The dimensional accuracy acceptance of burr removal in automotive chassis die-casting parts is directly related to the assembly accuracy, operational safety, and component service life of the chassis. It is necessary to strictly follow industry standards and develop scientific acceptance specifications based on the functional characteristics of the components.
The core basis of acceptance criteria includes industry standards and standards. In terms of industry standards, QC/T 273-1999 'Technical Conditions for Zinc Alloy, Aluminum Alloy, and Copper Alloy Die Casting Parts for Automobiles' is implemented, which clearly stipulates that the height of mesh burrs on the non machined surface of aluminum alloy die casting parts shall not exceed 0.1mm, and the height of mesh burrs on the non machined surface of copper alloy die casting parts shall not exceed 0.2mm. At the standard level, GB/T 15114-2023 'Aluminum Alloy Die Casting Parts' is followed, which states that defects such as mesh burrs are allowed in die casting parts, but the degree and quantity of defects must meet the agreement of both the supply and demand parties, and residues such as gates and burrs in non functional areas must be controlled within a reasonable range. At the same time, dimensional tolerances should refer to GB/T 6414 'Dimensional tolerances, geometric tolerances, and machining allowances for castings', and automotive chassis die-casting parts usually need to achieve dimensional tolerance levels of CT7-CT9.
The specific acceptance requirements for burr height need to be divided according to the functional differences of the parts. In non machined surfaces, the upper limit of burr height acceptance for aluminum alloy castings is 0.1mm, and for copper alloys it is 0.2mm. The burr height on the surface of general functional areas should not exceed 0.2mm. After cleaning the burrs inside the holes, the height should be controlled within 0.3mm to avoid affecting bolt assembly or pipeline conductivity. For safety critical components such as suspension system connectors, brake system supports, etc., the burr height requirement is more stringent, usually not exceeding 0.05mm, to prevent burr detachment and component jamming. After cleaning the residual gate, it should not be higher than 0.5mm above the surface of the casting, and the transition with the surface should be smooth and free of edges and corners; The residual height of the parting surface after trimming cleaning shall not exceed 0.2mm, and the width shall not exceed 0.4mm; the depth of the protrusion or recess of the top rod trace shall not exceed 0.4mm, and there shall be no protrusion marks on the process reference surface and mating surface. The surface roughness caused by deburring should not exceed 0.6mm and should not affect the assembly function and appearance quality of the components.
Dimensional tolerance and geometric tolerance are important contents of acceptance. In terms of linear dimensions, the general dimensions are controlled according to CT7-CT9 tolerance levels. Depending on the size of the parts, the tolerance value is approximately between 0.1-0.5mm; The tolerance level for key dimensions such as installation hole spacing and bearing seat aperture needs to be increased by 1-2 levels and controlled within ± 0.05mm; The dimensions without specified tolerances shall comply with the m-level requirements in GB/T 1804-2020 'General Tolerances - Tolerances for Linear and Angular Dimensions without Specified Tolerances', which allows for a deviation of ± 0.5mm. In terms of form and position tolerances, the flatness requirement shall not exceed 0.1mm per 100mm length, and the critical installation plane shall not exceed 0.05mm per 100mm length; the verticality shall not exceed 0.25mm within a measuring length of ≤ 50mm, and the assembly positioning surface shall not exceed 0.12mm; the coaxiality of key parts such as bearing holes shall not exceed 0.05mm, and that of ordinary holes shall not exceed 0.1mm; The roundness of precision shaft neck shall not exceed 0.03mm, and that of ordinary shaft neck shall not exceed 0.05mm.
Acceptance testing requires the use of professional equipment to ensure accuracy. Linear dimension and positional tolerance detection can be carried out using a coordinate measuring instrument with an accuracy of 0.001mm, which can accurately obtain key dimension data; The burr height detection adopts optical microscope or digital burr height gauge, with a magnification of not less than 50 times, to ensure accurate reading of small burr sizes. During testing, typical testing points should be selected, with no less than 3 testing points for critical functional surfaces and no less than 2 for ordinary surfaces. The testing data should be recorded completely to ensure traceability. When conducting acceptance judgment, if the height of burrs, dimensional tolerances, and geometric tolerances are all within the allowable range of the standard, and there are no defects that damage the casting body or affect assembly function, it is judged as qualified; If one of the indicators exceeds the standard, it is necessary to clean the burrs again and retest until it meets the acceptance criteria.
