# Pre-Control Chart - Limits are set at 2/3 of the specification

F

#### Fluidfont

I'm an industrial engineering major working on a case study for my statistical quality control class. I was able to obtain a case from my friend's work where they are utilizing control charts to control a process. However, I cannot seem to find any information about this chart. Here is a link to it.

I am Sorry that I am unable to disclose specific information. But basically on the chart there are 8 same processes done on a single machine, but each has a different target value. You can think of punching holes of different diameters simultaneously into a board if you want. This chart is plotting the deviation of each sample from the target value over time. The upper and lower lines you see are just the lowest and highest values traced. I was told that this was a multi-variable control chart, but I cannot seem to find information on it. It seems like a group chart combined with a running location chart or something. Please let me know what information you can find about this type of control chart.

#### Geoff Cotton

##### Quite Involved in Discussions
Welcome to the cove.

Looks like a "zero mean" chart to me. We use them but only to record one characteristic i.e a spigot diameter.

If I had to guess I'd say they are ploting eight different features (holes) and their deviation from the mean.

B

#### ben sortin

It is a "pre control chart." The limits are set at 2/3 of the specification. The recordings of the eight features are uniquely identified by color and symbol. The lines are plotted at the extremes of the subgroup. This identifies which characteristic has the largest deviation from the target in both directions (high/low). I would react to any point outside the limits and any one symbol which ends up being plotted on the same line seven times in a row. Keep an eye on any one characteristic that jumps from one line to the other. Not bad for tool wear monitoring on an eight station screw machine (Acme Gridley circa 1978).

#### Darius

##### Quite Involved in Discussions
I tink both are right (Geoff and Ben)

As Geoff said, the Min and Max lines on the chart is a Group Chart and with the data centered on Zero looks like a target chart (so a Group - Target Chart).

Normally this kind of chart only Max and Min are charted (not control limits and not the other points).

The spec limits are charted on the chart, that's wrong for SPC, unless a precontrol chart, that's is why Ben is right.

So it looks like a mixture to me.

For group charts: There is too litle about them on the net

Innovative Control Charting - Practical SPC Solutions for Today Manufacturing Environment- By Stephen A. Wise and Douglas C. Fair. Editorial ASQ

Last edited:

#### bpritts

##### Involved - Posts
Looks like some of you folks remember more from your CQE than I do!

F

#### Fluidfont

Well, They said they use this control chart because it is able to give a full overview of the process. It is too much for them to make an individual X bar with whatever chart.

Ben- Each plot is not an individual feature. They are all identical processes with different nominal targets. Yes, they do spin also. Lets keep that on the DL.

Darius- I was thinking target and group combined also. What is gained from doing this? Other than reducing the waste from having to keep 8 individual measurements.

#### Darius

##### Quite Involved in Discussions
It may also be a Group short run target chart if different variations are expected from the different locations.

I agree that the most of it is reduce the number of chart but Group Charts are used for evaluating the consistency of the characteristics, parameters (from location to location) or process streams. Are recommended also when monitoring processes where x and y or x,y,z axes are simultaneously monitored. On similar but independent processes produccing simular a product not only cuts down the number of control charts but also helps to focus on processes whose output begins to change significatly compared to the other.

Interpretation:
One should look for consecutive repeating locations appearing in the MAX or MIN (four or more is a run and indicate the presence of an assignable cause), or check for the percentage of the presence of the attribute on the MIN or MAX (also with the ranges)

It’s important that the number of locations should be held to 5 or less, if more the likelihood of missing a trend is higher.

:thedeal:

