Usually the black spot occurs inside the head of the stainless steel screw. This is because the punch hits the part at high speed when the screw is produced. If there is a problem with the material, some of its impurities will accumulate in these parts during the extrusion process. The inside of the cross recess or hexagon socket screw. If it is such a black spot, it is a material problem, and the result will be known after testing. The solution is to replace the good stainless steel screw.
There is also a kind of black shift, which is caused by the production technology. The quality of the mold is not good, and the speed and force of the punch production do not meet the national standards. And produce some color variation. This kind of black shift can be solved by adding some polishing agent during the later cleaning, but the final solution has to deal with the mold problem.
Sometimes there is no problem with the mold, it is because the production environment causes the temperature to be too high to cause black shifts. At this time, we can consider changing the simple structure of the machine, such as adding a cooling pipe, using high-quality coolant to make the mold and screws The temperature drops rapidly.
