Structural requirements for making automobile checking fixtures
1 Structural requirements of substructure
Its function is to install the checking fixture body, clamping part and other additional parts, determine the coordinate system position of the whole vehicle, and realize the functions of handling, lifting, dragging, etc. It is required to realize the overall movement of the checking fixture through the crane (the bearing capacity of the crane is 5 tons). Main components of the base:
（1） Substructure: platform+frame structure (that is, double-layer square copper and steel plate structure). Seating: the final thickness of the steel plate shall be no less than 10-25. The bottom plate shall be subject to appropriate heat treatment to eliminate the internal stress of welding. The structure of the substructure shall have sufficient strength and shall not produce any bending deformation under normal use.
a) The length+width (600~1200rnm) frame adopts 50×50 mm square tube. The base plate thickness is 10-l2mm:
b) 50 * 50 * 3mm square tube is used for the length+width (1200~1800mm) frame, and the base plate thickness is 20-25mm:
c) Double deck platform type base with length+width (more than 1800mm) (i.e. channel steel and steel plate structure), the final thickness of upper copper plate of the base is 25mm, and the base shall be subject to appropriate heat treatment to eliminate welding internal stress. The structure of the base shall have sufficient strength, and shall not produce any bending deformation under normal use.
d) Cast bright aluminum base can be used for length+width (≤ 500mm). The cast aluminum structure shall comply with the manufacturer’s standard, and the wall thickness of each part of the base shall be 30mm.
The flatness of the base shall not exceed ± 0 05mm/M, flat and requires fine grinding, and the roughness Ra is less than 1 6um, the surface is treated with varnish for rust prevention.
The depth and width of the grid line of the base are 0.2mm, the grid line corresponds to the coordinate line, and the coordinate value is marked. 100-200mm coordinate grid lines shall be engraved on the base plate and the checking fixture profile of large and medium-sized parts, and 50-100mm coordinate grid lines shall be engraved on small parts. The coordinate network lines shall be clear and engraved on the visible surface of the checking fixture
The base shall be set with four rollers at the front and back, and the two rollers at the back shall have self-locking function. The roller installation position shall not cover the datum plane or support surface of the checking fixture (for CMM detection). The lifting device shall be installed at an appropriate position to achieve various common ways of handling.
The following aspects must be taken into account in the design and manufacturing of lifting devices:
a) Ensure the levelness of the checking fixture during lifting:
b) The sling shall not contact the inspection support of the checking fixture:
c) Ensure that the lifting handle can bear enough weight.
2. Structural requirements for testing parts
（1） Benchmark: the primary and secondary locating pins are national locating pins.
（2） The clearance between the measuring tool and the measured part is 3mmo
（3） The clearance between the checking fixture and the surface of the hole of the part to be measured is 1mm (marking method, using acrylic).
（4） The distance between the measuring tool and the contact locating surface of the measured part is Ommo
（5） The clearance between the checking fixture and other auxiliary surfaces of the tested part is 3mm
（6） The hole position detection adopts x when manually detecting parts; J Wire pin, detection pin or floating pin shall be used for detection. yes φ When the hole below 6rnm adopts the scribing method, it is only like the center line of hole l. When the marking method is used for the hole above 6mm, the center line and center line of the circle shall be marked.
（7） The hole structure detected by the pin method shall be the steel sleeve structure, and the pin diameter or the size of the detection position shall be engraved on the pin handle. The value is: the theoretical size of the reference hole pin (D-0 1) 0/-0.05
Theoretical dimension of inspection hole pin (D-1) 0/-0.05
（8） The size and position of the working face of the positioning block (made of aluminum or steel) of the inspected parts of the checking fixture shall be subject to the data (confirmed by both parties).
（9） Clamping device shall be the product of Goodhand Company (or similar products), and the placement position of the clamping device shall not affect the loading, unloading and detection of stamping parts. The clamping direction shall be perpendicular to the shape surface of the pressed position, and the size of the clamping force shall be subject to that the measured part can ensure to fit on the positioning surface of the checking fixture.
（10） All detection pins, positioning pins, removable detection templates and all other removable parts shall be provided with corresponding storage boxes,and numbered.
（11） All detection pins and positioning pins shall be fastened with reliable thin chains that are not easy to fall off.