#### Operating skills of seam compensation for waterjet machine

When the wtaterjet cuts, according to the NC instructions, the trajectory of the cutting path is the theoretical size, and the actual cutting size will have a slight deviation. This is because there is a slit in the cutting process, and the slit is the loss part in the cutting process. Therefore, if the geometric size is not compensated, the actual size of the cut part outline part is long. The dimension of the inner contour becomes larger when the degree direction is smaller (the width of the slit is exactly half of the difference between the two sides, and the width of the slit is half of the difference between the two sides).

For example, if we want to cut a circular workpiece with a diameter of 100 mm, the diameter of the water beam is 1 m, then the cutting trajectory of the water knife is cut according to a circular trajectory with a diameter of 101 mm (the cutting trajectory is the trajectory of the cutting water beam center, and the motion coordinates shown by the G code generated in the CAD/CAM software are the coordinates of the cutting trajectory). If the trajectory is 100mm, the diameter of the workpiece is only 99mm, and the circumference of the workpiece is one radius smaller than the required 100mm (that is, the radius of the cutting water beam). In order to compensate for the reduced cutting radius, it is necessary to add the trajectory on the basis of the workpiece size in the CAD/CAM software. A radius of cutting (if it is a cutting hole, it should be subtracted from a cutting radius), that is, the so-called radius compensation, so as to eventually be able to process the required size of the workpiece.

The following points should be paid attention to in setting up slot compensation:

There is no need to compensate in NC system after setting software compensation. Otherwise, there will be deviation in compensating repetitive size. But if the size of software compensation is still a little worse after cutting, it can be compensated through NC system.
If it is compensated by NC system, the compensation should be set to zero in software.
If we can’t determine how much size we should compensate, we can cut a rectangle on the scrap and measure the actual size and the programming size to calculate the required compensation.
It is difficult for NC system to deal with the compensation of small arc. If the arc is smaller than the compensation radius, it can not be cut out, nor can it be correctly compensated (the theoretical upper half radius becomes negative), in this case, we should consider modifying part drawings or using software compensation to find problems in time.