Located at 6 o'clock the proper understanding of law and application
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source:PERFSO CNC Machining
Summary: In the light of the tradition fixed position law put the issue that be in at 6 o'clock, put forward proper understanding and application to located at 6 o'clock the new thinking of law. Fixed position law was the basic principle that directive clamping apparatus designs 6 o'clock, already continue to use a few years, but law itself is not perfect, also exist to the understanding of law and application a lot of confused place, because this is necessary,discuss again to locating law undertakes at 6 o'clock. The essence that 1 tradition located the meaning workpiece of law locates at 6 o'clock makes workpiece holds firm position in clamping apparatus namely, the fixed position problem because of this workpiece but the issue that translate into decides position of rigid body coordinate in department of dimensional rectangular coordinates will discuss. In department of dimensional rectangular coordinates, rigid body has 6 freedom to spend, 3 freedom that move along axis of X, Y, Z namely are spent and circle 3 freedom that this 3 axes rotate to spend. With 6 reasonable 6 freedom of the workpiece of bearing dot limitation that distributing are spent, make workpiece holds correct position in clamping apparatus, call located at 6 o'clock law. People is elaborating constant to in an attempt to showed fixed position law 1 times at 6 o'clock mill is illogical groovy case will try to explain: A1, A2, A3 is nodded 3 times reflect advocate A of fixed position face, the whirl that restricts direction of X, Y is spent freely and the mobile freedom of Z direction is spent; A4, A5 is nodded twice reflect flank B, the mobile freedom that limits X direction is spent and the whirl of Z direction is spent freely; A6 dot is reflected stop the C that choose a side, the mobile freedom that limits Y direction is spent. Such, 6 freedom of workpiece are spent be restricted entirely, call complete fixed position. Of course, fixed position just assures workpiece to decide in the position in clamping apparatus, can not make sure the workpiece in be being machined is not mobile, reason still needs clamp. Fixed position and clamp are two different ideas. Graph A6 of ～ of 1 graph 2a1 calls point of 6 fixed position in some monograph, call 6 bearing point in some document, in fact this is two different ideas. Bearing dot should be installation the component of specific fixed position that contacts with workpiece directly on clamping apparatus, be like bearing hammer, backing plate, V form piece, in machining a process they participate in balance cutting force, gravitational, clamping force to wait even; And fixed position dot should be an abstract concept, it is the limitation that points to orientation way to be spent to freedom. Limitation is spent freely call a fixed position to nod, more or less to have nothing to do with what bearing nods. For example, when workpiece locates with plane directly, should restrict 3 freedom to spend, only due dot of 3 fixed position, and in fact right now bearing speck is remote more than 3. And fall in a few special situations, specific bearing feature is not had at all when workpiece locates, if be common on lathe,use work of clamp of 4 ungual chuck, search with dial gauge, share fixed position without specific bearing feature right now, work place is finished surely really by dial gauge, the model of circumstance similarly hereinafter that way of this kind of orientation is ordering without bearing can realize fixed position. Fixed position law resulted from at 6 o'clock geostatics, the actual condition that designs with clamping apparatus agrees not completely. On one hand, clamping apparatus and workpiece all are elastomer, locating, especially easy generation flexibility is out of shape when clamp; On the other hand, fixed position deputy between put in clearance mostly. And traditional located at 6 o'clock law oversight flexibility is out of shape and the existence of clearance. In fact, flexibility is out of shape and the existence of clearance has main effect to the fixed position of workpiece. Passing fixed position question is clamping apparatus design and the sensitive issue in using. Will locate the definition is too commonly in document and monograph " dot of bearing of a few fixed position repeats limitation same each by degree, this kind of phenomenon has called fixed position. ... when plan of certain work location, cannot have appeared to locate commonly " . But in be designed in clamping apparatus in fact and applying, the circumstance that locates too is not scarce, and a few locate clamping apparatus uses the effect too pretty good. If graph 3a place shows fixed position pattern, the whirl of direction of planar limitation X, Y is spent freely and the mobile freedom of Z direction is spent, the whirl of direction of X of core axis limitation, Y is spent freely and move to be spent freely, two kinds of whirl that locate means repeats direction of limitative X, Y are spent freely, by cross fixed position definition actively to had belonged to fixed position, should avoid to use, but commonly used however in be machined actually way of this kind of orientation will roll angrily annulus, if pursue,2 are shown. Must have an accurate explanation to crossing fixed position accordingly, locating in order to avoid the disorder is caused on the problem too. Located 3 pairs at 6 o'clock of law when discussing what using a convention to located law decides workpiece locates whether plan and judgement had attributed fixed position at 6 o'clock again, oversight of a lot of people the influence of fixed position deputy error. In fact, the error of the fixed position face of clamping apparatus and workpiece and fixed position component is very big to fixed position influence. Although had attributed fixed position,graph 3a place shows fixed position pattern, but the measure that wants workpiece and range of clamping apparatus fixed position only, appearance, position all free of error, core axis and end panel can locate with clamping apparatus the be identical of workpiece face posture of component, mutual between the limitation that spends to freedom won't produce contradiction. Apparent, the fixed position below this kind of condition is successful, this clamping apparatus can be used. Reason should not spend limitation be repetitioned simply to decide according to freedom fixed position plan has attributed fixed position. If graph 