JMP can compute PPK metric for non-normal distribution. You do this by specifying the distribution type you wish to use when launching the process capability platform or you can do it from within the process capability report by selecting "Compare Distributions" from the Capability red triangle. The example below shows a capability metric computed using a Weibull distribution.
dt = Open( "$SAMPLE_DATA/Tablet Measurements.jmp" );
dt << Process Capability(
Process Variables( :Purity & Dist( Weibull ) ),
Moving Range Method( Average of Moving Ranges ),
Individual Detail Reports( 1 ),
Capability Box Plots( 1 ),
Capability Index Plot( 1 ),
SendToReport(
Dispatch(
{"Individual Detail Reports", "Purity(Weibull) Capability", "Histogram"},
"Process Capability Analysis Histogram",
FrameBox,
{Frame Size( 320, 20 )}
)
)
);