Main difference between X-bar sigma chart / X-bar range chart

[ondrisek_SK]

I would like to ask you which main difference is between xbar r chart between xbar s chart and using in production of needle roller bearings.

thank you

 

[DRAMMAN]

They essentially do the same thing. The R-chart (sample set range) and S-chart (sample set std deviation) each monitor the process variation. The S-chart works better for larger sample sizes although you don't want the sample size to be too large. SPC was invented in the 1920's(?) and expecting someone to calculate the standard deviation of each sample would have been a bit time consuming and would require a stronger mathematics level. So some smart people came up with the range method of estimating variation and control limits which is far simpler. With the power of computerized stat software like minitab you can easily run your charts both ways. When ever I have done this I get virtually the same results regarding identifying out of control conditions. Maybe someone will chime in with some more expertise on when to choose one over the other.

 

[t.PoN]

As DRAMMAN said:
S-chart works better for large samples. The R chart will be a poor estimate for large samples.
also for variable sample size, the S-chart works better. R-chart usually require a fixed sample size.

 

[Livika]

I agree with DRAMMAN and and t.PoN. For your production (I suppose big numbers and necessary stat software at your disposal) I should go with s-chart.
Maybe you could also appreciate information that you can find for example here http://elsmar.com/Forums/showthread.php?t=40690

 

[bobdoering]

I would like to ask you which main difference is between xbar r chart between xbar s chart and using in production of needle roller bearings.

I see two questions here: 1. what is the difference between R and s charts for dispersion and 2. whether either of them is applicable to needle roller bearings.

The first question was likely answerd well enough already.

But, as for the second question, what features and processes are you trying to control in needle bearing production? For some processes, neither chart is applicable!