If there is a large CNC machining residual stress, directly affects the performance of the machine tool, such as straightness, vertical degree of precision. In recent years, with the use of industrial robots and CNC machine tool makes intelligent production or "unmanned factory"has become the trend of development. The good situation gave birth to the high quality of theCNC machine tool. Do not remove the residual stress, also can use the excellent machine a year, therefore, it is important to eliminate stress.
We mainly from his casting up analysis and solve the problem of stress problems.
Next we look at in CNC machining in die casting process of two stress formation:
1 mechanical stress: Alloy shrinkage by stress or mould core mechanical resistance and the formation of.
Mechanical stress is temporary, after shakeout, will disappear. The mechanical stress and thermal stress interaction, may make certain parts increases the crack tendency.
Prevention methods: improve the mould and core.
2 thermal stress: Casting uneven thickness, cooling rate, shrinkage is not consistent.
Prevention methods: 1 uniform wall thickness 2 and solidification is arranged at the gate - thin,thick, cold iron
Advantages: Province riser, labor saving, material saving
: elastic state below the recrystallization temperature, under the action of external force, metalelastic deformation, deformation and stress continue to exist.
Thus, the temperature of each part is bigger, the thermal stress is also larger, slower coolingpart of the formation of tensile stress, rapid cooling to form part of the compressive stress.
Plastic state: metal above the recrystallization temperature above the solid cooling phase,deformation, hardening, recrystallization occurred at the same time reducing hardening offset,internal stress disappear. (say, in a state of yield, stress - deformation without stress)
Disadvantages: heart prone to shrinkage or porosity, applied to the iron tin bronze, iron forshrinkage, shrinkage, tin bronze paste solidification, with sequential solidification is also difficult to effectively eliminate the microporosity.
In China is faced with the problem of breakthrough of NC industry technology development from a technical key points, the lack of system demand analysis, there is no good abstraction and concept, logic design, the result is very difficult from the previous product to extract some useful, common technology for the later product the use of.