Production Part Approval Process (PPAP) is one of quality core tool in manufacturing industry. This is the documentation process to create and submit documents to customer in new product development stage. Checking Aids is one of the PPAP document, use to provide the list of all measurement equipment’s.
Many engineers don’t know the basics of checking aids documentation.
Therefore, in this article we will have look everything about checking aids.
Let’s dive in…
What is Checking Aids?
Checking Aids are tool or fixture, or gauges or equipment used to measure manufactured part dimensions. They help to maintain part quality by measuring dimensions, verify tolerances or conducting a functional test.
Therefore, checking aids helps PPAP submission by verifying product quality and make sure that the part meets customer specification.
Checking aids can be in many types, such as:
- Gauges
- Fixtures
- Measurement equipment
- Visual devices
- Test Equipment
These all-tools support measurement process and ensure that dimensions, tolerances and characteristics of product meet customer specification.
Types of Checking Aids in PPAP
Checking aids are in many type and forms, as you already seen above.
There are two type of measurement data categories, like Variable and Attribute measurement. You can learn about variable and attribute data in control chart article.
Here we have categorized as above. Let’s see each category in detail,
1. Gauges
Gauges are tools to measure product dimensions or features. They check product qualification to its specified tolerance range. Some common type of gauges include:
- Go/No-Go Gauges: These gauges check the parts within tolerance or not by providing two results. “Go” if the part fits within tolerance and “No-Go” if the part outside specified tolerance.
- Profile Gauges: These gauges matching the part profile and if it at accepted limit then your part is qualified as ok. Otherwise you can reject the part based on gauge profile not matching.
- Height Gauges: Use to measured height of part from its true position.
- Thread Gauges: These are use to check thread using thread gauge.
- Etc.
2. Measurement Devices
Other than gauges, measurement devices is one of the best method to do inspection. It is more accurate with results and data. The inspection using measurement devices will give you the exact value of measurement, then you have to verify it to the specification. This also gives you the variation present in your part.
Some common examples of measuring device include,
- Micrometer: These devices used to measure small dimensions. When you want more accuracy and precision the micrometer will help to give you the results. Even you will get the results in micron as well.
- Vernier Caliper: This is also another precision equipment and widely used in manufacturing industry. Majority of dimensions you can check using verniers are internal, external and depth dimensions.
- Coordinate Measuring Machines (CMMs): This is the advanced type of checking aid where you can accurately and precisely measure using computer program.
3. Fixtures
These devices are most commonly used to hold and clamp part for inspection. Fixtures hold your part so that you can have a detailed and accurate inspection on multiple points with same steady condition.
When we have a requirement to hold the part and check without variation then the application of fixtures is the best suitable checking aids.
4. visual Aids
Visual aids provide you the leverage of tool to quickly identify defects on parts. Best example of visual aids are inspection templates and Shadow boards.
Inspection Template: It is a kind of physical or digital template to compare the actual part with template. It is easy to identify defect with comparison.
Shadow Board: It is like projection of shadow o inspection table or in assembly area to identify missing object or part.
5. Test Equipment’s
Some products supplied in assembly condition and those assembly need functional testing. In this case we have some test equipment’s at end-of-line. Those equipment is also a kind of checking aids to verify product functionality and specifications as per customer requirements.
These are something complex type of tools or equipment’s.
Why Checking Aids important in PPAP?
There are many reasons and importance of checking aids, therefore it is done in PPAP documentation process during initial product development.
1. Accuracy and Precision: Manufacturing process has multiple involvement and steps, which leads to have a variation or deviations in part dimensions. Checking aids helps to have accurate and precise measurement, so that supplier can make sure that his part is ok as per customer specification.
2. Consistent Quality: We do PPAP to check that your manufacturing processes consistently produces good quality product which meet customer expectations. Checking aids will support all inspection process, so that you can verify that you produce a high quality product.
3. Prevent errors: Human inspection leads to have human errors and defective products may passed to customer. Checking aids support to prevent defects by providing standard tools for inspection and measurements.
