CN108319229B - Small straight line segment feeding speed control method for numerical control machining - Google Patents
Small straight line segment feeding speed control method for numerical control machining Download PDFInfo
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- CN108319229B CN108319229B CN201810222937.1A CN201810222937A CN108319229B CN 108319229 B CN108319229 B CN 108319229B CN 201810222937 A CN201810222937 A CN 201810222937A CN 108319229 B CN108319229 B CN 108319229B
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
- G05B19/416—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control of velocity, acceleration or deceleration
- G05B19/4163—Adaptive control of feed or cutting velocity
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/30—Nc systems
- G05B2219/36—Nc in input of data, input key till input tape
- G05B2219/36521—Select by combination of detected force, acceleration, speed, work rate
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Abstract
The invention discloses a feeding speed control method for a small linear segment in numerical control machining, which is used for carrying out feeding speed constraint and re-planning on the small linear segment which is smaller than the interpolation distance of the minimum interpolation period of a numerical control system and has larger direction cosine included angle change. The invention can optimize the feeding speed by combining interpolation parameters of a numerical control system in the post-processing process, and reduces the defects of part processing quality caused by the reasons of feeding delay caused by frequent speed change of small straight-line segments or over-speed of coordinate axes in the motion process and the like of a numerical control post-processing program on an actual machine tool.
Description
Technical Field
The invention relates to a numerical control machining process, in particular to a small straight line segment feeding speed control method based on a post-processing process.
Background
The smoothness of the feed rate is another key issue for numerically controlled machine tools and systems in addition to tracking accuracy, since it plays an important role in improving the quality of the machined curved surface. Fluctuations in the feed speed often occur when machining spatial curves consisting of a large number of short straight segments (G01 codes). This causes fluctuations in the load of the cutting tool, increases the machining time and leads to a reduction in the quality of the surface finish. The main reason for this is the non-uniformity of the straight line segment length due to Computer Aided Manufacturing (CAM) software algorithms. Conventional NC machines and system controllers use time division based on two-stage interpolation and fixed interpolation period to interpolate straight line segments. When the length of a given straight line segment is not equal to an integral multiple of the expected feeding speed, the zero-head distance problem occurs, so that the number of periods required for interpolating the straight line needs to be rounded, and the rounding can bring about the fluctuation of the feeding speed and reduce the processing quality. For NC code programs containing many straight line segments of non-uniform length, frequent feed speed fluctuations can result.
In addition, due to the limitation of the calculation speed in the CNC, the interpolation period T must be equal to or greater than the minimum period required for the CNC machine and the system to complete one interpolation. In the presence of this lower limit, the feed rate fluctuations can only be reduced passively to a lower level.
Disclosure of Invention
The invention provides a method for controlling the feeding speed of a short straight line section, which is smooth to control and reasonable to plan.
The invention provides a method for controlling the feeding speed of a small linear segment for numerical control machining, which comprises the following steps:
Step 2, according to the expected feeding speed in the numerical control programFAnd interpolation periodTcCalculating to obtain the maximum interpolation distance in the interpolation period of the machine toolΔS=F×Tc；
And 3, judging according to the length L of the straight-line segment obtained by the numerical control program and the direction cosine included angle theta of the adjacent straight-line segment: if it is notθ≤OrL≥ΔSNo speed control optimization is required ifθ >And isL < ΔS，Confirming that the straight line segment is a small straight line segment needing speed control, and entering a step 4;
step 4, according to the maximum interpolation distanceΔSAnd length of small straight line segmentLCalculating the length of the segment toLThe number of interpolation times required for the small straight line segment ofN=Ceiling(L÷ΔS)(Ceiling is an rounding function), the recalculated feed speed is calculatedFo=L÷(N×Tc)。
Compared with the prior art, the invention has the following positive effects:
the invention innovatively provides a small straight-line segment feeding speed control method based on post-processing, which can reduce abnormal phenomena such as speed delay, overspeed and the like generated in the small straight-line segment processing process of a numerical control machine tool and can effectively improve the quality and the operation efficiency in the small straight-line segment program processing.
