2.2　Lofting and Blanking

2.2.1　The lofting platform shall be stable and smooth,its levelness and perpendicularity shall meet machining accuracy requirements and its surface shall be free from any attachment or sundries that will disturb the marking out.

2.2.2　The computer design should be adopted for the lofting.When lofting on the lofting platform,the bulk sample shall be marked out as the 1∶1 proportion,and the lofting in segments should be adopted if the lofting dimension is oversize.

2.2.3　The fabrication of the sample plate and sample rod shall meet the following requirements:

1　The smooth material with good toughness and not subject to deformation shall be adopted for fabricating sample plates;the material that is straight and even with good rigidity shall be adopted for fabricating sample rods.The completely fabricated sample plates and sample rods shall be marked clearly.

2　The allowable deviation for fabricating sample plates and sample rods shall be in accordance with those specified in Table 2.2.3.

Table 2.2.3　Allowable deviation for fabricating sample plates and sample rods

2.2.4　The marking out of the parts shall meet the following requirements:

1　The appearance inspection shall be carried out for the material before marking out,as for the material that needs correction,its allowable deviation after correction shall be in accordance with those specified in Table 2.3.6.

2　The anti-carburizing isolation measures shall be taken for the marking out of stainless steel materials;the marking out shall be scratch-free and meet surface accuracy requirements.

3　Such edge of cutting,machining and welding shrinkage of materials shall be considered when marking out.

4　The allowable deviation of parts marking out shall be in accordance with those specified in Table 2.2.4.

Table 2.2.4　Allowable deviation of parts marking out(mm)

2.2.5　The blanking of carbon steel and ordinary alloy steel should adopt machine cutting or gas cutting;the blanking of stainless steel and nonferrous metal materials should adopt machine cutting or plasma cutting.

2.2.6　The enough machining allowance shall be kept for parts in need of edge preparation.

2.2.7　The cut surface of steels shall be free from iron oxide,cracks,slag inclusion,lamination,scrap iron or edge defects.