The process control points of the glass bottle forming process include temperature, flow rate, tank pressure, tin level, maintenance gas, and other control indicators. Similarly, in order to evaluate the process capability and control level of this process, the quality of the product glass should be determined. The elements representing the surface quality of formed glass include the defect content of the glass plate and the thickness deviation of the glass. However, the defect content of glass panels not only comes from the forming process, but also from the batching process and melting process, which have a significant impact on the surface quality of the glass. Therefore, it is meaningful to use the detection of thickness deviation and friction difference of glass to identify the process and control level of the forming process, and it can also better control the cost of glass

The thickness error requirements for glass products with different thicknesses are different. The national standard requires a thickness error of 0.2mm for 2-6mm, and a thickness error of 0.3mm for 8-12mm; The thickness error of 15mm is ± 0.5mm. Each production enterprise formulates stricter control standards based on customer needs. The smaller the thickness error of glass, the higher the production skills and control level of the enterprise. Of course, glass thickness errors below 3mm and above 15mm are more difficult to control. Generally, the quality inspection department conducts testing every 2 hours and promptly feeds back the testing data to the forming process. The skills department calculates and determines the process capability once a month

(1) Only the forming process can be accounted for

① First select a thickness of glass

② Randomly check 20-25 sets of thickness error data from last month and calculate their standard error value a.

③ Calculate the process capability index based on the upper and lower limits of the glass thickness deviation and the formula Cp=(Tu-T)/6a,

④ Determine whether the process is reasonable based on the size of Cp values in the table

(2) The Meaning of Controlling Process Ability

① The process capability of the forming process in a glass bottle factory is an important factor in ensuring and improving the quality of the forming process control. The process capability index comprehensively and quantitatively reflects the skill control level of the forming process.

② Through the manipulation of process talent, the process is standardized, abnormal elements are eliminated, and quality problems are discovered and handled. ③ Through the manipulation of process talent, process specifications and operational specifications can be economically and reasonably selected and confirmed. If the calculated C value is too large, the control indicators can be appropriately relaxed to reduce control costs

④ Correctly calculating and confirming the process is also a powerful measure for economically and reasonably conducting product design and process validation