Talk about the design of semifinished product dimension

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Summary: The design that offers semifinished product measure should not be a foundation with part drawing only, and Lv of take an examination machines craft, what when be being machined especially, choose is thick fiducial. Point out dimension of reasonable design semifinished product not only can make sure semifinished product has even and reasonable rough machining surplus each, and can assure to be not the position between treatment face and treatment face and dimension. Current, the dimension that semifinished product pursues is to be on the foundation of part drawing dimension, add decrease total mental allowance to get semifinished product measure, semifinished product each design is fiducial and general agree with part drawing. The author thinks method of this kind of design is unreasonable, because will tell and do not ask it and part drawing are consistent from the action of semifinished product dimension,this is, the requirement that raises to it is: (1) makes sure it is in machining from time to tome the evenest and reasonable rough machining surplus: (2) assures to be not treatment face and treatment face to have the exactest position and measure. 1 thick the thick fiducial dispute that spare parts of two fiducial main features uses when treatment constant important, it is having the effect of a connecting link between the preceding and the following, of dimension of influential to rough machining surplus all working procedure and semifinished product dimension collect point of intersection sure it is thick fiducial. (A)(b) pursues 1 feature the common difference of rough machining surplus of 1 thick datum plane is the least. Graph the 1 semifinished product that designs a form for two kinds pursues, nominal of each rough machining surplus is worth semifinished product to all take 10mm, m face is chosen to be when the spare parts is machined thick fiducial, graph 1a devises semifinished product measure by part drawing (tolerancepublic errand) is reached to devise measure inside bracket, graph 1b semifinished product all is each with thick fiducial M fiducial. Dimension of each working procedure is ordinal for: MB1: B1C1: B1D1: C1E1: D1M1(B1, c1, d1, ) of face of the B that M1 expresses to be machined for the first time, C, D, M. According to principle of technology measure formula, the rough machining surplus of M face is: MM1 → MB1D1M1, namely MM1=-MB1+B1D1+D1M1, this shows, the MM1 of rough machining surplus of M of thick datum plane mixes only MB1 of working procedure dimension: B1D1: D1M1 is concerned, have nothing to do with semifinished product dimension. The E of → of EE1 of rough machining surplus that we see E face again... MB1C1E1, can see EE1 divides with MB1 of working procedure dimension: B1C1: C1E1 has outside Shanghaiguan, still concern with the dimension between E of semifinished product face and thick fiducial M (can prove with manage, the rough machining surplus of thick datum plane is concerned with working procedure position error only, have nothing to do with the position error of semifinished product) , because the error of working procedure dimension is smaller than semifinished product, common difference of surplus of rough machining of thick datum plane is the consequently least. Graph the dimension between the face that 2 thick datum plane and other treatment cross 2 features and position error are the smallest. What the graph shows workpiece 2 times to add man-hour is thick fiducial for M face, m face does not need to machine, the positional relation that each working procedure assures is: M⊥ B1: B1 ⊥ D1: B1 ∥ E1: D1 ∥ P1. According to principle of technology measure formula, the positional relation of graph 2M face and P1 face is: MP1 of ∥ of D1 of ⊥ of B1 of ⊥ of M of ∥ P1 → . This shows, the position of M face and P1 face mixes only B1 of ⊥ of M of working procedure position: B1 ⊥ D1: D1 ∥ P1 is concerned, with semifinished product each position error has nothing to do, but to other the face that does not machine, for example face of N semifinished product and the P face that machine for the first time (P1 face) positional relation is: NN of ⊥ P1 → ... P1 of ∥ of D1 of ⊥ of M ⊥ B1. This explains, the positional relation of N face and P1 face is divided and M ⊥ B1, b1 ⊥ D1, d1 ∥ P1 has outside Shanghaiguan, still concern with the position error of N of semifinished product face and datum plane M. Manage together, because working procedure position error is far,compare semifinished product each position error is small, the position error of the face that consequently thick datum plane and other treatment cross is the smallest. Analysis of surplus of each rough machining calculates 2 semifinished product from above the analysis is knowable, do not be thick each rough machining surplus removes fiducial semifinished product and relevant working procedure measure has outside Shanghaiguan, inevitable still with corresponding semifinished product each are mixed thick fiducial the dimension between is concerned. Semifinished product each design is standard by part drawing place of the 1a that be like a graph is shown, semifinished product dimension is EC, DE, CB, BM, we beg the rough machining surplus of E face. Draw up above all the measurement formula of EE1: EE1 → ECBMB1C1E1, the MB1 of working procedure dimension that gets EE1=-EC-CB+BM-MB1+B1C1+C1E1(1) equality right from this is sealed, we can get BB1=BM-MB1=(620 ± 3)-MB1 by BB1 → BMB1, assume requirement BB1=10 ± 4, criterion MB1=610 ± 1mm, era enters type (1) gets ± of 3)+(300 of ± of 1)+(150 of ± of 3)-(610 of ± of 2)+(620 of ± of EE1=-(330 ± 3)-(150 0.

3)=10 ± 9.

