In your message dated Thursday 26, September 1996 you wrote : > TechNetters, here is another question about SPC. > > Is anyone using SPC at the board image printing operation? Our people > here have been, at times and in an undisciplined way, been taking energy > data from the printer. The gauge is put at 9 points in a grid and energy > delivered thus measured. (These 9 measurements are made at approximately > the same time, at the start of a shift, say.) To me, this approach > seems to lend itself to SPC. Presumably, the measurements would be done > on a regular schedule. > > Anyone care to comment or correspond? Lou Hart Quality Assurance > Compunetics 412-858-6117 Hello Lou This check does not need to be done very often. Once the characteristics of the unit have been plotted and the step wedge difference in the corners and the centre of the exposure area have been established, they are not going to change significantly in a short time. You might want to recheck every 3 months but we never find any change in the distribution. All that needs to be monitored daily is the exposure step achieved for the light units set, and the time it takes to achieve those light units. Time will increase as the lamps age and although the step may still be within limits, the image quality will deteriorate as the time increases. Daily plot the exposure step, and the time in seconds. Keep the step within recommended limits, and set a maximum time at which to change the lamp(s). This should be not more than 50% longer than new lamps ideally, but you could stretch them for longer depending on the type of work you are doing. Paul Gould EMail [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************