Pants sanitary napkin production line processing process, there are many factors that cause the size of the parts error, which processing positioning error calculation has become one of the important factors, master the correct error calculation method to minimize the error of the parts.
1. Pants sanitary napkin production line geometric method to calculate positioning error
Positioning error due to inaccurate positioning of trouser machine of sanitary napkin on the fixture caused by processing errors, in the use of adjustment method of processing, the positioning error of the workpiece is essentially the maximum change in the process reference in the direction of processing dimensions. Therefore, to calculate the positioning error, first of all, to find the process size of the process benchmark, and then seek its maximum change in the direction of the process size can be. For this purpose, it is possible to use either the collective method or the differential method.
Using the geometric method to calculate the positioning error usually have to draw the positioning sketch of the workpiece, and exaggerate the limit position of the workpiece change in the figure, and then use triangular geometry, to find out the process benchmark in the trouser sanitary napkin machine size direction of the maximum amount of change, that is, the positioning error.
If the process benchmark of the workpiece of the trouser-type sanitary napkin machine is the hole center, try to determine the positioning error when the hole-pin gap fit.
When the workpiece aperture is the largest, and the diameter of the positioning pin is the smallest, the maximum change in the hole center in any direction is the maximum amount of clearance between the hole and the pin, that is, regardless of the process size direction (as long as the process size direction is perpendicular to the axial direction of the hole, the positioning error of the hole-pin clearance fit in some special circumstances, the hole of the workpiece may be fixed contact with the positioning on the fixture, at this time to find the hole center in the contact point and the pin center line The maximum amount of change in the direction of , that is, half of the hole tolerance, if the workpiece process benchmark is still the hole center, and the process size direction and fixed contact point and pin center line for the direction of the same, then there are
The above formula is the technical formula for the positioning error in the case of trouser-type sanitary napkin production line hole-pin clearance fit and maintain fixed variable contact, the formula Damx, Dmin are the maximum and minimum diameter of the positioning hole, TD for the hole diameter project. Positioning in this case, the positioning of the hole on the pin has actually been transformed into the form of support positioning, positioning reference becomes a bus bar for the hole in contact with the fixed edge for the upper bus bar of the hole. At this time, the positioning error is due to the positioning reference and the process reference part overlap early into, belongs to the reference part overlap error, and has nothing to do with the pin diameter tolerance.
2. Trouser-type sanitary napkin production line differential method of calculating positioning error
The differential method of calculating the positioning error of trouser-type sanitary napkin production line is essentially the same as the dimensional chain calculation method, which is illustrated by the V-block positioning.
Using tiny increments instead of differential, and the size (including linear size and angular size) error as tiny increments, and taking into account that the size error can be positive or negative, the absolute value of each error, we can get the positioning error of the process size H as follows
where Td and Tα are the tolerance of the workpiece outer diameter and the angular tolerance of the V-block, respectively. If the angular error of the V-block is ignored (in fact, in the case of support positioning, the error of the positioning element - in this case the angular error of the V-block - can be compensated by adjusting the position of the tool relative to the fixture), the V-block can be used to For positioning of the outer surface, when the process reference is the center of the outer circle, the positioning error in the vertical direction is
If the process reference of the trouser sanitary napkin production line workpiece is the lower busbar C of the outer circle (the corresponding process dimension is H,), the positioning error can be found in the same way. At this time, the distance from point C to point A is
The full differentiation and ignoring the V-block angle error (i.e., α is considered as a constant) can be obtained as follows
The same method can also be used to find the positioning error when the process reference is the upper bus bar of the outer circle (the corresponding process dimension is H2,).
Using the differential method to calculate the positioning error is, in some cases, more straightforward than the geometric method.
It is important to note that the positioning error is generally always for batch production, and the adjustment method is used for machining. In the case of single-piece production, the same problem of positioning error exists when processing by the adjustment method (using a sample or a tool for a gauge), or when processing on a pant-type sanitary napkin machine. If processing is performed by the trial cut method, positioning error is generally considered.