4. Documentation and traceability: Checking aids record all details such as equipment ID, calibration details along with specifications. Therefore this creates a traceability in your system that for we use which equipment for this dimension. This is the key points in audit process as well.
How to create checking aids PPAP document?
A. Understand Design record (Drawing)
Drawing is the only document where we addressed all dimensional requirement of product. You should have a clear understanding of your design and their dimension from customer fit and function point of view.
Also, which characteristics is critical or not.
B. List out part dimensional requirements
List out all dimensions in checking aids document template. Where mention the part specification, with special characteristics identification if applicable.
C. Select correct Measurement tools and equipment
Measurement equipment selection is most important thing. If you select wrong instrument or tool, then there is a chance of incorrect data recording and part may got rejected due to non-standard measurement system.
But how do you select correct measurement tool or equipment?
Which Checking Aids need to select?
Condition 1: for variable data
Well, whatever dimension you measure, the list count of your measurement instrument should be 1/10th of your tolerance.
For example, you are going to measure dimension of length 10 +/-0.2. It means you have a tolerance of +/-0.2=0.4
Now 1/10th of 0.4 is 0.04.
So you can select any instrument which has the least count below 0.04mm.
Now vernier caliper has a least count of 0.02, it means you can measure minimum of 0.02mm from this vernier. You can select this instrument.
Condition 2: Attribute data
In attribute data you can use various type of gauges specifically designed or standard used for your part inspection.
It is now clear that you will select correct measuring equipment.
D. Create checking Aids document
Here is the role of checking aid format or template. You need to fill all information in checking aid report as list of checking aids.
The template needs some content such as,
Header section: This section must have your company logo, part number, drawing number, revision, engineering change levels, and Customer information.
All these information gives us a better understanding about the product and customer status.
Product Characteristics: Add product characteristics which you will measure to qualify the part.
Drawing Specifications: The actual dimensions according to drawings with tolerances.
Special characteristics Identification: Mention the dimension class, if any special characteristics identified on drawing.
Equipment Name: It is the name of actual equipment used as checking aids. E.g. Vernier Caliper, Micrometer, Gauge, etc.
Equipment Unique Identification Number: Every equipment in organization has its unique serial or identification number for traceability purpose. Mention that unique identification number over here.
Calibration frequency: Add the calibration frequency for that specific instrument or equipment.
E. Do PPAP submission
Once you complete the list, you need to attached it into PPAP documentation package.
F. Get customer approval
Submit the PPAP package to customer and once after validation get approved it from customer.
What other documents that checking aids supports in PPAP?
Checking aids are relatively used and linked to many documents, such as:
Dimensional Results: Checking aids used to verify and do measurement of all dimensions mentioned in dimensional results.
Measurement System Analysis: All checking aids devices need to have MSA done. And it should reflect in your MSA plan and MSA study report.
Layout Inspection Report: It is also a kind of dimensional result where all part dimensions need to verify. So, select the same checking aids what we have used in our PPAP submission work package.
Control Plan: All dimensional control methods and measuring controls should be same as we have mentioned in our checking aids documents.
This all linkage between checking aids, layout inspection, dimensional results and control plan may be verified in audit process. Either in process audit or in Layered Process Audit depends on process criticality.
Conclusion
Checking aids is one of the important documents of PPAP package. It is the evidence that which inspection method or device you are going to use to do the measurement and qualify the part.
You have to submit this document as a part of PPAP submission along with other PPAP documentation and get approval from customer.
For more information on quality tools and techniques, explore other articles on our website, and feel free to reach out and contact us with your queries.
Together, let’s build a manufacturing and quality excellence!
FAQs
No, checking aids does not applicable for bulk material requirement as per PPAP manual. The organization representative should clarify this requirement from customer.
Probably Yes or No, depends on your product complexity you can select the dimensions. It is better if you refer customer requirements on checking aids. If not, as such requirement form customer then you can do whatever as your guideline suggest. There is no hard rule on this. The aim is to fulfil part quality functions and requirement.
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