How to measure process capability (Cp & Cpk)? Download Excel Template
How to measure process capability (Cp & Cpk)? Download Excel Template
Hello readers! Today we will discuss how to measure process capability (Cp & Cpk). As you know that process capability and its index can be measured by using an Excel template or by using software like Minitab etc. We are offering to our readers for a limited time period to download the approved excel format, so download the template from the below link.
DOWNLOAD Excel Template of Cp & Cpk.
Process Capability (Cp):
- Process Capability (Cp) is a statistical measurement of a process’s ability to produce parts within specified limits on a consistent basis
- It gives us an idea of the width of the Bell curve.
- The Process Capability for a stable process is typically defined as ((USL-LSL)/ (6 x Standard Deviation)).
Process Capability Index (Cpk):
- It shows how closely a process is able to produce the output to its overall specifications
- More Value of Cpk means more process capable.
- Cpk value <1 means the bell curve will be out of USL/LSL
- Common Cpk vale=1,1.33,1.67 & 2
- The Cpk value of a start-up manufacturing organization is supposed to be 1.33.
- The Process Capability Index for a stable process is typically defined as the minimum of CPU or CPL
How to measure process capability (Cp & Cpk)? (Industrial Example):
| Characteristics | Green Sand Permeability |
| Process: | Green sand moulding process |
| USL | 200 |
| LSL | 180 |
Table-A
| Sl.No. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Subgroup1 | 190.00 | 189.00 | 189.00 | 191.00 | 190.00 | 192.00 | 188.00 | 191.00 | 189.00 | 189.00 |
| SG2 | 191.00 | 188.00 | 188.00 | 191.00 | 191.00 | 193.00 | 187.00 | 191.00 | 188.00 | 188.00 |
| Subgroup3 | 192.00 | 190.00 | 188.00 | 192.00 | 192.00 | 189.00 | 189.00 | 192.00 | 190.00 | 188.00 |
| SG4 | 192.00 | 188.00 | 189.00 | 189.00 | 192.00 | 190.00 | 189.00 | 189.00 | 188.00 | 189.00 |
| Subgroup5 | 193.00 | 189.00 | 190.00 | 190.00 | 193.00 | 188.00 | 190.00 | 190.00 | 189.00 | 190.00 |
| Mean | 191.60 | 188.80 | 188.80 | 190.60 | 191.60 | 190.40 | 188.60 | 190.60 | 188.80 | 188.80 |
| Max | 193.00 | 190.00 | 190.00 | 192.00 | 193.00 | 193.00 | 190.00 | 192.00 | 190.00 | 190.00 |
| Min | 190.00 | 188.00 | 188.00 | 189.00 | 190.00 | 188.00 | 187.00 | 189.00 | 188.00 | 188.00 |
| Range | 3.00 | 2.00 | 2.00 | 3.00 | 3.00 | 5.00 | 3.00 | 3.00 | 2.00 | 2.00 |
Table-B
| Sl.No. | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| Subgroup1 | 189.00 | 191.00 | 190.00 | 189.00 | 189.00 | 191.00 | 190.00 | 191.00 | 190.00 | 191.00 |
| SG2 | 188.00 | 191.00 | 191.00 | 188.00 | 188.00 | 191.00 | 191.00 | 191.00 | 191.00 | 191.00 |
| Subgroup3 | 190.00 | 192.00 | 192.00 | 188.00 | 190.00 | 192.00 | 192.00 | 192.00 | 192.00 | 192.00 |
| SG4 | 188.00 | 189.00 | 192.00 | 189.00 | 188.00 | 189.00 | 192.00 | 189.00 | 192.00 | 189.00 |
| Subgroup5 | 189.00 | 190.00 | 193.00 | 190.00 | 189.00 | 190.00 | 193.00 | 190.00 | 193.00 | 190.00 |
| Mean | 188.80 | 190.60 | 191.60 | 188.80 | 188.80 | 190.60 | 191.60 | 190.60 | 191.60 | 190.60 |
| Max | 190.00 | 192.00 | 193.00 | 190.00 | 190.00 | 192.00 | 193.00 | 192.00 | 193.00 | 192.00 |
| Min | 188.00 | 189.00 | 190.00 | 188.00 | 188.00 | 189.00 | 190.00 | 189.00 | 190.00 | 189.00 |
| Range | 2.00 | 3.00 | 3.00 | 2.00 | 2.00 | 3.00 | 3.00 | 3.00 | 3.00 | 3.00 |
| Average of Range | 2.75 |
| Averge of Mean | 190.11 |
| Std.Dev. | 1.182287188 |
| USL | 200 |
| LSL | 180 |
| Cp | 2.82 |
| Cpk | 2.8 |
To know more about the manual calculation then click-here.
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