Almost every quality engineer is familiar with the eight SPC out-of-control rules. However, in practice, the key is not familiarity, but application.
In many factories, SPC systems generate a large number of false alarms and missed detections every day. When there are too many alarms, they effectively lose their meaning. Real production environments are highly complex, and rigidly applying standard rules cannot meet the needs of refined and differentiated quality control.
Starting from the fundamental logic of statistics, NEX SPC, built on a new-generation B/S architecture, enables pixel-level and refined control of out-of-control rules.
1. Pain Points: Why Traditional SPC Rules Are Not Enough
Many legacy SPC systems based on C/S architecture have three critical limitations in rule configuration:
“One-size-fits-all” triggering mechanism
For example, the rule “one point beyond 3σ from the center line” is often configured to trigger an alarm whenever a limit is exceeded.
However, in practice:
- For some characteristics (e.g., impurity content, surface roughness), only the upper limit matters—the lower the better
- For others (e.g., tensile strength), only the lower limit matters
Triggering alarms on both sides simultaneously only increases unnecessary workload.
Rigid parameter settings
Rules are often hard-coded.
For example:
- The standard rule “14 points alternating up and down”
- But in some processes, 12 alternating points may already indicate significant systematic variation
Disconnection between rules and materials/processes
Different inspection items and material types have completely different process capabilities and variation characteristics.
A single global rule set should not be applied to all products.
2. Advanced Approach: How Bingo SPC Enables “Pixel-Level” Control
To address these issues, enterprise-level SPC systems must provide highly flexible parameter configuration.
In Bingo SPC:
- The classic 8 rules are extended to 11 rules
- Configuration is highly flexible
2.1 Precise One-Sided / Two-Sided Control
Take the basic “out-of-limit alarm” as an example:
NEX SPC allows users to define:
- Upper limit only
- Lower limit only
For the rule:
“2 out of 3 consecutive points beyond 2σ from the center line”
In traditional interpretation:
- One point may be above (+2σ)
- One point may be below (−2σ)
Mathematically, this satisfies the rule.
However, in process analysis:
Such “up-and-down fluctuation” is likely caused by different sources.
NEX SPC introduces the concept of “same-side condition”:
The rule is triggered only when the abnormal points are on the same side of the center line.
This refinement can eliminate at least 30% of invalid alarms.
2.2 Flexible Definition of Core Parameters
The definition of “rare events” varies across industries.
NEX SPC allows direct customization of rule parameters:
- Number of consecutive points
- e.g., change “9 consecutive points on one side” to “7 points”
- Trend length
- e.g., change “14 alternating points” to “12 alternating points”
This flexibility allows the SPC system to adapt to the process, rather than forcing the process to adapt to the software.
2.3 Dynamic Binding of Rule Groups to Inspection Items
This is the key to handling complex manufacturing processes.
NEX SPC introduces the concept of “rule groups”:
Create rule groups
- A “standard material rule group” with 5 rules
- A “high-precision material rule group” with all 11 rules
Bind on demand
Different inspection items and material types can be bound to different rule groups.
Final result
- Dimension inspection for Part A uses one rule set
- Hardness inspection for Material B uses another
All rules operate independently:
- Upper/lower limits
- Same-side conditions
Without interference.
3. Comparison: Traditional SPC vs NEX SPC
To better illustrate the difference, a structured comparison of core capabilities can be made.
4. Proven in Tier 1 Manufacturing
NEX SPC combines flexible rule configuration with robust underlying algorithms.
It supports:
- Normality testing
- Advanced algorithms such as Box-Cox transformation for non-normal data
This new-generation B/S-based SPC system has been validated in demanding industrial environments.
It is adopted by leading manufacturers and Tier 1 suppliers, including:
- Geely Group
- ZEEKR
- Li Auto
- Faurecia
as their automated quality data analysis and monitoring system.
5. Let Data Truly Serve Quality
Many companies invest significant effort in inspection and data collection.
However:
- Without SPC analysis
- Or with inaccurate rule settings
The data becomes nothing more than unused storage.
If your current SPC system still generates excessive invalid alarms
If you are not yet using SPC software
If you aim to build a flexible, refined, and material-specific quality control system like leading automotive manufacturers
It is time to adopt a modern SPC tool.
Use the right tools to perform high-value quality engineering.