S Pre-Control Chart for Single Side Tolerance Statistical Analysis Tools, Techniques and SPC 1
New(?) kind of control Chart? Pre-Control Chart Statistical Analysis Tools, Techniques and SPC 16
D Pre-Control Chart to guide in-process inspection / adjustment decisions Inspection, Prints (Drawings), Testing, Sampling and Related Topics 43
Is there any pre-defined Control plan format/template acc. VDA? VDA Standards - Germany's Automotive Standards 0
Why is Pre-Control not a Process Control tool? Statistical Analysis Tools, Techniques and SPC 13
J Are the Pre-Launch Control Plan and Pre-Launch PFMEA obligatory? FMEA and Control Plans 3
Q How Many Control Plans Needed? Prototype, Pre-launch and Production? FMEA and Control Plans 3
L Defining Pre-Control Zones - Statistical Process Control (SPC) Statistical Analysis Tools, Techniques and SPC 1
D Pre-control Software Statistical Analysis Tools, Techniques and SPC 2
V Pre-Launch Control Plan Contents - What should I include? FMEA and Control Plans 4
Supplier wants to perform pre-qualifications prior to every run instead of locking in parameters. Supplier Quality Assurance and other Supplier Issues 7
Internal Audit before Pre-Assessment ISO 17025 related Discussions 2
Queries: RFD & Pre-RFD Program Medical Device and FDA Regulations and Standards News 0
Design file for pre-existing products - Inputs and Outputs ISO 13485:2016 - Medical Device Quality Management Systems 5
Gauge R&R on pre-set torque wrench Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
Pre-Production Capability Assesment Reliability Analysis - Predictions, Testing and Standards 5
Pre-Submission after 510(K) Submission? Other US Medical Device Regulations 4
Pre-clinical Studies for RUO Product Other Medical Device Regulations World-Wide 1
Informational Health Canada guidance document – Pre-market Requirements for Medical Device Cybersecurity Medical Device and FDA Regulations and Standards News 0
Custom-made implants (Class IIb) and pre-commercialization clinical trials in Spain EU Medical Device Regulations 4
Shipping Medical Devices to US before pre market clearance US Food and Drug Administration (FDA) 1
UDI requirements for pre-filled combination devices - Box containing a pre-filled device US Food and Drug Administration (FDA) 2
Informational MDCG 2019-3 Interpretation of Article 54(2)b – Pre- market clinical evaluation consultation procedure with the involvement of expert panels Medical Device and FDA Regulations and Standards News 0
Redacted pre-submission bundle that you would be willing to share US Food and Drug Administration (FDA) 3
Bench Testing & Pre-verification vs. Formal verification 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 4
Medical Device News Health Canada – Consultation: Pre-market Requirements for Medical Device Cybersecurity Medical Device and FDA Regulations and Standards News 0
510 (K) Pre-Sub meeting - Does it worth? US Food and Drug Administration (FDA) 4
Examples of Pre-Sub, SRD, PMA Shells and Templates Other US Medical Device Regulations 3
Manufacturing site relocation of pre amendment Class II medical device Manufacturing and Related Processes 4
Users won't return devices from pre-CE performance evaluation study EU Medical Device Regulations 3
GM GP-12 Pre-Launch - They asking for a I chart Statistical Analysis Tools, Techniques and SPC 2
Pre-Work and Study for ISO 13485:2016 Lead Auditor Class ISO 13485:2016 - Medical Device Quality Management Systems 1
Pre-release version of the upcoming AIAG FMEA Revision 5 FMEA and Control Plans 1
Is 'Compliance' a pre-requisite or is it ok before Batch Release to Market? 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 5
V Writing a Pre-Submission to the FDA 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 44
P EASA STC (Supplemental Type Certificate) on a Pre-mod FAA STC Configuration EASA and JAA Aviation Standards and Requirements 1
H Pre compliance test for Glucometer Other Medical Device and Orthopedic Related Topics 1
Pre-dispensed API material received in predetermined quantities & given to production Pharmaceuticals (21 CFR Part 210, 21 CFR Part 211 and related Regulations) 1
Is pre-conditioning supplier component before incoming inspection tests allowed? Quality Manager and Management Related Issues 16
Pre-Announced FDA 4 Day Inspection, Class 2 Devices, Contract Manufacturer 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 11
FDA Consensus Standard for PMA (Pre-Market Approval) 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 1
Does anyone have experience providing a summary of Pre-IDE discussions in the 510k US Food and Drug Administration (FDA) 1
Format of Health Canada pre-market licence application Canada Medical Device Regulations 3
Humidity Pre-Conditioning before leakage current and dielectric strength tests IEC 60601 - Medical Electrical Equipment Safety Standards Series 7
V 510(K) Cyber Security Documentation for Pre-market Submission (Templates) Other US Medical Device Regulations 6
Infusion Pump - Pre-Clearance Inspections Learnings US Food and Drug Administration (FDA) 4
ISO/TS 16949 Pre-Audit Requirement IATF 16949 - Automotive Quality Systems Standard 18
USA to insist on pre-flight mobe power probe Travel - Hotels, Motels, Planes and Trains 3
G 510(k) Pre-market approval Application Requirements - Effectiveness of the product Other US Medical Device Regulations 1