for each process. etc. are input into the control device of the NC lathe as dimensions from the reference point in the direction of the main axis of the lathe and dimensions from the center of the main axis of the lathe in the direction orthogonal to the main axis, and together with this, common data regarding the dimensions of the material and tool specifications. , input process data and depth of cut into the control device, and feed a tool movement command pattern within the control device by one depth of cut in a direction perpendicular to the main axis of the lathe from the machining start point; Next, the cutting feed is moved parallel to the main axis of the lathe to the machining end point, and if the next machining start point is ahead in the cutting feed direction of the tool along the lathe main axis based on the current machining end point, the current machining end point is The first pattern is to move back to the next machining start point in the direction perpendicular to the lathe main axis by the dimension that takes into account the next machining start point dimension and the depth of cut, and then move the next machining start point to the current machining start point. When the machining end point is at the same position or behind the machining end point in the cutting feed direction of the tool along the lathe main axis, and the process input separately for the simple shape is different between the current machining start point and the next machining start point. In this case, there is a second pattern in which a slight quick return is made in the direction perpendicular to the lathe main axis from the current machining end point, and then a quick return in the lathe main axis direction to the next machining start point, and among the above conditions of the second pattern, this current If the machining start point and the next machining start point are in the same process, the third pattern is a slight quick return from the current machining end point in the direction perpendicular to the lathe main axis, and then a quick return in the lathe main axis direction to the current machining start point. In the control device, the machining allowance in the direction perpendicular to the lathe main axis, from the material dimensions to the machined shape, is sliced parallel to the lathe main axis with the above depth of cut, and each time The machining start point and machining end point of the tool movement command pattern are sequentially internally calculated using the calculation method corresponding to each machining shape to avoid interference with the machining shape, and the cutting path for rough machining is determined. Based on the calculation results, the cutting path of the material is calculated. A method for controlling rough machining in an NC lathe, characterized in that the tool is controlled to move according to the corresponding movement command pattern by determining the above three types of movement command patterns every time from a machining start point.