Guide: In the process of furniture production, factories often need a series of indicators to ensure the quality of furniture products, evaluate the quality of products, and reduce problems in the production process. These indexes include machining datum, machining precision, surface roughness and machining allowance.
In this issue, we will talk about three indicators of furniture production: processing benchmark, processing precision and surface roughness.
Processing datum
When machining the workpiece on the machine tool, in order to make the process meet the corresponding technical requirements, the workpiece must be positioned and clamped before machining. Positioning and clamping positioning: during cutting, the workpiece must be placed on the equipment or fixture to make it have a correct relative position with the tool. This relative position is called positioning. Clamping: after the workpiece is positioned, it cannot bear the cutting force during processing. In order to keep it in the correct position during processing, it is also required to fix it in the specified direction, which is called clamping. At the same time, it is an important preparation for machining to determine the machining benchmark before machining, which has a great impact on machining accuracy and production efficiency. The so-called machining datum is the point, line and surface used to determine the position of the tool and the part to be machined or the relative position between the parts in the product. Benchmarks can have multiple functions. According to different functions, they can be classified into two categories, namely design benchmark and process benchmark, while process benchmark can be divided into measurement benchmark, positioning benchmark and assembly benchmark according to different purposes. Design basis and process basis Design basis: those points, lines and surfaces used to determine the mutual positions between parts and components and between holes in the crystallization process on the drawings during product design. Process datum: refers to the point, line and surface scale process datum used to determine the relative position with other surfaces on the part or with other parts in the product during measurement, processing or assembly. In order to ensure product quality, we need to measure whether the size and shape of parts processing meet the requirements. It can be roughly classified into two evaluation methods: the standard of evaluation according to the degree of conformity between products and drawings is machining accuracy; The evaluation standard from the product and actual error value is the processing error. Processing precision and processing error Processing precision: refers to the degree to which the actual values of geometric parameters such as size, shape, position, etc. obtained after processing of the workpiece conform to the theoretical values (specified on the drawing). Processing error: refers to the deviation caused by the inconsistency between the actual size, shape and position of the workpiece after processing and the theoretical size, shape and position specified on the drawing. The production of machining error is accidental and inevitable. To sum up the two cases, the machining error can be divided into systematic error and accidental error. Systematic error and accidental error Systematic error: When a batch of parts are processed in sequence, the processing error remains unchanged or changes according to a certain rule. This error is called systematic error. Accidental error: When processing a batch of parts, the error value is not fixed, or does not conform to a certain law of shade, which is called accidental error or random error. In order to improve the production efficiency and reduce the production cost, when we determine the processing accuracy, we also need to make products or parts achieve a certain degree of interchangeability. The study of interchangeability is of great significance for enterprise production. The machining accuracy of surface roughness is an important index to measure the machining size and shape of parts, and the surface roughness is an important index to evaluate the surface machining quality of parts. Surface roughness: after cutting or pressure processing, wood or wood-based panels will leave a variety of processing marks or bumps on the processing surface. These micro unevenness are called wood processing surface roughness. The surface roughness can be divided into two forms according to the appearance size of defects, namely, macro roughness and micro roughness. Macro unevenness and micro unevenness Macro unevenness: single processing defect with large overall dimension. Micro unevenness: single processing defect with relatively small overall dimension. The surface roughness referred to in wood processing and production is usually the micro roughness. Common surface defects after wood processing are generally divided into the following six types: elastic recovery unevenness: when cutting, the tool is squeezed on the wood surface, and the wood is uneven due to elastic recovery after the pressure is relieved. Cutting tool trace and ripple: usually, the geometric shape of cutting tool and the trace left by cutting movement are called cutting tool trace; The displacement generated by the rigidity of the process system is called ripple, which is generally called ripple mark. Wood wool: One end of a single fiber is connected to the wood surface and the other end is erected or closely attached to the wood surface. Burr: Bundles or pieces of wood fibers have not been completely separated from the wood surface. Destruction unevenness: The result of peeling or tearing of bundles of wood fibers on the wood surface during processing. Structural unevenness: unevenness caused by cutting of wood cell cavity, or small gap caused by particle arrangement on particle board surface, or unevenness caused by drying shrinkage and swelling of wood surface.