3b place is shown, when workpiece fixed position face is put when verticality error, the limitation that end panel and core axis rotate to be spent freely to direction of X, Y can produce contradiction. If press planar fixed position, workpiece Ying Fangping; If press core axis fixed position, workpiece criterion should perpendicular. Of a batch of workpiece inside the actual clearance between aperture and core axis is change, the condition of two kinds of position that if place of graph 3b, 3c is shown,can form when clearance changes, such workpiece are decided with respect to inaccuracy in the position in clamping apparatus, had caused fixed position. Be like error of face of clamping apparatus fixed position and verticality of core axis existence, also can produce similar case. Apparent, repeat limitation to spend not regular meeting to had produced fixed position freely, locate deputy error just is the main reason that has produced fixed position. Graph 3 make as a result of existence error contradiction arises to call interference between way of two kinds of orientation. Inside interference limits, if have A, B,way of two kinds of orientation repeats limitative some freedom to spend, must plant with some certainly when the design orientation way is given priority to. If be given priority to with A means, produce B means to interfere A means, should reduce the interference of B means through reasonable design to the smallest, ensure with A means is given priority to have fixed position, vice versa. If show fixed position pattern to graph 3a place, a few clamping apparatus put forward in design monograph with main aspects face and short core axis are combined or small end panel and combination of long core axis make the same score improvement its locate function, think this kind of combination is nonexistent cross fixed position. We think this kind of explanation is imprecise. Main aspects face and the prime cause that short core axis is combined or small end panel and long core axis combine function of ameliorable fixed position were to use locate with a kind means is given priority to, reduced the interference of way of another kind of orientation, from say substantially, combination photograph compares the combination after this kind of improvement and main aspects face and long core axis, the verticality error between face of clamping apparatus fixed position is smaller, the fixed position that can satisfy workpiece thereby asks, won't have caused fixed position. Because locate deputy error is met,change and influence polarization pledge, reason should reduce fixed position deputy error as far as possible, but of clamping apparatus production precision rise to have certain limit after all, and locate pair of clearance between and locate deputy flexibility is out of shape can go up to undertake compensating to fixed position deputy error in certain level, go up objectively can reduce interference rate. If place of graph 3c, 3d is shown, in interference the circumstance falls, workpiece still can assure to be given priority to with large planar fixed position. Of course, the clearance that coordinates a side must satisfy workpiece to machine the requirement of precision, cannot expand arbitrarily. Be out of shape to flexibility, deflection fluctuates inside reasonable range won't have caused fixed position. Can think, in fixed position deputy error action falls, the contradiction that way of two kinds of orientation repeats limitation to be spent freely is interference in show of quantitative change stage, in qualitative change phase expression has been fixed position. Whether is interference met translate into crosses fixed position, depend on fixed position deputy error, locate the flexibility of axis of the core after pair of clearance between, clamp is out of shape wait for a variety of elements. The gear hobbing location that the graph shows 2 times attributes the fixed position that existence interferes, is not to locate too. The treatment precision that the 4 measure that had avoided fixed position raise face of clamping apparatus fixed position and work location datum plane is the basic method that has avoided fixed position. Rise as a result of what clamping apparatus machines precision have certain limit, when because this uses means of two kinds of fixed position,combination locates, answer to locate with a kind means is given priority to, reduce the interference of way of another kind of orientation, if use long core,short core axis is mixed combination of main aspects face, or when workpiece locates with one side double aperture, one is sold use lozenge to sell etc. From say substantially, this also is another kind of method that raises precision of face of clamping apparatus fixed position. The flexibility that uses the clearance between work location face and face of clamping apparatus fixed position and fixed position cell is out of shape will compensate an error, reduce interference. In analysis and judgement way of two kinds of orientation is below error action when belong to interference or locating too, must be out of shape to error, clearance and flexibility have integrated consideration, according to the treatment of workpiece at the same time precision asks ability makes correct judgement. Tell from broad sense, the fixed position means that should use only can make work location exact, can assure to machine precision, criterion way of this kind of orientation has not attributed fixed position, can use. 5 conclusion located the bearing in law is nodded at 6 o'clock is the component of specific fixed position that points to to be contacted with workpiece directly on clamping apparatus, and fixed position dot is the limitation that points to orientation way to be spent to freedom, it is an abstract concept, both cannot promiscuous, cannot replace more use. Cannot spend limitation be repetitioned to decide by freedom only had been fixed position, locate deputy error is the prime cause that has produced fixed position. The existence of the error makes repeat limitation to spend expression to locate to interfere and pass freely, interference is quantitative change phase, cross fixed position to be qualitative change phase. Interference clamping apparatus can be used, locate clamping apparatus destroys fixed position too, cannot use. When whether has judgement attributed fixed position, should undertake error, clearance and stretch metabolic are calculated integratedly, machine precision to ask ability makes correct judgement according to workpiece at the same time. CNC Milling