SPC concept SPC namely statistical process is controlled (Statistical Process Control) , SPC basically is to show applied statistic analyses a technology to undertake real time monitoring to producing a course, distinguish scientificly the random wave motion that gives quality of the product in producing a course and unusual wave motion, put forward early-warning to producing the unusual trend of the process thereby, so that produce administrator to take step in time, eliminate unusual, restore the stability of the process, achieve the goal that rise and controls quality thereby. In producing a course, the machines dimension wave motion of the product is inevitable. It is the fluctuant influence be caused by that waits for main factor by person, machine, material, method and environment. Fluctuant cent is two kinds: Normal wave motion and unusual wave motion. Normal wave motion is contingency reason (inevitable element) cause. It is lesser to product quality influence, eliminate hard on the technology, in economically undeserved also eliminate. Unusual wave motion is by systematic reason (unusual element) cause. It is very big to product quality influence, but can adopt measure avoids and eliminate. Process pilot purpose is eliminated namely, avoid unusual wave motion, make the process is in normal and fluctuant condition. The process that SPC of SPC technology principle is method of statistic of manage of number of a kind of have the aid of controls a tool. It undertakes analytic evaluating to producing a course, discover the sign that systematization element appears in time according to feedback information, adopt measure to eliminate its to affect, make the process is maintained in the controlled position that accepts impact of random sex element only, in order to achieve the goal of control quality. Suffer only when the process when random element influence, the process is in statistic to control state (abbreviation is controlled condition) ; When the influence of element of system of the existence in the process, the process is in condition of statistical out of control (condition of abbreviation out of control) . Because process wave motion has statistical regularity, when the process is controlled, what general obedience stabilizes process character is random distributing; And when out of control, the process distributings will produce a change. The Cheng of statistical regularity opposite that SPC uses a process to fluctuate just about undertakes analytic pilot. Consequently, it emphasizes a process be in controlled and capable move below condition, make product and service satisfy the client's requirement steadily thereby. Executive SPC cent is two phase, it is analytic phase, 2 it is monitoring phase. Analysing the job that level should have above all is manufacturing preparation, the raw material that wants manufacturing process place namely, labour force, equipment, measure a system to wait to ask to prepare according to the standard. The main job of monitoring phase is to use control to undertake monitoring with control graph. In the actual application of the factory, control a project to every, must pass above two phase, and be in can repeat when necessary undertake arriving from the analysis so the process of monitoring. SPC measures example to allow automatic and video measuring instrument to be with the day exemple, introduce a specific SPC example. Open software of day of Vispec of accurate automatic and video measuring instrument above all, measure 100 times to workpiece. 1. Click advocate in tool column " SPC " icon, play a SPC advocate interface; 2.
Click " be record in example " , choose Output catalog, be like,hit create a precedent " 2008-5-17 " subdirectory, choose data file; Nextpage3.
The data that doubleclicks need control in the data row on the right side of, play piece " setting control project " dialog box; 4.
Input mark fiducial value and tolerancepublic errand limits; 5.
Repeat 3-4 situation, add many control item; 6.
Switch arrives " control chart " , can examine the control chart such as XBar-R, XBar-S, XMed-R, X-RM. CNC Milling