Graph 1

Graph 2

1 foreword is in use process of numerical control lathe, be machined to reduce the surface roughness of workpiece surface, slow down cutting tool wears away, improve cutting tool life, normally form of circular arc of wear of blade of lathe tool point of a knife, circular arc radius is commonly between 0.4 ～ 1.6mm. Use radius of point of a knife compensates a function (the numerical control lathe of G41, G42) , want to press work measure process designing directly in machine program only, won’t cause machining error because of circular arc of point of a knife; And the numerical control lathe that does not have this function, can get in treatment the influence of circular arc of point of a knife, serious when, can cause workpiece out of tolerance to discard as useless. Pursue now the treatment with a spherical SR10-0.04 in showing work will discuss this issue. Analysis of 2 machining error is in the use of lathe of economy numerical control, we are used normally try cut a way to the knife, such, the knife that machine program place describes the dot is P dot (graph 2) , and what attend cutting actually is circular arc of point of a knife (radius of circular arc of here point of a knife is not P dot for 0.4 Mm) , because this P point is real nonexistent. So, the error of different level exists between the contrail that the P that machine program place describes nods and effective treatment outline. But round outside turning, inside when aperture and end panel, this error is 0. And when machining dambered surface and cone, this error is apparent. The machining error analysis with spherical SR10-0.04 sees a picture 2. In the graph, the contrail that the P that M line describes for machine program place nods, namely the theoretical size of workpiece, and the outline after be being machined actually is N line, the shadow is the hypostatic part of little cutting, namely machining error. We use CAXA electron plate medium ” elemental attribute inquires ” function, check N line is the circular arc that a paragraph of radius is 9.6mm, the biggest error is 0.17mm about, if this error is inside tolerancepublic errand limits, we are negligible it, otherwise we are about to adopt measure to eliminate it. The elimination of 3 errors method

- Method 1: When changing process designing of process designing dimension, adjust the contrail of point of a knife, make point of a knife of circular arc form actual treatment outline and ideal outline conform to. With SR10-0.04 spherical treatment is exemple, we need to make fine vehicle block following altering only when process designing can:
Before the change
After the change

…

N100 G00 X0 Z50

N105 G03 X10 Z42 R10 FO.1

…

N100 G00 X0 Z50

N105 G03 X10 Z42 R10.4 FO.1

… method 2: It is a knife with center of circular arc of point of a knife move of dot process designing is as follows: → of scale workpiece draft is feature of contrail of center of circular arc of computation of → of contrail of motion of circular arc of basis scale point of a knife to nod → process designing with R of radius of circular arc of point of a knife and work measure. Computation of the scale in contrail of center of circular arc of the point of a knife in this process and its feature dot shows a trouble slightly, if use the coordinate that the scale function that is apart from a line and dot wait for in CAD software to inquire the function comes,complete this work, appear very convenient. Additional, when using this kind of method to machine, handlers should notice the following at 2 o’clock: Whether is the R value of the radius of circular arc of point of a knife that 1) checks an use cutting tool worth conform to with the R in the program; 2) is right when the knife, want to consider R value to go in, namely: If to the knife that the knife receives filling value is X(X axis) with Y(Z axis) , filling value is the knife that should input actually X-2r and Y-r.

4 epilogue the article basically is beyond the treatment of arc of predestined relationship protruding is exemple undertake discussion, the dambered surface of other type, cone also is put in similar problem, the article no longer give uncecessary details.