1.- systematic. They, in turn, are divided into permanent and regularly changing.
2.- random;
Take a closer look.
Systematic constant error
Remain unchanged for each part and for parts in General. They are caused by constantly operating factors. Typical examples are errors caused by the inaccuracy of manufacture of cutting tools (drill, core drill, reamers, etc.), geometric inaccuracy of machine tool, etc. to Determine the magnitude of this error can be as a direct measurement of those elements that are the cause, and by measuring a batch of machined parts.
Changing systematic logical error.
May impact on the accuracy continuously during the processing, or periodically. For example, errors caused by dimensional tool wear is affected continuously, and the error from temperature deformations affect periodically.
Random error
For different workpieces the parties have different values and their appearance is not subject to the apparent pattern. They usually are caused by random factors that operate independently from each other. To determine in advance the time of occurrence and exact value for a specific batch of parts is impossible. For example, errors that are caused by deformations of the system AIDS as a result of instability of the cutting forces, errors installation, configuration (multiple settings). At present, theoretically can not always be explained by a causal link between the error (random) and the factors of its cause. For example, unsettled the factors causing the deviation of the sizes of holes in the processing of one scan. Due to random errors in dimensions of parts in the batch is different, i.e. the dispersion of sizes. Determination of accuracy of processing (determination of errors) can be performed either by analytical calculations, and experimental-statistical method (by determining the actual errors in the details).
In some cases, the introduction of new technological processes and equipment in unexplained causation experimental-statistical study of the accuracy is the only possible one. The manifestation of a random and changing some logical errors in the practice of engineering technology with sufficient accuracy obeys the characteristic laws of distribution of values of probability theory and mathematical statistics.