|
| Principle | Subitem | Manifestations and consequences | Typical examples/models |
|
| Bed factors | Rigidity | Deformation of the bed under load | Localized radial deviation of shape accuracy; localized divergence of position accuracy | Not enough allowance after roughing for finishing; poor geometric or position accuracy in a particular machining area of the machine tool |
| Geometric precision | Bed geometry deviations | Shape accuracy deviation; geometric deviation in position accuracy | Persistently poor geometrical accuracy in perpendicularity, parallelism, flatness, etc.; the position of the pore system deviates continuously from the geometrical pattern |
|
| Drive, lubrication, and CNC factors | Positioning deviation | Large absolute deviations in unidirectional positioning of the bed | Offset and stable position accuracy | Consistently and consistent poor position accuracy in the serial production on exact fixture |
| Reverse error | Large positioning deviation of the bed’s reciprocating motion | Offset and regular position accuracy | Exceedingly poor accuracy in rows or columns with toolpaths in opposite directions during complete column feature machining; poor positional accuracy and visible tool marks on curved surfaces in machine tools with frequent axis changes |
| Position distribution | High repetitive positioning deviation for unidirectional bed movement | Offset and instable position accuracy | There are no individual instances of failure, which are usually superimposed on the positioning bias factor in the results |
|
| Other factors | Payload | Changes in the geometric accuracy of the machine under load | Shape accuracy deviation; geometric deviation in position accuracy | After loading, the geometrical accuracy of perpendicularity, parallelism, flatness, etc., is consistently out of whack; after loading, the position of the pore system continues to deviate in a geometrical pattern |
| Vibration | Resonance of machine tools in specific operating conditions | Unusual vibration noise; poor surface quality of machined parts | The surface roughness is extremely poor, but the dimensions are acceptable; the machined surface has a regular knife pattern |
| Temperature fields | Deformation of bed components or workpieces with temperature rise | Offset and instable position accuracy | Difference in temperature between day and night in nontemperature-controlled workshops and variation in overall accuracy; parts with particularly long machining times and variations in local accuracy |
|