The method can plan the speed in advance in the post-processing process, reduces the difficulty of speed planning and calculation of the numerical control machine tool and the system in the execution process of the numerical control program, ensures that the feeding speed of the numerical control program optimized by the method is closer to the actual running speed of the machine tool, and can reflect the actual processing state of the numerical control program better.
The invention can carry out feeding speed constraint and re-planning on small straight-line segments which are smaller than the interpolation distance of the minimum interpolation period of the numerical control system and have larger direction cosine included angle changes; the feeding speed can be optimized by combining interpolation parameters of a numerical control system in the post-processing process, and the defects of part processing quality caused by reasons of feeding delay caused by frequent speed change of small straight-line segments or over speed of coordinate axes in the motion process and the like of a numerical control post-processing program on an actual machine tool are reduced.
Drawings
FIG. 1 is a schematic diagram of adjacent straight line segments in a numerical control program.
Fig. 2 is a schematic diagram of the optimized feed rate using the present invention.
Detailed Description
The present invention will be further described with reference to fig. 1 and 2, which are some examples of the post-processing of a nc machine tool, but the present invention is not limited thereto.
Tc =0.002 seconds =0.002 x (1/60) minutes =0.000033 minutes,
marginal angle of edge allowed by systemIs arranged as36°
Step 2, calculating the maximum interpolation distance in the interpolation period of the machine toolΔS=F×Tc。
The feed rate F in the program was 8000 mm/min, from which it was obtained：
Δ S = F × Tc =8000 × 0.000033333=0.266667 mm
Step 3, respectively calculating the lengths of adjacent straight line segmentsL anddirection cosine angleθAnd judging whether the straight line segment is a small straight line segment.
The distribution of adjacent straight line segments is schematically shown in figure 1, two adjacent straight line segmentsThe length and direction cosine included angle of the straight line segment are respectively：
L1=0.213 < ΔS，θ1=45°<
L2=0.154 < ΔS，θ2=48°<
Therefore, the two straight line segments are small straight line segments, and the feeding speed needs to be re-planned.
Step 4, calculating interpolation timesN and Fo after optimization。
N1=Ceiling(L÷ΔS)= Ceiling(0.79874)=1
N2=Ceiling(L÷ΔS)= Ceiling(0.95249)=1
The optimized feeding speeds of the two small straight line segments are respectively：
Fo1= L1 ÷ (N1 × Tc) = 0.213 ÷ (1 × 0.000033333) =6390 mm/min
Fo2= L2 ÷ (N2 × Tc) = 0.154 ÷ (1 × 0.000033333) =4620 mm/min
As shown in fig. 2.
Claims (1)
1. A method for controlling the feeding speed of a small straight line segment for numerical control machining comprises the following steps:
step 1, obtaining or setting interpolation period of numerical control machine tool and system to be post-processedTcAnd allowable marginal angle of edge；
Step 2, according to the expected feeding speed in the numerical control programFAnd interpolation periodTcCalculating to obtain the maximum interpolation distance in the interpolation period of the machine toolΔS=F×Tc；
Step 3, obtaining the length of the straight line segment according to the numerical control programLAnd the direction cosine included angle of adjacent straight line segmentsTheta is judged: if it is notθ≤OrL≥ΔSNo speed control optimization is required; if it is notθ >And isL < ΔS，Confirming that the straight line segment is a small straight line segment needing speed control, and entering a step 4;
step 4, according to the maximum interpolation distanceΔSAnd length of small straight line segmentLCalculating the length of the segment toLThe number of interpolation times required for the small straight line segment ofN=Ceiling(L÷ΔS)Then is fedThe speed Fo is controlled as Fo = L ÷ (N × Tc), where: ceiling is an Ceiling function.
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