Balancing SPC Data: CpK, X-Bar & R Charts

Automated Data Logging and Reports

With automatic data logging, BTI’s statistical software package does the work for you. Standard reports include histograms, trend analysis, R-bar, X-bar, Cpk, sigma, number of samples, max, min, and mean. The machine will automatically save the data directly to the machine’s hard drive; you can also save it to a filename and path on your network, or you can save it to a flash drive or external hard drive. The data is saved in a .csv (spreadsheet) format, so it can be easily imported into Excel, Minitab, DIAdem by LabVIEW, AQDEF, or STAT by SAS. The built-in calendar allows the data to be searched by date, time, and/or serial number where applicable.

Production data summary reports are typically displayed on the PLC, giving key plant personnel a quick and concise summary of how the equipment and line are performing. Common reporting includes parts per hour, parts by shift, current and last part cycle times, average part cycle times, total number of parts run, number of good parts, number of rejects, and a detailed cycle time breakdown of each process station. The cycle time breakdown of each process station enables plant personnel to rapidly identify any equipment bottlenecks.
Q-DAS BTI’s export interface has been certified by Q-DAS for “Advanced Quality Data Exchange Format” version 4.1 and “GMPT K-Field List with exceptions to AQDEF Standard 2014-09-16”

The Statistics Built In

Balance data is only useful if it can be argued with. BTI machines compute the studies a program is normally qualified against, on the machine, without exporting to a separate package first:

Number of readings, range, sigma, mean and standard deviation
Minimum and maximum unbalance
CpK
Incoming and outgoing distribution histograms
X-bar and R charts
Gage R&R studies

What Gets Recorded Per Part

Incoming part unbalance, outgoing part unbalance and the part parameters used are stored alongside date, time and part number. That combination is what lets you answer the two questions that actually come up: was this part in tolerance when it left, and was the machine behaving normally when it said so.

Getting Data Off the Machine

Records save to the machine’s solid-state drive and transfer over USB or Ethernet. Where a specific plant format or database interface is needed, custom software is quoted against your requirement rather than assumed.

Signal-Level Data, Not Just Results

Beyond pass/fail numbers, real-time analog and digital signal plots are available on screen — effectively an oscilloscope view of what the transducers are seeing. On dynamics-sensitive parts, that is often the only way to explain why a reading moved.