If 6(mm) (is calculated by probability law, criterion EE1=10 ± 4.

8mm) semifinished product each design is standard all be treatment when this workpiece thick fiducial place of the 1b that be like a graph is shown, semifinished product dimension is BM, CM, DM, EM, we still are calculated the rough machining surplus of E face. The measurement formula below this circumstance is EE1 → EMB1C1E1, get EE1=EM-MB1+B1C1+C1E1=(170 ± from this 1.

± of 5)-(610 ± 1)+(150 0.

3)+(300 ± 0.

3)=10 ± 3.

If 1(mm) (is calculated by probability law, criterion EE1=10 ± 1.

85mm) can see as a result from above computation, semifinished product presses the design form of graph 1b, only EM of dimension of a semifinished product affects EE1 of rough machining surplus, and the design form that semifinished product presses graph 1a, EC of dimension of 3 semifinished product, CB, BM affects EE1 of rough machining surplus. Accordingly, by graph 1b dimension of design semifinished product can make public errand of rough machining surplus is reduced greatly. Use same method to be able to undertake analytic computation to the rough machining surplus of other side, can get same conclusion, accordingly, this conclusion has common sense. The position error between face of 3 blame treatment and treatment face analyses to in an attempt to 2 for exemple, the N of → of P1 of ⊥ of positional relation N that analyses N of blame treatment face and P1 area... P1 of ∥ of D1 of ⊥ of M ⊥ B1, analyse with above surplus identical, if the positional design in face of the N in semifinished product graph is standard,be M face (M ⊥ N) , criterion P1 of ∥ of D1 of ⊥ of B1 of ⊥ of M of ⊥ of N of → of N ⊥ P1, only position error of this one semifinished product affects N ⊥ M N ⊥ P1, otherwise will more semifinished product position error affect N ⊥ P1. For example, graph of hypothesis semifinished product presses the design form of part drawing, of face of semifinished product N fiducial for D face (D ⊥ N) , of D face fiducial for E face (E ⊥ D) , of E face fiducial for M face (M ⊥ E) , criterion P1 of ∥ of D1 of ⊥ of B1 of ⊥ of M of ⊥ of E of ⊥ of D of ⊥ of N of → of N ⊥ P1, have D ⊥ N, e ⊥ D, m ⊥ E3 P1 of ⊥ of N of influence of semifinished product position error. Consider on one hand from the position error that reduces blame treatment face and treatment range consequently, to semifinished product each position error that put forward what still should use in order to machine this when semifinished product is thick fiducial for fiducial. In the analysis of above, what N represents is face of aleatoric blame treatment, what P1 represents is aleatoric treatment face, so the conclusion above also has common sense. No matter,principle of design of dimension of 4 semifinished product can see through the analysis above from reduce regard of respect of public errand of surplus of each rough machining, or from reduce the position error respect between blame treatment face and treatment face to consider, the author thinks to answer to regard semifinished product as each design with thick datum plane fiducial. "Each dimension designs semifinished product fiducial (include the place fiducial) should use treatment as far as possible what use when this semifinished product is thick fiducial " call semifinished product dimension to design a principle (call a principle) below. Follow this principle, it is to be able to make semifinished product common difference of each rough machining surplus is the least, can choose lesser mental allowance thereby, reduce material to use up: 2 it is to be able to make the relative position size between blame treatment face and treatment face the exactest, in order to raise the treatment precision of the spare parts. If two faces in part drawing do not need to machine,what ought to point out is, and part drawing is not treatment to these two there is dimension position demand between the face, criterion the tagging that the semifinished product dimension between this two sides should press part drawing means undertakes tagging. At present we just consider how to choose mental allowance of coarsen of thick fiducial ability when formulate machining craft change is the least and how can just assure to be not treatment the positional size between face and treatment face is the exactest, make through the analysis above we realise when to designing semifinished product, answer mature this. Pressing a principle to design semifinished product dimension to be in practice is feasible, this needs us to be made in the mould of semifinished product reach semifinished product to produce craft to reach principle birth semifinished product should be pressed as far as possible in examining (the pattern that with fast prototype production technology creates is very easy according to principle) . Of course, it is very difficult that some semifinished product produce craft to press a principle, also may not blame presses a principle cannot, but we should press a principle as far as possible, in order to make as far as possible the dimension between surplus of little rough machining of impact of semifinished product measure and blame treatment face and treatment face. The dimension of the semifinished product plan that devises by the principle and part drawing can compare a gender poorer, dimension calculation is more complex also, but and reduce material to use up, raise photograph of spare parts precision to compare, these cost are worthiness, and dimension of CAD semifinished product makes such dimension conversion won't become an obstacle. Actually, we develop " software of calculation of technology measure formula " the content that had contained this respect. The principle that the author advances devises semifinished product measure, it is to be able to reduce rough machining surplus, 2 it is to be able to raise the dimension position precision between blame treatment face and treatment face. The promotion application of this principle reduces material to use up to mechanical manufacturing industry, raise product quality to have important sense, at the same time this principle also can assist the basic principle that semifinished product dimension designs as the computer. CNC Milling